Where can I buy a counterbore for a 8-32 lockbolt with a 3/8" head?

[Rolf]

Where can I buy a counterbore for a 8-32 lockbolt with a 3/8" head?

Best regards
Rolf

[BOB HILL]

Rolf, I fashioned one from an old 3/8 spade wood bit. Works pretty good when used in drill press.
Bob

[P.W.Berkuta]

Where can I buy a counterbore for a 8-32 lockbolt with a 3/8" head?

Best regards
Rolf

Funny you should ask this question at this time --- I just countered bored my two 3/8" lock bolt heads two days ago. I did not have a counter bore that size, go figure. I took a buggered up 3/8" drill bit and ground the end to a 0.167"(approx) nib, squared the face of the bit and then ground the clearence angles on the drills flutes. It worked but it MUST be used with a drill press or it will "wallow" out the counter bore. AND --- last night I had a "vision" of making a real 3/8" counter bore with provisions for replaceable piolt guides. I've made them before to match the  internal lock screw heads so no big deal. I have a lathe & mill. May be I'll take some pictures when I make it then post them. Good project for a rainy day which today is.
 

[bob in the woods]

You beat me to it !   I too made one from a spade bit. It works fine

[Acer Saccharum]

Cutting brass is easily done with a scraping action, so a spade bit would work fine. It also won't grab.

Just make sure the pilot is a good fit in the hole, and you will have no issues.

[FDR]

Buy one here:  don't forget the pilot

http://www.use-enco.com/CGI/INPDFF?PMPAGE=69&PARTPG=INLMK32

Fred

[chubby]

I will chuck my .167 pin or cut off bolt and place in drill press bring down and line up hole n clamp pc. to table then put in 3/8 multable flute end mill and cut pocket works great can make all sizes.  Chubby

[Rolf]

Sorry, I should have spesified I want to counterbore  in steel.

Best regards
Rolf

[Acer Saccharum]

0-1 tool steel can be turned, filed/milled with cutting teeth, then hardened.

[Scota4570]

"0-1 tool steel can be turned, filed/milled with cutting teeth, then hardened."

That is how I do it. Actually it only needs one cutting edge.  Unless you are very carefull you will only get one working edge anyway.  I make mine like a half reamer,  sometimes like a paddle bit with a pilot.  I then relieve the cutting edge/edges with a 3-corner file.  I harden then draw back to a straw color.  Then I touch up the cutting edge with a Dremil cut off wheel.   

[sqrldog]

Rolf
Try MSC Industrial supply 1 800 645 7270 they list piloted counterbores. The pilots are interchangeable for different size holes that you might want to use the counterbore on. Hope this helps. Tim

[P.W.Berkuta]

Sorry, I have spesified I want to counterbore  in steel.

Best regards
Rolf

Here are two 3/8" counterbores that I just made out of O1 drill rod that are hardened & tempered this morning one has 12 teeth and the other has 6.  I also show two very small counter bores for internal lock screws and three mortice chisles that I use for thimble/trigger guard tang inletting. They are 0.55", 0.65" & 0.85" wide. They work very well.

[Scota4570]

Nice work.  I think I have "dividing head" envy. 

[davec2]

Scota4570,

You can do most of what you can do on a dividing head with a spin fixture....$46 bucks.....

http://www.grizzly.com/products/5-C-Spin-Index/G5649

I actually have both and use the spin fixture most of the time because it is so much simpler to set up.

[Bob Roller]

Nice work.  I think I have "dividing head" envy. 

A counter bore is easy to make from 0-1 drill rod of whatever diameter needed. For me,
I make a short hollow mill with 4 cutting edges and the hole thru it is usually .187. and
before it's hardened I install a set screw to capture the guide rod that goes thru the hole.
These cutting edges do NOT have to be laid out on a spin fixture and can be "eyeballed"
to be as good as needed for a one shot job. Recently I took a non center cutting,made in
China 3/8" end mill,annealed it and bored it out to .187 and then reamed it with a three flute
carbide end mill to the depth I wanted. Reheated it,quenched in water and left it alone and
it cuts fine. I use it to draft the back sides of sears and to form the posts of a four screw bridle
like the one I plan to use in a lock for Jud Brennan.

Bob Roller

[Dphariss]

I use a 3/8 end mill. But I have a Bridgeport copy mill.
But this will work if you can get or make the right pilot
http://www.mscdirect.com/product/details/08790248

Dan

[JBJ]

P.W.'s work is spot on. However, if you have access to a lathe to drill the central hole for the pilot(s) and make a few pilots, the rest can be done by hand. No, it is not as elegant or precise but totally functional. Just be sure to use a light touch when cutting and clear the chips often. And, if you make the cutter head of sufficient size, the same type of tool can be used (with the appropriate pilot) for the final facing off of a barrel should the need arise. When your budget is limited, you adapt.
J.B.

[Rolf]

I really liked the counterbores you made.  I'm going to try that when I get a mill for my workshop. What was the mill cutter you used?

Best regards
Rolf

[P.W.Berkuta]

It is a 3/4" 60 degree dove tail cutter. I use a 3/8"60 degree dove tail cutter for the smaller counter bores. On the 6 tooth counter bore I had to file the relief angle to finish off the tooth but on the 12 tooth counter bore the dove tail cutter took care of the relief angle. you just have to get the depth of cut to take care of the relief angle - I used a cutter depth of 0.070" on the 12 tooth counter bore and a 0.110" on the 6 tooth counter bore - i guess I could have gone deeper with the dove tail cutter but once the inner part of the tooth got pointed I did not want to mess up the tooth so I opted to use a small triangle file to point up the tooth. As others have said you can do the work with a file which I have done in the "pre-mill" days. Total machine time for the two was 2+ hours not including hardening & tempering.

[frogwalking]

I bought two different sizes from Enco as FDR said.  They work fine.

[David R. Pennington]

I made mine just like Berkuda but I didn't have a mill so I cut with jeweler's saw and files.

[vladp]

Hi
First time here.
I make my counter bores from standard twist drills. I just grind the tip flat, for brass and german silver I put a negative rake on the cutting edge so it doesn't bite and pull itself through the plate. Have a set of drill bits especially for drilling brass. End mills are even better.

[frogwalking]

http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA=368-6020&PMPXNO=947242

If you want to buy the tool, here is where to get it. 

[Ryan McNabb]

Why would you want to do that to your sideplate?  I've never noticed it done on originals but I don't pay much attention to anything after about 1800, maybe it's a later thing?

[BrianH]

Could also try a drill Kreg pocket jigs use they are a #8 pilot and a 3/8 counter bore and there available at Home Depot and lowes would use a drill press tho there not the strongest