I am in the process of building a 2x72 belt grinder. All welded construction, using many components available online. Main question is motor speed. I have two motors both 1hp 110vac. One at 1800rpm and the other at 3600rpm. Neither is totally enclosed fan cooled. But since I have them now, I will use one or both as time goes on. Which should I use, primarily for stock removal blade making and the occasional, forged blade.Thanks for any info you can share.
2x72 Belt Grinder Motor Speed
- Thread starter 4trout
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1800 vs 3600 rpm motor will depend on your use for the grinder, and what pulley arrangement you're using. If direct drive.... well, don't matter if direct drive or pulley drive. Look at the rpm of the drive wheel. Using a 4" drive wheel your belt speed will be slightly above the rpm of drive wheel. i.e. - 1800 rpm motor with 4" drive wheel will have around a 1900 SFPM belt speed. The larger the drive wheel, the faster the belt speed at same rpm.
Thanks for your comment. I am actually using a 5 inch drive wheel. So my belt speed with the 1800 rpm motor may be in them2100 rpm range. I may go with the step pulley arrangement in the future. Currently starting out with direct drive. I may start out with the lower speed until I get used to the new grinder. Thanks again!
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Are these both single phase motors? If you're building a fixed, single speed grinder, then I'd go with the slower of the two motors. Trying to finish a thin blade tip on a higher grit belt will be very difficult at higher speeds.
For 40-60 grit ceramic belt you need speed .For fine grit belts you need to slow down speed . I run my belt grinder on 6000 SFPM .Most knife maker as I read here run on 4000 SFPM . Now I almost finished my new grinder which will run on max. 9000 SFPM .You can use this to calculate speed with motors you have with different size drive wheel .............
https://www.blocklayer.com/Pulley-Belt.aspx
With your 5" drive pulley you'll have about 2350 SFPM belt speed at the 1800 rpm motor speed. With the 3600 rpm motor and 5" drive wheel that would be around 5700 SFPM belt speed. Just fine for profiling, but a real bugger to finish a knife with. I'd go with the 1800 rpm motor, 2350 will cut pretty good with cheap belts - not ceramic. For ceramic you'd need to put your 3600 rpm motor on with the 5" pulley for enough belt speed to make ceramic belts work good. Al-Oxide belts will be pretty good at that slower belt speeds.
With the 1800 rpm motor if you had a 3" to 3.5" drive wheel to swap out you'd have a nice slower speed for working with finish bevels and finer grit belts. 120 grit belt will work just fine with 2350 SFPM belt speed, but wouldn't go much finer grit at that speed. Will burn metal very quickly and belts won't last long at all.
The above is my opinion and would be interested in other ideas.
Ken H>
With the 1800 rpm motor if you had a 3" to 3.5" drive wheel to swap out you'd have a nice slower speed for working with finish bevels and finer grit belts. 120 grit belt will work just fine with 2350 SFPM belt speed, but wouldn't go much finer grit at that speed. Will burn metal very quickly and belts won't last long at all.
The above is my opinion and would be interested in other ideas.
Ken H>
Yes both are 110vac, single phase motors. I agree that the slower speed,will be better for knife finishing on a thin bale, or pretty much most blades that are not big choppers. I do prefer the smaller 4" type blades. Both motors are the same manufacturer, and I may be aple to swap them if I need a faster speed. I cut my stock on a Milwaukee portaband so not a lot to remove to profile. I plan to use ceramic belts from 60 to 120 grit and then finishing belts. Do you think the 1800rpm motor too slow fo ceramics? Thanks for the reply, I enjoy your YouTube videos!
Thanks for the reply. I was planning on using ceramic belts, regardless of motor speed. I do not understand why they do not work well at 2350rpm. I do not have any experience with a 2x72 grinder. Just in learning stage and trying to learn as much as I can from the experienced makers. I believe I can change out motors fairly easily. I do prefer direct drive regardless of motor speed. I also believe I could change the drive wheel size also. Thanks again!
Here's a link to fairly good info on belts, but I've not had much luck at finding a spec'd belt speed for ceramics. My understanding is 4,000 SFPM is about min for ceramics to work as they should.
https://www.artisansupplies.com.au/knifemakers-abrasive-belt-buyers-guide/
https://www.artisansupplies.com.au/knifemakers-abrasive-belt-buyers-guide/
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JTknives
Blade Heat Treating www.jarodtodd.com
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My grinder use to run at over 9000sfpm and honestly I'm much more happy with it slowed down a max of 4500
Ceramic belts are specced for pressure and speed. You can get consistent fracture of the grain from either. Give the helpful guys at tru grit abrasives a call.
They have more experience with belt manufacturers and their uses than we can hope to have in our whole lives.
Slower belt speed, push a bit harder or take a piece of hardened stock and jam it into the belt across and voila cuts a bit better.
They have more experience with belt manufacturers and their uses than we can hope to have in our whole lives.
Slower belt speed, push a bit harder or take a piece of hardened stock and jam it into the belt across and voila cuts a bit better.
From my personal and modest experience ceramic belts DON T work good on annealed steel .They self sharpen by fracturing only on hard materials .............with lot of pressure and SPEED 
PS . It would be great if someone made a call /say 3M/ and asked what is optimal and maximum allowed speed on ceramic belts
I just found this ...........From Norton
PS . It would be great if someone made a call /say 3M/ and asked what is optimal and maximum allowed speed on ceramic belts
I just found this ...........From Norton
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Good to read ........... https://multimedia.3m.com/mws/media...performance-of-abrasive-belts-white-paper.pdf
Thanks for the reply! After all the great replies I have begun to understand the need for speed with ceramic belts. I will work on that as well as slowing down speeds for finishing belts. Of course I will try them anyway and work towards getting all belts to work for me. Thanks again!
Thanks for the reply and the great link! I learned a lot,from it regarding belt use and types of steel. Typically I use 1084 from NJSB. I currently have a HB Freight 1x30 that moves pretty fast. My ceramic belts work ok, but I do have to be careful to keep the blade cool. I do use a jig, my old hands don't work as well as they used to. But I keep going. Thanks again for the great link!