[TowerTalk] Fwd: Re: Mast slippage

[Kim]

Yes, good stuff, Charlie!  Good bit.  Small hole, then a bigger one.  Slow.  And oil.  Works great and was not strenuous.

73, Kim - WG8S

> On 07/29/2020 2:04 PM Charlie at thegallos.com <charlie at thegallos.com> wrote:
> 
>  
> Thanks, I meant to send it to the list, oops
> 
> —  
> Charlie
> 73 de KG2V
> Http://www.thegallos.com
> 
> 
> > On Jul 29, 2020, at 2:58 PM, Grant Saviers <grants2 at pacbell.net> wrote:
> > 
> > Charlie sent this off list to me, great advice.
> > 
> > Grant KZ1W
> > 
> > 
> > -------- Forwarded Message --------
> > Subject: Re: [TowerTalk] Mast slippage
> > Date: Wed, 29 Jul 2020 11:43:48 -0400
> > From: Charles Gallo <charlie at thegallos.com>
> > To: Grant Saviers <grants2 at pacbell.net>
> > 
> > Geez,
> > How big a hole are you planning on drilling in that poor mast that you need a rotabroach?
> > 
> > Let's face we are probably talking somewhere in the 3/8-1/2 inch size range (I could not find a manual to see the size of the hole in the clamp)
> > 4130 is tough, but it isn't THAT bad (I drill a lot of 4140 pre hard)
> > 
> > Get a good 135 deg split point cobalt drill. something like https://www.travers.com/nachi-cobalt-jobbers-length-twist-drill/p/01-021-332/
> > don't want to spend that much, try
> > https://www.travers.com/ttc-surface-treated-jobbers-length-twist-drill/p/01-001-232/
> > or
> > https://www.travers.com/triumph-hss-jobbers-length-twist-drill/p/01-331-032/
> > 
> >  4130 is .30% carbon, which puts it on the border between mild and alloy steel  You probably want to keep it < 70sfm - which, for a 1/2" bit means 535rpm.  Let's be conservative, and keep it down to 400rpm or so
> > 
> > Use a coolant (cutting oil, not lubricating oil), and just go drill it. Use a simple jig to start things because pipe is round.
> > 
> > If you aren't getting a good chip, because you can't apply enough pressure, SLOW DOWN
> > 
> > You can also pre-drill with a smaller bit (why I recommended a split point, less need to pre-drill, and a 135 deg has shorter cutting edges than a 118, so less pressure needed )
> > 
> > Charlie
> > 
> > 
> >> On 2020-07-29 10:41, Grant Saviers wrote:
> >> Ron,
> >> I shouldn't generalize, as it is possible to mag drill on a tower as
> >> you are doing.  But rigging my 60# mag drill on a tower with a custom
> >> fixture and using Rota-Broach drills is not in most ham skills and
> >> toolboxes.  Maybe the fact my mags get heavier every year is another
> >> factor ;) .
> >> Grant KZ1W
> > 
> > -- 
> > 73 de KG2V
> > Charles Gallo
> > http://www.thegallos.com
> > _______________________________________________
> > 
> > 
> > 
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> > 
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