I routinely have to tap 6-32 holes in the sides of 6061 aluminum 1/4
round by the hundreds. I thought I had it wired for a while, because I
was able to go through about 500 pieces before breaking a tap. Not the
end of the world. But today I broke 4 to go through the same amount.
I'm doing it the same way I did in the past, but something is going
wrong.

At any rate, I feel it's the lateral movement that is hurting me. On
the ones where I'm able to get the tap to go in perfectly straight,
you can feel that there's less resistance. The problem is that because
it's a round, it is very hard to get the piece clamped so the hole is
perfectly straight. I've been using a power drill, mainly because it
allows me to kind of adjust the angle a little if I feel too much
resistance. I would prefer to use a drill press with tap head, but I
don't know how you would align the hole with the tap properly, since
the part is round.

I'm not sure how they would do this in automated tooling. I guess
maybe do both the hole and tap at the same time somehow. I can't put
each piece in a clamp and move it each time, because that would take
forever. So I'm kind of at a loss right now. Breaking $40 of taps a
day isn't an option. Not to mention the time spent remaking the parts,
as the tap almost always breaks off without anything left sticking out
to extract it.

I would prefer to use a drill press with tap head, but I
don't know how you would align the hole with the tap properly, since
the part is round.

You need a vee block guide:

http://www.use-enco.com/CGI/INSRIT?PMAKA=318-0150

The photo doesn't show it, but the bottom of this guide has vees to align
to round stock just like you want.

On Tue, 16 Dec 2008 17:14:37 -0800 (PST), wrote:

I routinely have to tap 6-32 holes in the sides of 6061 aluminum 1/4
round by the hundreds. I thought I had it wired for a while, because I
was able to go through about 500 pieces before breaking a tap. Not the
end of the world. But today I broke 4 to go through the same amount.
I'm doing it the same way I did in the past, but something is going
wrong.

At any rate, I feel it's the lateral movement that is hurting me. On
the ones where I'm able to get the tap to go in perfectly straight,
you can feel that there's less resistance. The problem is that because
it's a round, it is very hard to get the piece clamped so the hole is
perfectly straight. I've been using a power drill, mainly because it
allows me to kind of adjust the angle a little if I feel too much
resistance. I would prefer to use a drill press with tap head, but I
don't know how you would align the hole with the tap properly, since
the part is round.

I'm not sure how they would do this in automated tooling. I guess
maybe do both the hole and tap at the same time somehow. I can't put
each piece in a clamp and move it each time, because that would take
forever. So I'm kind of at a loss right now. Breaking $40 of taps a
day isn't an option. Not to mention the time spent remaking the parts,
as the tap almost always breaks off without anything left sticking out
to extract it.


Good Evening
Any chance you could use a Greenlee "drill and tap"?

Example:

http://www.drillspot.com/products/34...ountersink_Bit

No connection, just one of the results of a Google on 'Greenlee drill
and tap'

Good luck

Bob
rgentry at oz dot net

wrote:
I routinely have to tap 6-32 holes in the sides of 6061 aluminum 1/4
round by the hundreds. I thought I had it wired for a while, because I
was able to go through about 500 pieces before breaking a tap. Not the
end of the world. But today I broke 4 to go through the same amount.
I'm doing it the same way I did in the past, but something is going
wrong.


I usually hold round stock to be cross tapped in the vise, but with just
a bit of clearance so the part can float and align. Using parallels held
apart with springs or bent spring flat stock, the round stock will
pretty much self center. It's easy to find center between the jaws with
an edge finder. Personally, I don't have any trouble lining up the hole
to the tap close enough that it won't self align as the tap enters.

I have a simple part I make for one customer that is 1/4" SS rod into
which I drill and tap 4-40 cross holes. I have two fixtures with a deep
groove centered lengthwise, and expanding clamps that force the rods
against the sides of the groove. I spot drill both sides of each rod
(have through holes in the fixture) so I don't have to deburr the holes
manually, drill, then bring to the drill press where I tap them. This
insures they are aligned properly for tapping.
These rods are then sawn between each tapped hole and the ends deburred.
Sounds a bit like your parts.

