Direct drive is much better if you are buying a new grinder and there are so many choices.

LARRYZ10

LARRYZ10

Joined
Feb 6, 2010
Messages
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If you are buying a new grinder I would recommend that it have a gas piston tensioner or a ratchet apparatus for tension. I would also recommend that it have at least a 4 inch tracking wheel for smoothness. Most important to me is a second tool arm slot because I have several special tool rests for different jobs. Lastly it should be a direct drive with a good dustproof VFD preferably a KBAC drive.
Does this mean that I am going to get rid of my KMG grinder? No, because it is no longer a KMG grinder. I have made many modifications mostly from the advise of Matthew Gregory who makes great knives and has made super modifications to his problematic KMG grinder.
I made a short poorly filmed video of my Kmg at half speed ( about 2000 SFM) with a penny balanced on the tool arm. The penny would surely fall off at full 4000 sfm but I filmed this for an illustration only. I continue to make what I consider professional grade knives with this grinder. If I were starting now from scratch I would buy a Tag 101, a TW-90, or a Northridge grinder. There are other good grinders I have not mentioned. My best opinion... Larry
 
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Hey!! I just made one of those videos today. Def liking the direct drive 1000% better than my first 2x72 next to This one with pulleys and jack shafts. This is pushing it to at least 3600 SFPM I have the vfd set to max speed with 3600 rpm motor and 4" drive wheel.

Just got this one up and running today.

 
pleasanthill said:
.... This is pushing it to at least 3600 SFPM I have the vfd set to max speed with 3600 rpm motor and 4" drive wheel.
Click to expand...

Just a note for the record:
Most VFDs go from 0-120Hz ( or 0-200%). In that setting, when at "max" you would be running 7200RPM which is roughly 7200SF/M on a 4" wheel. If it is set for 0-60Hz or 0-100%, then you are correct that it is running 3600SF/M
 
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I'll have to check Stacy. No way I'm running 7200 rpm. Used enough stuff to know I'm not going that fast. My old grinder runs slightly faster and I know it's not going that fast. Not near the power, but a little faster.
 
Yup is was on 1x 2x is waaay faster.

What is the boost trimpit for? Book doesn't explain boost.
 
Don't take this for fact, but I believe the "boost" is to add a bit of RPM when the drive detects the motor slowing down under use. Once back to the set speed, it goes back to the normal regulation parameters. You might consider it the reverse of the deceleration trim pot that keeps the motor from briefly stopping when you lower the speed. A call to the tech line for the VFD maker would get you a more technical answer.
 
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