I need to drill and tap quite a few aluminum spacers. The spacers are
solid aluminum cylinders about 1/8" diameter and about 5/8" long.

I need to drill and tap all the way thru for 0-80 machines screws
which will hold down plates seperated by the spacers.

3/64" pilot bits and 0-80 taps break off too frequently even though
the material is aluminum and sometimes brass.

I've never used forming taps. Do they work well? I wouldn't think
they'd be as delicate since they don't have flutes. In addition the
pilot bit would be a tad beefier at #54 vs 3/64".

If I stick with cutting taps what tap qualities should I be looking
for in miniature taps for soft metals? (ie Coating, material, tap
style, manufacturer, etc)

On Nov 30, 1:20*pm, Bud wrote:
I need to drill and tap quite a few aluminum spacers. *The spacers are
solid aluminum cylinders about 1/8" diameter and about 5/8" long.

I need to drill and tap all the way thru for 0-80 machines screws
which will hold down plates seperated by the spacers.

3/64" pilot bits and 0-80 taps break off too frequently even though
the material is aluminum and sometimes brass.

I've never used forming taps. *Do they work well? *I wouldn't think
they'd be as delicate since they don't have flutes. *In addition the
pilot bit would be a tad beefier at #54 vs 3/64".

If I stick with cutting taps what tap qualities should I be looking
for in miniature taps for soft metals? (ie Coating, material, tap
style, manufacturer, etc)

Hi, Bud.
My first question is: how much holding power do you need for the
project? Second question is: Can you get self tapping screws that
small and would they work? Third question: Can you drill the hole
larger before tapping?

The problem I have found with small taps and AL is the taps keep
gumming up with AL and I have to back the tap out completely and clean
about once per turn. I guess I would look for two flute taps for the
project. And would try a forming tap to see if it will work for you,
at least in the AL spacers. I have had good luck with 4-40 screws
creating their own thread in soft aluminum.

Paul

"Bud" wrote in message
...
I need to drill and tap quite a few aluminum spacers. The spacers are
solid aluminum cylinders about 1/8" diameter and about 5/8" long.

I need to drill and tap all the way thru for 0-80 machines screws
which will hold down plates seperated by the spacers.

3/64" pilot bits and 0-80 taps break off too frequently even though
the material is aluminum and sometimes brass.

I've never used forming taps. Do they work well? I wouldn't think
they'd be as delicate since they don't have flutes. In addition the
pilot bit would be a tad beefier at #54 vs 3/64".

If I stick with cutting taps what tap qualities should I be looking
for in miniature taps for soft metals? (ie Coating, material, tap
style, manufacturer, etc)

I'm no expert on small hole tapping... But I'd think that you could "peck"
drill and tap to clear the chips and debris to help keep those tools from
breaking.

I forget what the best lubricant is for aluminum (kerosene? Crisco?) but
I'd say reapplying it on each peck is crucial regardless of whether it is a
cut or roll form tap.

The roll form tap tooling itself will be stronger... But it will also
require more power for the process. If the thread strength isn't too
critical, drill the hole slightly oversized a bit...

How are you tapping these? By hand? CNC?

Regards,
Joe Agro, Jr.
(800) 871-5022
01.908.542.0244
Automatic / Pneumatic Drills: http://www.AutoDrill.com
Multiple Spindle Drills: http://www.Multi-Drill.com
Production Tapping: http://Production-Tapping-Equipment.com/
Flagship Site: http://www.Drill-N-Tap.com
VIDEOS: http://www.youtube.com/user/AutoDrill

V8013-R

I need very little holding power and the machine screws I'm using are
0-80 X 1/8". Since the length is 2X the diameter I might try going
from a 3/64 pilot bit to a #54. That would still give me about 50%
thread contact.

I also read the spiral taps aren't the best if you have to back out
before the tip ejects the chips. I can't go thru hole with the tap
since it's effective cutting length is 5/16" and my part is 5/8".




On Nov 30, 1:47*pm, " wrote:
On Nov 30, 1:20*pm, Bud wrote:





I need to drill and tap quite a few aluminum spacers. *The spacers are
solid aluminum cylinders about 1/8" diameter and about 5/8" long.

