Deep Drilling Question

Instead of purchasing a gun drill, how about making your own?? The August 1965 issue of Popular Mechanics had an excellent article on the subject. You can read it at this link: https://books.google.com/books?id=XOMDAAAAMBAJ&pg=PA166&dq=popular+mechanics+making+deep+hole+drills&hl=en&sa=X&ved=0ahUKEwjPg5eK2p3LAhUluoMKHdzWAhsQ6AEINTAA#v=onepage&q=popular mechanics making deep hole drills&f=false

Another method is to make a simple D-bit using a length of drill rod, either W-1 or O-1.
  1. Cut a length of drill rod long enough to chuck up in your lathe or drill press and still drill the hole.
  2. Square the ends with a file, grinder, or belt sander. Remove any burrs from the end.
  3. Use a centering head on a combination square and scribe a couple of lines at right angles to each other on one end of the rod.
  4. Mill away almost one half the diameter for a distance of about 1" back from the end of the rod. Finish it with a file. If you cut away half or more of the diameter, the bit will cut undersize. You can probably get away with cutting up to within .010" or so of the center line. Try to avoid any sharp corners in the base of the bit in order to prevent breakage.
  5. Relieve the side of the cutter that does not do the cutting.
  6. Back off behind the cutting edge to provide clearance.
  7. Harden then temper to dark yellow, just on the cutting edge, not the whole drill.
  8. Sharpen cutting edge on a stone
D-Bits.JPG

Granted, this may be a fair piece of work for a soft material like nylon, but if you need the hole to be true and straight it would be the way to go.

D-bits do have a couple of drawbacks, but they are minor compared to the gains.
  1. They require a starting hole, typically about three times the diameter. This is easily done with a twist drill of the same size.
  2. They must be retracted from the hole often to clear chips. You will spend more time retracting and inserting the bit than you will actually drilling the hole.
ON EDIT: Randall found the old post where this was discussed at great length. I knew it was out there somewhere, but I could not find it. He posted it while I was writing this one up.
 
Last edited by a moderator:
I think that keeping the material straight is going to be a major problem. Can you shrink or press it into a 3/4" tube? I hope you have some material to experiment on.
 
Aircraft length bits come in all sorts of sizes, and about 18" long. Use some here at the shop.
 
My shop teacher in junior high brazed a rod to a jobbers drill bit and drilled a hole in a student's lamp base turning. Could you braze a rod to the end of the drill bit? My concern would be what do you do if the braze joint breaks.

Or maybe these from HF?

Bruce

upload_2016-2-29_16-51-31.png

upload_2016-2-29_16-52-3.png
 
Wow, thanks for all the tips guys! Any number of these solutions will work, so I appreciate it. I'll let you know what I go with - actually, I might order a bit that will work just for speed and try terrywerm's idea as well just for the heck of it
 
John Hasler said:
I think that keeping the material straight is going to be a major problem. Can you shrink or press it into a 3/4" tube? I hope you have some material to experiment on.
Click to expand...

I do - I have a bunch of it on hand, so if I f-it up, I can try, try again.
 
But you can't drill it .500 and turn the od to .500
 
I tried to drill some nylon once for a bore guide about 8" long, and found no matter what I did it was like trying to drill spaghetti. The better choice is Delrin, it machines about 1000 times better than nylon.
 
If you have a small lathe like a 9" South Bend, you could shove the material up in the spindle. Let the spindle hold it reasonable steady while you drill the material. Suggest drilling half way, turn it around and drill the rest of the way. You'll probably have a mis-match in the middle. Just use the drill bit as a reamer and run it deeper to blend in the two bores. That's how we used to do it on deep hole drilling machines, Trepanners we called them.
 
You must log in or register to reply here.
Back
Top