Any wisdom here to share when it comes to hand tapping with roll taps?
I ordered some 1/4-20 and 10-32 ones to play with. I was having problems
with threads being stripped out of an aluminum pipe with a 1/4-20 bolt
with a knob that's used to clamp onto an inner cylinder.
Are a couple drops of cutting oil suitable as lubricant?
It seems some of these taps have flutes, some don't. Does it matter much?
On Fri, 4 Oct 2013 16:46:34 +0000 (UTC), Cydrome Leader
You can use cutting oil for aluminum if tapping aluminum. The taps
that don't have flutes are not ground round. They are ground to have
high spots. If you grast the tap lightly and turn it you can feel the
eccentricity. A good hardware store will sell tapping fluid. The clear
works well for aluminum. For steel the dark sulfurized stuff is good.
You do know that hole size is critical for form taps? The hole will of
course be larger than for a cutting tap, but the size has less
tolerance than that for a cutting tap because the material is
displaced rather than cut.
I looked at some of the charts and other forums and the mention of using
larger and more specific hole sizes was mentioned.
Is it insanely hard to drive these things into metal, considering they
don't actually cut but form the threads with pressure?
I can't imagine their easier to drive than completely crossthreading a
First item: It is critical that you use a tap wrench to
minimize side loading and breaking the tap. Never use a
crescent wrench, vise grips, etc.
I never disconnect the quill spring, the quill clamp should
be adequate. There are several different ways to tap in the
drill press or mill.
First is to simply chuck the tap in the drill chuck and
start the tap one or two turns, loosen the chuck and
retract, and use a tap wrench to finish tapping. The
problem here is the tap shank is hard and the drill chuck
will tend to slip. This is compounded because when you
grasp the drill chuck to turn it, you tend to open it. Some
people make a pin or hook wrench to fit into the tightening
holes for the chuck key (which the higher quality Albrecht
type chucks don't have). While this is a good expedient for
smaller taps and occasional use, the guided tap wrench is a
much better option as it minimizes any side loading on the
tap, and insures the tap remains perpendicular. This can be
difficult when tapping into a curved or slanted surface, for
example mounting a scope. (it can be helpful to lightly
machine a counter bore into the workpiece with a flat
bottomed drill or end mill to make the surface flat) In use
a guide rod which fits closely into the tap wrench is
clamped in the drill chuck, and the tap is clamped on the
flats in the tap wrench. The tap wrench rotates/slides
freely on the guide rod.
As mentioned I bought both sizes of the WTTOOL tap guide and
these have worked well for me. I don't know if the ones
currently sold are the same but they look like it.
Another type is a spring loaded guide that centers the tap.
Almost all taps have either a center or a cone on the end
which will fit into the guide, and most of the fancier
t-handle tap wrenches* have a center hole in line with the
tap axis. Many of these guides have a reversible pin with a
point on one end and a center on the other. These are used
to start the tap straight, and are driven with a regular tap
One additional use I have found for these guides is with a
length of 3/16 drill rod with a center [regular 60 degree
seems to work as good as a bell center] in one end and a
sharp point on the other for use as a pump staff [with a
drop indicator] to accurately locate work on the lathe face
plate from layout prick [not center] punch marks.
The items shown are only examples and the other mill supply
houses should carry.
Hope this was of help.
Well ... *I* don't -- but I use a TapMatic tapping head, which
reverses the tap and speeds it up when withdrawing from the tapped hole.
I suspect that varies with the design of the drill press.
Mine has a flat spring wound up and connected to a notch in the
end of the shaft for the feed handles. The other end engages a groove
in a cup which is clamped to the side of the drill press. You adjust
the tension to balance the weight of the qulll plus the chuck (or the
tapping head) and add a little more lift for convenience -- and ideally
never touch that adjustment again.
I've not followed the URLs to see what was being described. You
might need to back off the tension if you were using it like the
so-called "tapping machines" where it guides the tap in vertically, but
you provide the turning of the tap with a crank on the upper end.
Aye, that's the same way mine is set up as well. I've read of fellows
talking about disconnecting the spring for tapping, but never really
figured out how exactly to go about doing it; it would probably be
enough to just back off the tension so the quill didn't retract, but I
don't know if the spring mechanism is really set up to be continually
adjusted like that.