I need to drill and tap all the way thru for 0-80 machines screws
which will hold down plates seperated by the spacers.

3/64" pilot bits and 0-80 taps break off too frequently even though
the material is aluminum and sometimes brass.

I've never used forming taps. *Do they work well? *I wouldn't think
they'd be as delicate since they don't have flutes. *In addition the
pilot bit would be a tad beefier at #54 vs 3/64".

If I stick with cutting taps what tap qualities should I be looking
for in miniature taps for soft metals? (ie Coating, material, tap
style, manufacturer, etc)

Hi, Bud.
My first question is: how much holding power do you need for the
project? Second question is: Can you get self tapping screws that
small and would they work? Third question: Can you drill the hole
larger before tapping?

The problem I have found with small taps and AL is the taps keep
gumming up with AL and I have to back the tap out completely and clean
about once per turn. I guess I would look for two flute taps for the
project. And would try a forming tap to see if it will work for you,
at least in the AL spacers. I have had good luck with 4-40 screws
creating their own thread in soft aluminum.

Paul- Hide quoted text -

- Show quoted text -

"Bud" wrote in message
...
I need to drill and tap quite a few aluminum spacers. The spacers are
solid aluminum cylinders about 1/8" diameter and about 5/8" long.

I need to drill and tap all the way thru for 0-80 machines screws
which will hold down plates seperated by the spacers.

3/64" pilot bits and 0-80 taps break off too frequently even though
the material is aluminum and sometimes brass.

I've never used forming taps. Do they work well? I wouldn't think
they'd be as delicate since they don't have flutes. In addition the
pilot bit would be a tad beefier at #54 vs 3/64".

If I stick with cutting taps what tap qualities should I be looking
for in miniature taps for soft metals? (ie Coating, material, tap
style, manufacturer, etc)


I dont know what you are doing or why, perhaps the option is available to
buy rather than make. Similar parts are not that expensive:

http://www.keyelco.com/products/prod...bCategoryID=94

On Nov 30, 10:16*pm, Bud wrote:

I also read the spiral taps aren't the best if you have to back out
before the tip ejects the chips. *I can't go thru hole with the tap
since it's effective cutting length is 5/16" and my part is 5/8".


I have no experience with real small taps. But your statement that
you can not go thru hole with the tap, made me think that you could go
thru hole with the drill. Or if not all the way thru, then enough so
the chips can have a place to go.

Could you use a drive screw? No tapping required.

http://www.hansonrivet.com/w58.htm


Dan

On Nov 30, 5:16*pm, Bud wrote:
I need very little holding power and the machine screws I'm using are
0-80 X 1/8". *Since the length is 2X the diameter I might try going
from a 3/64 pilot bit to a #54. *That would still give me about 50%
thread contact.

I also read the spiral taps aren't the best if you have to back out
before the tip ejects the chips. *I can't go thru hole with the tap
since it's effective cutting length is 5/16" and my part is 5/8".

Spiral point taps will leave chips inside that you can poke out with
the pilot drill. Would it hurt if a piece fell out at assembly?

An early prototype of the UAT
http://en.wikipedia.org/wiki/Automat...ance-broadcast
had about 120 0-80 screws holding on a cover I removed several times a
day. I changed to 2-56 tapped with a forming tap which slightly
reduced the nuisance factor and increased the parts yield from the
shop. The pilot holes were slightly oversized and the taps formed a
double ridge rather than a complete thread, so a screw could go in the
easy or the hard way. This wasn't visible to inspectors.

jsw

What's that Lassie? You say that Bud fell down the old
rec.crafts.metalworking mine and will die if we don't mount a rescue
by Mon, 30 Nov 2009 14:16:23 -0800 (PST):

I need very little holding power and the machine screws I'm using are
0-80 X 1/8". Since the length is 2X the diameter I might try going
from a 3/64 pilot bit to a #54. That would still give me about 50%
thread contact.

If your screws are 1/8" long, why do you need to tap all the way
though?