Another option if you have holes with regular spacing, would be to
machine a half round groove for the material. Drill a through hole to
clear the tap, and insert a pin centered along the groove at the hole to
hole distance. Pin need not pass through the part, setting into the
bottom of the groove will insure alignment so long as the pin is close
to hole dia at the bottom.

I've tapped a few hundred holes with a power drill. Haven't broken many
taps, but then I'm almost always tapping a hole perpendicular to a flat
surface, making it easier to reference if the tap is square.

Hope this helps a bit.

Jon

"Bob Gentry" wrote in message
...
On Tue, 16 Dec 2008 17:14:37 -0800 (PST), wrote:

I routinely have to tap 6-32 holes in the sides of 6061 aluminum 1/4
round by the hundreds. I thought I had it wired for a while, because I
was able to go through about 500 pieces before breaking a tap. Not the
end of the world. But today I broke 4 to go through the same amount.
I'm doing it the same way I did in the past, but something is going
wrong.

snip-----------------------


Good Evening
Any chance you could use a Greenlee "drill and tap"?

Example:

http://www.drillspot.com/products/34...ountersink_Bit

No connection, just one of the results of a Google on 'Greenlee drill
and tap'

Good luck

Bob
rgentry at oz dot net

As bob pointed out, get a "tap and drill" combination - several companies
make them - one shot gives you a tapped hole - and for aluminum you can use
a tap that forms the threads rather than cuts them - that way you get
stronger threads and a stronger tap and less swarf and much less change of a
swarf ball jamming up the tap

wrote in message
...
I routinely have to tap 6-32 holes in the sides of 6061 aluminum 1/4
round by the hundreds. I thought I had it wired for a while, because I
was able to go through about 500 pieces before breaking a tap. Not the
end of the world. But today I broke 4 to go through the same amount.
I'm doing it the same way I did in the past, but something is going
wrong.

At any rate, I feel it's the lateral movement that is hurting me. On
the ones where I'm able to get the tap to go in perfectly straight,
you can feel that there's less resistance. The problem is that because
it's a round, it is very hard to get the piece clamped so the hole is
perfectly straight. I've been using a power drill, mainly because it
allows me to kind of adjust the angle a little if I feel too much
resistance. I would prefer to use a drill press with tap head, but I
don't know how you would align the hole with the tap properly, since
the part is round.

I'm not sure how they would do this in automated tooling. I guess
maybe do both the hole and tap at the same time somehow. I can't put
each piece in a clamp and move it each time, because that would take
forever. So I'm kind of at a loss right now. Breaking $40 of taps a
day isn't an option. Not to mention the time spent remaking the parts,
as the tap almost always breaks off without anything left sticking out
to extract it.


Others ideas look good.

I've a similar job. I've mounted the motor/chuck from an old battery drill
adjacent a linear drawer slide with an angle bracket on it. I've wired a
reverse switch to the motor. I hold the work against the angle plate and
slide it on/off the tap controlling motor dirction with the other hand. I
can knock out M3 threads thru 2.5mm aluminium in about 10 seconds each.
Oddly enough I've been using methylated spirits for cutting fluid (flammable
I know). It seems to work ok and clean up is easy.

wrote in message
...
I routinely have to tap 6-32 holes in the sides of 6061 aluminum 1/4
round by the hundreds. I thought I had it wired for a while, because I
was able to go through about 500 pieces before breaking a tap. Not the
end of the world. But today I broke 4 to go through the same amount.
I'm doing it the same way I did in the past, but something is going
wrong.

At any rate, I feel it's the lateral movement that is hurting me. On
the ones where I'm able to get the tap to go in perfectly straight,
you can feel that there's less resistance. The problem is that because
it's a round, it is very hard to get the piece clamped so the hole is
perfectly straight. I've been using a power drill, mainly because it
allows me to kind of adjust the angle a little if I feel too much
resistance. I would prefer to use a drill press with tap head, but I
don't know how you would align the hole with the tap properly, since
the part is round.

