A Micrometer Stand

When you acquire a micrometer and begin making use of it, you soon discover that miking tiny parts with it is a very clumsy bit of business. You truly need a third hand, and the stand pictured does the job.

Before I built this, I looked into getting a ready-made one. They can be had, but not nearby or inexpensively. It somewhat surprised me that such a useful accessory for a micrometer would be such an obscure item.

Anyway, since I much prefer working to shopping, I went on a scrounge around my workshop and came up with the makings of a stand in short order.

The base is a steel, 3 1/4" diameter pulley. The pulley is heavy enough that the stand isn't tippy. A 4" spring clamp serves nicely for holding the micrometer. Two 3/4" corner braces and a few fasteners and washers provide the hinged mounting arrangement that permits adjustment of the micrometer's viewing angle.

The screw for the pivot-point is Loctited into a threaded hole in the lower corner brace, so the screw never loosens when the wing nut is loosened for adjustment. I should add a second screw or an interference-fit pin where the clamp is attached to its corner brace, so the clamp can't twist out of position sideways.

I won't hold my breath waiting to win any industrial design awards for it, but for the price it's been serving me well. (By the way, that oversize 1/4"-20 wing nut was once the cover fastener for a Ford Pinto's air cleaner. Think what you will of the Ford Pinto, they were good basic transportation, and they had fine air cleaner cover wing nuts.)

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Thursday, September 9, 2010

Addendum

I finally got around to doing what I should have done in the first place, I added a roll pin to the clamp/corner-brace attachment point so the clamp can't get torqued out of position.

This is a handy technique for securing interfaces against rotation when you have very little room for an additional threaded fastener. Drill one small hole, install a roll pin, problem solved.

That roll pin is tiny. It's 1/16" diameter x 3/16" long, but it's all that's needed.

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A Watering Can Repair

The old garage-sale-find watering can pictured is a nice piece of gear. There's a brand name on it; "Garden Club". It must be pretty old because it was made in the U.S.A., and the U.S.A. doesn't do that sort of thing anymore.

The body of it is still in fine condition, but the nozzle is past it -- embrittled and cracked in many places. The nozzle in the foreground is a good salvaged one that I can adapt once I get the duct tape adhesive muck off the can's spout. (I'm not a big fan of duct tape. I've spent quite enough time cleaning up what it leaves behind when it's removed, and I don't recall ever having enjoyed it.)

The difficulty here is that the replacement nozzle came from a can that had a considerably larger diameter spout-end on it than this can has. I could just slather the parts with a silicone gasket maker and assemble them that way, but it would be a poor job. The key to using adhesives and sealants is to never ask too much of them.

What's needed is a bushing of sorts to take up the space between the two diameters. That will minimize the amount of adhesive required, and make for a snug, sturdy interface. Sometimes you get lucky with these situations, and it turns out that some piece of standard-dimension thin-walled tubing is close enough to what's needed. But here, I'm dealing with a couple of very odd diameters, so I'll have to fabricate what I need.

- - -

Here's what I came up with:

That band was cut from a scrap of 0.020" thick aluminum window casing material, and rolled around a 9/16" socket wrench to form it. The replacement nozzle can just be slipped on over the band with a bit of force applied, so I've succeeded in taking up the bulk of the gap with solid material. The 1/8" diameter holes perforating the band are key to getting the strongest possible outcome here. I'll be using epoxy as an adhesive/filler.

What the holes do is they effectively turn two interfaces into one. The epoxy filling the male thread on the spout, and the epoxy filling the female thread in the nozzle won't be entirely isolated from one another. When the epoxy has cured, at every hole there'll be a tough, contiguous span of epoxy through the hole. So, there won't be two epoxy-adhered interfaces; there will be one aluminum-reinforced epoxy-adhered interface -- big difference. In normal use, the repair should be near indestructible.

Here's a shot of the inside of the nozzle (the sprinkler head is a snap fit and can be pried off fairly easily). You can make out the edge of the filler band, and see that the epoxy has formed a full and reasonably uniform fillet all around. That nozzle's not going anywhere without the can.

I'll leave that to fully cure overnight, snap the sprinkler head back on and photograph the finished item.

- - -

And here's the finished watering can out with its pals:

A good outcome. You'd never know to look at it that the can and nozzle weren't made for one another. And the purchase price was all of twenty-five cents, no sales tax.

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Nothing Lasts Forever -- WEDNESDAY, MAY 16, 2018

'Went to use the watering can, and discovered that the nozzle had acquired a nasty fracture.

'Don't know what happened there. It appears that either the nozzle shrank, or the epoxy adhesive/filler swelled up. In any event, what I have now is an insecure, leaky nozzle. I can fix that up so the watering can remains useable, but it won't be the most elegant repair I've ever done.

- - -

And here we are.

I wired the nozzle in place with 0.047" diameter (No. 18 U.S. Steel Wire Gauge) stainless steel wire, and slathered the fracture with hot-melt glue. It isn't pretty, but it will serve.

