Drill & tap, Midway, & my dumb mistake...


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jstein650
February 11, 2014, 11:45 AM
So my drill & tap set came in and I proceed with my Mauser scope mount project. I'm using the standard 6-48 tap and go ahead and drill my hole. The envelope says the drill is a #32, which is supposed to be 0.116", right? When I go tap the hole, I realize it is completely oversized! Frantically, I measure the drill to find it's actually 0.140". It honestly never occurred to me not to trust the packaging. Lesson learned. I have to wonder if anyone else has had this happen. I contacted Midway, and recounted the story. They gave me the standard "..you can return said defective product for credit, blah blah.." A little miffed, I responded that that wouldn't really help my situation and maybe they should send me the right damn drill bit. They then said they would as a "one time courtesy".
Anyway, I guess the lesson is measure first, drill later.

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fguffey
February 11, 2014, 12:09 PM
The envelope says the drill is a #32, which is supposed to be 0.116", right? When I go tap the hole, I realize it is completely oversized! Frantically, I measure the drill to find it's actually 0.140". It honestly never occurred to me not to trust the packaging. Lesson learned

There is Fastenal , GRANGER ETC., you have one hole too large to tap with #6-48 threads.

https://www.fastenal.com/web/home

Fine threads in thin metal increases the number of threads engaged. Some add a hole, others weld the hole and there is a larger diameter tap with fewer threads.

F. Guffey

jstein650
February 11, 2014, 12:59 PM
I think I'm going to go with a #8 for that hole. The other ones at the rear are OK.

BBBBill
February 11, 2014, 01:47 PM
8-40 are better anyway IMO.

LeonCarr
February 11, 2014, 01:54 PM
8-40s are better especially if that Mauser is gonna be rechambered for a cartridge with heavy recoil. Might be a blessing in disguise :).

Just my .02,
LeonCarr

jstein650
February 11, 2014, 02:09 PM
"Might be a blessing in disguise ." - You may be right. No, gonna keep it in 7x57. This was a project gun from way back.. It's a 95 Chilean. (I wish I would have gotten two when I bought it, I'd have kept one original) Anyway, barrel already been cut & crowned, the scope mount is forward, LER, 'scout' rifle idea.

Zeke/PA
February 12, 2014, 10:56 AM
I think I'm going to go with a #8 for that hole. The other ones at the rear are OK.
"8-32 for THAT hole"? Oh Boy! How are you drilling to start with? Drill Press, Bridgeport?? Consider letting a professional doing your drilling and tapping!

bmnloader
February 12, 2014, 11:07 AM
You can install a helicoil in that hole but it'll take about another $50 to get a kit. You can get them at Mcmaster-carr or any decent fastener supply house.

jstein650
February 12, 2014, 07:04 PM
"8-32 for THAT hole"? Oh Boy! How are you drilling to start with? Drill Press, Bridgeport?? "

8-40. The drill they sent turned out to be about a #28, or 0.140", perfect for an 8-40 tap. Drill press, maybe not a professional jig to hold the piece, but pretty solid, and seems to work if I go slow.

gamestalker
February 18, 2014, 01:55 AM
I honestly don't think a helicoil would be the right direction to go in for a firearm, especially for optic mounting systems.

GS

JoePfeiffer
February 18, 2014, 10:46 AM
I honestly don't think a helicoil would be the right direction to go in for a firearm, especially for optic mounting systems.
Why not? I've never heard of a thread repair application it wasn't good for, so I'm curious why this would be one.

thegiff
February 24, 2014, 05:01 PM
Helicoils aren't made in 6-48 though.

sansone
February 25, 2014, 08:37 AM
be careful tapping those holes, use lube, go slow and back out often (re-lube each time) if you break a tap in the hole you will enter a small piece of hell :evil:

JoePfeiffer
February 26, 2014, 01:32 AM
Helicoils aren't made in 6-48 though.

That's certainly a good reason not to use one here! The post I was responding to seemed to have a more general concern with them, however...

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