Belt grinder advices

[rendoman]

Hi all!
My uncle gave me some old but good engines, among which one 1,5hp - 2800 rpm, I'm thinking about building a belt grinder. I found on local flea market some abrasive belts, from 6cm to 12cm (2,3" - 4.7") various grit, very long.

My idea is to replicate a belt grinder with 4 pulleys, like kms (is that the name?) or like many good project seen on this forum.
I got a few doubts concerning diameters and width of the wheels:

- I havn't understood the use of large or small diameter in the final "cutting" wheel. I see very big, or couple of wheels (usually one bigger than the other) with a flat support, or smaller single one.

- If you need to build a belt grinder, which width of belt you should take? It may be worth building large width wheel (12cm)? Or It can be better make wheel for 6cm?

-Adjustable wheel for centering I see has "tip", I can immagine something between 5 and 10 degree, It can be useful?

- engine pulley diameter, as I understand it, it's only related to speed of the belt. For steel speed should be around 25-35 m/s and something less for wood. If I attach the first wheel at the shaft of engine, with 2800 rpm I should use some 150mm (6") or more in order to obtain cutting speed of something more than 20m/s.
...or maybe I should use a couple of pulleys to decouple engine and change speed? I think it's the right choice.

I'm searching for 6003 bearing, hope it's a good choice. I want also to add a cotton polishing arm

What do you think about?

[rendoman]

Shipping list updated

[rendoman]

Hi all!
I'm starting the project of belt grinder
I got long belts (3m - 120"), then size is not so compact, due to this point I chose to make a floor standing machine.
I was inspired by a youtube video of a diy grinder, very well made in my opinion.
I think I will make some attachments for cleaning - polishing.
Central tensioner needs a spring, don't know how much load belt needs, I will try maybe with attempts.
I'm also thinking to make a support with protractor, I have to think a good way to engrave steel
Some good idea to make the machine better?

[rendoman]

I'm thinking about use some high density polipropilene as bel support on the double wheel final part, or maybe it's better steel?
Next work will be build the wheels on lathe, don't know if making them straight, or with double angle, it can help?

[C-Bag]

It used to be that it was a given that you would always put a crown on the pulleys on a belt grinder but the one I have has no crown on either the drive or takeup pulley's. What I notice with this is the belt is more uniform in its usefulness. It doesn't have the slack edges that a belt on a crowned pulley would have. Mine also is tracked with what I think is ingenious method of twisting the take up wheel to track with. Personally I don't use long belts and use the disk sander more than belt sander and don't leave the belt on mine all the time so what do I know ?

[Toolmaker51]

[QUOTE=rendoman;67793]I'm thinking about use some high density polipropilene as bel support on the double wheel final part, or maybe it's better steel?

I'd tend toward poly/ urethane/ or non-metallic wheels to reduce inertia and heat retention. Aluminum tube with a plastic liner for bearings might work too.

Next work will be build the wheels on lathe, don't know if making them straight, or with double angle, it can help?
The tracking adjustment wheel might look flat, ok for regular speeds. Most have a very large radius, not a pair of angles, that's what stresses the belt. Crowned sheaves are used on things like toolpost grinders; high rpm, rubber with cords and 'no' stretch, perfect alignment and the crown keeps belt centered.

[Toolmaker51]

1,5hp - 2800 rpm is a lot of power and speed. A speed control might help if the calculations are too high drive ratio, and to handle different materials nicely. The belts you have will last a long time, spreading wear over more area than my 42'' (1066mm).
4 wheel sanders are called 'square wheel'. Typically there is a removable plate for smooth free-hand contour sanding. The plate makes it more like a grinder, to achieve flats, radius corners or chamfer edges.

... large or small diameter in the final "cutting" wheel. Larger wheels and 3 or 4 reduce belt stress, compared to bending around small wheels. Mine is 3500rpm and about 4'' drive wheel, upper about 2''. Mainly I think that is to gain distance between wheels. 42'' is not a common hardware store size. I ebay them.