A downside to the repair is that the nozzle isn't readily removeable, should one want to be able to pour water directly from the can's spout. But then, that was the case with my first repair as well, so I really haven't lost anything here.

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Wing Screws

Everything has its converse -- vice has virtue; joy has sorrow; hex sockets have hex keys and wing nuts have wing screws.

Wing screws are easily fabricated when the need arises. The only complication is that most screw heads in any given thread series are too large in diameter to fit directly between the wings of a wing nut. (The examples in the photo are 10-24.) An exception to that is hex socket head screws, but I don't care for the finished appearance (upper left); the hex socket head is too bulky to look right.

But a few minutes at the lathe with an ordinary round head screw gets you a reduced diameter screw head that's in good proportion to the wing nut (upper right).

Assemble the two pieces with red Loctite threadlocker or CA adhesive, and tighten very firmly.

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Addendum -- THURSDAY, OCTOBER 10, 2013

If you need an M4 wing screw, but only have 8-32 wing nuts, just run an M4 tap through an 8-32 wing nut and you're away. M4 and 8-32 are very near one another in diameter and pitch. (M4 is slightly smaller in diameter than 8-32.) The M4 thread you get from tapping an 8-32 wing nut is entirely adequate for this application.

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Roll Pins

Roll pins (aka 'rolled spring pins' or 'slotted spring tension pins') are a very good thing to have on hand. They come in a wide range of sizes; the two pictured give an idea. The large one is 3/8" diameter x 2" long. The small one is 3/32" diameter x 5/8" long. (There are metric dimensioned ones too, of course.)

The two shown here are from a 120-piece assortment I got from Princess Auto. Should I ever need a size or a quantity that the assortment doesn't provide for, I'll have to go to an industrial supply outfit like Spaenaur and buy a package quantity (typically 100 pieces).

The pins are made from quite hard spring steel, rolled into shape as the name implies. The key feature of them is the dimensioning. A roll pin's diameter as you receive it is always slightly oversize of nominal; e.g. a 1/8" (0.125") diameter roll pin will have an actual diameter of 0.131" to 0.135". To install one, drill a hole the nominal size and hammer in the pin. (One or both ends is/are always chamfered for ease of starting.) As the pin is driven, it contracts to fit the hole and effectively gives an interference fit of considerable strength.

An installed pin can be punched out and reused, which means that salvage can be a source of them. (A word of caution about punching them out: be sure to use an exact-size punch, and be especially careful if you're starting on a slightly protruding end of a pin. An undersize punch that manages to get down into the hollow centre of the pin can make a nasty mess of things. There are special punches available that have a centring point on them. You'd have to go to Spaenaur or a similar place for those; they're not something you're likely to find at the Home Depot.)

Uses are endless -- pinning gears or virtually anything to shafts; reinforcing glued up cylindrical assemblies; as motion-limiting stops in adjustable assemblies; what-have-you. Uses have a way of suggesting themselves when you have the pins at hand.

Occasionally, the hollow centre can be an undesirable feature; e.g. on a fertilizer spreader axle where corrosive material could get inside. In such cases, the centre can be filled with a length of soft steel wire or rod and epoxy or CA adhesive.

In closing, I must leave you with a word of caution about Princess Auto's assortment; the smaller diameter pins are poorly formed and seriously oversize, and will not install correctly in nominal size holes. To use them successfully, you have to mike them and select a suitable number size drill. For example, the 3/32" (0.09375") pins are about 0.113" in diameter. That's almost 0.020" oversize, and that's a lot for an interference fit. A No. 38 drill (0.1015" diameter) worked ok.

MONDAY, AUGUST 23, 2010

Addendum

Here's some information you may find helpful for dealing with oversize fractional inch diameter roll pins. Following is a list of all the available nominal diameters with some added information. Each entry is in the form:

Nominal Fractional Diameter; Nominal Decimal Diameter; Maximum Allowed Decimal Diameter*; Difference (Difference Rounded Off to the Nearest Thou)

* i.e. the maximum diameter that a given pin should have from the factory. A pin whose diameter exceeds this figure will be troublesome to install in a nominal-size hole.

1/16"; 0.0625"; 0.069"; 0.0065" (0.007")

5/64"; 0.078125"; 0.086"; 0.007875" (0.008")

3/32"; 0.09375; 0.103"; 0.00925" (0.009")

1/8"; 0.125"; 0.135"; 0.010" (0.010")

5/32"; 0.15625"; 0.167"; 0.01075" (0.011")

3/16"; 0.1875"; 0.199"; 0.0115" (0.12")

7/32"; 0.21875"; 0.232"; 0.01325" (0.013")

1/4"; 0.250"; 0.264"; 0.014" (0.014")

5/16"; 0.3125"; 0.330"; 0.0175" (0.018")

3/8"; 0.375"; 0.395"; 0.020"; (0.020")

1/2"; 0.500"; 0.524"; 0.024" (0.024")

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SUNDAY, JULY 3, 2011

Addendum -- Application Examples

Here's an example of a pin anchoring a stud at the end of a rod.

