Saturday, March 27, 2010

A Garden Fork Repair

Needless to say, the little marriage breakup pictured needs mending. This project will make an excellent illustration of the usefulness of CA adhesive and epoxy. But let me begin with a bit of fork terminology that I gleaned from the Lee Valley catalogue.

It seems that there are digging forks (bigger) and border forks (smaller). Lee Valley's digging forks have an 11" x 7" business end. Their border forks have an 8 1/2" x 5 1/2" business end. My fork measures 9 3/4" x 6 1/2" -- betwixt and between. So I've called it a garden fork and I'll leave it at that.

The Problem

Originally, the fork's tang was force-fitted into what I take to be hardwood inside the steel ferrule. There were no rivets securing it, which was fine so long as the hardwood remained sound. But water incursion and retention caused the hardwood to rot and the fork to come loose. What I have left in the ferrule is a loose bit of the original hardwood tang-surround sufficient to hold the tang in position, but hopelessly inadequate to secure it. Above that up to the bottom end of the handle is a cylindrical void roughly 1" long x 1 1/4" diameter.

Two things need to happen here. The loose tang-surround must be secured in the ferrule; and the void, fissures in the tang-surround and the tang/tang-surround interface must be filled with an unyielding material.

Securing the Tang-Surround

This is where CA adhesive really shines; it's very runny, and wicks into cracks and pores and interfaces by capillary action. With the dust blown out of the ferrule's cavity with compressed air, and the loose tang-surround in position, I only need to present drops of CA adhesive to its edges and the adhesive will make its way in to bond the piece in place to the ferrule, and to fortify what's left of the hardwood that's still halfway sound.

Filling the Void and Securing the Tang

This is where epoxy comes in. I've never found epoxy to be all that great for outright adhesion, but it has characteristics that can be exploited to achieve remarkable results. It hardens, without shrinking or swelling, to become quite a hard, very tough material. Since it starts out as a fluid, albeit a very viscous one, it will take the shape of whatever it's enclosed in; and therein we have the key to permanently retaining the fork's tang in its ferrule. Here's the wire-brushed tang ready for installation with epoxy.

Note the sequence of shallow grooves that were cut with a 1 1/4" diameter reinforced Dremel cut-off wheel. All four sides of the tang got that treatment. Consider what will happen when I shove that tang into the ferrule's opening after I've filled it with epoxy. The fluid epoxy will fill and conform to every cranny, fissure and groove in the tang-surround and the tang, and then harden there. The void and the tang/tang-surround interface will contain a contiguous, hard, tough incompressible filler. As a retention medium for the tang, one can't do any better.

The Epoxy

I usually use the five-minute type, but I bought the slow-curing variety for this job; this will take more epoxy than I'm accustomed to working with at one go.

A Little Math Digression

I wanted to calculate the volume of the cylindrical void in the ferrule, just to be certain that I had enough epoxy on hand, and it dawned on me how fuzzy I am on the fundamentals of metric volume units. (I really shouldn't have dropped out of high school. I'd know all that stuff if I had a diploma.)

Pop quiz: What's the definition of a litre?

(I'd love to know how many Canadian citizens, particularly the ones who are always spouting off about education and the 'knowledge economy', know that right off the top of their head.)

It's a cubic decimetre; i.e. the volume of a cube ten centimetres on each side. 10cm x 10cm x 10cm = 1,000 cubic centimetres = 1 litre. So, a millilitre is the same thing as a cubic centimetre (cc). That fact makes for an exceptionally easy way to find volumes in millilitres.

Normally, when using metric linear measure one is well advised to express everything in millimetres only, no matter how huge a thing may be. That practice is good insurance against decimal point placement errors, which are all too easy to make with centimetres. But for finding millilitre volumes, calculations based on centimetres work out directly as millilitres.

Pop quiz: What's the formula for finding the volume of a cylinder?

It's 3.1416r2h or 0.7854d2h.

Where r = radius, h = height and d = diameter.

Truthfully now, did you know that right off?

Anyway, plug in centimetre values and the answer will be in millilitres.

Using a rough conversion from my inch measurements for the void in the ferrule, we have:

0.7854 x 2.5cm diameter2 x 3.2cm height = 15.708ml. Call it 16ml.

That's well within 37ml, the volume of the epoxy tube I bought. (Actually, I knew I had enough epoxy just by looking at the size of the tube compared to the size of the ferrule, but this little math exercise was fun. And I know what you're thinking, "This guy doesn't get out enough".)

By the way, epoxy is a two-part adhesive -- resin and hardener. From what I've observed, if you mix up, say, 10ml of epoxy resin and 10ml of hardener, you'll end up with just a little more than 10ml of epoxy. The two components intermingle without increasing one another's volume by very much at all.

Mixing the Epoxy

As I said, I'm unaccustomed to working with so much epoxy at one time; most of my epoxy requirements are for quite small amounts, easily mixed on a business card with a small screwdriver.

I simply scaled up that method for this job, and it proved to be a clumsy way to go about it.
Were I doing it over again, I'd contrive a way to measure the needed amount of resin and hardener into a disposable cup and mix it there all at once. As it was I had to mix three consecutive batches to fill the ferrule.

Nonetheless, the outcome looks good. There was a tiny bit of subsidence at the rear of the tang. I back filled that with some five minute epoxy, and touched up all around to produce a nice fillet.