If you can go at it from both ends, a forming tap is the way to go.
Get some Tap magic tapping fluid, and make sure the tap is true to the
hole.

--

Dan H.
northshore MA.

On 2009-11-30, Bud wrote:
I need to drill and tap quite a few aluminum spacers. The spacers are
solid aluminum cylinders about 1/8" diameter and about 5/8" long.

I need to drill and tap all the way thru for 0-80 machines screws
which will hold down plates seperated by the spacers.

Hmm ... 5/8" sounds longer than I remember ever seeing as the
thread length on any 0-80 taps which I have ever had. Can you not use
short 0-80 studs and just tap from each end?

Even if the tap *is* that long, it is likely to be just barely
so, so the end threads will be still in the tapered section and thus too
tight on your screw.

3/64" pilot bits and 0-80 taps break off too frequently even though
the material is aluminum and sometimes brass.

Looking into the _Machinery's Handbook_ chart for tap drills,
after calculating that 3/64" is 0.0469" I find a listing of different
diameter tap drills for differing lengths of engagement. This is a
tradeoff between thread strength per thread and the number of threads
which will be holding the load vs the difficulty of drilling that deep a
hole.

The longest engagement range is 1-1/2D to 3D, and your
engagement is 10.41D, so the largest tap drill range shown 0.0479 to
0.0514 is indicated -- and that is noticeably larger than your tap
drill, so I would suggest a number drill not a fractional one. (I would
have anyway -- fractional sizes are seldom right as tap drills.)

You first want drill bits selected for the material you are
drilling. At a guess, a parabolic flute bit to give smoother chip
clearance. And the proper selection should vary with the aluminum
alloy, and is best suggested by the drill bit makers. They have numbers
to call to answer just such questions. I would suggest a hard aluminum
alloy -- like 6061-T6 would give clearer chip evacuation. Softer
aluminum alloys tend to produce very gummy chips which are more likely
to break the bits (and the taps).

Second -- how are you holding the drill and the aluminum rod. I
would hold the aluminum rod in collets in the lathe (through the lathe
spindle) and use a fairly high RPM if available. The bit needs sensitive
feed -- not the usual tailstock ram handwheel with crank. Perhaps one
of the sensitive drilling adaptors sold by various makers, and hand fed.

Note that that long and that small a hole is likely to wander
off center during the drilling.

Third -- the taps need to be guided in by the lathe tailstock
which has drilled the hole. (If you have a small bed turret on the lathe,
to allow you to both drill and tap in sequence (with the proper
releasing tap holder for the latter task.)

I've never used forming taps. Do they work well? I wouldn't think
they'd be as delicate since they don't have flutes. In addition the
pilot bit would be a tad beefier at #54 vs 3/64".

They do -- but they will need a proper lubricant, and it will
need to be applied frequently. And again -- do they have a long enough
thread?

Looking at MSC's web site, the first 0-80 tap which I find is a
gun tap (spiral point) (the right choice for power tapping), with TiN
coating (better/smoother chip flow), and it says thread length 5/16" --
in other words half of what you say you want.

And the first thread-forming tap which I find in that size has
an *overall* length of 1-5/8", with the illustration suggesting that at
most 1/3 of that length is threading (about 1/2"), but there is a
reduced diameter section which may allow you to tap as far as you need.

If I stick with cutting taps what tap qualities should I be looking
for in miniature taps for soft metals? (ie Coating, material, tap
style, manufacturer, etc)

Call a the help line at good manufacturer (e.g. Cleveland or
Greenfield Tap & Die), and ask for their suggestions. Note that we are
talking a bit over $25.00 per tap -- until you get enough to start
getting a quantity discount.

But really, consider drilling and taping from each end so you
don't need such extreme cutting conditions.

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 2009-11-30, Bud wrote:
I need very little holding power and the machine screws I'm using are
0-80 X 1/8". Since the length is 2X the diameter I might try going
from a 3/64 pilot bit to a #54. That would still give me about 50%
thread contact.

