Uncle Wong Rant

[peter nap]

I bought a half dozen letter C Drill Bits from a local tool supplier today and didn't take my Mic.

I need them to make the primer pocket in some bushings I put in 50 BMG cases.

Letter C is .242. Mt last one from McMasters that I broke was .242.

These are .247.

I'm as mad at myself as them. I drilled it ASSUMING they were correct and the primer falls out.
Won't make that mistake tomorrow.

[deltaenterprizes]

I had the same problem making a bullet mold. I drilled holes for the alignment pins and then used a 1/4'' reamer when I put the .251'' pin in it fell in.
I just made some .252'' pins.

[peter nap]

I had the same problem making a bullet mold. I drilled holes for the alignment pins and then used a 1/4'' reamer when I put the .251'' pin in it fell in.
I just made some .252'' pins.

Heard that..I think this case will get SPECIAL primers.:mrgreen:
http://www.made-in-china.com/image/2f0j00WBKtDVRyhQqCM/PTFE-Thread-Seal-Tape-Teflon-Tape-12MS.jpg

[bohica2xo]

Well, if the drill itself measures .247...

The supplier is selling some awful recycled scrap. Is the drill shank marked in any way?

There is no standard ".247" drill. The "C" drill is .242, and the "D" is .246 Even a 6.25mm metric drill is .2461 & 6.3mm is a .248 Nothing in standard diameters is .247

Having said that, a drill can easily be ground to cut larger than it measures. Getting a .242 drill to cut .247 in brass is not hard at all.

If you want a great selection of drill bits in sizes never listed, buy a Harbor Fright "grab bag" of drills. When setting up an automatic grinding machine, scrap drills get made in all kinds of interesting diameters. I have several .510 diameter drills in my box, right alongside some .372 diameter drills - that are marked "3/8".

It would seem that a reamer would be a better choice for size control in a close tolerance hole like a primer pocket.

B.

[peter nap]

Well, if the drill itself measures .247...

The supplier is selling some awful recycled scrap. Is the drill shank marked in any way?

There is no standard ".247" drill. The "C" drill is .242, and the "D" is .246 Even a 6.25mm metric drill is .2461 & 6.3mm is a .248 Nothing in standard diameters is .247

Having said that, a drill can easily be ground to cut larger than it measures. Getting a .242 drill to cut .247 in brass is not hard at all.

If you want a great selection of drill bits in sizes never listed, buy a Harbor Fright "grab bag" of drills. When setting up an automatic grinding machine, scrap drills get made in all kinds of interesting diameters. I have several .510 diameter drills in my box, right alongside some .372 diameter drills - that are marked "3/8".

It would seem that a reamer would be a better choice for size control in a close tolerance hole like a primer pocket.

B.

Nope, no markings at all. The shank measures .247.
A reamer would be better but I looked on McMaster and couldn't find one. They all seemed marked in ,010 steps.

I'm sure they have them, I just have trouble navigating their site, so I figured I'd get a few bits locally.
These bushings are steel, not brass.

[bohica2xo]

McMaster is not that hard to navigate, if you follow a "drill down" approach...

Search for "reamer"

Select "Chucking Reamer"

Select "Straight flute"

Click on the box "Select inch size"

Scroll down, reamers are listed in .0005 increments.


If I need more than a couple of reamers, I buy direct from L&I:

http://www.lavallee-ide.com/

I have a hard time buying imported cutting tools if given a choice.

Same goes for drill bits. I prefer to buy from New York Twist Drill http://www.newyorktwistdrill.com/ and get first quality US made drills. Michigan Drillhttp://www.michigandrill.com/ is also a reliable source.

A cheap twist drill in a production setup can cost ten times what it might have "saved" in the purchase price. I have NYTD tools in my box that are decades old, with plenty of life left.

B.

[lathesmith]

Nope, no markings at all. The shank measures .247.

If the shank measures .247, those drills should drill a hole more in the .250 range (1/4)". Drills should taper a bit from point to shank, to give a slight amount of drilled hole clearance.

lathesmith

[peter nap]

If the shank measures .247, those drills should drill a hole more in the .250 range (1/4)". Drills should taper a bit from point to shank, to give a slight amount of drilled hole clearance.

lathesmith

The new ones I got drill dead on at .242. Thankfully, I didn't waste but one shell.
No more Chinese stuff.