And here's a roll pin serving as a valve handle.

Scroll down in either and you'll get to it.

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Somewhere, a Saucepan Needs a Handle

Right about here, actually.

The saucepan pictured is quite a nice piece of cookware, but its handle went south a long time ago.

The handle attachment bracket that's spot-welded to the side of the pan is still perfectly sound. The bracket contains a square M5 nut for attaching the handle with a machine screw.

I have an idea how to go about this that will make a nice illustration of how common garden hose fittings can be employed as structural mechanical parts. The outcome won't be the most aesthetically pleasing thing I've ever done, but it will serve the purpose and keep this lovely piece of stainless steel manufacture out of the landfill. Here's a photo of some of what I'll be working with:

The hose fitting cap will be drilled for an M5 screw, and securely attached to the pan's handle bracket.

I'll strip the ferrule and hose remnant off the male hose fitting, and wed it to the end of the hardwood broomstick piece. I'll have a sturdy replacement handle for the saucepan with a unique feature -- it can be easily detached to make washing the saucepan easier.

The first thing to do is drill that cap through the centre for the attachment screw. A 3/16" hole will give me a slight interference fit for a 5mm screw, which is exactly what I want to have here -- minimal screw clearance so the final assembly will be as snug as possible. That raises an interesting point about inch vs. metric in the workshop. A little digression is in order.

Inch versus Metric Measure

There's a fallacy contained in the above sub-title; the word 'versus'. The two systems are not mutually exclusive. In working with both of them, I've come to regard them as a complement to one another; in a sense, I tend to see the two as one big seamless system that I happily put to use however it suits me. The 3/16" hole for a 5mm screw just mentioned is a small example. One encounters many such mixed uses of inch and metric in manufactured goods. My old Raleigh Grand Prix bike and my ancient 8" Beaver table saw both exhibit mixes of inch and metric dimensions/items where it suited the designers' purposes.

I grew up with fractional inch measure, and it will always be the system that I'm naturally inclined to think in. But in the workshop, one is well advised to be fully conversant with and equipped for the use of both systems.

I say that quite calmly now in spite of the fact that when Ottawa began to seriously embark on converting Canada to metric decades ago, it got my back up something fierce. Ottawa's embrace of metric measure had nothing to do with technical progress. It was a transparent, ham-fisted exercise in social engineering, and an opportunity to jettison another piece of our 'colonial' past. If nothing else, imperial measure is a cultural artifact of great beauty and utility. Ottawa would have had us discard it as if it were a worthless piece of trash. Ottawa can be pig-ignorant and tree-stump-stupid at times.

There, I got that off my chest. Back to the saucepan. This is a workshop blog, after all, not the op-ed page of the Globe & Star-Post.

Here's the pan with its new handle receiver:

The hose fitting cap had a yellow zinc dichromate plating on it that was a bit corroded in places, so I brushed it with the wire wheel machine and that took the plating off entirely, leaving me with a naked steel part. I spray-painted it with grey primer and some automotive silver paint. What the heat resistance of ordinary spray paints is I have no idea, and I can't find a mention of it on any manufacturer's website. I guess it's a secret. Time and use will tell if the cap's paint job will prove durable.

The original M5 screw was longer than needed, and it had a combination slot/Phillips recess that I didn't care for on a screw that will need to be tightened very firmly. I replaced it with a 12mm long hex socket head stainless steel screw, and added a split lockwasher and flat washer, both stainless steel. (And there's another inch/metric mixture; No. 10 inch washers fit M5 screws perfectly.)

Stainless steel fasteners are outrageously costly, but in places like this where they're truly called for, hang the cost. I happened to have what I needed on hand, but would have gladly parted with a dollar or two to get stainless steel parts if I hadn't. That points up the value of salvage to a workshop. It's a good idea to cultivate an eye for good items that can be found in discarded machinery and the like. You can build quite a valuable stock of useful fasteners and material that way.

I used red Loctite thread locker on the screw, and really tightened it firmly. Handles that loosen are a nuisance I want no part of.

The Handle-End Fitting

This is the part that's to be wedded to the end of the wooden handle so the handle can be screwed into the fitting attached to the pan. I was working here with a die-cast male hose fitting, which complicated things a bit. Were I doing this over, I'd use a fully machined fitting.

The problem with a die-cast part like this is that in its intended application, the precision of the bore is of no importance -- it just has to let water flow freely. Consequently, the manufacturer takes no pains to ensure that the bore has a uniform, concentric diameter.

I'll try to summarize the construction of this part without glazing your eyes over.