So you *can* tap separately from each end, instead of needing a
single continuous thread all the way through. As you wrote the original
question, it sounded as though the thread had to continue all the way
through, which caused me to ask questions in my previous answer (which
you have not yet had time to see, since I just sent it. :-)

I also read the spiral taps aren't the best if you have to back out
before the tip ejects the chips. I can't go thru hole with the tap
since it's effective cutting length is 5/16" and my part is 5/8".

If the *hole* goes all the way through, and you apply compressed
air to blow through the chips before starting to tap the second end, I
think that you should be fine. It is in shallow *blind* holes that the
spiral point taps run into problems.

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 ---

Thanks for all the suggestions!!

I'm drilling all the way through since one end of the spacer has a
well formed concave dimple which makes a perfect starting point for
the drill bit. (the other end does not) The vertical slit in my drill
press vise hold these spacers very well:

[IMG]http://i530.photobucket.com/albums/dd350/davefr_98/
geartrainrepair005.jpg[/IMG]

However I'm taping from each end since the cutting end of the tap
isn't quite long enough:

[IMG]http://i530.photobucket.com/albums/dd350/davefr_98/
geartrainrepair006.jpg[/IMG]

I only care about enough thread on each end to accomodate 1/8" machine
screws. I'm not sure my spiral point tap get an opportunity to eject
chips into the remaining hole before I have to reverse direction. (I
think tap stress and chip fragments causes the tap to break).

The machine screws have to have a low profile binding head since the
spacers originally had rivet style peened ends that get ground off.

I ordered a thread forming tap and #54 bit from MSC. I definately
want to get a little more bit to tap clearance and bit strength even
if I have to sacrifice some screw holding power.

On 2009-12-01, Bud wrote:
Thanks for all the suggestions!!

I'm drilling all the way through since one end of the spacer has a
well formed concave dimple which makes a perfect starting point for
the drill bit. (the other end does not) The vertical slit in my drill
press vise hold these spacers very well:

[IMG]http://i530.photobucket.com/albums/dd350/davefr_98/
geartrainrepair005.jpg[/IMG]

So you are not using a lathe to center drill the workpieces.

And this suggests that you are starting with already formed
workpieces, so you have no idea what alloy of aluminum it is.

What RPM are you using on the drill press? And what is the
fastest you can get it to run?

As for controlling the feed -- with that small a drill, you need
a sensitive adapter, which MSC has under part number 08597809, and a
matching 1/8" Albrecht chuck (MSC part number 08591034), but that adds
up to being a lot more expensive than they were when I got mine.

O.K. Here is one with a keyed chuck, completely assembled, for
$197.16 (MSC part number 01136514)

I can't find any on eBay at the moment -- sometimes they have
very affordable versions.

But it is gripped in a 1/2" drill chuck (or a milling machine
collet), and while it is spinning, you grip the flange/disc with your
hand and pull down. The flange is mounted to the spindle by a ball
bearing assembly, and a spring pulls the whole assembly up when you are
not pulling it down. It allows fine control of the feed, and the
Albrecht chuck allows holding bits down to the smallest that I have, the
#80,

What it doesn't do is to provide a speed high enough to be
reasonable for that small a drill bit. Even going with the 0.060"
diameter for a clearance hole, if you can get up to 2000 RPM, that is
still only about 31 SFM -- way slow for aluminum with a HSS drill bit.
You might look into the drill stand for a Dremel, which would give you a
high enough RPM, and very fine feed -- but you will need a smaller work
holder on that tiny table.

You don't mention what other tools you have. We know now that
you have a drill press (though we don't know the speeds which it can
accomplish, we do know that it can hold a 1/2" drill bit, so it probably
does not go very fast even at its fastest.

Do you have a lathe? A small one (e.g. Unimat, Sherline, Taig)
would be much better for the drilling and for starting the tap at least.

However I'm taping from each end since the cutting end of the tap
isn't quite long enough:

[IMG]http://i530.photobucket.com/albums/dd350/davefr_98/
geartrainrepair006.jpg[/IMG]

As I felt.

