Well I finished up a tool today that I've been wanting
for some time. It's a basic tap starting alignment tool
that can be clamped in a drill chuck, etc. A 1/2" diameter
rod clamps into the drill chuck and a hollow cylinder
with a tap wrench mounted on the end slides and rotates
on the rod. This doo-dad could also double as a "sensitive
drill chuck" in a lathe's tailstock.

The design difficulty I had was that I have two sizes of
tap wrench and I wanted them both to mount onto the end
of the cylinder. The large wrench has an O.D. of .75"
and the small one has an O.D. of .375", so I bored out
a .755" diameter socket in the end of the cylinder deep
enough to hold the wrench. I then milled a slot through
the socket wide and deep enough to accept the t-handle
of the wrench, so that when seated in the cylinder, the
butt of the wrench bottoms out in the socket while the
t-handle bottoms out in the slot. For the smaller wrench
I turned a collar .75" O.D., .380" I.D. and about .25"
longer than the socket is deep. Next I milled a slot
similar to the one in the socket, only for the snaller
diameter t-handle. To use the smaller wrench I just slip
the collar onto its end and then slip it into the cylinder.
(I might cross drill and tap a small hole for a set screw
in the collar and attach it permanently to the small wrench).

I got my first chance to try it out tonight on a chunk
of steel that I'm temporarily using as a toolpost on my
lathe. This chunk of steel is just bolted to the topslide
and has a 1/2" wide and deep slot milled into its side
to take 1/2" toolbits. Three 7/16" set screws clamp the bit
from the top. I got tired of removing the thing each time
I wanted to mount a boring bar (1/2" shank HSS) so I drilled
a 1/2" hole in the side of this chunk of steel, rotated it
90 deg. and cross drilled a tap hole for 7/16-14. All of
this was done with the work mounted in position on the
topslide and the drill bits clamped in the 3-jaw chuck.
Next was tapping the hole of the clamp screw. I chucked
my new tap alignment tool in the 3-jaw and went to tapping
the hole. It worked bee-uuu-tif-ully!! No muss, no fuss,
no sidewinding threads! The t-handle cleared the ways nicely,
even when extended to increase leverage.

There is a bit of slop where the cylinder slides on the rod,
and that's because I could only drill the .5" hole and it's
not completely straight, forcing me to turn the rod undersized.
I should be able to ream the hole oversize a bit and make a new
rod with a true slip fit. Once I get a reamer....

Now I'll have to dig out my knurling tool and make it pretty!

Artemia Salina

There is a bit of slop where the cylinder slides on the rod,
and that's because I could only drill the .5" hole and it's
not completely straight, forcing me to turn the rod undersized.
I should be able to ream the hole oversize a bit and make a new
rod with a true slip fit. Once I get a reamer....

If you drill undersized and then single-point bore you get closer.
If you use a piece of drill rod for the rod, then try to match it as close as
you can get in machining the sleeve--that may be the way to get a good slip
fit.

Half inch, etc. reamers should be common on the used market locally in CT.

Frank Morrison

On Fri, 10 Sep 2004 01:32:31 +0000, Fdmorrison wrote:

Artemia Salina

There is a bit of slop where the cylinder slides on the rod,
and that's because I could only drill the .5" hole and it's
not completely straight, forcing me to turn the rod undersized.
I should be able to ream the hole oversize a bit and make a new
rod with a true slip fit. Once I get a reamer....

If you drill undersized and then single-point bore you get closer.

This was my first plan, but I realized that I didn't have a boring bar
in my set that was long enough. I would've had to have bored half way
in and then flipped the sleeve and finished from the other end. It seemed
too error prone and I have very little spare stock for the sleeve.

I'm not sure what the steel is, some sort of high carbon stuff I think.
It was in my junk collection. But although it is harder than mild steel
the finish produced when truing up the OD was excellent.

If you use a piece of drill rod for the rod, then try to match it as close as
you can get in machining the sleeve--that may be the way to get a good slip
fit.

The rod I'm using is an old grinding wheel arbor shaft that I bought from
Sears hardware. Very inexpensive IIRC but the finish is outstanding when
turned. I had a little left over so today I was practicing single pointing
threads with it, and I remain impressed with it. The threads were smooth as
silk with no tearing, even when viewed under a strong magnifying glass.
The stuff is about 5/8" in diameter and about 8 or 10" long, overall.
I mention this in case anyone is in a bind and needs short lengths of
steel rod that has to give a good finish in a hurry.

Half inch, etc. reamers should be common on the used market locally in CT.

I wonder if Al Babin is still in CT? :-)