The hose fitting's bore was something of a taper. I chucked the fitting in the lathe and bored it through 11mm diameter to get a more-or-less straight, consistent bore. The threaded rod is a piece of undersize 3/8"-16 rod with a 9mm diameter. (Not all threaded rod is created equal. This piece had quite flattened thread crests which made it undersize, and just what I needed for this.) I needed a bushing to take up the 2mm diameter difference, so I turned one from a length of thick-walled mild steel tubing that had a 9mm bore. With those three items done, I had the makings of what you see in the photograph. The missing piece of the puzzle was a suitable adhesive/filler to bond them all together with.

And that brings us to an epoxy product that's new to me; something known as 'J-B Weld'. The manufacturer claims that it will withstand 500 degrees Fahrenheit, so that should make it suitable for a saucepan handle application. I mixed up a batch of the stuff, slathered all the mating surfaces of the fitting components with it and clamped it up in the lathe so it would all be held straightly and concentrically while the J-B Weld hardened. Here's how the setup looked:

J-B Weld is a slow-hardening epoxy (fifteen hours for a full cure). I left it like that overnight, and the next day the outcome looked good. Just for good measure, I pinned the assembly through in two places with 3/32" roll pins, and now I've got my handle-end fitting as you see it in the preceding photograph.

Next, I have to fabricate the hardwood handle. That's going to be a bit of a challenge.

Boring and Turning Wood Parts

Wood turning can produce some remarkable items, but it's a process that needs to be approached with a great deal of forethought. Every wood turning project has its correct sequence of operations, and that sequence needs to be thought out before beginning. An oversight in planning a job can result in a situation where a necessary step gets rendered difficult or impossible to do because a preceding step was taken without regard for its effect.

The wood handle-blank needs to be bored to accept the mechanical interface part that I've just made. The difficulty for me here is that my metal lathe is too small to take the wood handle-blank in its hollow spindle. If I could set up the handle-blank that way, the boring job would be a breeze. But I have to come up with another way to do it.

Another complication is that I decided I'd best add a brass ferrule to the handle for strength of the final assembly. A brass coupling nut for a faucet supply tube fitting will serve for a ferrule. What I have to work out is a sequence to do it all in, keeping in mind how each step will affect the steps that must follow.

Here's a point-by-point list of how it was done:

1) Prepare the handle blank for turning between centres -- spur centre at the headstock; live centre with a point only at the tailstock, not a point/cup style of centre. (The books will tell you not to do that; that the tailstock end must be supported by both the point and the cup of a woodturning centre. I'd go along with that if I were turning a porch column here, but what I'm setting up for will be a very light bit of work, entirely safely supportable by a point centre only.)

2) Mount the work and square off the tailstock end with a parting tool as far as the centre will allow. Turn a 3/4" diameter land to accept the ferrule.

3) Dismount the blank and set it up for boring on the metal lathe. Here's how the setup looked:

With a somewhat unorthodox use of the steady-rest, I managed to get around the lathe's small spindle hole diameter. This boring arrangement worked well. The steady-rest is supporting a 3/4" bore ball bearing, which in turn is supporting the work.

4) Bore 9/16" diameter sufficient depth for the hose fitting's barbed nipple.

5) Bore 9mm diameter sufficient depth for the threaded rod.

6) Dismantle the boring setup. Do a trial fit of everything. Glue it all together with J-B Weld and mount it in the wood lathe to clamp it up like so:

This worked out nicely in that the cup of my wood lathe's live tail centre just fits the inside diameter of the hose fitting. I have a perfectly good setup here for turning the handle.

7) Turn the handle blank to a uniform cylinder to eliminate any out-of-roundness.

8) Determine the length dimension, and imagine/sketch the profile to be ended up with.

9) Turn and sand. (N.B. This is a nerve-racking place to be at. By this point, you have a lot of work invested. One blunder with a chisel can ruin the whole thing. Be sober as a judge and proceed with caution.)

10) Part off and dismount the finished handle.

And here's the handle out on the job. A good example of how humble, dirt-cheap bits of hardware and material can be put to very good use, but by no means a claim that it's 'easy'. A lot of thought went into this, and a lot of resources were brought to bear on it. Beware of publications that make repair/fabrication work appear to be a breeze. It's not.

TUESDAY, OCTOBER 5, 2010

Addendum

I appear to have the makings of a system here. A good thing, too, because our household just lost a frying pan handle to time and metal fatigue. Pictured below is the wreckage. Fortunately, no one was injured in the incident. A frying pan handle breaking while one is pouring hot bacon grease from the pan could be a frightful bit of business.

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Here I have the opposite case to the saucepan handle -- the handle still exists, but the attachment point at the pan is a ruin. If I can salvage enough of what was a threaded boss, I can fit a hose fitting cap to the pan and attach the saucepan's handle to it.

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Here's what I did to 'renew' the handle attachment boss, and prepare it to receive a new handle:

1) Saw off the boss remnant at an appropriate angle. (On an object like this one, you just have to eyeball and guesstimate angles as best you can.)

