Remind me to pay attention to things that don't pertain to me at the
time but......... Broken 6-32 tap in a small 6061 aluminum part, hole
is all the way through. Which acid to use? What strength?

"RoyJ" wrote in message
...
Remind me to pay attention to things that don't pertain to me at the time
but......... Broken 6-32 tap in a small 6061 aluminum part, hole is all
the way through. Which acid to use? What strength?

Nitric, straight from the bottle
--
Stupendous Man,
Defender of Freedom, Advocate of Liberty

RoyJ wrote:

Remind me to pay attention to things that don't pertain to me at the
time but......... Broken 6-32 tap in a small 6061 aluminum part, hole
is all the way through. Which acid to use? What strength?

Roy, you could do the job with nitric acid, but good luck trying to buy
some! There is a kit you can buy which will do this for you. The kit is
called "Tap Out" and the only place I know for sure where to get it is
at Swift Tool, a machinist supply house local to Seattle. I haven't
had any luck finding it online, sorry.

Grant

"RoyJ" wrote in message
...
Remind me to pay attention to things that don't pertain to me at the time
but......... Broken 6-32 tap in a small 6061 aluminum part, hole is all
the way through. Which acid to use? What strength?

Nitric won't dissolve aluminum, while other acids (H2SO4 or HCl) will. It
will etch the alloying elements in the stuff, however, so if you have
critical sizes, that may not be in your best interest.

I used to use nitric to clean 6061-T6 aluminum parts after buffing. It was
the easiest way to remove the buffing compound. I found sizes changed by a
tenth or two. My parts were placed in a dish of tech grade nitric and
water, maybe 25% acid, 75% water, and heated to below boiling. You
should be able to do the same thing with a broken tap, but allow plenty of
time for the tap to dissolve. It may not be very fast.

Harold

"Stupendous Man" wrote in message
...

"RoyJ" wrote in message
...
Remind me to pay attention to things that don't pertain to me at the time
but......... Broken 6-32 tap in a small 6061 aluminum part, hole is all
the way through. Which acid to use? What strength?

Nitric, straight from the bottle
--
Stupendous Man,
Defender of Freedom, Advocate of Liberty


It's actually better to include some water (hydronium ion).

Harold

According to RoyJ :
Remind me to pay attention to things that don't pertain to me at the
time but......... Broken 6-32 tap in a small 6061 aluminum part, hole
is all the way through. Which acid to use? What strength?

Others have covered that part of your question, but I have to
ask whether you have tried the broken tap extractors.

For No. 6 taps, they are made in 2-flute, 3-flute and 4-flute
sizes, though you can use the four-flute one for 2-flute taps with care.

You need to grind the broken tap off close to flush with the
surface of the workpiece (assuming that it projects outside the hole),
or to grind it flat inside using a small mounted grinding point in a
Dremel or equivalent so the fingers don't shear off. (Be sure to read
the instructions which come with it.) I've got a built-up set which
covers from #4 screws up through 1/2" at least. The set came from an
eBay auction, which was filled out (there were a couple missing) and
extended to the smaller sizes from MSC purchases.

I think that the brand is "Waldrom", but the set is downstairs,
and the MSC web site is not happy at the moment. :-)

I did recently use the set to remove a four-flute 1/2-13 tap
which broke off in the workpiece -- and I replaced the tap with a couple
of 1/2-13 spiral point gun taps for better results.

Enjoy,
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 ---

The part is question is a simple 'U' bracket with set screws on either
side as part of a student project. It was the last hole, he got
overconfident. My guess is the tap drill size was too small. If it
doesn't come out with tossing it into a beaker of acid, I'll just have
him remake the part.

DoN. Nichols wrote:
According to RoyJ :
Remind me to pay attention to things that don't pertain to me at the
time but......... Broken 6-32 tap in a small 6061 aluminum part, hole
is all the way through. Which acid to use? What strength?

Others have covered that part of your question, but I have to
ask whether you have tried the broken tap extractors.

For No. 6 taps, they are made in 2-flute, 3-flute and 4-flute
sizes, though you can use the four-flute one for 2-flute taps with care.

You need to grind the broken tap off close to flush with the
surface of the workpiece (assuming that it projects outside the hole),
or to grind it flat inside using a small mounted grinding point in a
Dremel or equivalent so the fingers don't shear off. (Be sure to read
the instructions which come with it.) I've got a built-up set which
covers from #4 screws up through 1/2" at least. The set came from an
eBay auction, which was filled out (there were a couple missing) and
extended to the smaller sizes from MSC purchases.

I think that the brand is "Waldrom", but the set is downstairs,
and the MSC web site is not happy at the moment. :-)

I did recently use the set to remove a four-flute 1/2-13 tap
which broke off in the workpiece -- and I replaced the tap with a couple
of 1/2-13 spiral point gun taps for better results.

Enjoy,
DoN.

Go down to an old style drugstore and buy some alum. It'll be in the aisle
with the boric acid and epsom salts.

Get a beaker with enough volume to hold your part. immerse your bracket in a
saturated solution of alum in water and heat to around 150-180 deg f. You
will soon see bubbles coming off your tap. Add enough water to counter
evaporation. Continue til the tap dissolves.

