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