Width to me = wider is better. Cutting them narrow could break the band of fabric or stretch unevenly. Design the plate to move side ways a little so you can sand right into a corner

-Adjustable wheel for centering I see has "tip", between 5 and 10 degree, It can be useful? That's the adjustment an eases the belt on without any tension. Mine sounds just like what C-Bag describes.


- engine pulley diameter, ... same as motorcycle gearing for different engines. Mine's 3500 rpm sometimes faster than I want. It sands wood fast enough to burn with a fine grit. Grinds metal well, iron or aluminum. Haven't found a belt good for thermoplastic, [those that melt], has to be brand new sharp. I think you could reference commercially made sanders for rpm they run in, but to actually to vary speed is way better. We'd probably use a step pulley.
Being able to change speed will allow a range for polishing too.

[C-Bag]

I totally concur Dr. TM51, especially about speed and hp. I know it's counter what most folks on here want but as one who's gotten tangled with grinders I don't want or need more rpm's and ESPECIALLY more hp.

My dad gave me a big old 1.5hp 8" bench grinder and I dubbed it widowmaker as it about sucked me into it way more times than I want to admit. And I'm one of the more paranoid users of tools I know. Even though I was terrified every time I used widowmaker if I ever got distracted it would bite me....hard! The best thing ever was when it decided it bit me enough and burned up one day. I don't ever remember being happy when a pivotal piece of equipement died but I did a little jig when I dumped that thing in the recycler bin. I felt like I'd outlasted an opponent not mourned the lose of a valued ally as I view all my tools. It got replaced by a Jet 1/2hp 6" grinder that I keep a wire wheel and the other side has a Multitool w/36"x4" belt 7" sanding disk on the other side.

It's as handy as a shirt pocket and has more than enough power for me. More is not better for me. I'd rather something bog down and stop instead of pulling me in to end losing a finger or worse. Just my 2c.

[rendoman]

Thank you very much, both of you are a mine of information!
Maybe I made wrong calculations, 2800rpm engine, with 2,5" final pulley I calculated final speed of 8500rpm to reach speed in range of 20\35 ms of the belt. I have to search the paper for better accuracy.

I come back in few hours, time to go out see the match Ita - Ger

[Frank S]

Grinders, grinders, and more grinders.
I guess that I've never found one with too much power.
the old blacksmith shop where I apprenticed had 3 old arbor grinders 1 had a little 3 Hp motor on it with 2" wide 14" inch diameter fine grit finishing wheels on it that was the one we used to sharpen small cultivator shears.
One had a 10 Hp motor not real high speed but 4" by 20" coarse wheels would remove metal by the pound
The last one had a 45 Hp 4 cylinder Wisconsin it had 2 belt driven arbors on it 1 was horizontal with a single 10 inch wide 20 inch diameter wire wheel the other arbor was vertical with a single 20 inch diameter cupped wheel. this was used for grinding shear blades
One of my tasks was to keep all of the wheels dressed and true. In today's society I would no more trust a 12 or 13 year old young man with a diamond wheel dresser on a 1/2 hp 6" grinder let alone have him anywhere near those monsters. but I used them almost daily.
I like the OP's idea for a 1 1/5 Hp 2800 RPM motor fora belt sander/ grinder I would probably go with a 3.5 or 4" diameter 8 grove serpentine pulley to a 1.5" or possibly 2" driven arbor to power the flat drive sanding belt pulley make it changeable from about 4" in diameter to 6" in diameter
1 1/5 Hp will be a little on the small side in my opinion for a belt wider than 4 inches though and nowhere near enough for a disc much larger than 8"
My Delta 12" disc & 6 by 48" belt sander had a 3 HP 2800 RPM motor with a 3.5" pulley and the arbor had a 2" pulley it did a fine job but could be bogged down