[BillMe]

I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

[Snag[_3_]]

BillMe wrote:
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?

Thanks,

Bill A

yes

--
Snag
Got Guns ?

[Ed Huntress]

"BillMe" wrote in message
...
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

There are such taps. I have one, 1/2" x 10 Acme.

Boring a female Acme thread is something I've never tried. I still scratch
my head over single-point turning of *external* Acme threads. Some of the
old books tell you to cut both flanks at once, but I've never figured out
why. I made a couple of Acme threaded shafts in 1/2" x 10, and cutting on
one flank, just scraping the other, seemed to work Ok.

--
Ed Huntress

[Larry Jaques[_2_]]

On Fri, 25 Jun 2010 10:44:27 -0400, BillMe wrote the
following:

I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Sure it's ACME and 'Murrican?

http://fwd4.me/URM shows a 5/8-8 ACME tap.

http://www.victornet.com/reference/Acme_Tap_Drill.html shows standard
ACME tap sizes at 5/8-8 and 3/4-6.

UNC is 5/8-11, UNF is 5/8-18.

--
Pain makes man think. Thought makes man wise. Wisdom makes life endurable.
-- John Patrick

[Pete C.]

BillMe wrote:

I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

ACME taps are readily available but are expensive. They also are often
in sets for roughing and finishing, though some are multi stage with a
roughing section followed by a finishing stage and are even more
expensive. A quick look on the McMaster site shows a number of ACME
taps, including the tandem ones, ranging from $60 to $300.

Typically unless you need to make a bunch of parts, it's cheaper to buy
a ready made ACME nut assembly and install it in your part. McMaster
lists a lot of precision ACME nuts, but the typical bronze thread in
ACME nut that you thread into your part and secure with a setscrew,
locktite, etc. runs $20-$30. These also make the nut readily replaceable
for wear.

[Robert Swinney]

That worry kinda goes away if you grind an accurate Acme profile and feed straight in, slowly.

Bob Swinney
"Ed Huntress" wrote in message ...

"BillMe" wrote in message
...
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

There are such taps. I have one, 1/2" x 10 Acme.

Boring a female Acme thread is something I've never tried. I still scratch
my head over single-point turning of *external* Acme threads. Some of the
old books tell you to cut both flanks at once, but I've never figured out
why. I made a couple of Acme threaded shafts in 1/2" x 10, and cutting on
one flank, just scraping the other, seemed to work Ok.

--
Ed Huntress

[Ed Huntress]

"Robert Swinney" wrote in message
...
That worry kinda goes away if you grind an accurate Acme profile and feed
straight in, slowly.

Bob Swinney
"Ed Huntress" wrote in message
...

"BillMe" wrote in message
...
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

There are such taps. I have one, 1/2" x 10 Acme.

Boring a female Acme thread is something I've never tried. I still scratch
my head over single-point turning of *external* Acme threads. Some of the
old books tell you to cut both flanks at once, but I've never figured out
why. I made a couple of Acme threaded shafts in 1/2" x 10, and cutting on
one flank, just scraping the other, seemed to work Ok.

--
Ed Huntress

I've never seen an explanation of what you do that, Bob. Why plunge straight
in, nearly doubling the chip load, rather than feeding in on an angle and
cutting on one flank, as with conventional threads?

There must be some simple reason that I've just never come across.

--
Ed Huntress

[Ignoramus31989]

On 2010-06-25, BillMe wrote:
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

ACME taps are very common and easy to buy in any size, if you have the
money of course. McMaster has them. I may have a tap in that size.

i

[Tim Wescott[_3_]]

On 06/25/2010 07:44 AM, BillMe wrote:
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

McMaster-Carr: Google for machinists.

http://www.mcmaster.com/#taps/=7oq9iz

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

[Tim Wescott[_3_]]

On 06/25/2010 08:12 AM, Robert Swinney wrote:
(top posting fixed)
Bob Swinney
"Ed wrote in message ...

wrote in message
...
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

There are such taps. I have one, 1/2" x 10 Acme.

Boring a female Acme thread is something I've never tried. I still scratch
my head over single-point turning of *external* Acme threads. Some of the
old books tell you to cut both flanks at once, but I've never figured out
why. I made a couple of Acme threaded shafts in 1/2" x 10, and cutting on
one flank, just scraping the other, seemed to work Ok.