I'm not sure how they would do this in automated tooling. I guess
maybe do both the hole and tap at the same time somehow. I can't put
each piece in a clamp and move it each time, because that would take
forever. So I'm kind of at a loss right now. Breaking $40 of taps a
day isn't an option. Not to mention the time spent remaking the parts,
as the tap almost always breaks off without anything left sticking out
to extract it.
How about a drilling/tapping block with a hole for the rod and a cross hole
for the drill and tap? If you are doing it by hand making the cross hole
large enough for the tap would likely align the drill close enough. Or you
could use two holes and slide the rod accordingly.

Don Young

These are all good ideas guys, thanks. I think there's multiple
options. I think the idea of not holding the part in a 100% fixed
position is good. I actually think that's the biggest problem. I think
if I did fix it so the part is held, but still allows to adjust
itself, that could help. Maybe if I had the tap head I could almost
just hand hold it in a V block and kind of guide it, while allowing
the tap itself to kind of adjust it slightly as it goes in.

If I just tried using the forming type of tap in the hand power drill,
do you think I'd break less by doing that than the normal gun taps?

I would ultimately love to use the combination drill/tap. That would
be a huge time saver. But that would at the least need the reversing
tap head. The Tapmatic ones are more money than my whole press is
worth. Has anybody ever had success with any that are a little less?

Also... On the combo ones, it would seem like there would be a lot of
room to screw up. The drill portion and tap portion are obviously
working at two different speeds, so even if you were doing it with a
reverse tapping head, I would assume that theoretically you could
start the tapping portion in before the drilling portion is finished.
I'd think that using something like that would work best with
something automated, where you could control things more exactly.

wrote:
I routinely have to tap 6-32 holes in the sides of 6061 aluminum 1/4
round by the hundreds. I thought I had it wired for a while, because I
was able to go through about 500 pieces before breaking a tap. Not the
end of the world. But today I broke 4 to go through the same amount.
I'm doing it the same way I did in the past, but something is going
wrong.

At any rate, I feel it's the lateral movement that is hurting me. On
the ones where I'm able to get the tap to go in perfectly straight,
you can feel that there's less resistance. The problem is that because
it's a round, it is very hard to get the piece clamped so the hole is
perfectly straight. I've been using a power drill, mainly because it
allows me to kind of adjust the angle a little if I feel too much
resistance. I would prefer to use a drill press with tap head, but I
don't know how you would align the hole with the tap properly, since
the part is round.

I'm not sure how they would do this in automated tooling. I guess
maybe do both the hole and tap at the same time somehow. I can't put
each piece in a clamp and move it each time, because that would take
forever. So I'm kind of at a loss right now. Breaking $40 of taps a
day isn't an option. Not to mention the time spent remaking the parts,
as the tap almost always breaks off without anything left sticking out
to extract it.
I use combined drill-taps for volume tapping.
They go for about $8 each. When things are going
right, I can do many hundreds of holes with one tap.

It may be hard to do if you are trying to start on
a curves side, though.
Usually, you would do this in at LEAST a drill
press, and possibly spot with a spotting drill or
lathe center drill first, then use the tap. In a
really rigid setup, though, you could probably
start the drill very slowly, and then increase the
feed after it has a good start.

I had been using a Procunier tapping head that
reverses when you start to retract the tap. I
have now got my CNC'd mini-mill set up with a
spindle encoder and a servo drive on the spindle
motor, so it can reverse to back the tap out of
the hole. It centers, drills and taps the hole in
about 10 seconds.

By doing the center, drill and tap all in one
operation, there is no question that it is
straight. I'm doing this mostly with 4-40 holes.
I really think even 6-32 is way too fragile for
hand feed with a drill. It is too heavy and the
torque throws off your feel of the forces on the
tap. Still, you might try spiral-flute (NOT
spiral point!) taps to see if they are more supple.

Sounds like you are not into CNC there, but you
CAN get a Tap-Matic tapping head for a drill
press. With the combined tap-drill, you'd do both
operations with hand feed in the same fixturing of
the part, so it would be straight. You need a
depth stop on the drill press so the tap can't goo
too deep. A wobbly drill press won't do on this
round part, it needs to have a rigid quill to
start the hole dead center. A bench-top
mill-drill should handle it, though.
Jon

wrote:

I would ultimately love to use the combination drill/tap. That would
be a huge time saver. But that would at the least need the reversing
tap head. The Tapmatic ones are more money than my whole press is
worth. Has anybody ever had success with any that are a little less?
I bought an $800 Procunier CNC tapping head for
about $100 on eBay.
I suspect the TapMatics are going for even less.

