Disc flattening technique.

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SS369

Joined
Nov 29, 2015
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Hello all.
I have a 9 inch disc sander, variable speed and I am looking for some reasons and answers to flattening scale material, etc. on it.

I seems that I always have a non-flat outcome using it, in that the front and rear of the material always has more taken off it. Not flat.

I've tried many different positions and methods of hold it, flipping if this way and that and different parts of the disc surface, light pressure and heavy, to have the same outcome. I know some hand sanding, figure 8 style will eventually get it right, but, I have read and read that it is the correct tool to get things flat.

Anyone have some suggestions?
Thanks, Scott
 
Do you have a beveled disc? The 1° bevel?
If that’s the case, you’re always going to follow up with granite plate or glass and sandpaper.
What disc do you use?
Even with a flat disc I have to go to the granite and sandpaper to get truly flat.
 
Thanks Josh.

I have a flat aluminum disc, no bevel. I've tried different grits, 80 and 120.
I don't mind doing the final flattening by hand, I just don't think that I am doing something correctly.
I swear it is flatter coming off my saw after splitting the materials.
 
SS369 said:
I seems that I always have a non-flat outcome using it, in that the front and rear of the material always has more taken off it. Not flat.
Click to expand...
Maybe you push to hard on wood ? How thick are scale ?
 
SS369 said:
Thanks Josh.

I have a flat aluminum disc, no bevel. I've tried different grits, 80 and 120.
I don't mind doing the final flattening by hand, I just don't think that I am doing something correctly.
I swear it is flatter coming off my saw after splitting the materials.
Click to expand...
Sounds like you’re aren’t using the right pressure on the scales. The end going into the cut requires less pressure Also slow your disk down if you can.
 
Thanks Natlek and Laurence.

I have tried soft, hard and in between and all over the disc surface. My scales are generally .25 - .375 inches thick.
I very rarely use the disc beyond 25% of max rpm's. Most times just off idle.
 
What are you sanding? G10 bone horn or wood?
Used to have the same issue
Try two things: Push in the center only using a piece of tape folded onto itself so there is sticky on both sides Be gentle and LOOK at the bottom frequently use new paper if possible and slow speed
Do the same thing using a flat stick (Like a paint stir stick) to give a larger reference for flatness
Might try a drop of super glue and use De-Bonder to separate
Also if the wheel is horizontal not vertical that helps alot
Hope that helps
 
I have one horizontal disk grinder hooked up to a vfD (I also use this vfD to run another machine, switching between the two using a 4pdt switch) but I wired in a momentary foot switch (within the vfD on the run/stop switch). I can turn the disc grinder on, step on the foot switch to totally stop the disc, apply my handle material, let up on the foot switch to grind the material flat and then step on the foot switch to totally stop the disc to take off the handle material without worrying about rounding off a corner. Works excellent.

You could also do this with a single phase (super low RPM ideally) motor.
 
Josh Rider said:
Do you have a beveled disc? The 1° bevel?
If that’s the case, you’re always going to follow up with granite plate or glass and sandpaper.
What disc do you use?
Even with a flat disc I have to go to the granite and sandpaper to get truly flat.
Click to expand...
+1 on always going to granite plate to get it flat! Me too
 
Thanks Hankins.
I'll try a center mounted push stick.
BTW, my grinder is horizontal, but I was thinking that maybe vertical would worth a try.
 
I don’t have a disc sander nor have I ever used one, but I think I have a basic understanding of how things work.
The center of the disc has the least amount of abrasive moving across it as opposed to the outer edges where the highest amount crosses per revolution. So more work is being done (material removed) towards the outer edges. If you were to hold a piece in place with one edge near the center and the other edge towards the outer edge with equal pressure the side near the outer edge would have more material removed.
 
Thanks bjansen.
Actually my disc is mounted to a DC 1 hp motor with a variable speed control (no reverse).
I don't know if a foot switch would effect the controller, because when it is turned on it "winds up" to speed.
 
Hi 3fifty7.
I generally use the outer most area of the disc and switch the scale end for end, being careful not lead in with the end.
 
I move the scale straight across the top half of the disc, flip it over and do it again. I always keep it moving. After I feel like it's pretty close I scribble over the whole area with pencil before I go to the surface plate.
Usually only takes a minute to finish up.
 
My disc doesn't have variable speed so I have to be careful. I have two of Nathan's discs, one flat and one 1˚. From my own personal experience, the abrasive toward to outer edge does wear faster as it is moving faster and more cutting and shaping tends to happen at the edge of the disc. For handle scales I will use a work rest and I move the scales around and across the disc as well as rotating the orientation of the scales. I'm sure these are all things you've tried. But in my work it usually comes down to pressure. Handle materials will flex a bit. If I push at all it will result in a non-flat scale. I use a very light touch and let the disc do the work. I keep a 9X12 surface plate next to the disc sander to constantly check progress. If I place the scale down on the surface plate and feel a slight vacuum or resistance when I try to lift it back up I know it's pretty flat. I always end up hand lapping later anyway but if I get the suction off the surface plate I'm pretty much there. The only other thing I can suggest is just to get a verified straight edge and check the face of your disc to rule that out as a variable.
 
Other thing that can happen is first contact of wood with scale .If edge make that contact first because of small surface in contact with disk will remove lot of material .Same can happen when we pull scale from disc when we think that we are done with work .That s way I like foot stop-run pedal.....
 
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