9" Disk (flat) grinder

jtdesigns

New Member
Okay, I am new to the forum and somewhat new to knife making but have so far have made 2 KMG clone grinders and 1 EF-48 clone horizontal grinder. I am starting to get a full shop built up and recently purchased a 9" disk from Rob at Beaumont Metal Works. I would like to do one of the following to make a flat disk grinder:

1.) Use an existing 3/4 to 1 hp motor with a cheap variable speed pedal but don't know how this will work.

2.) The other option is to turn one end of a piece of 5/8" drill rod down to 1/2" (have metal lathe) and attempt to chuck it up in a Freud 3 1/4 hp variable speed router (soft start). This would seem like a good idea but don't know if it will over amp the motor trying to start spinning the 9" aluminum disk. Any thoughts on this would be appreciated.


Jeff Tate
JT Designs
 
Also, not excited about spending $600 dollars for a VFD motor and controller. Managed so far to make my own equipment without a great deal of money invested and don't have any plans to start spending a lot to make it happen. Anyone have any ideas or sources to purchase a more economical motor set up. I do have a tread mill I bought for $20 but not very knowledgeable about the wiring and such.
 
The router is not a good idea. Consider that the lowest speed for yours is somewhere around 8000 RPM. Spinning a 9" disc that fast is asking for trouble somewhere.

Don't know about the pedal setup. I do know that you can't use the variable speed controls designed for one type of motor on another type of motor (motor with brushes vs. one without).

There are some possibilities with the treadmill motor, and even some nice threads on successful disc grinder projects using one.
 
I plan on using a cheap 1hp motor and getting a madrel and 4 step pully system like tracy sells.
 
Okay, I am new to the forum and somewhat new to knife making but have so far have made 2 KMG clone grinders and 1 EF-48 clone horizontal grinder. I am starting to get a full shop built up and recently purchased a 9" disk from Rob at Beaumont Metal Works. I would like to do one of the following to make a flat disk grinder:

1.) Use an existing 3/4 to 1 hp motor with a cheap variable speed pedal but don't know how this will work.

2.) The other option is to turn one end of a piece of 5/8" drill rod down to 1/2" (have metal lathe) and attempt to chuck it up in a Freud 3 1/4 hp variable speed router (soft start). This would seem like a good idea but don't know if it will over amp the motor trying to start spinning the 9" aluminum disk. Any thoughts on this would be appreciated.


Jeff Tate
JT Designs

The only variable speed you might get out of a pedal will be for a DC motor. This won't work with an AC induction motor. The problem might be finding one for that big of a DC motor that will give you the speeds you want.

As for the router, as rob said, it's probably going to be way too fast to be of any use (safety might be a concern as well)

A treadmill motor may work, but since they are typically of an open design, you will have to keep the dust blown out of it.


Your best bet is going to be a VFD for an THREE PHASE AC motor or a variable control for a DC motor. If you already have the DC motor, you could probably find a used DC controller for fairly cheap. Unfortunately, there really aren't any "cheap" VFDs that are worth having, IMO.

You could probably get set up with a VFD for a 1HP motor for less than $400 though.

I've seen the KBAC-24D VFDs priced around $255, and you can likely find a used 1HP 3ph AC motor for less than $100 if you look hard enough.
 
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Hello,
Is the variable speed a must? I have a 9" disc I built myself with a 1725 rpm 1hp ac motor, with a reversible drum switch. Served me well for many years!
Clint
 
Baldor has a motor that is AC 1/3hp 1140 rpms, and works good as a disk sander. I also use it at times with a on & off foot switch without any problems.
 
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He sure does. He serves as inspiration for me as I too would rather build my own (when possible) than to pay for questionable quality from faceless companies.
 
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