If you are doing HUNDREDS of these parts, then
such tools start to make a LOT of sense! If you
haven't seen these tap drills work, you'll CRY
when you first see one do it's stuff!

Also... On the combo ones, it would seem like there would be a lot of
room to screw up. The drill portion and tap portion are obviously
working at two different speeds, so even if you were doing it with a
reverse tapping head, I would assume that theoretically you could
start the tapping portion in before the drilling portion is finished.
I'd think that using something like that would work best with
something automated, where you could control things more exactly.

Yes, it does, no question about it. But, the
distance between the drill and thread is built
into the tool. I assume you can get them with
different lengths of drill, to make sure the drill
is all the way through before picking up the feed
for the tapping.

Jon

On 2008-12-17, wrote:
I routinely have to tap 6-32 holes in the sides of 6061 aluminum 1/4
round by the hundreds. I thought I had it wired for a while, because I
was able to go through about 500 pieces before breaking a tap. Not the
end of the world. But today I broke 4 to go through the same amount.
I'm doing it the same way I did in the past, but something is going
wrong.

Well ... aside from the fact that you're using 6-32, the weakest
thread and the most likely to break in the inch thread sizes ...

Did you change the brand of tap?

The style of tap? (e.g. replaced two flute spiral point gun
taps with standard plug taps?) A starting tap could get you
started a bit better, but you might have to change to plug taps
to get proper depth threads all the way through the workpiece.

The size of tap drill?

The alloy of aluminum?

The coolant which you are using with the tap? (For coolant in
aluminum, spritz the tap and hole with WD-40. It is almost
kerosene, which works fine for the purpose too.

At any rate, I feel it's the lateral movement that is hurting me. On
the ones where I'm able to get the tap to go in perfectly straight,
you can feel that there's less resistance. The problem is that because
it's a round, it is very hard to get the piece clamped so the hole is
perfectly straight. I've been using a power drill, mainly because it
allows me to kind of adjust the angle a little if I feel too much
resistance. I would prefer to use a drill press with tap head, but I
don't know how you would align the hole with the tap properly, since
the part is round.

Hmm ... with a tapping head, you might be able to use
combination drill and taps for this job. The drill part would break
through before the tap start started working I would think.

O.K.


================================================== ====================
MSC part # 00574186
Price: $14.48 ea

Description: HSS Combination Drill-Taps Thread Size: 6-32 Size: 0.1115
In. Material: HSS
Thread Size: 6-32
Number of Flutes: 2
Ground Thread Limit: H3
Size (Decimal Inch): 0.1115
Length (Inch): 5/16
Thread Length (Inch): 15/32
Material: HSS
Overall Length (Inch): 2
Big Book Page #: 215
================================================== ====================


O.K. It looks as though the drill part is 5/16" long, so it
would break through before the tapping starts. The tap section is
15/32" long -- enough to do a proper thread through the 1/4" diameter
round stock.

Use a tapping head of the kind which has a torque limit. Start
with the limit set to the minimum. Drill through with cutting fluid.
The start the tap. The clutch should start to slip. Slowly increase it
until you can complete the hole, and then adjust the clutch just a bit
more torque. Then, when to clutch starts to slip again, it is a sign
that the tap has gotten too dull to continue to use, and you should
replace it -- *don't* increase the torque setting, or you will break
more taps.

Since your hole will be drilled by the same tool as the thread
tapping is done, they *will* be in line. Anything which requires
changing tools will lead to misalignment.

Set up some kind of jig to guide a center punch between the jaws
of the vise so you will have a center punch truly on the top so the
drill won't try to skitter sideways around the curve of the round stock.

The expensive part will be the tapping head -- especially if you
need to buy it new. (I got mine over time from eBay sales and similar.)

