Changing PC A3 belt sander gears

[Michael Helms]

I ran my treasured antique Porter Cable A3 worm-drive dry, terrible blunder that I can remedy with new gears that I managed to find and buy, but I'm stumped as to how the armature shaft is properly removed from the aft part of the frame/gear housing. I've managed to remove the front housing containing the field so the armature is exposed. The armature shaft and bearing seal can be shifted fore and aft about 1/4" in the housing, but seems to be held in place, I believe by the retaining nut (#210) aft of the worm gear. I suspect that removing this nut will release the shaft, but accessing the nut with a socket through the small oil fill hole seems like a nearly impossible task, so I'm thinking there is another way. The brass gear on the perpendicular jack shaft which is driven by the worm gear and connected to the belt drive pulley by a chain also needs to be removed and replaced. I think removing the jack shaft nut and gear on the chain side and unscrewing the cover plate below the jack shaft drive gear will free the jack shaft so that I can change the brass gear. Maybe this will also free the armature and steel worm gear.

Anyway, I'm hoping someone still active on the forum has worked on the PC A3 and can offer guidance. There is a 2012 post here byMike Meadors a forum member who apparently has done the change:

http://www.sawmillcreek.org/showthre...04-belt-sander

I'll try to contact him, but like me he apparently hasn't been active on the forum lately. If anyone else has advice, I'd appreciate hearing from you. Thanks,
Mike

[Simon Dupay]

Try owwm.org lots of info on old PC tools over there I never taken apart an a3 but as I recall my 500 had a nut on the end of the shaft that held the fan on and held the gear on

[Michael Helms]

Thanks for the link, I'll check out the forum. I think the nut you reference is the one that retains the worm gear. The correct way to access it is probably by removing the nuts on the chain sprockets and the cover panel below them in the chain housing, but I'd prefer to get some confirmation before I dive in. Thanks again.

[Michael Helms]

Searching the forum from Simon's owwm.org link yielded this very useful photo-rich rebuild post by Jonathan Martin:

http://www.owwm.org/viewtopic.php?f=...ble+A3#p372033

There is also a separate webpage with (unfortunately unlabeled) links to photos of the dissassembled A3, most of which I believe are in the thread:

http://niblet.us/thisoldserver/pcsander/

I suspect the armature jackshaft removal which damaged the seal on Jonathan's A3 was not performed by the "book," and I'm not clear on how he reassembled his A3 with the new seal in place without damaging it. I'm wondering if driving the jackshaft out first would be a better approach. Links to Youtube videos also come up both on searches of the owwm.org forum and Google web searches. I haven't found a video that is specific to the A3 armature/jackshaft removal and reassembly yet though there were some videos of a newer model being rebuilt.

[Michael Helms]

So I'm still working on the A3 belt-sander rebuild, and still seeking guidance. Jonathan Martin's sander (mentioned in an earlier post in the thread) is apparently a slightly newer model with a different (steel?) cooling fan, and a slightly different assortment/order of seals and bearings on the armature shaft. My older model has a cast (zinc?) alloy fan on the shaft. After soaking the armature shaft where it enters the gear box/bearing housing with liquid wrench, I was able to drive the shaft and bearing out by placing some metal bars as supports across the front side of the housing then inserting a punch against the rear of the shaft through the rear oil cap opening to drive the assembly out with a hammer. It came out quite easily, and possibly because the seal is on the armature side of the bearing on this model, there was none of the damage to the seal that happened to Jonathan's A3. I then removed all the screws in the cover plate under the chain on the chain side of the gearbox housing. There were five screws on this plate, one hiding under the chain and accumulated grease—don't miss it because the laterally mounted gear jackshaft (and pulley shaft driven by the chain) apparently can't be driven out if the cover plate isn't free from the housing.

My current problem is that after removing the retaining nut and rubber sleeved drive-pulley, I can't seem to free the woodruff key that is on the pulley side of the pulley shaft. This is a small insert which meshes in slots in the shaft and pulley, maybe 1/2" long by 1/8" thick in a slot on the shaft that only projects about 3/32" proud of the shaft—enough to prevent the shaft from being driven through from the chain drive side of the housing. I can't get a grip on the key with my parallel jaw pliers to pull it out. Tried liquid wrench and even heated the shaft a bit with a plumbing torch, and various tapping, gripping, and pulling methods to extract it, but the little guy wont budge. I don't want to heat the shaft too much, and I'm at a loss as to how to grip and remove this key. Because the chain connects the jackshaft end sprocket that drives the pulley sprocket, I don't think I can remove the jackshaft with the pulley shaft left in place, and I want to replace the pulley shaft bearings if possible.

So, still hoping for guidance and solutions from anyone with ideas on the forum. Thanks, Mike

[Rod Sheridan]

woodruff keys are curved, try driving it in the same direction as the shaft and see if it will come out............Rod.

[Michael Helms]

That's the first thing I tried. Because the shaft is captured in the body of the sander, I can only drive the key in one direction—toward the housing. I only succeeded in reshaping the driven end of the key. I may be mistaken but I believe it's a woodruff key. The little bugger is of course mostly buried in the shaft, and the diagram illustration of the loose key is too miniscule to really tell. I found a thread on another forum which makes it plain that these things can be a real pain to extract. One of the methods mentioned there is to use side-cutters to grip the (tiny) projecting portion of the key. Heading out to the shop to try that.

Thanks a bunch for taking the time to post a reply.

[Michael Helms]

Success! I located some end-nippers that I'd ground down for another project. I'd ground the top of the nippers so that they were very sharp where the edges meet with basically no "V" on them and tried gripping the slightly projecting woodruff key with them. However, though this tool bit into the key and did not slip off, my quivering best geezer-level effort still wouldn't budge the little thing. I cut a slot in a tin can top with my shears to shield the shaft so that I could heat the key itself with a minimum of heat transfer to the shaft. Still no go, not while it was still warm, not after it cooled off. So I decided to drill the key along its tiny upper surface and try to crush it and pull it out. I backed up the shaft with some wooden wedges between the shaft and housing, took my center punch and made three or four indentations to center the drill bit, but then thought I might as well give it one more tug before drilling it. The key came out pretty easily with the nippers then, presumably because I'd loosened it with the center punch. Up until that time I'd restricted the hammering to strikes on the single accessible end of the key (parallel to the shaft) with a punch and later a sacrificial 1/4" wood chisel (which I'll need to re-grind and sharpen). Backing up the shaft and striking with the center punch along the top rather than the end of the key seemed to be the answer in this case.