That worry kinda goes away if you grind an accurate Acme profile
and feed straight in, slowly.

Doesn't that mean then that you need a different threading bit for each
diameter and pitch of Acme thread you'll ever do? Or do you just need a
different bit for each pitch, with enough clearance for the smaller
diameters?

--
Tim Wescott
Control system and signal processing consulting
www.wescottdesign.com

[Bob La Londe]

"BillMe" wrote in message
...
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

I have seen ACME taps for sale on Ebay. Probably some of the better on-line
machine parts sellers will have them.

[F. George McDuffee]

On Fri, 25 Jun 2010 10:44:27 -0400, BillMe
wrote:

I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A
============
Given the cost of the taps [Acme usually has two, roughing
and finishing] you may want to consider a threaded insert.
This makes the thread easly renewable. Also if a
replacement part, left hand acme threads are frequently used
for adjustment. Be sure which one you have. There is also
a metric trapizoidal thread with a 30 degree thread angle
rather than the 29 degree acme.

mother lode of information on Acme threaded products
http://www.nookindustries.com/pdf/NookAcmeTechnical.pdf

for some examples see
http://www.use-enco.com/CGI/INPDFF?P...PARTPG=INLMK32
http://medmaninc.com/rbs/pdf/acme/pg69-AcmeScrews.pdf
http://www.amazon.com/gp/offer-listi...ag=155vvvvv-20

also see
http://www.tapsndies.com/catalog/ite...93/6827980.htm
http://www.toolsavings.com/default.a...emcode=2331132

If you machine your own threads you will need a thread gage
to sharpen the lathe tool to the correct profile.
http://www1.mscdirect.com/PDF/2008/849431.pdf
http://www.use-enco.com/CGI/INPDFF?P...MITEM=327-9543
--

-- 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).

[Wes[_5_]]

BillMe wrote:

I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

Serial tap. A series of taps that work you up to an agressive thread form.

Wes

[Wes[_5_]]

"Ed Huntress" wrote:

Ed Huntress

I've never seen an explanation of what you do that, Bob. Why plunge straight
in, nearly doubling the chip load, rather than feeding in on an angle and
cutting on one flank, as with conventional threads?

There must be some simple reason that I've just never come across.

Why wouldn't you set the compound at 14.5 degrees and make your infeeds via the compound?

Wes

[Ed Huntress]

"Wes" wrote in message
...
"Ed Huntress" wrote:

Ed Huntress

I've never seen an explanation of what you do that, Bob. Why plunge
straight
in, nearly doubling the chip load, rather than feeding in on an angle and
cutting on one flank, as with conventional threads?

There must be some simple reason that I've just never come across.

Why wouldn't you set the compound at 14.5 degrees and make your infeeds
via the compound?

Wes

That's the question I'm asking. And that's what I did. But that's not what
Bob is saying -- and what Bob is saying is the same thing said by every
source I've ever seen.

Plunge straight in, they say. Why?, I ask. It nearly doubles the chip load,
and I can't see a good reason for it. There probably is one, but I don't get
it.

--
Ed Huntress

[whit3rd]

On Jun 25, 2:21*pm, "Ed Huntress" wrote:

Plunge straight in, they say. Why?, I ask. It nearly doubles the chip load,
and I can't see a good reason for it. There probably is one, but I don't get
it.

Maybe it's to keep the tool tip from bending left/right? The tip
isn't as
well supported as a 60 degree tool would be.

[Wes[_5_]]

"Ed Huntress" wrote:

That's the question I'm asking. And that's what I did. But that's not what
Bob is saying -- and what Bob is saying is the same thing said by every
source I've ever seen.

Plunge straight in, they say. Why?, I ask. It nearly doubles the chip load,
and I can't see a good reason for it. There probably is one, but I don't get
it.

I'll wait to have it explained. Now if we were using cnc's we could get creative in how
we cut the profile. I seem to remember reading in the Sandvik book a technique for
alternating between both flanks to reduce cutting forces.

Google is my bud.

D. Alternating flank infeed

This method alternately feeds the insert along both thread flanks, and therefore it uses
both flanks of the insert to form the thread. The method delivers longer tool life because
both sides of the insert nose are used. However, the method also can result in chip flow
problems that can affect surface finish and tool life. This method is usually only used
for very large pitches and for such thread forms as Acme and Trapeze.

http://www.cncinformation.com/cnc-wo...ing-on-a-lathe

This wouldn't work very well using engine lathes with screws with backlash which is about
all of them, mine for sure.

