Someday I'm going to get to buy a good used tapping head that doesn't go up
to almost new price.

Anyway, in the mean time I have been looking at the various taps and
suggestions for use with a tapping head. It seems like a regular straight
tap like comes in every generic tap & die set can't, or atleast shouldn't,
be used in a continuous tapping machine. The stuff I've read seems to say
you need to use either a spiral tap or a gun tap.

Here is what I understand about the two types. Please correct me where I go
wrong.

BOTH. Bother are designed to move chips out of the hole.

Gun taps shoot the chips forward and are suitable for through hole tapping.

Spiral taps conveyor the chips up flutes on the tap and back out the top of
the hole and are suitable for blind hole tapping.

Here are my questions. Should you only use them as described above? Is
there any reason not to use a spiral tap for both through holes and blind
holes? Obviously the gun tap would have a problem in blind holes if tapping
to depth.

In article ,
"Bob La Londe" wrote:

Someday I'm going to get to buy a good used tapping head that doesn't go up
to almost new price.

Anyway, in the mean time I have been looking at the various taps and
suggestions for use with a tapping head. It seems like a regular straight
tap like comes in every generic tap & die set can't, or at least shouldn't,
be used in a continuous tapping machine. The stuff I've read seems to say
you need to use either a spiral tap or a gun tap.

Yep. The standard straight plug tap needs to be reversed every turn or
so, to break the chips, and backed out to clear the chips. Gun taps are
far better.


Here is what I understand about the two types. Please correct me where I go
wrong.

BOTH. Both are designed to move chips out of the hole.

Gun taps shoot the chips forward and are suitable for through hole tapping.

Spiral taps conveyor the chips up flutes on the tap and back out the top of
the hole and are suitable for blind hole tapping.

Yes.


Here are my questions. Should you only use them as described above? Is
there any reason not to use a spiral tap for both through holes and blind
holes? Obviously the gun tap would have a problem in blind holes if tapping
to depth.

When hand tapping, I often use a gun tap in a short blind hole, but with
care. I manually remove the ball of stringy chips, then finish the job
with a bottoming tap.

If the blind hole is deep enough, one can skip the followup with the
bottoming tap, but one should always remove the ball of chips, lest it
get into the threads and jam the screw.

Joe Gwinn

On Dec 6, 2:01*am, "Bob La Londe" wrote:
Someday I'm going to get to buy a good used tapping head that doesn't go up
to almost new price.

Anyway, in the mean time I have been looking at the various taps and
suggestions for use with a tapping head. *It seems like a regular straight
tap like comes in every generic tap & die set can't, or atleast shouldn't,
be used in a continuous tapping machine. *The stuff I've read seems to say
you need to use either a spiral tap or a gun tap.

Here is what I understand about the two types. *Please correct me where I go
wrong.

BOTH. *Bother are designed to move chips out of the hole.

Gun taps shoot the chips forward and are suitable for through hole tapping.

Spiral taps conveyor the chips up flutes on the tap and back out the top of
the hole and are suitable for blind hole tapping.

Here are my questions. *Should you only use them as described above? *Is
there any reason not to use a spiral tap for both through holes and blind
holes? *Obviously the gun tap would have a problem in blind holes if tapping
to depth.

You need to look into Form Taps. They don't have any chips.
The drilled hole is larger, and the tap FORMS the threads by squeezing
the metal into the thread form.

The threads can be much stronger, and the taps themselves are much
stronger!

Not much more force to tap, but the taps last and last...
You may never want to go back to cutting taps.

--Fun with form taps: if you like them you'll want a Formdrill too:
http://www.formdrill.eu/?gclid=CIHcr...FRBNgwodxleyjg


Cross-Slide wrote:

You need to look into Form Taps. They don't have any chips.
The drilled hole is larger, and the tap FORMS the threads by squeezing
the metal into the thread form.

The threads can be much stronger, and the taps themselves are much
stronger!

Not much more force to tap, but the taps last and last...
You may never want to go back to cutting taps.

--
"Steamboat Ed" Haas : Time flies like an arrow
Hacking the Trailing Edge! : Fruit flies like a banana
www.nmpproducts.com
---Decks a-wash in a sea of words---

Joseph Gwinn wrote:

When hand tapping, I often use a gun tap in a short blind hole, but with
care. I manually remove the ball of stringy chips, then finish the job
with a bottoming tap.

If the blind hole is deep enough, one can skip the followup with the
bottoming tap, but one should always remove the ball of chips, lest it
get into the threads and jam the screw.

Joe Gwinn
I do too. I found that a little right angle bent on the
end of a piece of mig wire makes a great thing to pull that
"ball of chips" out on any thing bigger that a #8. I bend
a loop about 1/2" on the other end to hold and twist CCW
with.

Oh I prefer to call them "spiral point" and "spiral flute"
...lew...

