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View Full Version : Mill Powered Belt Sander..??



glenj
07-24-2004, 08:03 PM
I have done some research and found that the best way to cope or miter very thin walled tubing is with a belt sander using the correct size of drive drum for the tube you wish to join.

I'm thinking of building a mill powered clamp on belt sander to take advantage of the speed control, rigidity and ease of positioning tubes accurately.

Could you have a look at the photo below and see if there is anything I'm missing? There are a lot of experienced people here and I'd like to pick their brains before I start cutting aluminum. The one thing not included so far is a handle to retract the idler for easy belt changes.

Thanks for your help/opinions/ideas...

Glen
http://img30.photobucket.com/albums/v91/glenjohannesson/Belt%20Sander/belt_sander.jpg

J. R. Williams
07-24-2004, 08:59 PM
The unit would need very good shaft seals to protect the limear bearings. The thought of using an abrasive on a mill is not good. Mills are made to handle chips not abrasive dust.

JRW

glenj
07-24-2004, 09:25 PM
I planned on covering the mill table and ways with large masonite pieces to avoid contamination. Between that and running the shop vac it may not be an issue.

The linear beaings I have lying around have a pretty stiff rubber lip seal so I hope they'd keep most of the big chunks out.

The tubing I need to miter is only 0.5mm thick so there won't be a lot of material being removed anyway.

Thanks for the suggestions/warnings.

rockrat
07-24-2004, 10:03 PM
An off topic question if I may. Nice rendering by the way. What software are you using? I'm a big AutoCAD fan with alternate education in ProE. It almost looks like Solid Works.

Good luck with your project, and post lots of photos when you get it finished.

Forrest Addy
07-24-2004, 10:11 PM
Glen, the abrasive dust will fly everywhere and stick to anything oily. Mere covers will be inadequate as a dust barrier.

You'll have to drape the machine in an impervious material like blue tarp. The removel of this tarp will require care so that spillage of abrasive residues don't find their way into sensitive machine parts. This is a matter of rolliing the edges into the center, folding over the ends and so-on to trap the dust resides. The tarp will then have to be thoroughly cleaned for its next use.

You have the start of making a very nice stand-alone belt sander. I suggest completing it would require only a pair of lower bearings, some sructure to hold it all togehter, a motor, a belt tracking adjustment, a two or three speed belt drive, and a work rest.

Infinitely variable speed in a belt sander might seem nice but close speed control is not critical. For that reason I suggest a step pully to lower speeds for heat sensitive materials.

darryl
07-24-2004, 11:07 PM
Is there a low-friction surface for the back side of the belt to bear against when pressure is put on it? You might be able to have this surface in two sections, one that is hard for shaping cutting edges, and one that is softer for deburring. Just a thought. Maybe you only intend to use the belt where it rounds the spindle though. Maybe add a dust collection hood to catch as much swarf as possible. Also it might be nice to have that clamping 'c' swinging from one side of the main arm, so it stays with the arm for quicker mounting. Maybe you have something in mind for that, I can't tell from the diagram. Just another thought.

[This message has been edited by darryl (edited 07-24-2004).]

sandman2234
07-25-2004, 06:15 AM
I agree with Forest. Grinding dust has no business around a mill. A stand-alone unit, preferably in a separate room would be much better. Another idea might be to just use different size abrasive tubes and forget the belt part of your idea. (provided this is just for coping) That would un-complicate things alot.
david from jax

Evan
07-25-2004, 07:25 AM
Why not buy a belt sander and put it in the next room, as mentioned. When I tool post grind on my lathe I spend an hour or two cleaning.

ibewgypsie
07-25-2004, 08:02 AM
I kinda agree, it is so simple to make a belt sander it is a shame to tie up a machine with a attachment.

WE used to make them for the knife makers that was on a piece of square tubing, the motor was a 1750 rpm job of whatever was laying around and the end roll would slide up and down on the sq tube to work with whatever belt was around.

People made knives on these. From the cutting to the polish.

Next: anyone know of a way to glue the roll-emery cloth into sander belts?


David

glenj
07-25-2004, 09:14 AM
Thank for all the suggestions. I guess I'll have to think twice about the grinding dust issue.

The rendering was done in Solidworks 2004. I've used it for 8 years at work and find it great for just about any project planning.

The reason I wanted to make it mill based was for accurately holding and positioning the tubes. They are heat treated high strength steel bicycle frame tubes and are very thin. The miters have to be a very close fit to make TIG welding possible and for accurate frame geometry.

I'll have a look at making a stand alone unit with an add on tube positioning system and a motor driven shaft with some bearings...seems like a lot of extra work though. Then again that's half the fun.

Great bunch of helpful people here...thanks again.

Glen

sandman2234
07-25-2004, 02:28 PM
Just wondering why your using 3/8" shafts with linear bearings. Doesn't seem like there would be enough movement at that point to require bearings. A slide out of an old printer might be just as good if you find one that isn't worn out, and save several dollars on it. Sliding metal against metal for that minimum amount might be better than having to remove and clean all the grit out of the ballbearings in linear bearings. Maybe something in plastic would be better as far as the bearings.
David from jax

glenj
07-25-2004, 05:08 PM
David from jax:

I have a few 2' lengths of 3/8" Thompson case hardened shaft and 20-25 matching linear bearings and figured I might as well use a few, otherwise I would be going with a Delrin bushing arrangement...which I will drop in place of the bearings if they don't work out.

For the dust issue I might look at builing a shroud around the whole thing with an outlet for a shop vac at the back.

zl1byz
07-25-2004, 05:35 PM
Why not just use good cutters the correct size. I used to tig weld a lot of stainless pipe for the food industry and we would use HSS mill cutters or for larger pipes quality hole saws, mounted on a sturdy mill you don't need the pilot drill.

John.

[This message has been edited by zl1byz (edited 07-25-2004).]

glenj
07-25-2004, 10:01 PM
I have good cutters in the correct size and they work wonderfully on thicker tubing. 4130 cuts like butter compared to the new tubes I'm using which have a 195,000psi yeild strength and Rc 45-50 hardness. At almost $100 per tube I can't afford too many errors.

Sprocket
07-25-2004, 11:28 PM
Whacha buildin'?

glenj
07-26-2004, 08:11 AM
I'm building some very light, very strong custom bicycle frames...

http://img30.photobucket.com/albums/v91/glenjohannesson/Shop%20Photos/Frame%20Building/Road_Frame_1.jpg
http://img30.photobucket.com/albums/v91/glenjohannesson/Shop%20Photos/Frame%20Building/Tubes_In_Jig.jpg


[This message has been edited by glenj (edited 07-26-2004).]

Techtchr
07-26-2004, 09:25 AM
David,
I make my own belts by using two coats of contact cement with about a 1" lap joint. Proceedure is: cut belt to length + about 2" put a layer of contact cement on about 1" of each end on opposite sides of the belt. Let dry, put a second layer of contact cement on. When it drys,(about 5-10 min) stick the ends of the belt together making a lap joint. I then clamp the joint between two blocks of wood in my vise just to make sure they're stuck together good.
Matt

Sprocket
07-26-2004, 10:28 PM
Nice joints. My first mountain bike was one I made. CR-MO and silver fillet braze. It's still around, though I've gone on to better bikes. That one doesn't look like it's built for mud.