Wes

[DoN. Nichols]

On 2010-06-25, BillMe wrote:
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Acme taps do exist, and the better ones are longer with a
roughing and a finishing section separated by very little.

Looking through MSC's on-line catalog, 5/8" typically has 8 TPI,
and 7/8" has 6 TPI.

The 5/8-8 goes for $81.59 for the combination tap.

The 7/8-6 goes for $221.25 for the combination tap.

Be sure to order the correct one. Leadscrews turned by
handwheels often have left-hand threads so clockwise advances the nut.

As for single-pointing it with a lathe and a boring bar -- I
think that it is unusually coarse for that, though I guess that it could
be done by someone sufficiently skilled.

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 ---

[DoN. Nichols]

On 2010-06-25, Ed Huntress wrote:

"BillMe" wrote in message
...
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

There are such taps. I have one, 1/2" x 10 Acme.

Boring a female Acme thread is something I've never tried. I still scratch
my head over single-point turning of *external* Acme threads. Some of the
old books tell you to cut both flanks at once, but I've never figured out
why. I made a couple of Acme threaded shafts in 1/2" x 10, and cutting on
one flank, just scraping the other, seemed to work Ok.

I've single-point turned an Acme thread in a bronze nut (for a
friend's log splitter). I think that it was something like a 1-1/4"
major diameter or so. There was enough room for a reasonable boring bar
to hold the tool, and I used a sine plate and some other tricks to grind
the tool itself. But if he really is working with a 5/8" major
diameter, and 6 TPI, that does not leave much room for a rigid enough
boring bar.

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]

On 2010-06-25, Tim Wescott wrote:
On 06/25/2010 08:12 AM, Robert Swinney wrote:
(top posting fixed)
Bob Swinney
"Ed wrote in message ...

wrote in message
...
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?

[ ... ]

Boring a female Acme thread is something I've never tried. I still scratch
my head over single-point turning of *external* Acme threads. Some of the
old books tell you to cut both flanks at once, but I've never figured out
why. I made a couple of Acme threaded shafts in 1/2" x 10, and cutting on
one flank, just scraping the other, seemed to work Ok.

That worry kinda goes away if you grind an accurate Acme profile
and feed straight in, slowly.

Doesn't that mean then that you need a different threading bit for each
diameter and pitch of Acme thread you'll ever do? Or do you just need a
different bit for each pitch, with enough clearance for the smaller
diameters?

I fed in at an angle of 14 degrees (a little less than the
half-way point). But I ground a bit specifically for the thread I was
cutting, including side clearance angles calculated for 5 degree
clearance with the pitch and diameter I was working with for maximum
strength. A more general tip (more clearance to adopt to various
diameters and thus different thread angles) would have to be weaker.

And yes -- you make (or buy) a separate tool for each pitch you
cut. My 12x24" Clausing can handle insert tools for above 10 TPI, but
not up to the big bronze nut I was making -- so I had to make my own
tool bit from HSS there.

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]

"whit3rd" wrote in message
...
On Jun 25, 2:21 pm, "Ed Huntress" wrote:

Plunge straight in, they say. Why?, I ask. It nearly doubles the chip
load,
and I can't see a good reason for it. There probably is one, but I don't
get
it.

Maybe it's to keep the tool tip from bending left/right? The tip
isn't as
well supported as a 60 degree tool would be.

'Don't know. I think it's mentioned in the Atlas lathe manual, and maybe in
the South Bend _How to Run a Lathe_ book. But neither one, if I recall
correctly, says why.

I have a few really old, old lathe operating books, but they're in storage
right now as we juggle some family arrangements and I'm trying to make room.

--
Ed Huntress

[Ed Huntress]

"Wes" wrote in message
...
"Ed Huntress" wrote:

That's the question I'm asking. And that's what I did. But that's not what
Bob is saying -- and what Bob is saying is the same thing said by every
source I've ever seen.

Plunge straight in, they say. Why?, I ask. It nearly doubles the chip
load,
and I can't see a good reason for it. There probably is one, but I don't
get
it.

I'll wait to have it explained.

