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Re: [Emc-users] Machining question Gene Heskett Wed Jul 22 14:01:54 2009

On Wednesday 22 July 2009, [EMAIL PROTECTED] wrote:
>A fabricated bushing as mentioned, split if need be.  Indicate the work if
>a jaw chuck is used,
>
> and
>
>A bushing at the left end of the headstock to hold the rod true is advised.
>
>That said,  a three foot long piece of 3/8th rod is not likely to be
>straight.
>EVER.
>
>CalG
>
Even supposedly good acme stock isn't straight. I bought a 3 foot piece of 
1/2" 10tpi from McCarr that had a 3/16" bow in the middle right out of the 
packing, which showed no signs of miss-handling.

So I rigged up a length of plank with risers on each end, put a V in the 
middle of the risers, cut a similar v in the end of a handy hunk of cherry, 
and whaled away at it with a 4 pounder until I couldn't see any noticeable 
wobble when I rolled it in the v's.

Then I cut it to a swag length and turned one end to take my homemade 
couplings.  That was when it was still on the back of the post on my 
micromill.  Even with a 425 motor on it, I could only get about 5 pounds of 
downforce due to racking of the head on the post binding it up.  So I used the 
rest of it to make a new, longer screw, built a new overhead to hold the motor 
and the belt drive to the nut(s), that bolted to the sides of the post, turned 
the gear head 90 degrees to expose some of the heads casting in front of the 
post, and planted the end of the screw in a hole in the casting about 2.25" in 
front of the post.  The motor now drives the nut(s) and the screw rises and 
falls with the head.

I can now push the down button on the keyboard with bathroom scales under the 
spindle & make 155 pounds when the 425 cogs the first time. I'd say a 31x 
increase in the available force was worth it, as now I can program to drill 
holes and if the steel isn't too fancy, just drill the hole(s) at a very good 
feed rate.

Fancy steel, like in a 10" Avanti (Freud) table saw blade a inch & a half from 
the spindle hole, I still have to use EDM for.  Boy are those holes neat & 
clean. :)  But darn is it noisy, the last EDM power supply I built is about 80 
volts, 4 to 5 amps and 10 uf.  With a playdough dam around the hole, and 1/4" 
of kero in it, my ears were ringing noticeably by halfway through the first 
one, so I went after my gun muffs for the rest of that job.  I'm already deaf 
enough from wearing out rifle barrels in past years.

I probably should find a smaller capacitor which would be quieter & raise the 
frequency too & now that the old analog GE transmitter has been shut down 
forever, I may go see if I can dig around in the spares. :)

Darn, get me started and I don't know when to shut up. :)

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
The NRA is offering FREE Associate memberships to anyone who wants them.
<https://www.nrahq.org/nrabonus/accept-membership.asp>

Certainly there are things in life that money can't buy,
But it's very funny -- did you ever try buying them without money?
                -- Ogden Nash


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