I would never disconnect the spring, it's not going to provide any positive
benefit even when tapping and it's also very annoying having to unlock the
quill with one hand while having to also simultaniously use the other hand
just to keep the tool from suddenly dropping down into your work.
I suppose if a person had three hands then if might not be quite as bad.
I drill and tap on a Clausing mill that lacks a return spring, which
trades one set of annoyances for another. Having the tool slam onto
the work is considerably worse than having it rise when released. I
replaced the plastic ball on the quill feed lever with a brass one
heavy enough to counterbalance the chuck, and tighten the quill lock
just enough that a drill bit has to be pushed through the bottom of
the work. Mine is the early model with one hex bolt for the quill
Ball-bearing Jacobs chucks usually grip taps well enough to start them
straight in the hole before switching to a tee handle. Resting the
chuck jaws on the cone at the end of the tap gives some indication if
it wobbles. I suppose I could hang a weight on the quill feed to make
the chuck jaws push and center the tap while I turn the tee handle
with equal pressure from both hands. A few times I've loosened the
chuck so it only guides and started the tap with a wrench on the upper
end of the flutes. This area can be ground flat a little to give the
wrench a better grip. I don't grind past the thread roots to avoid
weakening the tap.
I don't know about using that tool above, but for taps clamped in the
chuck or collet, no, you don't remove the spring. It helps the tap to
back itself out cleanly. Just leave your hand on the ball as it taps,
providing an equalizing pressure to overcome the spring tension, then
remove it (I hover) for the backout. Piece o' cake.
On Friday, October 4, 2013 8:31:21 PM UTC-4, F. George McDuffee wrote:
A tap block can be even simpler. I have just used a short piece of 2 by 4.
Just drill a hole thru it using the same drill you used to drill the hole
that you are tapping. Run the tap thru it. If you get it started crooked
, it will be fairly obvious. In that case drill another hole and try again
. Or drill a hole slightly bigger and try that. And when you are done you
can toss the bit of 2 by 4 and not worry about finding it the next time yo
u have to tap a holo.
The first taps arrived yesterday. They were some ebay special Brubaker HSS
10-32 H4 ones with a fairly shiny finish.
The test was pieces of 6061 and something else that was much softer and
As with any tap chart, the more you look, the more answers you get for the
nominal drill to use.
The charts from a few makers seemed to suggest someting close to #17 drill
for about 75% thread, so that's what I used.
It worked fine. I used the wax stick for a bandsaw as lube and each and
every time the taps went straight into the aluminum with no problems. I
used a small tapping block for some holes, and did the rest with a lathe
to hold the tap straight. I did notice they started easier than cutting
taps and didn't try to wander on the first cut.
I didn't measure torque, but they felt much smoother than any cutting
taps I've used, even the good ones. No crunchines, no sticking, no need to
back out all the time. Backing out still required a wrench, but not much
effort. I did some bottom-out tests and it was easier to feel the bottom
of a hole with the roll tap.
The thread quality is clearly better too, fasteners go in smoother and
there's no fuss with cleaning crud out of the threads when you're done.
The one thing the databooks warn about is how the threads will make a
volcano shape if you thread straight into a flat surface. I actually
noticed the 6061 would split and flake more than in would make a nice
Countersinking before threading just resulted in the protrustion to occur
out of the way. Countersinking after threading solved this and gave the
The 1/4-20 tap should arrive in the next few days. I'll try some brass and
steel with both next.
So far, two thumbs up. these things are pretty cool.
On Tue, 8 Oct 2013 16:54:20 +0000 (UTC), Cydrome Leader
Though the brass will be easy to tap the results may not be so good.
When half hard free machining brass (the most common) is formed by the
tap it may flake. Tiny flakes may come off of the threads. You will be
able to see them easily with a magnifier. And the threads may be
weaker that cut threads. Gummy materials work the best for form
tapping, so mild steel and 5000 series aluminum work well. I have form
tapped many 10-32 holes in 304 SS, even though the torque required was
you were right about the brass. The threads were pretty flakey and the
pieces I tested actually deformed quite a bit. The volcano shape around
the threads exceeded the diameter of the threads for the 10-32 thread in a
piece about 3/16" thick.
I tapped around an existing 1/2" hole and this hole which was about 1/4"
away actually changed shapes and no long press fit the mating part.
I guess the lesson is, just cut brass threads, which is no problem since
they're strong enough anyways.
Next test is to see what happens with copper.
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