Here is the one which looks right for your task:

================================================== ====================
MSC #: 00447391
Price: $661.97 ea

Description: Standard - Tapping Heads & Accessories Tap Size: M1.4 - M6
0 - 1/4 Mount: 3/8 - 24 Style: 30X
Tap Size: M1.4 - M6
0 - 1/4
Mount: 3/8 - 24
Style: 30X
Metalworking Catalog: 1182
================================================== ====================

The photo shows that it has the torque limit collar at the top,
and the 30X is the right size for the smaller taps -- #0 up to 1/4"

If you look through their catalog, you will find various mounts.
This one is 3/8-24, which means that you will need an arbor to screw
into it -- either one which will be held in the chuck, or better one
which converts it to the Morse taper for your drill press. The heads are
made with Jacobs taper sockets so you can use standard drill chuck
arbors. I took a No. 2 Morse Taper blank and turned the end to fit the
threaded socket in my head -- a larger diameter thread, IIRC.

I'm not sure how they would do this in automated tooling. I guess
maybe do both the hole and tap at the same time somehow.

That's what I've described above.

An alternative involves a CNC mill which would drill then
automatically change to a thread forming tap and do a thread forming
pass on the workpiece, which would make better threads in soft aluminum,
but which would be a problem when you have to change between drill and
tap unless you have a turret head on the drill press, like a Burgmaster
(which is what my first tapping head was made and marked for.)

I can't put
each piece in a clamp and move it each time, because that would take
forever. So I'm kind of at a loss right now. Breaking $40 of taps a
day isn't an option. Not to mention the time spent remaking the parts,
as the tap almost always breaks off without anything left sticking out
to extract it.

There are also good broken tap extractors. Check Waldrom, and
you need to have the right version for the number of flutes your tap
has. A gun (spiral point) tap will have two flutes in that size, and
will be a lot better for the task than a 3-fluted hand tap. The spiral
point chases the chips ahead of the tap so you don't have to constantly
reverse the tap to break chips. The combination tap and drill has a
spiral flute tap which tends to move the chips up above the workpiece.

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 ---

On 2008-12-17, Bill Noble wrote:

[ ... ]

As bob pointed out, get a "tap and drill" combination - several companies
make them - one shot gives you a tapped hole - and for aluminum you can use
a tap that forms the threads rather than cuts them - that way you get
stronger threads and a stronger tap and less swarf and much less change of a
swarf ball jamming up the tap

But can you use the combination drill and tap with thread
forming taps? Thread forming taps need to have the holes somewhat lager
to allow the stock displaced by the tap to form threads near the center
of the hole, and when you try to back the tap out, you will wind up
trying to cut away that displaced stock -- with the drill bit running
backwards.

I think that with thread forming, you are stuck with a separate
drill and tap.

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 ---

On 2008-12-17, wrote:
These are all good ideas guys, thanks. I think there's multiple
options. I think the idea of not holding the part in a 100% fixed
position is good. I actually think that's the biggest problem. I think
if I did fix it so the part is held, but still allows to adjust
itself, that could help. Maybe if I had the tap head I could almost
just hand hold it in a V block and kind of guide it, while allowing
the tap itself to kind of adjust it slightly as it goes in.

If I just tried using the forming type of tap in the hand power drill,
do you think I'd break less by doing that than the normal gun taps?

A thread forming tap has less lead-in taper than a gun tap, so
it requires a more automated system than you can handle manually --
unless you have quick-change collets to swap drill and tap in the same
head.

I would ultimately love to use the combination drill/tap. That would
be a huge time saver. But that would at the least need the reversing
tap head. The Tapmatic ones are more money than my whole press is
worth. Has anybody ever had success with any that are a little less?

Have you looked at eBay? I find four of the 30X ones there at
the moment, and only one is even up to serious money as I type:

Auctions:

310108611663 $117.50 (1 Hour 45 minutes) With MT-2 shank and adaptor for
R-8 mill spindle.
16 bids

110325747423 $10.50 (3 hours 20 mins) (five of them, but you need to
get your arbor for your drill.)
2 bids

150315664537 $51.00 (3 days 21 hours) 1/2" straight shank to go
into your drill chuck.
4 bids

130276363480 $9.99 (6 days 1 hour) 1/2-20 thread mount to arbor.
no bids yet.

