[TowerTalk] Grinding hole in thick steel plate?

Tue Sep 8 17:54:31 EDT 2015

The company I found locally has a water jet set up and If I reshaped the hole there was too much metal gone for my comfort.   We could have welded in the holes...but after discussion we decided to start over and it will be perfect this time. And half the cost of the original job!  

The water jet system is quite the machine!!

Thanks...
Rich

-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of Roger (K8RI) on TT
Sent: Tuesday, September 08, 2015 1:41 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Grinding hole in thick steel plate?

Not the cheapest route, although that depends on the shop and the cost of the steel plate, but starting over with a set of tolerances up front in thousandths of an inch permissible, or fractions like 1/64th? should 
give the strongest, safest, and most accurate base.   It's really the 
best all around route.  Many shop tolerances are 1/8th inch unless otherwise specified.  If they know the bolts are already set in concrete, they will know the need for close tolerances.

I really messed up on my tower base for the LM-470.  I used to be able to take measurements like that and come out really close, but this one had the top hole on one ear almost far enough to drill a new hole. I'm going to have to start hiring more of this stuff done.  Measuring once and cutting twice is no longer sufficient <:-)  Had I remeasured before each additional tack weld, I'd most likely been OK.  As I can make a new ear in less than an hour, cut the old one off. bolt the new one on and then weld it to the base in another hour or so, I may just go that route.

73 and good luck on this one.

Roger (K8RI)

On 9/8/2015 3:48 PM, Rich Hallman - N7TR wrote:
> I've decided to have another machine shop build me a new plate.  Trying to fix this one was going to be an issue on several fronts.
>
> Thanks again for all the info and ideas...   Rich
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of 
> Rich Hallman - N7TR
> Sent: Monday, September 07, 2015 3:38 PM
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Grinding hole in thick steel plate?
>
> Thanks for all the ideas so far.   If I need to I may take the plate to a fabricator and see if they can mill these to the correct locations, but I would rather do this at my house for now.    For those who asked...The plate is 3/4 inch thick steel plate.   The holes are 1 1/4 in diameter for the 1 1/8 inch all-thread anchor bolts.
>
> I have purchased and should be here tomorrow...the below Die Grinder as well as several 1 1/2 inch diameter 1 inch long carbide burr bits.  These are double cut.  Would a single cut be better for this need?
> http://www.amazon.com/gp/product/B00FDLB9OC?psc=1&redirect=true&ref_=o
> h_aui_detailpage_o03_s01
> http://www.amazon.com/gp/product/B00ECMMOW4?psc=1&redirect=true&ref_=o
> h_aui_detailpage_o01_s00
>
> I wonder if I need to get a 3/4 inch or 1 inch diameter carbide burr bit?
>
> Thanks....
> Rich
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces at contesting.com] On Behalf Of 
> Rich Hallman - N7TR
> Sent: Monday, September 07, 2015 11:33 AM
> To: towertalk at contesting.com
> Subject: [TowerTalk] Grinding hole in thick steel plate?
>
> 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>
> http://www.qrz.com/db/N7TR
> Telnet: dxc.n7tr.com N7TR DXCluster
>
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-- 

73

Roger (K8RI)

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