belt grinder speed

[Luke March]

This brings up a question I have. I am planning a belt grinder build, and, at least to begin with, the speed will not be adjustable. So I have two choices; should I get the 4" drive wheel and have it run at 3600 fpm, or should I get the 6" drive wheel and have it run at 5400 fpm?

The intended use of the grinder will be for blades, armor, and general purpose.

[Rich Hale]

I use three belt grinders a lot and for all metal work pay a lot of money for belts that I have found that will do the work I want right. That includes a commercial variable speed grinder, a comercial fixed speed grinder and a home made variable speed grinder set up with small contact wheels. I use several different brands of belts and all of them have a speed preference. even same brand belts with same grit size. As i grind on variable speed machines I will adjust the speed to get the belt to cut like I expect. And again a few of the brands of belts require more pressure when working than others. I use the fixed speed grinder for rouigh work like blade profiling. Not for blade or handle finishing. So for me the answer for this is simply grind alot with several different belts and different speeds and see wot speed works for you. A note book may be handy til you get it all sorted out.

[Luke March]

I appreciate the advice Rich.

My dilemma is that I don't have a way to vary the speed, at least not to begin with. I'm wondering which belt speed would be better for the single speed until I am able to upgrade to variable; 3600 ft/min, or 5400 ft/min?

[Dave Mestdagh]

Am in the process of building a 2" x72" belt grinder & have been reading & using this site for info & help on speeds, motors etc. I have found a site that will make calculating FPM & pulley sizes very easy to calculate. The website is at the following website and is great.

https://www.blocklayer.com/pulley-belteng.aspx

Hope everybody finds this as useful as I have during my planning stages. Also, we'll I'm at it, I'll give you the link of a young fellow, named  Jeremy Schmidtwho's built a very fine homemade unit, which I am hoping to duplicate, as closely as possible. Let me know what you think. Am sure some of the other members here must have seen this video as well.

https://m.youtube.com/watch?v=a_RlL1O-bK4&index=54&t=306s&list=PL7xh-HzSRHqmBUT0K3hL-AgySq_slHk5H

 

[JHCC]

Welcome to IFI, Dave! If you haven't yet, please READ THIS FIRST!!!

[eutrophicated1]

High, Dave, and welcome.  I'm a newer member here as well.  I have seen Jeremy's videos, and am impressed with that 2x72 design, and implementation.  Jeremy is a prodigy for sure.  And I plan on using his videos and documentation to build my own belt grinder.

The only caution I would give is that the design requires significant fabrication and welding skills, and a high degree of dedication to the time needed to complete the project.  This is a complex build, with quick-change attachments for: platen, 10 inch contact wheel, small wheels, small radius grinds and several types of table rests.

I've seen videos of professional fabricators trying to build this beast of a machine, and messing up the job.  Jeremy's build showed clearances of only .008" on the sliding accessory tube;  the pros had to have twice that just to get the sliding fixtures to work.  Sloppy.  I would really appreciate seeing the progress of someone having a good result with the build.  I believe that there are others on this forum who would also enjoy seeing your thread of such a build.

 

[EDL]

Ah, Jeremy's grinder is the one I'm planning to build as well.  There are quite a few videos on youtube of folks who have built it and all seem to have gotten it done quite well.  Of course, some folks have also changed the design to some degree, such as using heavy wall square tube instead of fabricating the the tubes from 3/8 stock like Jeremy did. 

I also plan to make some changes to the design, specifically I want to see about changing the dimensions enough to fit a 12" contact wheel, or possibly even a 14".  Looking at the design, I believe this is possible without losing any rigidity (I mean, the thing is made entirely of 3/8 stock, it's a tank!).  I'll probably mock up my version out of cardboard or something suitable just to ensure the measurements or what I may need to change (I don't have a fancy CAD/CAM program and no real skill with them even if I did).  If such a change becomes unwieldy, then I'll just build as designed and not worry about it.  A different approach would be to skip the tensioning wheel and route the belt to a 2-wheel set up for the larger contact wheel.  This would provide a few more inches of belt length to extend the tool arm to clear a larger wheel without the need to shorten the holder tube, but that would require some method of tracking adjustment via the contact wheel, which may not be optimal (I've seen 2-wheel grinders, so a little research into how they operate is warranted).

I'd also like to have a go at making a rotary platen for it as I'm quite fond of convex grinds for sharpening, especially the kitchen knives.  It seems to provide a great balance between cutting and longevity to the edge.  Straight up slack belting though makes it difficult to control as the belt is a bit too sloppy.  A rotary platen would be awesome for that.

I don't know that I would call the build particularly complex, it's pretty straight forward and Jeremy designed it to be that way.  Besides, as he says, "If you can't make it precise, at least make it adjustable" and I think he's done a fabulous job in that respect.  The key to the tube clearances is the method he uses to make them with the shim pieces.  You do still run the chance of warping the tube in final welding, or shrinking the fit too much, but if you've watched the video, he changes his shims from two layers of soda can material to utility knife blades which added some more clearance.  If you have experience sticking metal together with a welder and have the patience, I think anyone willing to take it carefully could build one of these easy enough.  The "hardest" part of the build, to me, is all the cutting of 3/8 material, that's a test of patience in time and effort (especially if you don't have a bandsaw).  As with any metal contraption, the key is straight and square and if you aren't sure how to achieve that, there are tons of videos with tips and tricks on how to do it, usually quite simply.  Anyway, that's my $0.02 worth.  Building a tool or machine there is always the chance of issues or outright failure, but that's part of the fun and learning.  :-)

[Donal Harris]

It has been a little over a year since EDL made the above post and EDL hasn’t been back since last December, but it might save time for someone else to know Jeremy said in a video he will not be putting out any plans for modifications to his grinder to take contact wheels larger than 10”.   It is fairly early in this video where he explains why.