There are also four more in the "Store" section of the list, ranging
from $150.00 to $505.00

The last of those looks like the best bet (other than the lack
of an arbor), because it has all of the wrenches needed. The wrenches
need to be thinner than the typical open-end wrench. I just got through
using a surface grinder to grind down one open end wrench to fit part of
mine, and I still need to do so on another wrench (5/8" IIRC) to handle
the larger fitting on the collet closer nose. The Allen key is to
adjust the clamping plates for the square end of the tap's shank. The
Rubberflex collet resists pull-out of the tap.

You'll still have to buy the right size RubberFlex collet (the
smaller of the two listed in MSC for the tapping head) for your 6-32
taps. I had to by new Rubberflex collets for each of my Tapmatic heads,
as there was only one in the whole combination, and it had the rubber
attacked by a cleaning solvent or heat and turning to goo. :-)

Also... On the combo ones, it would seem like there would be a lot of
room to screw up. The drill portion and tap portion are obviously
working at two different speeds,

Why? The drill speed calculated is for maximum production and
wears out the drill sooner than a slower speed. Select a speed for the
tapping part, and just be a little more patient in the drilling. You'll
save so much time in not having to change drill and tap all the time
that you will be ahead of the game to start with.

so even if you were doing it with a
reverse tapping head, I would assume that theoretically you could
start the tapping portion in before the drilling portion is finished.

If the workpiece it too thick. The one which I found for 6-32
in MSC has the drill part 5/16" long, so the point will exit before the
tap starts its work. If you were using something thicker, you would
have problems, because the tip really *must* clear the workpiece before
the tap starts to work. Otherwise, it tries to feed the drill too fast.

BTW -- if you set things up right, you could probably hold a square
collet block in a drill press vise, and just slide the workpiece into a
1/4" 5C collet. They collet block sets have both square and hex, and
have either a screw in or a lever closing collet closer. Go for the
lever one for this -- and if you need the cross holes a specific
distance from the end, add a collet stop inside the collet to make
things repeatable.

I'd think that using something like that would work best with
something automated, where you could control things more exactly.

This applies more to the thread forming tap than to the
TapMatic, I think.

BTW I've no connection to any of the auctions which I listed. They were
simply what an eBay search for:

Tapmatic 30X

turned up. If I did not already have that size, I would
probably be bidding on one myself. The prices have gotten nicer
over the years. :-)

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---

Hey Xray,

If this is something that you have been doing with success in the
past, and now without anything else in your methods changing you are
having trouble, then look first to the aluminum material being a
different grade or quality, and second to the taps as being either a
poor grade or somewhat odd-size as in plus .003" or something like
that.

Take care.

Brian Lawson,
Bothwell, Ontario.
XXXXXXXXXXXXXXXXXXXXX

On Tue, 16 Dec 2008 17:14:37 -0800 (PST), wrote:

I routinely have to tap 6-32 holes in the sides of 6061 aluminum 1/4
round by the hundreds. I thought I had it wired for a while, because I
was able to go through about 500 pieces before breaking a tap. Not the
end of the world. But today I broke 4 to go through the same amount.
I'm doing it the same way I did in the past, but something is going
wrong.


SNIP

On Tue, 16 Dec 2008 19:48:33 -0800 (PST) in rec.crafts.metalworking,
wrote,
if I did fix it so the part is held, but still allows to adjust
itself, that could help. Maybe if I had the tap head I could almost
just hand hold it in a V block and kind of guide it, while allowing
the tap itself to kind of adjust it slightly as it goes in.

In my experience, that's a bad idea. It's most important to start the
tap as straight as possible. As soon as the tap cuts the first crooked
thread, it will try to use that to guide itself the rest of the way. Not
the hole. #1 cause of broken taps in hand tapping.

You don't say what's attached to the rod, but if you're going to end up
putting screws into the holes, see if you can't just use self-tapping
screws.

I can't imagine how you're able to drill or tap that many holes anywhere
near where they need to be with a handheld drill motor.
I wouldn't even attempt 50 holes in round stock, let alone 500 without a
drill press and some sort of improvised fixture.
And a good cutting lube.
And good lighting.

A cheap Chinese drill press costs about $50, but may not last long, but a
better drill press would run for quite a while, but that's a lot of stopping
and restarting.