I only care about enough thread on each end to accomodate 1/8" machine
screws. I'm not sure my spiral point tap get an opportunity to eject
chips into the remaining hole before I have to reverse direction. (I
think tap stress and chip fragments causes the tap to break).

With a hard alloy, such as 6061-T6 aluminum, the spiral point
should chase the chips ahead of the tip without binding, and you only
have to reverse the tap to remove it. However, with a soft aluminum
alloy, you will get stringy chips which will almost certainly bundle up
into a mess.

The machine screws have to have a low profile binding head since the
spacers originally had rivet style peened ends that get ground off.

And if they were designed to be riveted, they are almost
certainly a soft gummy alloy, not a good machinable alloy like the
6061-T6 which I suggested.

I ordered a thread forming tap and #54 bit from MSC. I definately
want to get a little more bit to tap clearance and bit strength even
if I have to sacrifice some screw holding power.

O.K. I see that _Machinery's Handbook_ suggests the #54 bit for
55% thread (the loosest that they suggest).

At least a thread forming tap should be the better choice for
the material which you apparently are stuck with -- as long as you have
a way to guide it into the workpiece on center.

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 2009-12-01, Bud wrote:
Thanks for all the suggestions!!

I'm drilling all the way through since one end of the spacer has a
well formed concave dimple which makes a perfect starting point for
the drill bit. (the other end does not) The vertical slit in my drill
press vise hold these spacers very well:

[IMG]http://i530.photobucket.com/albums/dd350/davefr_98/
geartrainrepair005.jpg[/IMG]

So you are not using a lathe to center drill the workpieces.

And this suggests that you are starting with already formed
workpieces, so you have no idea what alloy of aluminum it is.

What RPM are you using on the drill press? And what is the
fastest you can get it to run?

As for controlling the feed -- with that small a drill, you need
a sensitive adapter, which MSC has under part number 08597809, and a
matching 1/8" Albrecht chuck (MSC part number 08591034), but that adds
up to being a lot more expensive than they were when I got mine.

O.K. Here is one with a keyed chuck, completely assembled, for
$197.16 (MSC part number 01136514)

I can't find any on eBay at the moment -- sometimes they have
very affordable versions.

But it is gripped in a 1/2" drill chuck (or a milling machine
collet), and while it is spinning, you grip the flange/disc with your
hand and pull down. The flange is mounted to the spindle by a ball
bearing assembly, and a spring pulls the whole assembly up when you are
not pulling it down. It allows fine control of the feed, and the
Albrecht chuck allows holding bits down to the smallest that I have, the
#80,

What it doesn't do is to provide a speed high enough to be
reasonable for that small a drill bit. Even going with the 0.060"
diameter for a clearance hole, if you can get up to 2000 RPM, that is
still only about 31 SFM -- way slow for aluminum with a HSS drill bit.
You might look into the drill stand for a Dremel, which would give you a
high enough RPM, and very fine feed -- but you will need a smaller work
holder on that tiny table.

You don't mention what other tools you have. We know now that
you have a drill press (though we don't know the speeds which it can
accomplish, we do know that it can hold a 1/2" drill bit, so it probably
does not go very fast even at its fastest.

Do you have a lathe? A small one (e.g. Unimat, Sherline, Taig)
would be much better for the drilling and for starting the tap at least.

However I'm taping from each end since the cutting end of the tap
isn't quite long enough:

[IMG]http://i530.photobucket.com/albums/dd350/davefr_98/
geartrainrepair006.jpg[/IMG]

As I felt.

I only care about enough thread on each end to accomodate 1/8" machine
screws. I'm not sure my spiral point tap get an opportunity to eject
chips into the remaining hole before I have to reverse direction. (I
think tap stress and chip fragments causes the tap to break).

With a hard alloy, such as 6061-T6 aluminum, the spiral point
should chase the chips ahead of the tip without binding, and you only
have to reverse the tap to remove it. However, with a soft aluminum
alloy, you will get stringy chips which will almost certainly bundle up
into a mess.

The machine screws have to have a low profile binding head since the
spacers originally had rivet style peened ends that get ground off.

And if they were designed to be riveted, they are almost
certainly a soft gummy alloy, not a good machinable alloy like the
6061-T6 which I suggested.