It is cheap, safe, reasonably non toxic, and (best of all) you don't end up
with yellow nitric acid stains on your fingers.

Paul K. Dickman

"RoyJ" wrote in message
...
Remind me to pay attention to things that don't pertain to me at the time
but......... Broken 6-32 tap in a small 6061 aluminum part, hole is all
the way through. Which acid to use? What strength?

According to RoyJ :
The part is question is a simple 'U' bracket with set screws on either
side as part of a student project. It was the last hole,

Always. :-) (Though actually, the 1/2-13 that I broke recently
was the first of two holes -- and I had had the tap for a long time, so
it may have gotten dull, too.

he got
overconfident.

The 6-32 is probably the easiest tap to break in the common
sizes. If *you* assigned the part, then you really wanted to test his
threading. :-)

My guess is the tap drill size was too small.

That depends. Some aluminum alloys gum up rather easily, and if
you don't reverse (assuming a normal tap instead of a spiral-point "gun"
tap) you do run the risk of breaking it more easily than when tapping a
nice steel like 12L14.

If it
doesn't come out with tossing it into a beaker of acid, I'll just have
him remake the part.

O.K.

Enjoy,
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 ---

Grant Erwin wrote:
Roy, you could do the job with nitric acid, but good luck trying to buy
some! ...

http://www.sciencelab.com/page/S/CTGY/10421
Scroll way down to "nitric acid" (not alphabetical list). Many
different concentrations. NOT cheap & subject to hazmat shipping charges.

Bob

Heh, you think I get to OK every detail with 18 teams working on
prototype projects? Nope, just get the "what do I do now? part. It gets
real hectic toward the end of the semester.

Now that I think about it, it was probably an 8-32. Didn't seem to be
real relevant at the point where I was looking at it. And all I was
looking at was the flush stub of the tap.

Oh well, back at it in the AM.

DoN. Nichols wrote:
According to RoyJ :
The part is question is a simple 'U' bracket with set screws on either
side as part of a student project. It was the last hole,

Always. :-) (Though actually, the 1/2-13 that I broke recently
was the first of two holes -- and I had had the tap for a long time, so
it may have gotten dull, too.

he got
overconfident.

The 6-32 is probably the easiest tap to break in the common
sizes. If *you* assigned the part, then you really wanted to test his
threading. :-)

My guess is the tap drill size was too small.

That depends. Some aluminum alloys gum up rather easily, and if
you don't reverse (assuming a normal tap instead of a spiral-point "gun"
tap) you do run the risk of breaking it more easily than when tapping a
nice steel like 12L14.

If it
doesn't come out with tossing it into a beaker of acid, I'll just have
him remake the part.

O.K.

Enjoy,
DoN.

"Paul K. Dickman" wrote in
:

Go down to an old style drugstore and buy some alum. It'll
be in the aisle with the boric acid and epsom salts.

Get a beaker with enough volume to hold your part. immerse
your bracket in a saturated solution of alum in water and
heat to around 150-180 deg f. You will soon see bubbles
coming off your tap. Add enough water to counter
evaporation. Continue til the tap dissolves.

It is cheap, safe, reasonably non toxic, and (best of all)
you don't end up with yellow nitric acid stains on your
fingers.

Paul K. Dickman

"RoyJ" wrote in message
...
Remind me to pay attention to things that don't pertain to
me at the time but......... Broken 6-32 tap in a small
6061 aluminum part, hole is all the way through. Which
acid to use? What strength?



I agree Paul!

I'm one of the posters from the past that used aluminium
ammonium sulfate to remove small (2-56 and 4-40 taps and tap
drills) from aluminum parts my students were machining. These
were small and took a week (weekdays only) in a heated bath
of water and alum on a stirred hot plate. I use lab grade
aluminium ammonium sulfate (alum) from our chem stock room.
It worked. I tried the same thing with alum from the grocery
store's spice rack recently and it didn't seem as effective
(I was also in a hurry too).

Ken

According to RoyJ :
Heh, you think I get to OK every detail with 18 teams working on
prototype projects? Nope, just get the "what do I do now? part. It gets
real hectic toward the end of the semester.

O.K. You have about as much choice as the students do. :-)

Now that I think about it, it was probably an 8-32. Didn't seem to be
real relevant at the point where I was looking at it. And all I was
looking at was the flush stub of the tap.

Hmm ... any of the break angling inside the hole, or is it all
right at or above the surface. If the latter, the broken tap extractors
really can do a good job -- if whoever uses them takes the time to read
and *obey* the instruction sheet which comes with it.

Anyway -- tonight it is early enough so I've gone down to the
shop to get my set and check the brand. It is "Walton", and my
collection goes from #4 (both 2-flute and 3-flute) up through 5/8"
4-flute only in my collection). The #8 one also is specified as being
for 4mm metric screws. The smallest size which *officially* fits in my
set is the 5/16" 4-flute. All of the smaller sizes sort of rest between
the larger ones in their fitted pockets. The set (not quite complete)
appears to have cost me $25.00 at some form of flea market with four or
five of the official six present. Filling out the set certainly cost me
as much as the set if there were two missing -- not counting what I
added in the smaller sizes.

Oh well, back at it in the AM.

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 ---