What speed for grinding

roxtar

roxtar

Joined
Mar 11, 2010
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85
Search turned up a lot of how-to info about variable speed grinders but I couldn't find anything about what speeds work best for various jobs.
I'm currently working on the pulley configuration for my 2x72 and was wondering what speeds (in fpm or fps) I should aim for.
I assume the slowest speed would be for final, after HT, platen grinding (I have a small 1X30 belt sander for handle work)
 
I have a couple 3 step pullys on my KMG and always keep it on the slowest it will go for every grit of belt I run. The faster it is the easier it will be to screw it up.
 
I have a three pully set up on a coote and the fastest is 4500 fpm, that is a direct one to one ratio on the pully to a 10" wheel with a 1750rpm motor (math??). The next I belive is about 3000 and the slowest is about 1500. 4500 is quick enough for me to do alot of damage, I work at 3000 for most of my grids unless I have alot of stock to remove. belts finer than 120 I will go down to 1500 to get more life out of the belt, prevent mistakes and avoid over heating.
 
i myself like to be able to see the seam go by. i was talking to rupert lucius one night about paper wheels and speeds. i told him i wanted to know how fast my high speed buffer was running. he told me that with the following pulleys i was running at 14,190 linear feet per minute with a 10" paper wheel which i wouldnt run that fast. my buffer has a 2 3/4" drive pulley and 1 3/4 driven pulley. the motor runs at 3450 rpm. he sent me this link later. http://www.csgnetwork.com/pulleybeltcalc.html
 
I use a 4 sheave setup from 1000 SFM to 5000 SFM, which is fairly typical. You use the lower speeds with finer grits to keep them from glazeing up. You use the higher speeds with lower grits to get your work done. Many belts are designed for higher speeds and higher pressure than most of us use.

I rough at 5000 SFM up to 120. I slow a bit for 220. I slow more for 400 grit and use the lowest speed for anything finer than that. I also use the slowest speed for scotchbrite belts.

A little higher and lower range might have some utility, but not much (for me anyway)
 
For removing material my grinding will be running at 5400 sfm. This is especially true when using ceramic belts in the 40 50 grit rating.
The finer the grit the slower the belt speed is a good rule of thumb.


The grains on a ceramic belt can be fractured by pushing a hardened file against the belt while it is running at high speed. This gives you an almost new surface to grind with.

There is no substitute for HP. Get as much motor as you can afford.

Good luck with your project, Fred
 
I gotta try the file trick, I have a bunch of belts where the grit is visable but pretty smooth, lots of pressure work good for profile.
 
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