Here's the fork back in its natural habitat.

This fork wasn't always the dowdy looking thing you see in the photo. In its youth, it had a glossy yellow fibreglass-clad handle. Beware of fibreglass-clad handles on yard tools.

What they are is a hardwood core in a fibreglass sleeve. If the sleeve acquires a slight fissure, and the tool gets left out in the rain, water will wick into the fissure and be unable to evaporate out at any appreciable rate. The hardwood core will rot and you'll end up with this:

So much for the glossy yellow handle. It looked good in the store.

Anyway, I expect this repair to be a complete, durable success. This was a great example of the sort of application that epoxy excels at.

Something I Didn't Foresee -- SUNDAY, DECEMBER 9, 2012

The fork got left out in the rain, the wooden handle took on moisture, swelled up and split the ferrule of the all-plastic handle. A couple of hose clamps are in order, like so.

That'll work fine.

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Saturday, March 13, 2010

Delta Midi Lathe Notes

I've finally gotten around to attaching the lathe bed extension to my Model LA-200 Delta Midi Lathe, so I'll post a few hints and observations here while I'm at it. There's a bit of a back story to this lathe here if you'd care to read it.

I'll remove the headstock and motor to make the thing easier to handle while I attach the extension, and locate mounting fasteners for the fully assembled lathe bed. While I'm at that, I'll correct what strikes me as a silly bit of over-engineering. It's pictured below.

Why on earth they felt compelled to provide that hole in the casting for the motor's power cord is beyond me. It accomplishes next to nothing in the way of protection for the power cord, and it needlessly complicates removal of the motor. I'll reroute the cord so it bypasses the hole.

The best place to disconnect the motor's cord is at the switch box. The hot lead has a spade terminal on it, the ground lead has a screw-fastened ring terminal. The neutral is connected by a crimped 'top hat' splice, so it's the one wire that needs to be cut. A wire nut is all that will be needed to restore the connection.

I did look under the motor's capacitor cover first, but the wiring there is all crimp-connected and quite densely packed -- it's an area best left well enough alone.

Here's the disconnected motor cord freed from its needless lathe-bed hole. Much better.

I'll tin that stripped neutral wire end before I reconnect it with a wire nut.

With that out of the way, removing the headstock and motor should be a breeze, and I can get on with attaching the extension and setting up the complete lathe bed.

Attaching the Extension

The extension is fastened to the main lathe bed by two M10x40mm hex socket head screws with split lock washers and flat washers. (Delta kindly includes an 8mm hex key.) Here's a way to ensure good alignment of the two bed sections as you tighten the screws.

Install the screws with their washers and get them finger tight. Then position the tailstock directly over the join and clamp it in place there. Now fully tighten the screws and you're done.

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Sunday, March 7, 2010

Belt Repair for the Urban Hillbilly

Don't laugh. This would have been a 'Sunday go to meetin' belt for Pappy Yokum (he's the fifth from the left). It's certainly a step up from a length of rope. We can file this under 'fashion accessories for after the collapse of the global economic system'.

The cut-off end of the black pleather belt pictured was beyond salvation -- embrittled and cracked in several places. I looked into my bin of leather and felt odds and ends and found a piece of tan-coloured suede belt about the right length, and just a bit wider than the black belt. Some hole punching and three rivets later, I had a serviceable belt back.

The rivets are 1/8" diameter x 5/16" long truss-head aluminum ones that I bought a supply of years ago when we still had a proper hardware store in the area. The washers that I used for peening plates are GC Electronics No. 4 flat washers that I got from an industrial electronics supply house. (A No. 4 washer just fits nicely on a 1/8" rivet.) Hardware items like these that are just a little out of the ordinary can be difficult to come by. In Canada, I have Spaenaur to fall back on. Spaenaur is a good outfit, but they're an industrial supplier so you have to buy in package quantities (typically 100 pieces), and there's a minimum order amount (I think it was $25.00 the last time I dealt with them). A hard-copy catalogue from a place like Spaenaur is a wonderful resource for learning of all sorts of things you never knew exist.

A 12-ounce ball-peen hammer is about right for this work. Peening is one of those skills that are easy to master well enough to get acceptable, useful results from, but difficult to master well enough to get elegant, aesthetically pleasing results from.

In any case, the important thing when riveting leather is to end up with the leather well compressed under the rivet head and the peening plate. A riveted join where the peening plate ends up merely clinched, but the leather not compressed, will be far weaker than a compressed join. It's helpful at the start to press down on the peening plate with the flat side of a slender screwdriver. That will help to get the rivet end's outward expansion started well enough above the peening plate that further peening will result in a compressed join, not just a clinched peening plate.

The all-metal leather punch pictured on the left is a cheap one. These are widely available but beware, they tend to be poorly made. The brass anvil on the one in the photo barely aligns with a punch die's detented position. The black and yellow one on the right is a much better tool. I recall that its price was reasonable, but I can't remember where I got it. I found the Taiwanese manufacturer's website, but it's no help regarding distributors. If you see one, buy it. It's a decent tool for the price. I've never seen a really fine quality leather punch offered anywhere, and I'm afraid to think about what the price will be if I ever do see one.

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Update -- SATURDAY, DECEMBER 27, 2014

That lasted well over four years.

So here we go again.

I put the 'new' end on the inside this time. We'll see how that works out.

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