I brought this up once before and got a lot of good advice. The
original problem was tapping 6-32 holes in side of 1/4" aluminum
round. Each piece has one hole. I use to do this by drilling the holes
on the press, then tapping with a power drill. Sounds primitive, but
it worked... On hundreds of them, no problem. Then it stopped working
and I never did figure out why. I can't get through 15 without
breaking a tap now and I've tried everything. The first time the
consensus seemed to be that it would be best to use a combo drill/tap
bit on a tapping head. I agree, except, I never got around to it. The
need for these parts hadn't happen since the last time... but I
decided I would do it that way when it comes up again. Well, it came
up again... Except this time the rounds already had the #36 holes
drilled in them... Hundreds of them. So I have no choice but to tap
them as is. Long story longer, I went through about $50 worth of taps
today just trying to get through 40 of them. And even just that took a
ridiculous effort.

So now what? I haven't tried it yet, but I'm thinking maybe opening
the holes to 7/64" would help? Or would that weaken the thread too
much? I don't know, I'm pretty much desperate for a solution at this
point. I've tried every type of tap, tap fluid, technique... I'm out
of ideas.

Dave D wrote:
I brought this up once before and got a lot of good advice. The
original problem was tapping 6-32 holes in side of 1/4" aluminum
round. Each piece has one hole. I use to do this by drilling the holes
on the press, then tapping with a power drill. Sounds primitive, but
it worked... On hundreds of them, no problem. Then it stopped working
and I never did figure out why. I can't get through 15 without
breaking a tap now and I've tried everything. The first time the
consensus seemed to be that it would be best to use a combo drill/tap
bit on a tapping head. I agree, except, I never got around to it. The
need for these parts hadn't happen since the last time... but I
decided I would do it that way when it comes up again. Well, it came
up again... Except this time the rounds already had the #36 holes
drilled in them... Hundreds of them. So I have no choice but to tap
them as is. Long story longer, I went through about $50 worth of taps
today just trying to get through 40 of them. And even just that took a
ridiculous effort.

So now what? I haven't tried it yet, but I'm thinking maybe opening
the holes to 7/64" would help? Or would that weaken the thread too
much? I don't know, I'm pretty much desperate for a solution at this
point. I've tried every type of tap, tap fluid, technique... I'm out
of ideas.

Bypassing obvious questions but one:

I understand these came with the hole already in them, so maybe the
supplier used a different grade of AL than you used the first time.

and not so obvious, are you holding them differently, maybe squeezing
them tighter, or out of round than the first time?



--
Steve Walker
(remove wallet to reply)

On Jan 5, 7:32*pm, Steve Walker wrote:
Dave D wrote:
I brought this up once before and got a lot of good advice. The
original problem was tapping 6-32 holes in side of 1/4" aluminum
round. Each piece has one hole. I use to do this by drilling the holes
on the press, then tapping with a power drill. Sounds primitive, but
it worked... On hundreds of them, no problem. Then it stopped working
and I never did figure out why. I can't get through 15 without
breaking a tap now and I've tried everything. The first time the
consensus seemed to be that it would be best to use a combo drill/tap
bit on a tapping head. I agree, except, I never got around to it. The
need for these parts hadn't happen since the last time... but I
decided I would do it that way when it comes up again. Well, it came
up again... Except this time the rounds already had the #36 holes
drilled in them... Hundreds of them. So I have no choice but to tap
them as is. Long story longer, I went through about $50 worth of taps
today just trying to get through 40 of them. And even just that took a
ridiculous effort.

So now what? I haven't tried it yet, but I'm thinking maybe opening
the holes to 7/64" would help? Or would that weaken the thread too
much? I don't know, I'm pretty much desperate for a solution at this
point. I've tried every type of tap, tap fluid, technique... I'm out
of ideas.

Bypassing obvious questions but one:

I understand these came with the hole already in them, so maybe the
supplier used a different grade of AL than you used the first time.

and not so obvious, *are you holding them differently, maybe squeezing
them tighter, or out of round than the first time?