Cheap AC motor machines don't reverse to remove the tap, so a balanced
handwheel on top of the spindle pulley would allow the operator to back the
tap out (6 turns, maybe).

A better solution would be a cheap drill press, but replacing the AC motor
with a DC motor which would be reversible, and could handle the repeated
stopping and starting much better.
There wouldn't be much coasting to deal with, but an electric brake
(normally on when motor is stopped) would almost eliminate any coasting of
the motor armature and spindle motion.

If the drill was properly guided to hit the centerline, a cheap quick change
hex bit chuck (the kind available for swapping bits in drill motors) would
be adequate for that size drill and tap. They would both be too small to
just grind a 1/4" hex on their shanks, but a little lathe work with some
1/4" hex brass would turn out some hex adapters very quickly.

Instead of swapping the drill and tap repeatedly, the combo drill-tap tool
would most likely last a long time if guided, supported and aligned
properly, rather than being run with a handheld drill motor.

Those are some impressive quantities that you were able to do by hand,
though.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


wrote in message
...
I routinely have to tap 6-32 holes in the sides of 6061 aluminum 1/4
round by the hundreds. I thought I had it wired for a while, because I
was able to go through about 500 pieces before breaking a tap. Not the
end of the world. But today I broke 4 to go through the same amount.
I'm doing it the same way I did in the past, but something is going
wrong.

At any rate, I feel it's the lateral movement that is hurting me. On
the ones where I'm able to get the tap to go in perfectly straight,
you can feel that there's less resistance. The problem is that because
it's a round, it is very hard to get the piece clamped so the hole is
perfectly straight. I've been using a power drill, mainly because it
allows me to kind of adjust the angle a little if I feel too much
resistance. I would prefer to use a drill press with tap head, but I
don't know how you would align the hole with the tap properly, since
the part is round.

I'm not sure how they would do this in automated tooling. I guess
maybe do both the hole and tap at the same time somehow. I can't put
each piece in a clamp and move it each time, because that would take
forever. So I'm kind of at a loss right now. Breaking $40 of taps a
day isn't an option. Not to mention the time spent remaking the parts,
as the tap almost always breaks off without anything left sticking out
to extract it.

You don't say what's attached to the rod, but if you're going to end up
putting screws into the holes, see if you can't just use self-tapping
screws.

I can't imagine how you're able to drill or tap that many holes anywhere
near where they need to be with a handheld drill motor.
I wouldn't even attempt 50 holes in round stock, let alone 500 without a
drill press and some sort of improvised fixture.
And a good cutting lube.
And good lighting.

A cheap Chinese drill press costs about $50, but may not last long, but a
better drill press would run for quite a while, but that's a lot of stopping
and restarting.

Cheap AC motor machines don't reverse to remove the tap, so a balanced
handwheel on top of the spindle pulley would allow the operator to back the
tap out (6 turns, maybe).

A better solution would be a cheap drill press, but replacing the AC motor
with a DC motor which would be reversible, and could handle the repeated
stopping and starting much better.
There wouldn't be much coasting to deal with, but an electric brake
(normally on when motor is stopped) would almost eliminate any coasting of
the motor armature and spindle motion.

If the drill was properly guided to hit the centerline, a cheap quick change
hex bit chuck (the kind available for swapping bits in drill motors) would
be adequate for that size drill and tap. They would both be too small to
just grind a 1/4" hex on their shanks, but a little lathe work with some
1/4" hex brass would turn out some hex adapters very quickly.

Instead of swapping the drill and tap repeatedly, the combo drill-tap tool
would most likely last a long time if guided, supported and aligned
properly, rather than being run with a handheld drill motor.

Those are some impressive quantities that you were able to do by hand,
though.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


wrote in message
...
I routinely have to tap 6-32 holes in the sides of 6061 aluminum 1/4
round by the hundreds. I thought I had it wired for a while, because I
was able to go through about 500 pieces before breaking a tap. Not the
end of the world. But today I broke 4 to go through the same amount.
I'm doing it the same way I did in the past, but something is going
wrong.

