[TowerTalk] [Bulk] Grinding hole in thick steel plate?

Grant Saviers grants2 at pacbell.net
Mon Sep 7 20:39:07 EDT 2015


Rich,

The most available solution is to take it to another machine shop and 
have them re-bore the holes in the right spot.   This can be easily done 
on a manual mill with a single point boring tool and boring head, since 
you already have a lead-in hole that is close to true position.  A 
backyard/garage machinist and Bridgeport can do this.  Best to use Dykem 
to color the surface, clamp the parts together for best average fit and 
carefully scribe the fix.  A decent machinist will get it true within 
1/32" or better to the scribed arc, since you have a known diameter target.

Grinding out 1/4" x 3/4" will be painfully slow and hard to get 
straight/perpendicular.  Several good carbide burrs and a 1/4" die 
grinder will set you back more than the hour or two of mill time to do 
it right.

Grant KZ1W



On 9/7/2015 11:33 AM, Rich Hallman - N7TR wrote:
> I had a ¾ inch steel plate made up that will be used to retrofit a HDX589 base foundation to a HDX572 base.   After giving both bases to the machine shop and asking them to make sure all of the holes are exactly the same location as the base, some of the holes are 1/8 to ¼ inch off.   I had a major issue with this machine shop so I will not take it back for now.
>
> I wanted to see what others have done to grind out holes in thick steel plate.
>
> I was looking at the Carbide Burr bits and getting a ¾ inch burr bit to see if that would grid enough from the hole so it would then fit the bases.
>
> The holes are pretty close....so I thought grinding them out would be the best solution for now.
>
> Any thoughts?
>
> Thanks....Rich
>
> Rich N7TR
> ex KI3V, N3AMK, WB3JOV
> www.n7tr.com<http://www.n7tr.com>
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