Thanks... To my knowledge it is 6061. I don't really have a way of
knowing more than that. That's what they were supposed to be before,
and that's what they're supposed to be now. The way I do them now is
exactly as I did them before, but I have changed everything just to
see what the problem is, and nothing seems to work. I clamp them in
the same way, don't put pressure where the hole is going... Hold the
drill the same way. Tried going fast, tried going slow... I tried by
hand and the tap seems tight to me, but maybe that's me. I did check
the holes and they are for sure #36. I could use one of those hand
turn jigs where it lines it up, but that still wouldn't guarantee the
hole is clamped straight, plus it would be brutally slow. I have no
idea how I use to go through hundreds of these no problem. But however
I did, I'm stuck with these. The only thing I can think to do is drill
them out with a 7/64, but I'm afraid that would weaken them.

Is this stock more or less "gummy" than previously?---

Could it be that the heat treatment has changed from earlier lots where
things worked well? You never know what the purchasing dept might have
done.

Have you tried tapping some holes in some totally different pieces of 6061?

See:
http://www.galcit.caltech.edu/~tongc...Alloy_6061.pdf
to see all the heat treatment options.

Pete Stanaitis
-------------------

"Dave D" wrote in message
...
I brought this up once before and got a lot of good advice. The
original problem was tapping 6-32 holes in side of 1/4" aluminum
round. Each piece has one hole. I use to do this by drilling the holes
on the press, then tapping with a power drill. Sounds primitive, but
it worked... On hundreds of them, no problem. Then it stopped working
and I never did figure out why. I can't get through 15 without
breaking a tap now and I've tried everything. The first time the
consensus seemed to be that it would be best to use a combo drill/tap
bit on a tapping head. I agree, except, I never got around to it. The
need for these parts hadn't happen since the last time... but I
decided I would do it that way when it comes up again. Well, it came
up again... Except this time the rounds already had the #36 holes
drilled in them... Hundreds of them. So I have no choice but to tap
them as is. Long story longer, I went through about $50 worth of taps
today just trying to get through 40 of them. And even just that took a
ridiculous effort.

So now what? I haven't tried it yet, but I'm thinking maybe opening
the holes to 7/64" would help? Or would that weaken the thread too
much? I don't know, I'm pretty much desperate for a solution at this
point. I've tried every type of tap, tap fluid, technique... I'm out
of ideas.

Did the problem start in the middle of a successful run, after changing a
tap?

This happened to me, rigid tapping in a VMC. Everything was fine, except
after someone broke the tap, and the new tap tore up the threads, no matter
what we did.

The consensus was that the first tap had a coating or finish conducive to
clean threads in 6061 Al.
With the new tap, the coolant in the vmc was not adequate, and the solution
was manually coating the tap between cycles with tap magic. There were
other tapping fluids people really liked, forgot what they were -- Moly D
might have been one.

You need to develop a sleuthing strategy -- mebbe try tapping other sized
holes -- 5-40, 8-32, see if you have similar problems, which would indicate
a material problem.
You should get a feel for manually tapping a hole, to try to assess if the
hole is "right", by how hard the hand process feels. Mebbe the material
changed unbeknownst to you, got gummy/****ty.

What's nice about tapping heads is that you can peck, with the safety of a
clutch.
Speaking of which, mebbe a cordless drill with a decent clutch should help
your breakage problem, in the meantime.

But a tapping head would hedge a few bets at once.
--
EA

On Jan 5, 8:54*pm, Dave D wrote:
I brought this up once before and got a lot of good advice. The
original problem was tapping 6-32 holes in side of 1/4" aluminum
round. Each piece has one hole. I use to do this by drilling the holes
on the press, then tapping with a power drill. Sounds primitive, but
it worked... On hundreds of them, no problem. Then it stopped working
and I never did figure out why. I can't get through 15 without
breaking a tap now and I've tried everything. The first time the
consensus seemed to be that it would be best to use a combo drill/tap
bit on a tapping head. I agree, except, I never got around to it. The
need for these parts hadn't happen since the last time... but I
decided I would do it that way when it comes up again. Well, it came
up again... Except this time the rounds already had the #36 holes
drilled in them... Hundreds of them. So I have no choice but to tap
them as is. Long story longer, I went through about $50 worth of taps
today just trying to get through 40 of them. And even just that took a
ridiculous effort.