2) File the sawn-off boss smooth.

3) Drill through the pan's wall with a tap-size drill for a 1/4"-20 thread. (No. 7 drill -- 0.201" dia.)

4) Thread the hole 1/4"-20.

5) Bore through the centre of a machined, solid-brass hose fitting cap with a No. 7 drill and thread it 1/4"-20.

6) Round up a stainless steel screw and flat washer. Cut the screw to a length that's just a little longer than needed. (To cut a stainless steel screw, use a 1 1/4" diameter reinforced cut-off wheel in a Dremel hand grinder or equivalent. Stainless steel is hard stuff.) Do a trial fit of everything.

In the following photo you can see the prepared boss and hose fitting cap.

Next, I installed the screw w/flat washer in the cap very firmly with red Loctite applied, then I installed the cap/screw assembly in the pan's boss very, very firmly with red Loctite applied.

At the inner wall of the frying pan, I had a slightly protruding screw-end that needed to be ground flush with the pan's wall. I didn't want to do the grinding until the Loctite had cured, but I didn't want to wait for that overnight. I stuck the pan in the oven at 170 degrees Fahrenheit for about twenty minutes, then switched off the oven and let it cool on its own. (Heat is quite an effective accelerator for Loctite curing.)

I used the Dremel cut-off wheel to grind the protruding screw-end flush, swiped the handle from the saucepan and installed it, and here we are; the frying pan has a handle again.

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Now I have to make another handle. I hope this is the last of broken pan handles around here. Mass-production is not an interest of mine.

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A 19/32" Bicycle Cone Spanner (Wrench)

I'm restoring an elderly, long neglected Raleigh Grand Prix 10-speed road bike to road worthiness. It's proving to be an interesting project, not least for some of the arcane tooling and methods that one must come up with to deal with some aspects. Bicycle mechanics is a world apart from all other mechanical work that I'm familiar with. A masterful bike mechanic is a real mechanic who understands the nature and the interrelationships of a bike's components, and can make them work harmoniously; he's not just a parts swapper.

One of the arcane bits of tooling requirement that I came across was for a 19/32" spanner for the cones and jam nuts on the wheel axles. Good luck finding one of those.

But 15mm spanners are readily available, and 15mm is just shy of 19/32"; like so:

19/32" = 15.08mm (i.e. 15mm + 0.08mm = 19/32").

What that tells us is that you only need to widen the jaws of a 15mm spanner by 8/100ths of a millimetre and you have a 19/32" spanner.

I have a 15mm spanner on hand, but it's a top quality one that I didn't want to mess with. The local bike shop had a two-piece set of medium quality cone spanners for $9.95 -- a 15mm and a 16mm. I didn't already have a 16mm, so I bought the set to get me a 15mm spanner that I wouldn't mind modifying, and a 16mm to add to my collection of useful standard tools to have on hand.

The spanner is made of pretty hard tool steel, but it's not file-hard. A few firm passes with a suitable mill file were all it took to get the spanner's jaws opened up a bit, and voila, a 19/32" cone spanner:

'Spanner' vs. 'Wrench'

This is one of English's little quirks that has long puzzled me.

The words are interchangeable, really. The Brits seem to use the word 'spanner' for a wrench of any kind. In Canada and the USA, we use the word 'wrench' for most anything that one would think of as a more-or-less ordinary sort of wrench, reserving the word 'spanner' for specialized forms of wrench, such as these thin ones for bicycle axle cones and jam nuts.

In any event, I now have a 19/32" spanner/wrench/implement-for-dealing-with-Raleigh-cones/whatever.

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Ryobi 10" Table Saw (BTS12S) Overhaul

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[Update -- THURSDAY, OCTOBER 17, 2013: I finally did return to this project and finished it up, the operative word being 'finished'.]

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[Note -- WEDNESDAY, NOVEMBER 23, 2011: I have yet to complete this project. The cost of getting motor brushes and bearings shipped to Canada turned out to be prohibitive; why that should be so is beyond me. I've set the thing aside for now. Someday, I may return to it.

In any event, following is lots of detailed information about tearing the machine down for an overhaul. If you can readily obtain parts at reasonable cost, you may find some of it helpful.]

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I seem to have acquired another ailing saw from my employer. It's a Ryobi model BTS12S 10'' table saw that he was using for cutting up firewood from shipping pallets. The story of his Poulan chainsaw's resurrection is here.

This saw is reportedly making nasty noises. I'm not even going to plug it in for a listen; I'll just go directly to removing and tearing down the motor/gearbox and see what's what with it.

Notes:

- All screw heads are No. 2 Phillips recess unless otherwise indicated.
- A/F = Across Flats
- w/ = with

Motor Removal

1) Blade Opening Insert
- Two M4x10mm truss head threading screws.
- The insert is 47mm x 260mm; red enamelled with a textured effect.
- The two screws thread into Tinnerman nuts that are semi-permanently clipped onto lips of the table casting at either end of the insert's position.

