Wide Belt Wonder with pictures ..

[Rick Fisher]

Sander is a small 25" SCM Sandya Win ... Vintage 2001

For a long time, I have only bought paper belts for my Wide Belt, and only Fuji Star lately ..

I got 3 x SIA Cloth belts, but they wouldn't track .. Simply ran right off the side of the drums and tripped the switch which shuts down the machine ..

My last good belt is trashed and its a long weekend . I need my sander so I tried the cloth belts again they ran right off the side .. just like before ..

This time however I noticed and compared .. switched belts and watched ..

There is a piston which slowly moves back and forth, tilting the top drum, keeping the belt in the right spot.. It basically creates the oscillation.. I noticed how slow it worked and wonder .. how can it not keep the other belt in line..

When running the other belt, I noticed.. It doesn't move at all ????

This is the piston ..

http://i335.photobucket.com/albums/m455/jokerbird_photo/P1020540.jpg

I was going to adjust it but its so slow .. It does so little .. I cant see it .. but it does move with the old belt.. With the new belt, it sits idle until the belt trips the switch ..

So I tore it apart .. and found the little electric eye that tracks it .. until now, I didn't think it had one .. lol

I wonder .. If the eye tells the piston to move .. it cant be noticing the cloth belt ..

Here are the belts .

http://i335.photobucket.com/albums/m455/jokerbird_photo/P1020546.jpg

The good belt which tracks is the light one .. the dark one ( cloth ) .. doesn't activate the tracking piston

I am thinking my red eye cant see the dark belt .. or its prejudiced against Swiss belts.. I dunno ..

[Rick Fisher]

I found an article on another site where the fella talked about spraying the inside edge of the belt with white paint ..

Anyone ever heard of this problem before ?

[Carl Beckett]

I dont know the exact type of sensor, but its entirely possible a reflective type of optical pickup and not enough reflection to activate the sensor.

On other designs the sensor shoots through to a receiver side - when the belt trips this it blocks the light from going across (like those garage door safety sensors).

If it has a receiver - painting the belt wont help and its something else causing the problem.

If its a reflective - and possible (meaning safe) - you could put a little stick with some foil or white paper taped to it in front of it while its running, and see if it tried to activate (motion of the piston might not be a lot - more about putting more force on one side to get the tracking to drift back the other way). If this worked, then its an indication that not enough reflection.

And then finally, if its not getting a strong enough reflective signal, you might move it closer to the belt.

[J.R. Rutter]

Does flipping the belt around (running it backwards) help?

I have had belts that were asymmetrical enough to want to run off one side or the other. The piston could not move far enough to get them to track the other way. On my sander, the piston for oscillation is mounted on the back end with an eccentric pivot point, so you can loosen a set screw, turn the eccentric bolt, and retighten. It changes the stroke enough to push the belt back.

https://lh3.googleusercontent.com/-QTSe_Dbqvik/UHL3ZCWMHQI/AAAAAAAACKg/y37-6NmmjbA/s912/P1020540.jpeg

[Thomas love]

Rick JR is correct ,
I think you can also adjust the piston by loosening the lock nut and turning it ... meaning the piston. I loosen up the lock nut and adjust while running . I am pretty sure at least on my machine those two brass screw that JR circled will let you set the speed at which the piston reciprocates. With the machine running I turn the piston until I get the belt to stop running to one side then watch the oscillation and adjust so the belt rides back and forth evenly. Maybe Rick Lizek will chime in I am sure he could explain it better. I have had a dual head 25 "wide belt for twenty years and have had to do this from time to time .

[Jeff Duncan]

On my sander it reflects off a mirror so the color has no affect. However one thing that may affect it is pressure? On my sander the PO trained me to set the PSI for 40 on paper and 60 on cloth. Anyone else do this???

JeffD

[Rick Fisher]

JR .. I tried flipping the belt .. Either direction, the belt runs off towards the same side.. So its not the belt..

What really puzzled me was that the piston doesn't move with the newer dark belt.. The belt slowly runs off the side while the piston sits idle, until eventually the machine shuts down .. I stand there and am yelling . move dangit .. ! Then put the the older white belt on ( which is destroyed ) .. and it moves back and forth like nothing..

My sensor has a red light and a circle shaped hole of sorts. I painted the inside edge of a belt white with oil based rust paint .. I am going to go out and try it ..

Thomas .. I was going to adjust it while it was running but noticed with the cloth belt the piston wasn't operating at all .. So I figured I would look for something else..

Jeff .. I will make sure my pressure it at 60 .. I think its already there .. Its measured in BAR ..
'

[Rick Fisher]

Last night I spray painted the inside of a cloth belt with white rust paint .. Put it on the machine just now and it runs like a top . Amazing ..

[J.R. Rutter]

Good to know! Thanks for the follow up to close out the issue. Which side was the belt running off?

[Carl Beckett]

Kinda implies not a strong enough reflective light signal. Means either alignment ( get the signal to bounce straight back instead of off at an angle), or move the sensor closer to the belt.

Or keep painting.......