I ordered a thread forming tap and #54 bit from MSC. I definately
want to get a little more bit to tap clearance and bit strength even
if I have to sacrifice some screw holding power.

O.K. I see that _Machinery's Handbook_ suggests the #54 bit for
55% thread (the loosest that they suggest).

At least a thread forming tap should be the better choice for
the material which you apparently are stuck with -- as long as you have
a way to guide it into the workpiece on center.

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 ---

--What are you using for a lubricant?

--
"Steamboat Ed" Haas : Currently broke and
Hacking the Trailing Edge! : looking for a job...
www.nmpproducts.com
---Decks a-wash in a sea of words---

Bud writes:

I've never used forming taps. Do they work well?

I use them frequently including in 0-80 size in aluminum. They don't make
a proper thread form. What you get is sort of like two waves crashing into
each other with a split down the middle. If you start the screw very
carefully, or maybe follow up with a regular tap, then it works. The
problem is that there is a sort of "ghost" thread that is half a pitch
offset, where the two sides of the cold form have heaped up against each
other, and you can pretty easily start the screw into that instead of the
proper thread channel. But tapping a 2nd time (with a careful start) using
a regular tap tends to clean this up.

I made a little knurled holder out of 1/2 inch aluminum with a setscrew to
hold the tap. Then I spin the tap with fingertips, aligning with the drill
chuck.

Richard J Kinch wrote:
I use them frequently including in 0-80 size in aluminum. They don't make
a proper thread form. What you get is sort of like two waves crashing into
each other with a split down the middle. If you start the screw very
carefully, or maybe follow up with a regular tap, then it works. The
problem is that there is a sort of "ghost" thread that is half a pitch
offset, where the two sides of the cold form have heaped up against each
other, and you can pretty easily start the screw into that instead of the
proper thread channel. But tapping a 2nd time (with a careful start) using
a regular tap tends to clean this up.

Sounds to me as though you are using too large a drill.
That way the "turned up" bits did not meet. The correct size
drill bit can be difficult to find for some size form-taps.
...lew...

Lewis Hartswick writes:

Sounds to me as though you are using too large a drill.
That way the "turned up" bits did not meet. The correct size
drill bit can be difficult to find for some size form-taps.

Hole sizes are given in formulas in _Machinery's Handbook_. For example,
for 0-80 cold form, it is #54 for 55 percent or 1.35mm for 75 percent.

On 2009-12-04, Richard J Kinch wrote:
Lewis Hartswick writes:

Sounds to me as though you are using too large a drill.
That way the "turned up" bits did not meet. The correct size
drill bit can be difficult to find for some size form-taps.

Hole sizes are given in formulas in _Machinery's Handbook_. For example,
for 0-80 cold form, it is #54 for 55 percent or 1.35mm for 75 percent.

Those figures are in the "Cold Form Tapping" tap drill chart, on
page 1829 of the 25th edition (as the nearest available standard drill
bit size). The next page does give the formula for the theoretical
size, which is just what you want if you are able to make or buy drill
bits to non-standard sizes. The formula is:

Theoretical_hole_size =
Basic_Tap_OD - (0.0068 * percent_of_full_thread)/ (threads_per_inch)

And a 55% thread will probably create the false thread in
between formed by the flow of the metal from both sides. 75% probably
will form much less of one of these.

They also suggest that a good lubricating oil be used instead of
a conventional cutting oil. So -- probably Mobil One would be a good
choice for this with metals.

They say that the torque to be expected is about 1.5 x the
torque of a thread cutting 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 ---

DoN. Nichols writes:

And a 55% thread will probably create the false thread in
between formed by the flow of the metal from both sides. 75% probably
will form much less of one of these.

You may have those notions if you have no experience in this, but the fact
is that cold form threads are necessarily of poor quality compared to cut
threads. Cold form threads are essentially sloppy burrs that happen to
clear the conjugate thread form. Now that poor thread is still acceptable
for many applications, and the utter convenience of just spinning in a tap
with one operation, instead of all the back-and-forth and pecking needed to
cut threads, makes them a useful expedient, when the application permits.

