I just finished a KMG clone grinder and have been using some old 60grit norzon belts that I got a couple of boxes of for free. They are 96" x6" I have split them down to 2" wide and I built the tooling arm long so I could use these belts. My question is what is the highest speed that these belts should be run at? When I first ran one of these with a 4" drive wheel at 3500rpm the belt flapped and blew appart. I then tightened the belt a little and used a belt a fair bit before it too came appart at the joint. Am I running these too fast? I am using a slack belt setup. I have $350 worth of finer belts coming Monday or Tuesday and would prefer not to destroy too many of these. I am not using these for knives but I figured this was where the most belt sander experience would be.

You said 3,500 rpm - what's the fpm rate?

At the KMG site they specify

3500 ft/min,
1750 ft/min
800 ft/min.

for the three speed pulley kit

I'm not sure what the max speed rating would be on the belt it's self but most beltsanders that I have used are 1400-1500 ft/min max speed.
If you bought new belts then they may have a max speed on the package but if not I'm sure you could contact the co. and they could tell you, espeacially if they are a high quality belt.

welder19

For rougher grits I run my Bader B3 at close to 6,000 Ft/min, above 220/400 grit I slow down to about 3k, I can run from 1000 to 7400 ft/min.

While I am sure the belts from 3M and Norton are recommended to run slower... I know a maker that runs around 9,000 ft/min. So it may not be the belts fault they are flying apart. Look into the machine, if you find out why and fix it, you will be surprised how fast you can clean up stock at higher belt speeds.

Thanks for the replies. I did the math and the belts are running at 3600 fpm which did not seem to quick and its good to hear that it is not. It may be the age of the belts but it may also be that my spring is too short and I am bottoming it out and then overloading the belt.

how old are the belts ???

i have had issues with old belts in that the joints would fail

Well I got them about 6 years ago and they had been in a shut down shop for at least a couple of years. They might be as much as 15-20 years old. I got my new belts today 80,220.320,400.600. (120 is on backorder) I ran all of them at full speed and had no problems although I found the 600 seemed to cut a little better a little slower. All except the 80 are ceramic, man do they cut fast, I barely missed the 120 grit belts.
I am thinking about finding a way to adjust the belt tension on the fly though certain spots I want the belt really slack others tighter.

not sure why you even bother to get 320, as I found 220 then to 400 is fine,

You may have miss typed when you said all except 80 is ceramic, as I have never seen fine grits in ceramic. But if thats not a typo, then where did you find those?

I bought them from my local industrial supply house. EN tool in Stoney Creek Ontario. The belts are made by VSM, I spoke to the regional Salesman from VSM and he was the one that suggested getting the ceramic belts. I will post the part numbers tomorrow when I am down at the shop.

most ceramics outlast the other type many times, AO leaves a fine finish but wear so fast, Love to get 220 and 400 in ceramic too , thanks !

most ceramics outlast the other type many times, AO leaves a fine finish but wear so fast, Love to get 220 and 400 in ceramic too , thanks !

steve see Abrasive belts atarting with size 2x72-9

3m regallite( spelling) ceramics in fine grits about 2/3 of the way down the page

I just checked the belts and then VSM's web site this morning and I was incorrect the belts I have in the finer sizes are not ceramic. My 80 grit is ceramic.
The finer grits are something that VSM calls compactgrain. They are strange in that when I pulled out the 400 grit I thought they were printed wrong the belt felt like it was 80 grit but when I used it, it was definately the finer grit.

Never noticed that before, found the 220 in 3m Regalite and Norton 823 and 984 thanks.

Never noticed that before, found the 220 in 3m Regalite and Norton 823 and 984 thanks.

actually i checked into after your post..........let me know if you get some how they work out for you...........john

I just restocked all my belts 2 weeks ago, it may be a while before I re order.

I just restocked all my belts 2 weeks ago, it may be a while before I re order.

understood thanks

I'm working on building a belt grinder as well. Im using a 1hp motor rated at 3450rpm. How do i go about calculating the ft/min. Is there an equation that i plug the roller size and motor speed numbers into??

You need to determine how fast the drive wheel is turning. (pi)*(diameter of the drive wheel in inches)*(drive wheel RPM)/12 = surface feet per minute, assuming no slippage. There'll be a little slippage, but there shouldn't be enough to worry about.

Drive wheel speed depends on your drive setup. Is it direct drive? Pulley driven?

Matt- I plan to use a shaft mounted drive wheel that is 2.25" in diameter. Motor speed is 3450rpm with a 5/8" shaft. If i calculated right that should equal about 2031 fpm. Is that right? Is 2031 fpm a decent midrange number? I will be unable to adjust speed unless i end up applying a step pulley system. I do not intend on doing any heavy duty stock removal. I'll be using it primarily for shaping and polishing knives and the like and i try to forge my blades as close to finished shape as possible. Thanks for the help.

John, it's definately the age of your belts that is the problem.

John, it's definately the age of your belts that is the problem.

Must be why I'm falling apart! :wacko:

Must be why I'm falling apart!

Just can't run you at 3565 SFPM LOL

The faster they run the harder they act and less aggressive as noticed in the fine belts. Run the recommended surface feet per minute and then make your adjustments. As stated above there are to many variables to give cast in stone advice.

The faster they run the harder they act and less aggressive as noticed in the fine belts. Run the recommended surface feet per minute and then make your adjustments. As stated above there are to many variables to give cast in stone advice.

No, no, no! "Cast in concrete, chiseled in stone". :blink:

I have found that slightly slower speeds in course grit give a more agressive result ,It feels like the grains are having time to "bite". but I think that your own personal variable of applied pressure makes a big difference to this as well.