Subject: Question on Bench grinder & burning.

From: [email-masked] (Hackwood)
Date: 12 Feb 1997 19:54:23 GMT

I have a 8" bench grinder with a 8"x1" pink Norton stone (fine). The
grinder runs at 1725 rpm. I set my plane irons on the Veratis jig and do a
quick light pass then dunk the iron into ice water with each and every
pass. The edges still turn blue. The stone has been trued with a diamond
point.

Is there any way I can slow the grinder down like you can with those
attachments you add onto routers?  I'd like to run the grinder a lot
slower to avoid the burning.  TIA.

Weasel (tm)

"I have something to say: It's better to burn out, then to fade away"

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From: [email-masked](John F Schaper)
Date: 14 Feb 1997 04:03:42 GMT

>"I have something to say: It's better to burn out, then to fade away"
There is a device that can be used to slow equipment down by reducing
voltage. It's called a VariAC. I've seen them for sale used several
times at reasonable prices. It is a box about the size 4"x4"x4" and has
a cord with plug. The box has a dial for setting variable voltage and a
female socket to plug you equipment cord into.
I bought one that would handle a 15 amp buffer all day. Also note that
paint buffing is done best at 1500 rpm or less to avoid heat buildup,
the slower the better.

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From: [email-masked] (John Jordan)
Date: Fri, 14 Feb 1997 04:32:16 GMT

>paint buffing is done best at 1500 rpm or less to avoid heat buildup,

You didn't say what grit the "fine" wheel was, but a 60 grit, "J"
hardness alum oxide wheel will do the trick. Keep it cleanly dreessed
at all times.

The speed controller will only work with universal (brush type)
motors, not on a bench grinder.

John Jordan

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From: [email-masked] (Richard MacDonald)
Date: Fri, 14 Feb 1997 10:19:23 -0700

On Fri, 14 Feb 1997 04:32:16 GMT, [email-masked] (John Jordan) may

>>female socket to plug you equipment cord into.

A Variac is a variable transformer and when rotated changes the voltage
supplied to the motor. Some motors can be damaged and may burn out windings
if you reduce the voltage below the normal range. Most grinders also use
induction motors which are synchronous and won't change speed just from
reducing the voltage.

Universal motors such as used in electric drills, etc. can often be safely
powered from a variac, but if you value your grinder don't try using it on a
variac.

And, by the way, variacs come in a number of sizes and power ratings. If you
use one that is too small it will probably burn out before whatever it is
powering does. One in a 4 inch cube won't handle very much power and is
possibly too small to run a 1/3 horsepower motor. Check it's amperage rating
before trying to use it. 

Dick MacDonald
dickmac@(delete this to reply)fastservice.com
The extra info is included to foil the automated collection 'bots.