2) Blade
- One hex nut, 23mm A/F. A purpose-made wrench is provided.
- Was it ever tight. I had to put my 15" Crescent wrench on it for sufficient leverage to loosen it. There's really no need to tighten saw blade nuts excessively. Given the blade's direction of rotation, a right-hand-threaded nut will have no tendency to loosen due to inertia effects -- quite the opposite, in fact.
- One Belleville washer; 5/8" I.D. x 1 25/32" O.D.
- The motor must be lowered fully for blade removal, else the blade can't be manoeuvred out.
- The blade on this saw is not the original. It's a 40-tooth, carbide-tipped Skil blade, in rough condition -- many chipped teeth.
- The fixed shoulder on the spindle has two flats on it, 32mm across. A purpose-made wrench is provided for holding it from turning when loosening or tightening the hex nut. I'm accustomed to just using a block of wood to jam a saw's blade when I need to undo its nut, and to tightening saw blade nuts no tighter than I can by simply holding the blade with my fingers.
- The spindle turns easily enough in its normal direction of rotation, but jams when reversed -- not a good sign.
- I just flipped the saw upside down for access to the motor and its wiring, and I heard something rattle. Now that it's upside down, the spindle can be turned in either direction. Curiouser and curiouser.

3) Switch Cover
- Four M4x16mm truss head threading screws. There's a little line cord clamp insert that falls away when the cover is removed.
- Was it ever loaded with sawdust.

4) Line Cord & Motor Cord
- Hot (black) leads; a 1/4" female spade terminal at two terminals on the switch.
- Ground (green) lead; a ring terminal secured by an M4x5mm pan head screw -- combination plain slot/No. 2 Phillips recess. An offset screwdriver is needed. There's an M4 external tooth washer under the ring terminal. The motor's cord has no ground wire. The motor must be a double-insulated design.
- Neutral (white) leads; spliced by a crimped top-hat connector. Cut it. A wire nut will do nicely for reconnecting it. Whenever I'm cutting a top-hat splice, I like to first cut away the 'skirt' portion of the top-hat's insulator so I can cut the wires right at the crimp barrel. That way I shorten the leads as little as possible. It can make a difference in tight wiring enclosures where there's very little slack provided.

5) Mystery Part
- At the bottom rear of the saw's base, there's a little ledge affair about 2 1/2" x 2 5/8" directly in line with the blade's plane. It's not really an obstacle to removing the motor, but it's not helpful either. I'll remove it.
- Two M4x15mm pan head screws.
- Two M4 hex nuts w/integral lock washers, 7mm A/F.

6) Blade Guard
- Two M5 hex nuts; 8mm A/F.
- Two M5 external tooth washers.

7) Motor/Gearbox
- Three hex head screws w/integral lock washers, 10mm A/F. The motor must be fully elevated for good access to these. They're in pretty tightly, and the uppermost one is awkward to get a wrench onto. I needed my 3/8" square drive breaker bar to get it to loosen -- just barely doable with the limited clearance there is to swing a wrench.
- The screws are M6x18mm.
- I lifted out the motor and a bearing ball fell out. This is shaping up to be a repeat of the Poulan motor failure.

Motor/Gearbox Teardown

1) Commutator End Cover
- One squeeze-type line cord strain relief. Squeeze it with Channellocks to free it.
- Three M4x12mm pan head screws w/captive split lock washers.
- The commutator end bearing has spilled its balls, exactly as happened to the Poulan chainsaw's motor.

2) Motor/Gearbox Separation
- Three M5 pan head screws w/captive split lock and flat washers.
- One screw is 30mm long. I've marked its location on the gearbox casting and the motor's shell with an engraver.
- Two screws are 75mm long. These two double as the mounting studs for the blade guard.
- With the gearbox end clamped gently in the woodworking vise, the screws are easily removed, and the motor end just lifts away with a little twisting and coaxing.
- One carbon brush is completely worn out, but the brush holders appear to be an excellent design. The brushes, what's left of them, are still free-sliding. It's common for brushes to become jammed in their holders because of dust fouling. The symptom is a motor that won't start, or that runs poorly because the brushes can no longer make good contact with the commutator.

3) Armature
- It pulls out of the gearbox casting with its bearing attached with hand force only.
- The commutator looks quite worn, and the helical gear teeth on the shaft's output end have seen better days; the grease in the gearbox has pretty much expired and dried out.

4) Gearbox Output End Cover
- Three M4x12mm pan head screws w/captive split lock washers.
- NOTE the notch in the rim of the gearbox cap that's just under the pressed steel cover. On reassembly, that notch must align with the end of the motor's output gear, else the cap will jam the motor as the cover is tightened down. There is no 'keying' to prevent you from getting it wrong.