If you could make a decent thread with one spin of a thread-forming tap
(and no risk of breakage!), why would anyone put up with the tedium and
riskiness of a thread-cutting tap?

"Richard J Kinch" wrote in message
.. .
DoN. Nichols writes:

And a 55% thread will probably create the false thread in
between formed by the flow of the metal from both sides. 75% probably
will form much less of one of these.

You may have those notions if you have no experience in this, but the fact
is that cold form threads are necessarily of poor quality compared to cut
threads. Cold form threads are essentially sloppy burrs that happen to
clear the conjugate thread form. Now that poor thread is still acceptable
for many applications, and the utter convenience of just spinning in a tap
with one operation, instead of all the back-and-forth and pecking needed
to
cut threads, makes them a useful expedient, when the application permits.

If you could make a decent thread with one spin of a thread-forming tap
(and no risk of breakage!), why would anyone put up with the tedium and
riskiness of a thread-cutting tap?

I think you may want to revisit that idea, Rich. For at least the last 35
years or so, thread forming has been preferred to thread cutting in
production, where the process can be fine-tuned. Cutting threads is what
they do when they can't form them, usually because the metal is too hard.

Formed threads, under many conditions, are stronger and more precise. Most
of the major tap makers who make both kinds of taps will tell you the same
thing.

Here's a recent _Manufacturing Engineering_ (SME) article on the subject,
but I was interviewing engineers in some of the same companies and getting
the same answers 30 years ago:

http://www.sme.org/cgi-bin/find-arti...&&SME&#article

--
Ed Huntress

"Ed Huntress" wrote in message
...

"Richard J Kinch" wrote in message
.. .
DoN. Nichols writes:

And a 55% thread will probably create the false thread in
between formed by the flow of the metal from both sides. 75% probably
will form much less of one of these.

You may have those notions if you have no experience in this, but the
fact
is that cold form threads are necessarily of poor quality compared to cut
threads. Cold form threads are essentially sloppy burrs that happen to
clear the conjugate thread form. Now that poor thread is still
acceptable
for many applications, and the utter convenience of just spinning in a
tap
with one operation, instead of all the back-and-forth and pecking needed
to
cut threads, makes them a useful expedient, when the application permits.

If you could make a decent thread with one spin of a thread-forming tap
(and no risk of breakage!), why would anyone put up with the tedium and
riskiness of a thread-cutting tap?

I think you may want to revisit that idea, Rich. For at least the last 35
years or so, thread forming has been preferred to thread cutting in
production, where the process can be fine-tuned. Cutting threads is what
they do when they can't form them, usually because the metal is too hard.

Formed threads, under many conditions, are stronger and more precise. Most
of the major tap makers who make both kinds of taps will tell you the same
thing.

Here's a recent _Manufacturing Engineering_ (SME) article on the subject,
but I was interviewing engineers in some of the same companies and getting
the same answers 30 years ago:

http://www.sme.org/cgi-bin/find-arti...&&SME&#article

--
Ed Huntress

thanks Ed for correcting the falsehood, saving me the trouble - SEM analysis
of formed threads shows how the grain boundaries deform making it much
stronger (like a forging), this effect does not take place with cut threads
to any significant extent.

"Bill Noble" wrote in message
...


"Ed Huntress" wrote in message
...

"Richard J Kinch" wrote in message
.. .
DoN. Nichols writes:

And a 55% thread will probably create the false thread in
between formed by the flow of the metal from both sides. 75% probably
will form much less of one of these.

You may have those notions if you have no experience in this, but the
fact
is that cold form threads are necessarily of poor quality compared to
cut
threads. Cold form threads are essentially sloppy burrs that happen to
clear the conjugate thread form. Now that poor thread is still
acceptable
for many applications, and the utter convenience of just spinning in a
tap
with one operation, instead of all the back-and-forth and pecking needed
to
cut threads, makes them a useful expedient, when the application
permits.

If you could make a decent thread with one spin of a thread-forming tap
(and no risk of breakage!), why would anyone put up with the tedium and
riskiness of a thread-cutting tap?

