Guys, I am making a drill bit that is 1 1/4" in diameter. This bit is for
drilling end grain wood on a wood lathe. That is, the drill bit will not
turn, but the wood does. Essentially the cutter is a piece of 5/8" wide
planer blade that is brazed to the end of a 1 1/4" tube. The trailing side
of the planer blade is ground away so the leading edge is in contact with
the wood. I want the drill bit to advance 1/8" per revolution. What is the
clearance angle I need too achieve this. That is, what angle should the
bottom of the cutter make with the axis of the bit? Incidentally, an air
tube ending just above the cutter takes the shaving out the top of the bit,
very similar to a rifle drill.

Gotta be someone on this group who can tell me the answer.

TIA,
James Johnson

"JRJohnson" wrote in
:

Guys, I am making a drill bit that is 1 1/4" in diameter. This bit is
for drilling end grain wood on a wood lathe. That is, the drill bit
will not turn, but the wood does. Essentially the cutter is a piece
of 5/8" wide planer blade that is brazed to the end of a 1 1/4" tube.
The trailing side of the planer blade is ground away so the leading
edge is in contact with the wood. I want the drill bit to advance
1/8" per revolution. What is the clearance angle I need too achieve
this. That is, what angle should the bottom of the cutter make with
the axis of the bit? Incidentally, an air tube ending just above the
cutter takes the shaving out the top of the bit, very similar to a
rifle drill.

Gotta be someone on this group who can tell me the answer.

TIA,
James Johnson





If the cutting face is perpendicular to the work (no rake), 8-12° should
work fine.



--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

Remove sp to reply via email

What you've made is basically a spade bit. If you advance 1/8"/ rev. it
is going to make a very rough hole and possibly jam or split the wood.
Ideally the bit will take about .003" to .005 per rev. and make a nice
clean hole zero to three degrees of relief should work.
Bugs

"Bugs" wrote in message
oups.com...
What you've made is basically a spade bit. If you advance 1/8"/ rev. it
is going to make a very rough hole and possibly jam or split the wood.
Ideally the bit will take about .003" to .005 per rev. and make a nice
clean hole zero to three degrees of relief should work.
Bugs


Actually, Bugs, the one I made which drills 1/9"/rev actually makes a very
clean hole. Plus, the hole is only so the woodturner doesn't have to turn
out the center of the piece, which is not moving very much in relation to
most of the piece. I can measure the clearance angle of the one I made and
guestimate, but thought I would give the group something to think about.

Also, after the hole is drilled, the inside of the piece is immediately
turned away, so the actual smoothness of the hole is of no consequence.

Regards, James Johnson

On Thu, 14 Apr 2005 20:15:32 GMT, "JRJohnson" wrote:


"Bugs" wrote in message
roups.com...
What you've made is basically a spade bit. If you advance 1/8"/ rev. it
is going to make a very rough hole and possibly jam or split the wood.
Ideally the bit will take about .003" to .005 per rev. and make a nice
clean hole zero to three degrees of relief should work.
Bugs


Actually, Bugs, the one I made which drills 1/9"/rev actually makes a very
clean hole. Plus, the hole is only so the woodturner doesn't have to turn
out the center of the piece, which is not moving very much in relation to
most of the piece. I can measure the clearance angle of the one I made and
guestimate, but thought I would give the group something to think about.

Also, after the hole is drilled, the inside of the piece is immediately
turned away, so the actual smoothness of the hole is of no consequence.

Regards, James Johnson


How about using a Forstner bit?


Mark Rand
RTFM

Bugs wrote:

What you've made is basically a spade bit. If you advance 1/8"/ rev. it
is going to make a very rough hole and possibly jam or split the wood.
Ideally the bit will take about .003" to .005 per rev. and make a nice
clean hole zero to three degrees of relief should work.
Bugs


Yea. Can you imagine 1/8 in feed per rev. ???? :-) I wonder how many
horse power that drill press has? and what sort of down feed gearing??
Sorry. I was going to ignore this but I see there is a at least one
response. :-)
...lew...