A cutting torch works as a great drill for me.
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heaven knows we need them down here!
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----- Original Message -----
From: "Jim Thomson" <Jim.firstname.lastname@example.org>
Sent: Wednesday, March 24, 2010 3:38 AM
Subject: [TowerTalk] Drill bits
> Date: Wed, 24 Mar 2010 04:11:35 +0000
> From: Guy Molinari <email@example.com>
> Subject: [TowerTalk] Drill bits
> To: <firstname.lastname@example.org>
> Message-ID: <BAY129-W14493CAE03D374CEF078CDE8250@phx.gbl>
> Content-Type: text/plain; charset="Windows-1252"
> Hi all,
> I don't know why this is so hard. I'm trying to drill out some hole
> on some 3/8" steel plates that I'm going to have galvanized. I bought a
> 13/32" drill bit and it worked great for about 10 holes or so. The
> problem is that I have about 140 more to go. Any recommendations on a
> good quality drill bit?
> Guy, N7ZG
> ## 13/32 = .40625" 3/8= .375" .40625- .375 = .03125" That's
> a big difference in diameters... even with galvanizing. I think the
> galvanizing is only aprx .004"' thick. If these holes are for 3/8"
> bolts, perhaps you should be using a 25/64" drill
> bit?? I have tried them all... and was not impressed with the
> titanium bits. The packaging on the cobalt bits warns of not overheating
> cobalt bits. I worked on loan at our tool crib at work one summer, abt
> 30 yrs ago. The Dormer brand, and also the Butterfield brand HSS drill
> bits [ both made in the UK] didn't fare too well. I ended up
> lately, using Zirconium bits. They appear to last a long time, and also
> have THREE sides to the shank, so they never slip in a chuck.
> I don't have my book handy either, but for 13/32 holes in 3/8" thick mild
> steel plate,,,, it has to be slow... I think around 300 rpm or less.
> How hard is the plate ?? As noted, you need lots of cutting fluid.
> Overheat the bit.. and it's toast, it will have lost it's temper....
> Plan B is have em all punched. I bought one of these small roper
> whitney #5 jr compound hand punchs for 1/8" thick and less...
> 6061-T6.... but they only go up to 9/32" I have a requirement to
> punch a lot of 3/8" holes in 3/8" thick 6061-T6 plate.... so bought a
> bigger roper whitney punch.... think it was a model #16 or #17..... with
> a 3.5" throat. Think my new punch is 7-9 tons. It will punch
> holes up to 9/16". When punching holes in 6061-T6.... only 60% of the
> tonnage is required VS mild steel of the same thickness.
> If your local machine shop wants a small fortune to punch 140 x
> holes..... I would be inclined to buy/beg/borrow a larger roper whitney
> punch. My new one has a 25" steel forged handle.. and is bench mounted.
> It's a cam action arrangement. The secret to using the punch is to
> bring the work piece up into the center punch mark.. and not the other
> way around..... but this is not always possible. I'm sold on punchs.
> We used electric-hydraulic punch's at work yrs ago, and punched literally
> hundreds of 3/8" holes in 1/4...3/8" thick mild steel. If ur just
> drilling 20 x holes or less... a drill bit will suffice... but with 140 x
> holes.. a punch will make short work of it. Drill presses are slow and
> cumbersome as is. Material has to be precisely aligned, everything
> clamped down, check, and make sure nothing shifted a fraction of a mm.
> Then add lubricant, drill, then clean up the mess.. undo 3 x clamps, and
> repeat for next hole. Bottom line is... I can pu
> nch 15 x holes faster that I can drill just one. The punched holes are
> always dead on, and clean holes.
> The punch must have the correct diam die for the thickness of steel to
> be punched though. The thicker the steel, the dies have to be oversized
> even more... or they will bind. Oversized dies will not work on thin
> stuff... you will get ..'roll over' on the edges. I just came back
> late today from the metal store.. with a trunk full of 6061-T6 3/8"
> plate.. for boom to mast plates... and also a bunch of 4" channel
> 6061-T6. [ 40m brackets, since the F-12 flat plates ones all bent
> slightly, 340N] The new punch will make short work on the new plates.
> I have also used punched holes.. as pilot holes, that are in turn drilled
> out to a bigger diam. This is in cases, where I didn't have the correct
> size large punch + die... or the larger punch was beyond the tonnage
> capacity of my punching tool.
> I wish I had bought one years ago.
> Later... Jim VE7RF
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