So now what? I haven't tried it yet, but I'm thinking maybe opening
the holes to 7/64" would help? Or would that weaken the thread too
much? I don't know, I'm pretty much desperate for a solution at this
point. I've tried every type of tap, tap fluid, technique... I'm out
of ideas.

If the holes that you're tapping are off the centerline of the 1/4"
round, that could explain why you're having problems. (One side of
the hole could be slightly longer than the other side and might force
the tap to bend or bind.) Could you sand or machine a slight flat
before tapping the hole?

The off center thing might be an issue I hadn't thought of. But
they're as accurate as before, so that doesn't explain the huge
breaking problem now and not before. It may be a difference in the
aluminum like mentioned.

What if a drilled them out to 1/8" and used a form tap? Those are much
stronger, aren't they? Would I have to counter sink again after the
threading doing that?

On Jan 5, 11:58*pm, Dave D wrote:
The off center thing might be an issue I hadn't thought of. But
they're as accurate as before, so that doesn't explain the huge
breaking problem now and not before. It may be a difference in the
aluminum like mentioned.

What if a drilled them out to 1/8" and used a form tap? Those are much
stronger, aren't they? Would I have to counter sink again after the
threading doing that?

At least you won't have the aluminum tearing with the form taps. I'm
not sure if countersinking will help a lot (unless you go deep). It
doesn't seem that you have much meat on the sides of the holes. You
still might have to do some deburring depending on what is expected
for this part.

Do you think there would then be too little material on the side, so
deforming could be an issue?

I'm still wondering if using a 7/64 hole with the cutting tap might
loosen it up just enough. I would think that would still give a decent
thread %.

I was taking to someone about this, and they said the way they did
small round, was to lay them in a half circle bed that is slightly
wider than the stock, and that way it allows it to adjust itself to
the tap as it goes in. I'm looking at a tapping head, but the machine
I want to dedicate to it doesn't have the separate arbor... so I'm not
sure if the built in arbor would fit the head. I'm wondering if it
would work to use a straight shank arbor on the head and then put that
in the press chuck?

On Jan 6, 3:52*am, Dave D wrote:
I was taking to someone about this, and they said the way they did
small round, was to lay them in a half circle bed that is slightly
wider than the stock, and that way it allows it to adjust itself to
the tap as it goes in. I'm looking at a tapping head, but the machine
I want to dedicate to it doesn't have the separate arbor... so I'm not
sure if the built in arbor would fit the head. I'm wondering if it
would work to use a straight shank arbor on the head and then put that
in the press chuck?

I always like to try the easiest solutions first. Opening them to
7/64" would work, but first check to see if the shank of a #36 drill
fits the existing hole. Maybe the hole got distorted somehow (metal
relaxed, bumping around, cut-off operation?). Maybe redrilling them
with the #36 drill bit will solve the problem.

On Jan 6, 2:54*am, Dave D wrote:

So now what? I haven't tried it yet, but I'm thinking maybe opening
the holes to 7/64" would help? Or would that weaken the thread too
much? I don't know, I'm pretty much desperate for a solution at this
point. I've tried every type of tap, tap fluid, technique... I'm out
of ideas.

Carpenter Technology has an excellent book entitled " Guide to
machining Carpenter Specialty Alloys". You can down load it from
their website.

http://www.cartech.com/productliterature.aspx

It addresses tapping and gives a lot of good information on selecting
drills for tapping. Opening the hole will help. The Carpenter Tech
guide has some info on how much it will weaken the thread. And when
it matters. If the threaded hole length is twice the bolt diameter,
it is different from when the threaded bolt length is equal to the
diameter.

So I encourage you to download the book. It is 6 megs for the pfd
file.