Cross-Slide wrote:
You need to look into Form Taps. They don't have any chips.
The drilled hole is larger, and the tap FORMS the threads by squeezing
the metal into the thread form.

The threads can be much stronger, and the taps themselves are much
stronger!

Not much more force to tap, but the taps last and last...
You may never want to go back to cutting taps.

GREAT for aluminum but with the tight and odd size requirement
for the tap drill, I don't use them on steel. For aluminum
the tolerance can be let a little looser. :-)
...lew...

steamer wrote:
--Fun with form taps: if you like them you'll want a Formdrill too:
http://www.formdrill.eu/?gclid=CIHcr...FRBNgwodxleyjg


Cross-Slide wrote:

You need to look into Form Taps. They don't have any chips.
The drilled hole is larger, and the tap FORMS the threads by squeezing
the metal into the thread form.

The threads can be much stronger, and the taps themselves are much
stronger!

Not much more force to tap, but the taps last and last...
You may never want to go back to cutting taps.


The next thing to consider is "stir-welding".
That form drill is pretty slick but I wonder if its
practical for manual operation. Oh! and how high a
speed is required for a #4 screw?
...Lew...

On 2010-12-06, Bob La Londe wrote:
Someday I'm going to get to buy a good used tapping head that doesn't go up
to almost new price.

Anyway, in the mean time I have been looking at the various taps and
suggestions for use with a tapping head. It seems like a regular straight
tap like comes in every generic tap & die set can't, or atleast shouldn't,
be used in a continuous tapping machine.

Not unless you are looking for lots of practice at removing
broken taps. :-)

Standard taps require frequent reversal of the tap to break off
chips before they get too long and clog the hole. Tapping heads don't
do that reversal normally. If you back out frequently enough with a
slow enough RPM, I guess you might get away with it, but I wouldn't
bother.

The stuff I've read seems to say
you need to use either a spiral tap or a gun tap.

Here is what I understand about the two types. Please correct me where I go
wrong.

BOTH. Bother are designed to move chips out of the hole.

Correct.

Gun taps shoot the chips forward and are suitable for through hole tapping.

Correct.

Spiral taps conveyor the chips up flutes on the tap and back out the top of
the hole and are suitable for blind hole tapping.

Correct.

Here are my questions. Should you only use them as described above? Is
there any reason not to use a spiral tap for both through holes and blind
holes? Obviously the gun tap would have a problem in blind holes if tapping
to depth.

You can use the gun taps with blind holes -- *if* there is
enough extra depth to accept the chips beyond the maximum required
thread penetration. I've done this with threading through holes (well,
holes intended to be through when things are parted off) for multiple
identical parts on a lathe with a bed turret. Drill deep, tap deep
enough, and part off. Every so often, I had to do another parting about
3/4" past the first when the hole started to walk too far off center, as
each hole was a continuation of the previous, while the second part off
allowed me to make a fresh start. Next time I set up for these, I
intend to try the thread forming taps, which should save me a few inches
over the length of a 6' bar. :-)

I've not used the spiral flute taps, so I don't know for sure,
but my feeling is that with tougher materials, the spiral will tend to
unwind a little changing the effective thread pitch, and perhaps causing
it to bind when backing it out.

Of course, for *through* holes, another option which is nice if
the holes are not too deep are the combination drill and tap (where the
tap has to be spiral to match the spiral of the drill part).

So -- you have my opinion. It will be interesting to compare
that to those of others.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Bob La Londe wrote:

Spiral taps conveyor the chips up flutes on the tap and back out the
top of the hole and are suitable for blind hole tapping.

Here are my questions. Should you only use them as described above?
Is there any reason not to use a spiral tap for both through holes and
blind holes? Obviously the gun tap would have a problem in blind
holes if tapping to depth.
Spiral FLUTE taps are what you are talking about. They look like twist
drills with threads in them, and bring the chips up the same way a drill
bit does. There are different from spiral POINT taps.

My experience with spiral flute taps is they are great for shallow blind
holes or through holes in thin material. They don't work well on DEEP
blind holes, like deeper than 5X diameter or so. The chips eventually
bind the tap. Much better to drill deeper and use a gun tap for the
deep holes. A spiral point tap also pushes the chips ahead.

Jon

Lewis Hartswick wrote:
The next thing to consider is "stir-welding".
That form drill is pretty slick but I wonder if its
practical for manual operation. Oh! and how high a
speed is required for a #4 screw?
...Lew...
--Yah that might be an issue. I run #10s at about 2800rpm; 1/4" is
something like 2200 IIRC. And forget about doing it with a hand drill: you
definitely need the force multiplier of a feed handle; I do my stuff on a
Bridgeport. Still and all it's an awesome process.

--
"Steamboat Ed" Haas : Time flies like an arrow
Hacking the Trailing Edge! : Fruit flies like a banana
www.nmpproducts.com
---Decks a-wash in a sea of words---