5) Spindle Assembly
- It didn't want to pull out, so I adapted my slide hammer to it. That was easy because the spindle's 5/8"-18 thread is the same as the thread on the end of my slide hammer. One little tap with the slide and it popped out.
- Ryobi's parts website calls this item the 'jackshaft' assembly, and doesn't break it down at all. Pressing this item apart would be problematical, to say the least. The bearing feels ok. A good thing to leave well enough alone.

6) Commutator End Bearing Inner Race
- 'Managed to adapt a small two-jaw puller and pull it off. 'Had to snip the loose shield to get it out of the way first. The bearing is a 6001ZZ; 12mm bore x 28mm O.D. x 8mm wide, shielded both sides.

7) Commutator End Bearing Outer Race
- It's a light press fit in the plastic housing. It can be 'walked' out by lightly punching all around from the outboard end.
- There's a wavy washer in behind it for a bit of axial preload.
- It looks as if this bearing must have seized briefly before it spilled its balls. There's evidence of the outer race having been turning in its plastic housing.

8) Output End Bearing
- Dimension from outer face of inner race to end of shaft is 23.5mm.
- This one was easy to get a puller onto. It's a 6201Z; 12mm bore x 32mm O.D. x 10mm wide, shielded both sides.
- I popped out a shield from one side and I've left it for a nice, leisurely soak in the parts washer.
- It turns out that I didn't need to record the axial position dimension after all; the bearing's inner race butts up against a shoulder. Nonetheless, I couldn't be certain of that until I got the bearing off. It's always better to have a record of anything doubtful.

Time Out for a few Digressions --

On Saw Motor Bearing Failures

This is the second saw motor I've seen with a catastrophic bearing failure at the commutator end. Two factors appear to be at work to cause this.

a) Universal motors are high speed machines that can run pretty warm. They typically run in excess of 20,000 rpm. I'm told that sealed bearings are not on for such speeds and temperatures; the seals won't take it, so shielded, not sealed, bearings are used.

b) The bearing at the commutator end is relatively exposed to airborne particulate matter, of which there's no end in a saw application. The bearing at the output end is relatively sheltered so even though it's the more heavily loaded bearing, it's less prone to fail.

The upshot of all that is that commutator end bearings in saw motors are all ultimately doomed.

On Adapting Pullers

This is an aspect of serious mechanical work where the patience of Job is a virtue. Fumbly, short-cut methods are likely to fail and frustrate. Whenever a pulling job calls for an adapter to be fabricated, or a puller to be modified, it's time to relax, tell the clock to take a hike and set about doing the job properly.

The puller I had for pulling the commutator end bearing was a little short on screw reach for this job. Something to increase the effective length of the screw was needed. I modified a 1/4"-20 coupling nut in the lathe, and made a pointy setscrew for it from a bit of threaded rod for a centring point. Here's the result:

It worked quite nicely, and may well prove useful again in some other application; well worth the time and trouble, and very satisfying work in its own right.

This sort of thing arises often when a puller is needed, and dealing with it calmly and elegantly is something that separates the mechanics from the tinkers. It also points up the necessity of having a lathe if you mean to do any serious machinery restoration work, and of having a good selection of threaded fasteners and rod material at hand. Coupling nuts are one item that I've found to be extremely versatile.

On Obtaining Parts

Ryobi's U.S. website has an impressive parts catalogue -- it appears that virtually any component is available as a service replacement. Some of the pricing is a bit odd, though.

I can get a 6001ZZ bearing and two brushes for a total of $12.37 US, plus whatever the shipping charge would be. That's actually pretty reasonable, but 'reasonable' is not how I would characterize some other items' prices.

A new armature is $101.84. A complete new motor/gearbox assembly is $239.38. A new saw complete with stand is $129.00 CDN at the Home Depot.

I won't be emailing Ryobi to ask them how they rationalize that; whatever nonsense they'd tell me, if they'd even bother to reply, might make my head explode.

I'll think about how to proceed, and I'll update this post as I make progress.

- - -

Update -- SATURDAY, OCTOBER 16, 2010

On September 19th, I got my son and his credit card in on this and we ordered the bearing and two brushes from Ryobi's US website. The parts came to $12.37 US, and they quoted us $8.00 for shipping from Columbus, Ohio via Fedex ground-residential; $20.37 US all together -- within reason.

Three weeks went by and no sign of the parts, so I checked on the order reference number and was told that the order had been cancelled. I asked my son if he knew what was with that. He looked into his junk emails and found an email from Ryobi saying that the shipping fee was going to be $35.00, not $8.00, and they'd cancel the order if they didn't hear back. Needless to say, I'm glad they cancelled the order. $35.00 for shipping a few ounces of parts is not within reason.

I look at the price Ryobi wants for a complete motor/gearbox assembly, and I look at this incident and I begin to wonder whether Ryobi actually means to ever sell anyone any part. So much for their parts catalogue. On to plan 'B'.

