mill pulley ratios

Diecutter

Diecutter

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I'm building a small knee mill from scratch and am wondering what pulleys to use. Will two 4 step pulleys work, similar to what's on a drill press? Also considering a large spindle pulley and a step pulley on my 1/2 hp motor (1140/1725 dual speed motor) Also possible is two step pulleys and one large one on the spindle if really low rpms would be desirable. I'm hoping to be able to make decent cuts in steel stock. My ER-20 spindle has a max. of 1/2" dia. tool capacity. I have all the pulleys and motor, so it's a matter of what might be practical. Never ran a mill, so your insights are appreciated.
 
Low RPMs are desirable; do some calcs. on FPM with the largest cutter that you intend to use in steel, and figure on about 80 - 100 FPM maximum.
If both cone pulleys are the same size, I think the speed may be too fast at the lowest speed, you could use a countershaft and pulleys for lower speed ranges.
 
Diecutter, I can't necessarily help answerve your question but I have a 3 or 4 step craftsman pulley as well as an assortment of single groove pulleys I bought yesterday ranging from large to small. Haven't had time to post for sale yet.
 
If you want a decent range of speeds, you'll need 3 step pulleys like this:
DSC02652.JPG
This will run from 260 to 2100 rpm.
 
benmychree said:
Low RPMs are desirable; do some calcs. on FPM with the largest cutter that you intend to use in steel, and figure on about 80 - 100 FPM maximum.
If both cone pulleys are the same size, I think the speed may be too fast at the lowest speed, you could use a countershaft and pulleys for lower speed ranges.
Click to expand...
bbenmychree, All good points which give me a place to start off. Thanks
 
DiscoDan said:
Diecutter, I can't necessarily help answerve your question but I have a 3 or 4 step craftsman pulley as well as an assortment of single groove pulleys I bought yesterday ranging from large to small. Haven't had time to post for sale yet.
Click to expand...
DiscoDan, I have two 4 step pulleys and a 6" single pulley in my shop. I'm trying to configure these to maximum effect. Thanks for the input.
 
Circumference at the pitch diameter determines the ratio between V-belt sheaves. The pitch diameters vary depending on belt tension and wear of the belt and sheaves and slip making this calculation undefined.
If a fixed ratio is required use a timing belt drive.
 
The machine I envision won't be that finely tuned; more like really slow, slow, fast, and really fast would satisfy me.
 
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