I think you may want to revisit that idea, Rich. For at least the last 35
years or so, thread forming has been preferred to thread cutting in
production, where the process can be fine-tuned. Cutting threads is what
they do when they can't form them, usually because the metal is too hard.

Formed threads, under many conditions, are stronger and more precise.
Most of the major tap makers who make both kinds of taps will tell you
the same thing.

Here's a recent _Manufacturing Engineering_ (SME) article on the subject,
but I was interviewing engineers in some of the same companies and
getting the same answers 30 years ago:

http://www.sme.org/cgi-bin/find-arti...&&SME&#article

--
Ed Huntress

thanks Ed for correcting the falsehood, saving me the trouble - SEM
analysis of formed threads shows how the grain boundaries deform making it
much stronger (like a forging), this effect does not take place with cut
threads to any significant extent.

Right. They've been showing those etched photomicrographs, like the one in
the ME article, for decades.

My memory is a little fuzzy on this but IIRC, the hole diameter is more
critical with thread forming, and it is possible to mess it up and produce
bad threads. Rich may just have had bad experience with it.

--
Ed Huntress

On 2009-12-07, Richard J Kinch wrote:
DoN. Nichols writes:

And a 55% thread will probably create the false thread in
between formed by the flow of the metal from both sides. 75% probably
will form much less of one of these.

You may have those notions if you have no experience in this, but the fact
is that cold form threads are necessarily of poor quality compared to cut
threads.

Well ... that depends on what characteristics are important to
you. The cold-formed threads are a lot harder than the cut tapped
threads in softer materials.

Cold form threads are essentially sloppy burrs that happen to
clear the conjugate thread form. Now that poor thread is still acceptable
for many applications, and the utter convenience of just spinning in a tap
with one operation, instead of all the back-and-forth and pecking needed to
cut threads, makes them a useful expedient, when the application permits.

Hmm ... as long as it is not a blind hole -- or even if it is
and you have enough extra depth beyond the needed thread depth, you can
do it with a gun (spiral point) tap in a single pass. I've done a lot
of these in 360L brass in my lathe with a bed turret. But I am going to
try thread forming taps the next time I do this to eliminate one minor
problem. The extra depth for accumulating the chips (in what I make) is
enough so you wind up with the remains of the hole being there to start
the next hole after parting off, and after about a half dozen holes I
need to part off a sacrificial piece to be able to re-start the hole with
a center drill, as it has started to walk off to the side enough to be a
problem. (It would break a smaller tap than the 1/4-20 which I am
using. :-)

If you could make a decent thread with one spin of a thread-forming tap
(and no risk of breakage!), why would anyone put up with the tedium and
riskiness of a thread-cutting tap?

But I can make a decent thread with a thread-forming tap under
the same conditions -- so the main reason to try a thread-forming tap
for me is to eliminate an extra 1" length of 3/4" diameter brass round
stock per six parts.

Whether the quality of the thread will tell me that I can
continue this or must discontinue it remains to be seen. But if it
works, I expect a longer wear life on the thread (which, being a tripod
thread, will be likely taken off and put on many times in its life.

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 ---

Ed Huntress writes:

Formed threads, under many conditions, are stronger and more precise.

Define "precise". Yes, the grain structure and closer clearance might
beat a cut thread for strength. But the formed thread has a sloppy
crest that does not start well, and just doesn't look right.

Think about it. It is like two guys with bulldozers pushing snow banks
towards each other. The face formed by the dozer blade is strong and
precise. Where the two mounds meet in the middle is an sloppy mess with
a cleavage boundary running down the middle.

Maybe I have to mill a cross-section sample and post photomicrographs of
my own. If you've not seen them, it will surprise you.

My proof stands: forming taps are so much easier, faster, and less prone
to breakage; no one would use cutting taps if forming worked well.

http://www.sme.org/...

You are citing an article written to sell a thread-forming product, not
a fair comparison to cutting. There are advantages to forming, and I
use them frequently. But they have disadvantages that usually prohibit
their use.