Dan

"Denis G." wrote in message
...
On Jan 6, 3:52 am, Dave D wrote:
I was taking to someone about this, and they said the way they did
small round, was to lay them in a half circle bed that is slightly
wider than the stock, and that way it allows it to adjust itself to
the tap as it goes in. I'm looking at a tapping head, but the machine
I want to dedicate to it doesn't have the separate arbor... so I'm not
sure if the built in arbor would fit the head. I'm wondering if it
would work to use a straight shank arbor on the head and then put that
in the press chuck?

I always like to try the easiest solutions first. Opening them to
7/64" would work, but first check to see if the shank of a #36 drill
fits the existing hole. Maybe the hole got distorted somehow (metal
relaxed, bumping around, cut-off operation?). Maybe redrilling them
with the #36 drill bit will solve the problem.

Wouldn't that work harden the surface too maybe making it harder to tap?

On Jan 6, 10:07*am, "Bob La Londe" wrote:
"Denis G." wrote in message

...

On Jan 6, 3:52 am, Dave D wrote:
I was taking to someone about this, and they said the way they did
small round, was to lay them in a half circle bed that is slightly
wider than the stock, and that way it allows it to adjust itself to
the tap as it goes in. I'm looking at a tapping head, but the machine
I want to dedicate to it doesn't have the separate arbor... so I'm not
sure if the built in arbor would fit the head. I'm wondering if it
would work to use a straight shank arbor on the head and then put that
in the press chuck?

I always like to try the easiest solutions first. Opening them to
7/64" would work, but first check to see if the shank of a #36 drill
fits the existing hole. *Maybe the hole got distorted somehow (metal
relaxed, bumping around, cut-off operation?). *Maybe redrilling them
with the #36 drill bit will solve the problem.

Wouldn't that work harden the surface too maybe making it harder to tap?

I think that the OP was working with aluminum (6061), so I don't think
that he should have this problem. It's more common to see work
hardening problems with stainless steels.

"Denis G." wrote in message
...
On Jan 6, 10:07 am, "Bob La Londe" wrote:
"Denis G." wrote in message

...

On Jan 6, 3:52 am, Dave D wrote:
I was taking to someone about this, and they said the way they did
small round, was to lay them in a half circle bed that is slightly
wider than the stock, and that way it allows it to adjust itself to
the tap as it goes in. I'm looking at a tapping head, but the machine
I want to dedicate to it doesn't have the separate arbor... so I'm not
sure if the built in arbor would fit the head. I'm wondering if it
would work to use a straight shank arbor on the head and then put that
in the press chuck?

I always like to try the easiest solutions first. Opening them to
7/64" would work, but first check to see if the shank of a #36 drill
fits the existing hole. Maybe the hole got distorted somehow (metal
relaxed, bumping around, cut-off operation?). Maybe redrilling them
with the #36 drill bit will solve the problem.

Wouldn't that work harden the surface too maybe making it harder to tap?

I think that the OP was working with aluminum (6061), so I don't think
that he should have this problem. It's more common to see work
hardening problems with stainless steels.

A lot of aluminum alloys work harden too. 5052 sure does. That is one of
the two reasons its very important to blow or wash chips clear when
machining. The other is that the oxidized coating is harder than the base
metal.

"Bob La Londe" wrote in message
...
"Denis G." wrote in message
...
On Jan 6, 10:07 am, "Bob La Londe" wrote:
"Denis G." wrote in message

...

On Jan 6, 3:52 am, Dave D wrote:
I was taking to someone about this, and they said the way they did
small round, was to lay them in a half circle bed that is slightly
wider than the stock, and that way it allows it to adjust itself to
the tap as it goes in. I'm looking at a tapping head, but the machine
I want to dedicate to it doesn't have the separate arbor... so I'm
not
sure if the built in arbor would fit the head. I'm wondering if it
would work to use a straight shank arbor on the head and then put
that
in the press chuck?

I always like to try the easiest solutions first. Opening them to
7/64" would work, but first check to see if the shank of a #36 drill
fits the existing hole. Maybe the hole got distorted somehow (metal
relaxed, bumping around, cut-off operation?). Maybe redrilling them
with the #36 drill bit will solve the problem.

Wouldn't that work harden the surface too maybe making it harder to tap?

