Grinder speed selection 4 a new grinder

F

Frontier Forge

Joined
Aug 25, 2002
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Grinder speed question.....I just brought a KMG grinder into my shop and for the life of me I cant remember a suggested motor size or speed? Can anyone help? The manufacture doesnt post that info on his site. Either does the retailer.
 
rob will be glad to help. you genrally want a 1 1/2 hp 1800rpm. then by using step pulleys you can make it ajustable.
 
Or if you want to go whole hog, you could install a variable speed motor on it. With that you can vary the speed by the simple turn of a dial. It is more expensive though.
If you opt for a single speed, 1800 RPM, like Laurence said
 
Hello Frontier Forge,

Welcome to the forums!

The sky is the limit as to what you can do for a motor and speed choices.

I have a few questions. Do you already have a motor? if so what is it? What kind of electrical power is available?...ie. 110V , 220V? Home work shop...or industrial building?

You really need speed options for knifemaking...in which you can get from a Variable speed motor, or from Single speed motor with step pulleys to change the speed.

I've surveyed dozens of makers to get a feel for common speeds....only to find that belt speeds vary as much as the makers.

But here are a few guide lines to get you in the ball park with your KMG1.

You should be able to spin the drive shaft on the grinder up to about 3500-4000 rpm for reckless rough grinding with very coarse grit belts...say 30-80grit. This speed is good for profiling, debarking, and gross metal removal. Then you should be able to slow it down to about 1000-2000 rpm for more refined work and finer grit belts...then as slow as 500-1000 rpm for finishing work. These speeds are strickly the rpm of the drive shaft of the KMG1. Consequently for this machine, the drive shaft speed is also the belt speed in ft/min...so if the drive shaft is running 1000rpm, then the belt speed is 1000ft/min.

If you need to get a motor, you can use about anything...however some will work better than others on this machine. I recommend at least 1hp....but encourage you to get 1.5 or more. In a single speed motor, I like the 1725 rpm frames better, and if you use a DC variable speed motor, I prefer the 2500rpm models.


Here is a picture of a step pulley setup:

steppulley2.jpg



I hope this answers some of your questions. Feel free to phone me and I'm sure I can answer about anything that might come up.

Sincerely,
Rob

Shop phone; 614/263-5656 9-5 EST
 
I can buttress what Rob just said, cuz he helped me get my KMG-1 in order. I learned a number of things getting mine set up. You can read all the gory details about problems, vibrations, and cures here.

To cut to the chase, you want a good quality belt with no high spots, and a three-step pulley from Maska Mfg. in Canada. (USA distributors all over) USE NO SUBSTITUTES! They are machined, not cast, and run true and vibration free. I took Rob's suggestion and ordered the 2"/3"/4" version.

I also ordered a 1.5 hp AC motor from Enco for $150 delivered.

Good luck!

Coop (who is only practicing, still...)
 
Rob, Just a question about belt speed. Don't you need
to take into account the contact wheel circumfrence?
My 10" wheel is about 25" in cir. shaft speed
@1000x25"=25000in/min diveded by 12=2080ft/min
is this right or am I doing it wrong. Gib
 
Great question Gib,

Here are my thoughts:

You can determine the belt speed based on any wheel on the grinder as long as you know the speed of that particular wheel. For me, with the KMG1, I use the drive wheel in the back which is 4" in diameter...or 1 ft in circumference. If I know the motor speed and the pulley ratio from the motor to the grinder...then I can determine the drive shaft speed of the grinder. The contact wheel on these machines just coast along with the belt since they are not driven....so a 10" contact wheel will make a partial rev for every rev of the 4" drive roller....4:10...or 40%.

On the other hand if your machine is driven by the contact wheel...such as the Burking, hardcore, coote, griz...etc, then it would be easy to determine the belt speed as you did...given that you know the rpm of the 10" wheel.

I'm sure if you ask 10 different people...you'll get 10 different explainations.....:confused:

Take care,
Rob
 
Rob right you are, I did not know that you used a
small wheel to drive the contact wheel, I was just
thinking in Burr King terms. Thanks for inlighting
me Gib
 
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