help with Bridgewood 15" wide belt oscillation

[al ladd]

My 15" Bridgewood open ended belt sander stopped oscillating this morning. The ceramic limiting arm had fallen off on the side with the pneumatic controls, and it's likely the errant belt created the problem. But I can't track it down.

The photos show the relevant parts. I am getting an airstream to the inside of that fork that the belt is supposed to periodically interrupt, prompting the oscillation cycle. But it doesn't oscillate. I can see that with the belt off, by turning the air on and off the tensioning cylinder is engaged, raising the top drum, and the oscillating cylinder sends the top drum rotating in one direction as the air enters, and it reverses that rotation as it deflates.

Left valve, attached to the cylinder that mechanically creates the oscillation, adjusts osciallation frequency, and the right valve the oscillation magnitude.

Oscillation has always been completely reliable since I bought the machine new, 25 or more years ago.

Bridgewood no longer exists. Most of the pneumatic parts seem to be the same or similar as in the current Powermatic (last pic), though they're assembled in different relative locations.

Can anyone describe next steps for troubleshooting, or likely part(s) to try replacing? This isn't the sort of thing I'm real adept at....
Thanks!

[Jim Andrew]

Did you get the belt over the Y where the air fittings attach? One of the first times I used my Grizzly 15" sander, I got the belt over the Y instead of behind it, and ground off one of the air fittings. If you open the right side door, can't you see the hose hanging? Would think you could call Grizzly and get parts.

[Brian Burns VT]

Have you checked the diaphragm inside that disk thing? We have a powermatic that has the same set up and had a similar problem and that was the answer. It was torn and a very easy fix once we figured it out. Hope that helps

[Carl Beckett]

I want to follow for future reference.

The design is setup for the belt to slowly drift to one end. Then when it gets to a certain point, pneumatics kick in and tilt the upper drum and it tracks back to the other end. repeat. But yours isnt oscillating.

Check alignment of the air stream that shoot across the belt edge. That is the sensor. That stream of air might create a pressure that goes to that 'disc' (my guess is a diaphram, takes a small pressure to then actuate). If that air stream wasnt shooting straight into the opposite orifice, it would not build pressure. Maybe it was knocked out of alignment or clogged. Or as suggested, if the diaphram is torn (inside the housing) it wouldnt actuate. Also check if you can oscillate by hand (if something jammed it or not)

Am happy to 'test' for anything that might be helpful on mine as you troubleshoot. (mine is a Jet, which is powermatic, which looks quite similar to yours)

I need replacements on those ceramic fingers if you happen to know where to get those lmk.

[al ladd]

Thanks for these replies, they were helpful. This is such a great forum. Such a kind offer Carl!

It turned out that the belt, unrestrained by the limit switch, had sanded half way through the nipple and a nut threaded over it, where the air stream gets sent across the fork, and it must have distorted the air steam so it wasn't received correctly. I was thinking interrupting the air being emitted would be the cycle starting event, but it's actually the receipt of the air stream, as Carl pointed out.


There's a little red plastic tube inside the brass air eye outlet at the tip, which also got sanded part way through and by messing with that I was able to bridge the gash and get it working. It's pretty banged up so it would be nice to replace that fitting. it's a nominal 3/8" fully threaded brass straight fitting turned to a cone on the tip with a very small opening (.03"?) at the tip that couples to the plastic air line on the other end. The Bridgewood parts break down describes it as: 3/8"-UNF air eyelet (out). It seems like current Powermatics use a similar set up, so maybe the analogous part would work. Anyone know best place to get small parts like this from a Powermatic dealer?


It looks like current Grizzly small wide belts use ceramic limit switches that would be compatible with the Bridgewood. I ordered a couple.

It's not oscillating the same as it did before, only moving about 3/8" instead of more like 3/4", but I'm happy enough with that. I think the difference is the position of the air eye, which is fixed by a single phillips head screw that's annoyingly inaccessible, so it's all but impossible to tighten with control. Just not designed to be adjusted after initial assembly it seems.

I think I paid something like $3500 for this machine new. It's paid for itself many times over, but I'd love to keep it running as long I continue woodworking!

[Richard Coers]

It would not be unusual for 25 year old valves and cylinders would need to be replaced. What kind of water filter and water traps do you use between the compressor and the sander? I'm guessing you will find corrosion inside several different places.

[Carl Beckett]

You are onto it. I see sanders listed for sale from time to time where they have replaced the air switch with an electronic one. So it can be done... you might research what it would take to go with an electronic sensor before spending too much on repairing the pneumatic

When you say it doesnt oscillate 'as much', do you mean the belt doesnt drift as far before oscillation, or the tilt of the drum seems less than before?

[al ladd]

"When you say it doesnt oscillate 'as much', do you mean the belt doesn't drift as far before oscillation, or the tilt of the drum seems less than before?"

I meant belt travel. I just looked at a couple videos of Sunhill 15"ers working, and they looked more like what I have now than what I had before-small travel, maybe faster oscillation. This is probably what it should be. With the longer oscillation I had issues of the osci track being somewhat visible as periodic waves in the work--better perhaps to have that less wavy. One of those things that might have been wrong from the start, or slowly drifted over the years without me noticing. It's not like I ever see other peoples wide belt sanders oscillate!

I think I'll shore up my damaged air eye outlet fitting with some JB Weld. Seems to be a non-stock item I can't find anywhere, unless there is a friendly Powermatic small parts dealer somewhere. Powermatic's main web-site that sells parts only shows larger componants. This is where Grizzly really shines, stocking almost every component of every machine.....

[Louie Law]

Just had that problem and Grizzly no longer stocks the plastic part (P9983518 C6-1/8) that receives the air flow. I was able to locate some from an industrial supplier. Problem is they sell bags of 5 for $19.22+$13.85 shipping.....ouch! So, I will likely have four that I would gladly help someone out with for the $4.00 + postage that it cost me. The company is Misumi USA out of California if you wish to part with your money!!!!