The bearing is a common enough thing that I can get locally. For the brushes, I'll try visiting a proper motor repair outfit and see what they can do.

- - -

Back At It -- SATURDAY, SEPTEMBER 7, 2013

Time flies, eh? I noticed the date just above, and it's been almost three years since I shelved this project. Anyway, I got a replacement bearing locally. I'll see if can still get some life, at least, out of the badly worn brush.

I had meant to tear this machine down completely, both to clean it up, and to familiarize myself with evey detail of it. Since I've returned to the project, I'll carry on with that and get it over with. Then, I can return to the motor and get this thing back to operability.

The Feet

This saw must have been over-tightened onto its stand at one time, because the foot sockets are all cracked and splayed like this one.

I'd like to correct that, and have all four feet solidly mounted and at a uniform height.

- - -

I can see why that damage happens when the saw is over-tightened down:

The feet are shorter than their sockets are deep, so the bottom ends of the feet act like wedges, and splay out the walls of the sockets.

The two front feet are easily dealt with. All I have to do is add a 3/8"-16 hex nut to each foot, like so,

and those two feet will be solidly supported at the correct height.

The two rear feet are a different story; the sockets are deeper, and they're not flat-bottomed. Hmmm.

- - -

With a combination of nuts and washers, I got the rear foot sockets shimmed up to support the feet more-or-less properly, at more-or-less the correct height. I added a fair amount of CA adhesive to all four feet for good measure, and that matter is taken care of.

- - -

Base/Table Separation -- SATURDAY, OCTOBER 5, 2013

[I did all the following out of curiosity. I don't recommend doing any of it without good reason to -- otherwise it's quite needless. I include the information here just for the record.]

1) Line Cord Clamp

2) Line Cord w/Grommet

3) On/Off Switch

4) Handwheel Spinner

5) Handwheel Centre Insert
- Pry it out.

6) Handwheel w/3/8"-16 Elevation Screw and Spring
- Two 1/4"-20, 10mm A/F hex nuts locked together. You'll need two wrenches, one of them a thin, open-end wrench. (A 10mm ignition wrench is ideal.)
- Note the positions of the two 1/4" flat washers.
- Elevation nut. (Ryobi calls it the "driving block".) It's free to slip out. Remove it

7) Bevel Indicator
- One 12mm A/F hex nut w/external tooth lockwasher.

8) Bevel Lock Lever Repositioning Cap w/Spring and Flat Washer
- Unscrew it (6mm hex key).

9) Bevel Lock Lever w/Washers
- Unscrew it.

10) Bevel Drag Spring w/Two Washers
- NOTE that the larger washer goes outboard.

10) Base/Table Separation
- Four M6x25mm hex washerhead screws, 10mm A/F hex.
- The base lifts off and slides forward off the bevel lock lever's stud.
- NOTE the 1/4" flat washer that's left behind loose on the bevel lock lever's stud.

- - -

Motor/Gearbox Reassembly Notes

Here's a view of the armature with its commutator burnished, and both bearings pressed on.

The replacement for the ruined 6001ZZ commutator end bearing I got locally.

The 6201Z output end bearing has been cleaned and repacked. Its shield that I had removed for cleaning wouldn't snap back in place (no surprise, that), so that bearing is without a shield on its gearbox side, where it doesn't much matter.

The worn out brush I've dealt with for now by lengthening that brush's lead, like so.

That should serve for the time being. I only need the motor to run long enough to let me check out the machine, and make whatever adjustments might be necessary.

Here's a view of the commutator end of the motor with the brushes and brush holders back in place.

I can't fault the design or construction of this motor; it's a beautiful piece of gear.

Here's the complete motor/gearbox all buttoned up and back in place.

That view is from the right side of the machine, with the motor fully elevated.

From here, I'll just carry on executing the teardown sequence in reverse, and I'll soon be able to try the saw out.

- - -

Wrapping Up -- THURSDAY, OCTOBER 17, 2013

I got the saw back together completely, and ran into some trouble that appears to be inherent to the cheesy blade tilt mechanism. The story of how I resolved that is here.

After dealing with that, I looked into how blade-plane/mitre-gauge-slot parallelism is adjusted on these machines, and made some improvement to that aspect. I adjusted the mitre gauge and the rip fence, and tried the machine out. My conclusion? The Ryobi BTS12S is not worth the powder to blow it to hell.

If all you need is a dirt-cheap saw that you can plug in and make sawdust with, the BTS12S may fill the bill. The original owner of this saw had the right sort of application -- all he used it for was to cut up shipping palettes into firewood in his garage. If you're looking for a serious woodworking tool, stay away -- far, far away.

I'll salvage the stand and some fasteners, and the power cord for an extension cord. Aside from that, my son can take this machine to the scrapyard on his next scrap metal run, and that will be the end of my interest in Ryobi's bench tools.

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