Re: [ATM] Big Ol' Grinding Machines

[Mark Cowan <toolontop@yahoo.com>]

Stuart:

Well, yeah, you can at least turn the system with a
smallish motor that's geared down enough but I prefer
not to burn up the motor - I figure around 1/2 hp on a
20" setup...  What'll kill you is overloading a
bearing that was made for thrust with a side-force.

What I meant by "off-center" is indeed the overhang. 
This is going to increase with size as well as the
power needed to turn the workpiece - I use a lot of
weight on a fixed spindle setup that has 18" capacity,
but it's based off an auto torque tube shaft.  Bigger
laps = more weight.  The power needed to use a 11" lap
on a 16" mirror under optimum polishing conditions at
42rpm is enough to make me very glad for the machine
;) but I can't say what it is exactly.  I am going to
be swapping out my 2/3hp motor for a free 1/4hp one on
the small machine and using the bigger one on a 28"
version.  The big motor never seems to be laboring
under the load. 

Cheers,
Mark

--- Stuart Hutchins <stuart452@earthlink.net> wrote:
> Mark,  Thanks for the quick response. That is
> valuable information.  The
> only technical point of reference I have on machine
> grinding/polishing is
> the Mirror-o-Matic design by Dennis Rech.  He uses
> 1/4 to 1/3 horsepower ac
> motor and I believe he turns a 20 inch table on a 1
> inch shaft.  I can back
> the torques out of that data.
> 
> By "off center forces" do you mean the overhang
> moments on shaft or
> bearings?
> 
> In polishing/figuring what is the force required to
> push a 16 inch lap?  My
> experience stops at 8 inches, and I never measured
> the drag.
> 
> Stuart



	
		
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