[Rick Fisher]

I wish I had taken a picture of the sensor .. To find it I stripped the sheet metal off the rear of the sander .. Not really a big deal .. I cleaned it while it was apart which makes me happy .. My sander is so small that its impossible for me to clean it simply through the door ..

I believe this thread will help somebody one day .. Its been really frustrating to figure this out ..

Here is a picture of what I did ..

http://i335.photobucket.com/albums/m455/jokerbird_photo/P1020553.jpg


The belt would always run off the " belt change side " of the sander .. I kinda think the machine is set up so the belt runs that direction, and the sensor notices when the belt crosses past it, and tells the piston to move it back the other way ..

Not sure how it decides to come back ..

http://i335.photobucket.com/albums/m455/jokerbird_photo/P1020554.jpg


I used Oil based Rust paint on a cloth belt.. No idea if it will shorten the belt's lifespan but I don't really care because the belt was useless.


Wide Belts aren't a big topic on this board but I appreciate people trying to help .. I also figure I will remove the sheet metal and clean on a regular basis, I found Wenge dust in the sander and I haven't really used it in a few years.

[Jim Andrew]

My Grizzly sander uses a stream of air to change the direction of oscillation. When the edge of the belt closes off the stream of air, the belt changes direction. It is a small nozzle inside the machine, and sprays at a opening. Simple, and seems practically foolproof.

[Jeff Duncan]

Rick, I'm curious how your electric eye works? My machine, (really old Timesaver), "sends" the belt the other direction towards the back. The light is on the outside of the belt and there's a mirror on the inside. When the belt interrupts the light from reflecting off a mirror and going back to the sensor, it shifts the drum which sends the belt back the other way. Sounds like yours is working differently where the eye needs to 'see' the belt? I'm just curious as how other machines work?

Mine actually originally had the pneumatic tracking also....for some reason it was replaced along the way with the electronic eye. I have no idea what the advantage of the eye is over pneumatic tracking?

JeffD

[Rick Fisher]

Hey Jeff ..

Mine is a little grey box which sits inside the belt .. I mean, its on a flat steel bar with a roller above and below it .. It reads the inside of the belt .. Basically its a box with a red light on it .. There is a hole next to the light .. I assume the red light reflects off the inside of the belt when the belt passes in front of it, and the hole next to it somehow picks up the reflection.. Not entirely sure but painting the inside of the belt white seems to have fixed the problem . I ran the sander about 20 minutes tonight with the cloth belt and its running like a top ..

[Greg Bender]

Rick,
sounds like you are dealing with a proximity sensor, if you spray silver spray paint that will work like a champ. It is more reflective than the white and can be done while the belt is still on the sander.
Greg

[Rick Fisher]

Good to know Greg. I found the old can of white .. but I have 3 belts .. Silver works fine for the next two .. Interesting to see how the cloth belts compare to the paper .. supposed to be more durable but time will tell .

[David Kumm]

I've been told by belt suppliers that paper gives a finer finish than cloth. Anyone have opinions? Dave

[Jeff Duncan]

Definitely more durable....trying to get those 43" wide paper belts onto the machine can be a frustrating experience:( The edges are always catching and if I'm not careful can tear fairly easily. Cloth ones hold up better in that scenario anyway. As far as in use.....I honestly can't say, but looking forward to hearing other guys opinions!

JeffD

[Rick Fisher]

Too early for me to say if paper leaves a better finish .. My first cloth belt is on the machine .. I gotta say however that the finish from the cloth seems fine .. I have been sanding Afromosia .. which is hard .. really, really hard..

The benefit of a wide belt is that the product is ready to be final sanded and final sanding is really quick after the wide belt is finished.. I always use 150 grit belts.. After the sanding machine is finished, the board is dead flat and scratch free.. Ready to be finish sanded .. A quick pass with 180 and / or 220 and your done .. I still have to final sand..

So far the cloth belt has not changed the procedure but I have only sanded one species of really hard wood.. It would be interesting to check it on a softer species..

[J.R. Rutter]

I've been told by belt suppliers that paper gives a finer finish than cloth. Anyone have opinions? Dave

This applies to finish level grits (150-240), but I evaluated both cloth and paper belts using samples from 3 different suppliers. With equal grits, paper gives a better finish. You can step up to a finer grit to get similar results from cloth. I think that it has to do with the uniformity of the substrate that the grit is glued to. Paper is smoother than cloth. I have never had a paper belt break on my sander. I have damaged edges of belts hanging on the wall, but not on the machine. YMMV.

[Carl Beckett]

I have some 24 x 60? belts I can't use if anyone wants them

[David Kumm]

Any experiences with SIA belts? They have been recommended but I've not used them. Dave

[Mel Fulks]

I had not heard that before. Always good to hear test results. As for damaging the belt edges ,I have always thought that a couple of funnel type jigs with magnets would make belt changing easier, but I never seen any.

[J.R. Rutter]

Any experiences with SIA belts? They have been recommended but I've not used them. Dave

I use them now. Good bang for the buck.

[Rick Fisher]

So far the SIA cloth belt seems pretty good..

I found the SIA Top Tech paper belts burned too easy and switched to the Fuji star.