I think that the OP was working with aluminum (6061), so I don't think
that he should have this problem. It's more common to see work
hardening problems with stainless steels.

A lot of aluminum alloys work harden too. 5052 sure does. That is one of
the two reasons its very important to blow or wash chips clear when
machining. The other is that the oxidized coating is harder than the base
metal.


Which brings up another question. How long are your aluminum pieces sitting
between processes? 5 minutes? 5 hours? I don't know about from a
machining perspective, but from a welding perspective that is a huge
difference.

Thanks for the PDF Dan, I'll check it out. Since the hole is twice the
screw width, I think it should be OK. I could probably even do #35. I
did a stress test and I couldn't get it to strip by hand.

If the work hardening thing is true, that could be something. I don't
know how they drilled these... But on the last batch that I drilled
myself and started having problems, I believe I did run the drill
faster than other times. But not even up to recommended speed though.
But maybe it still made a difference. There was probably more heat.
There's considerable time between drilling and tapping, but there
always has been.

I checked all the bits today and they all seem to spec. The #36 shaft
does fit back in the finished hole fine. I drilled out some of them to
7/64 then tapped by hand to see what it felt like. It was easier, but
I still felt like it would be likely that they would break fairly
easily. It gets that clogging feeling where it stops and you need to
back up a bit. That was on a spiral gun three flute. I'm using that
because it seems stronger. Helical taps seems to go through easier
over all without the binding, but they are weaker overall.

The only thing left is just the fact that it's 6-32, which I know is
not a favorite. But it is what it is. I can't believe changing the
thread size would be the difference between all the breaks and no
breaks. I still think there's something inherently wrong with how
we're doing it.

So has anybody ever tried using a tapping head with a straight shank
arbor chucked directly in the drill chuck?

Dave D wrote in news:26fb9af6-0454-483d-a348-
:

Thanks for the PDF Dan, I'll check it out. Since the hole is twice the
screw width, I think it should be OK. I could probably even do #35. I
did a stress test and I couldn't get it to strip by hand.

If the work hardening thing is true, that could be something. I don't
know how they drilled these... But on the last batch that I drilled
myself and started having problems, I believe I did run the drill
faster than other times. But not even up to recommended speed though.
But maybe it still made a difference. There was probably more heat.
There's considerable time between drilling and tapping, but there
always has been.

I checked all the bits today and they all seem to spec. The #36 shaft
does fit back in the finished hole fine. I drilled out some of them to
7/64 then tapped by hand to see what it felt like. It was easier, but
I still felt like it would be likely that they would break fairly
easily. It gets that clogging feeling where it stops and you need to
back up a bit. That was on a spiral gun three flute. I'm using that
because it seems stronger. Helical taps seems to go through easier
over all without the binding, but they are weaker overall.

The only thing left is just the fact that it's 6-32, which I know is
not a favorite. But it is what it is. I can't believe changing the
thread size would be the difference between all the breaks and no
breaks. I still think there's something inherently wrong with how
we're doing it.

So has anybody ever tried using a tapping head with a straight shank
arbor chucked directly in the drill chuck?

I really think you've got a problem with the alloy. I've never had a
problem with 6061-T6 work hardening to the point that it made tapping
difficult. 6-32 is definitely the nastiest thread size for tap breakage.
I recently made a simple bracket out of some scrap 1/8" aluminum panel
material. It was HORRIBLE stuff to work with. The aluminum was chewy,
and stuck instantly to the drill bits. The chips were stringy, and
clogged things up terribly. I sincerely doubt I would have been able to
tap a 6-32 thread in it without fits of one sort or another.

Doug White

Dave D wrote:

On hundreds of them, no problem. Then it stopped working
and I never did figure out why. I can't get through 15 without
breaking a tap now and I've tried everything.



Did the materials change? Reason I ask is we used to turn a bunch of 2xxx series
aluminum, life was good, parts are good. We bust open a pallet of stock and suddenly we
can't do anything right. In the morning, day shift figured that we recieved some 6061
delivered by mistake.

