Counter boring for lock screws

[NSBrown]

On my current build I have lock screws with heads 7/16" in diameter. The counter bores I own have pilots for #8 or #10 clearance holes but the second tier does not clear for the diameter of the head. Where can I find a bit with a #8 pilot and a 7/16'' bore?

Or is there another solution?

[Dphariss]

Cut down the screw heads.
Good piloted counter bores are getting pricey and something odd would be even worse

Check MSCdirect.com
They have an imported interchangable pilot 7/16 counterbore for about $30 with no pilot. Made in USA is about 8 bucks more.
Dan

[NSBrown]

I don't really want to reduce the screw head. It's an early Virginia, .58 cal. build that the generous screw heads look appropriate on.

Guess I'll start a search.

[James Wilson Everett]

Stewart,

It is easy enough to make the tool - 18th c style.  See the photo of a mid 19th c gunsmith counterbore with a pilot.  In the time it takes to post the question/answer on this site, you could nearly complete the tool.  Beware, you might get infected with the bug that causes you to make an 18th c gun in the 18th c manner!  Maybe if you do this you will be more proud of the counterbored hole than you are of the Chambers lock and Getz barrel - because YOU actually did it!

Jim Everett

[NSBrown]

Great idea! I'll give it a go. Thank you Jim.

[David R. Pennington]

Jim, thanks so much for posting these pictures of original tools. I'm inspired to make one of these counterbores! I love your posts on original tools and methods. Fascinating to me. This should be in another topic but I've been wondering about wrought iron. You have stated in other posts that you use wrought iron for a lot of your handmade parts. Is there a contemporary source for this material or are you scavenging it. If old metal is your source what do you look for?

[James Wilson Everett]

David,

Wrought iron is often easy to find if you know what to look for.  I find it in old hand forged blacksmith tongs, wagon wheel rims, barn hinges and the like.  If possible I file a small section of the metal looking for the black, linear slag streaks that are present in wrought iron.  You can see the streaks in the gun barrel under the topic of octagon barrels.  Usually you can find the stuff for free of for a low cost.  Very fine wrought iron - the really good stuff - will have such fine slag streaks that the are not easily visible.  I use some muriatic acid to etch the metal, wrought iron will look like wood grain, hickory like after etching.  Very often people throw it out in the garbage!  See the slag streaks in this piece of oil well pump rod from Oil City, PA.



You can buy it from:

http://www.wisconsinwoodchuck.net/treasures.htm

[Jim Kibler]

Another option is to make the pilot seperate from the cutter.  This can be easily accomplished with a lathe.  Cutting the teeth becomes a bit easier when using this process since the pilot doesn't get in the way.   

[dannybb55]

Is your counterbore about 1 1/2 long? Also did you cut the spaces between the teeth with a hot chisel or a cold file?