At any rate, I feel it's the lateral movement that is hurting me. On
the ones where I'm able to get the tap to go in perfectly straight,
you can feel that there's less resistance. The problem is that because
it's a round, it is very hard to get the piece clamped so the hole is
perfectly straight. I've been using a power drill, mainly because it
allows me to kind of adjust the angle a little if I feel too much
resistance. I would prefer to use a drill press with tap head, but I
don't know how you would align the hole with the tap properly, since
the part is round.

I'm not sure how they would do this in automated tooling. I guess
maybe do both the hole and tap at the same time somehow. I can't put
each piece in a clamp and move it each time, because that would take
forever. So I'm kind of at a loss right now. Breaking $40 of taps a
day isn't an option. Not to mention the time spent remaking the parts,
as the tap almost always breaks off without anything left sticking out
to extract it.

I haven't tried anything like this, but maybe you could custom grind a tap
to create a pilot, the way counterbore cutters are formed.

I would think it could possibly just be a waste of a tap, but grinding an
accurate pilot on the end of a forming tap may actually help get the tap
closely aligned with the hole. I have a drill from a fleamarket junk box
that has a pilot brazed to the drill point, and it works better than I
thought it would.
I would guess that about the only way to accomplish a pilot on a tap would
be with a precision tool and cutter grinder, forming a tapered lead-in that
duplicates the original start for the forming portion of the tap.

What Brian and some others suggested, the alloy may be different (maybe the
most likely change), and/or the tap size designation Hx, or the hole size
may be different due to feed/speed changes etc, or possibly even the drill
size may be slightly different.

--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html


wrote in message
...
I routinely have to tap 6-32 holes in the sides of 6061 aluminum 1/4
round by the hundreds. I thought I had it wired for a while, because I
was able to go through about 500 pieces before breaking a tap. Not the
end of the world. But today I broke 4 to go through the same amount.
I'm doing it the same way I did in the past, but something is going
wrong.

At any rate, I feel it's the lateral movement that is hurting me. On
the ones where I'm able to get the tap to go in perfectly straight,
you can feel that there's less resistance. The problem is that because
it's a round, it is very hard to get the piece clamped so the hole is
perfectly straight. I've been using a power drill, mainly because it
allows me to kind of adjust the angle a little if I feel too much
resistance. I would prefer to use a drill press with tap head, but I
don't know how you would align the hole with the tap properly, since
the part is round.

I'm not sure how they would do this in automated tooling. I guess
maybe do both the hole and tap at the same time somehow. I can't put
each piece in a clamp and move it each time, because that would take
forever. So I'm kind of at a loss right now. Breaking $40 of taps a
day isn't an option. Not to mention the time spent remaking the parts,
as the tap almost always breaks off without anything left sticking out
to extract it.

Thanks for all the help everybody, I appreciate the effort. The holes
themselves are drilled on a press. I do that with a jig I built that
has quick release clamps that just locks the round in. I can't use the
press to do the tapping because I don't have the reverse head. But if
I did, I would just go with the combo drill/tap, because it would be
silly not to, and it would be too hard to re-align the hole for the
tap once you take it out of the clamp. I've been doing the counter
sink by just pressing each one against a counter sink for a few secs.

But yes, believe it or not, up until now I had been doing 500 or more
on one tap by just putting the piece in a vise and using a power
drill. I put a dab of lube in the hole and it seemed to work fine. I
was using the same aluminum from the same dealer, same alloy as far as
I can tell, and the taps look to be exactly the same as the past ones.
So I don't know what started going wrong.

But I will probably get the tap head and that will save a lot of time
in the end. I notice HF has one, but it doesn't appear to have the
safety clutch.

On Tue, 16 Dec 2008 17:14:37 -0800 (PST), wrote:


I'm not sure how they would do this in automated tooling. I guess
maybe do both the hole and tap at the same time somehow.


They drill then tap using either a CNC miller of some sort, or a
Burgmeister turret drill and tapmatic tapping heads

The trick is to NOT move the workpiece between operations

Or index it in some repeatable fashion

Gunner

"They couldn't hit an elephant at this dist..."
Maj. Gen. John Sedgewick, killed by a sniper in 1864 at the battle of Spotsylvania