Wes
--
"Additionally as a security officer, I carry a gun to protect
government officials but my life isn't worth protecting at home
in their eyes." Dick Anthony Heller

On Jan 7, 7:22*pm, "Roger Shoaf" wrote:
"Dave D" wrote in message

So has anybody ever tried using a tapping head with a straight shank
arbor chucked directly in the drill chuck?

Yes it works fine, just run the drill press at a slow speed. *I seem to
recall the setup requiring an extension to the Tap-Matic to keep it from
spinning.


Thanks... I think I'm going to try that. Someone I talked to says he
thinks it is due to side forces, which will be eliminated with a
taping head. I hope so. But it still feels like it's catching when I
do it by hand though, so we'll see. It may very well be the aluminum.

On 2010-01-08, Dave D wrote:
On Jan 7, 7:22*pm, "Roger Shoaf" wrote:
"Dave D" wrote in message

So has anybody ever tried using a tapping head with a straight shank
arbor chucked directly in the drill chuck?

Yes it works fine, just run the drill press at a slow speed. *I seem to
recall the setup requiring an extension to the Tap-Matic to keep it from
spinning.


Thanks... I think I'm going to try that. Someone I talked to says he
thinks it is due to side forces, which will be eliminated with a
taping head. I hope so. But it still feels like it's catching when I
do it by hand though, so we'll see. It may very well be the aluminum.

Just out of curiosity -- is it possible that someone handed you
a batch of titanium rods instead of aluminum? I would expect serious
tapping difficulties with that.

And, BTW, I would prefer a two-flute gun tap to a three-flute
one, especially in 6-32 size.

Good Luck,
DoN.

--
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 ---

Update: I got hold of a pretty decent tapping head. I tried it out
today. It took a while to get the hang of it... I underestimated how
much pressure you need to put on it going down. I wasn't helping
through enough to start, and that was kind of screwing things up. But
once I got the hang of it, I got through about 100 pieces no problem.
It sounds stupid, but I actually just made a little holder out of a
piece of wood, then two little pieces of wood glued on top to fit the
round in-between. The whole thing can slide around and adjust, plus
the sides hold them loose enough that they can adjust. I backed the
torque off until it was disengaging, then put it a little above that.
Unfortunately it doesn't look like I will be able to use the combo
drill/taps on this drill, as there is too much run-out. But maybe on a
different one some day. But I'm just happy to stop breaking taps at
this point.

But anyway... Knock on wood, it looks like it's working. Thanks
everybody for the help.

On Sat, 16 Jan 2010 17:32:49 -0800 (PST), Dave D
wrote:
snip
But anyway... Knock on wood, it looks like it's working. Thanks
everybody for the help.
======
Its good to hear that somebody can still make something work.
Should be on the national news. Did you apply for your stimulus
funding yet? ;-)


Unka George (George McDuffee)
...............................
The past is a foreign country;
they do things differently there.
L. P. Hartley (1895-1972), British author.
The Go-Between, Prologue (1953).

I guess I jinxed it because I broke two today. If I back the torque
clutch off as far as it will go and still be able to do it, they still
break. So obviously there is some sort of inherent binding. I tried
hand tapping a few with both a #36 size hole and also 7/64" hole. When
examining I can see the tips of the threads are just slightly flatter
on the 7/64", but they still seem to hold as well as the ones done in
#36. But with the #36 I can feel there's a point where the tap just
sort of hits a hard part where it doesn't want to go further. You can
push it further, but that's where you start to feel like it could
break. I think that's the point where they are breaking, because
they're hitting that higher pressure point. On the 7/64" size holes,
it is more of a constant pressure through, without the point where it
binds. So I guess it will have to be 7/64".

OK, did like 500 today and didn't break a single thing. Woo hoo! I had
to ream all of them up to 7/64" to do it though. Bottom line, the taps
will simply not go through a #36 hole in one pass. I don't think it's
me, I just think that's the way it is. Maybe it's an inherent thing
with the 6-32 size and aluminum, or maybe if it wasn't going though
1/4" it would be better. But there's no way it will go through in one
pass on a #36. You can do it by hand, backing it off, but that's it.