I've floated this question a couple of times before. I never got a solid
answer, just possibilities.

Now if we were using cnc's we could get creative in how
we cut the profile. I seem to remember reading in the Sandvik book a
technique for
alternating between both flanks to reduce cutting forces.

Google is my bud.

D. Alternating flank infeed

This method alternately feeds the insert along both thread flanks, and
therefore it uses
both flanks of the insert to form the thread. The method delivers longer
tool life because
both sides of the insert nose are used. However, the method also can
result in chip flow
problems that can affect surface finish and tool life. This method is
usually only used
for very large pitches and for such thread forms as Acme and Trapeze.

http://www.cncinformation.com/cnc-wo...ing-on-a-lathe

This wouldn't work very well using engine lathes with screws with backlash
which is about
all of them, mine for sure.

That's interesting, but, as you say, it isn't what the original instruction
was about. We need someone who's even older than me to answer it. Most such
people are dead. d8-)

--
Ed Huntress

[Gunner Asch[_6_]]

On Fri, 25 Jun 2010 10:44:27 -0400, BillMe wrote:

I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A


I may have one of that size. Ill check in the morning

Gunner

One could not be a successful Leftwinger without realizing that,
in contrast to the popular conception supported by newspapers
and mothers of Leftwingers, a goodly number of Leftwingers are
not only narrow-minded and dull, but also just stupid.
Gunner Asch

[BillMe]

Thanks guys for all the insight. Think I will try a boring bar
approach. Its nothing too demanding of an application. The female
thread wore on a bench vice. I hate to throw a good condition vice in
the trash.

Thanks again,

Bill A


On Fri, 25 Jun 2010 10:44:27 -0400, BillMe wrote:

I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

[Doug White]

BillMe wrote in news:fj0c265vn1a5bugo6v9qssp36oo4h0btcf@
4ax.com:

Thanks guys for all the insight. Think I will try a boring bar
approach. Its nothing too demanding of an application. The female
thread wore on a bench vice. I hate to throw a good condition vice in
the trash.

Thanks again,

Bill A

Probably not an option here, but there is a thread (pardon the pun) on the
Clausing Yahoo group about this. One fellow made a tap out of a piece of
ACME threaded rod. Cut a taper on it, and then cut flutes into it.
Apparently it worked fine, but took a LOT of torque. Presumably
lengthening the taper would help with that.

Doug White

[Wes[_5_]]

"Ed Huntress" wrote:


"Wes" wrote in message
...
"Ed Huntress" wrote:

That's the question I'm asking. And that's what I did. But that's not what
Bob is saying -- and what Bob is saying is the same thing said by every
source I've ever seen.

Plunge straight in, they say. Why?, I ask. It nearly doubles the chip
load,
and I can't see a good reason for it. There probably is one, but I don't
get
it.

I'll wait to have it explained.

I've floated this question a couple of times before. I never got a solid
answer, just possibilities.

I've think I remember you asking before.



Now if we were using cnc's we could get creative in how
we cut the profile. I seem to remember reading in the Sandvik book a
technique for
alternating between both flanks to reduce cutting forces.

Google is my bud.

D. Alternating flank infeed

This method alternately feeds the insert along both thread flanks, and
therefore it uses
both flanks of the insert to form the thread. The method delivers longer
tool life because
both sides of the insert nose are used. However, the method also can
result in chip flow
problems that can affect surface finish and tool life. This method is
usually only used
for very large pitches and for such thread forms as Acme and Trapeze.

http://www.cncinformation.com/cnc-wo...ing-on-a-lathe

This wouldn't work very well using engine lathes with screws with backlash
which is about
all of them, mine for sure.

That's interesting, but, as you say, it isn't what the original instruction
was about. We need someone who's even older than me to answer it. Most such
people are dead. d8-)

There seems to be a problem with people winking out that have the old skills. I'm reading
one of Tubal Cains books when I visit the reading room.

I wonder if John from amdinc has experience cutting acme? He repairs a lot of big
machinery.

Wes

[Ed Huntress]

"Wes" wrote in message
...
"Ed Huntress" wrote:


"Wes" wrote in message
...
"Ed Huntress" wrote:

That's the question I'm asking. And that's what I did. But that's not
what
Bob is saying -- and what Bob is saying is the same thing said by every
source I've ever seen.

Plunge straight in, they say. Why?, I ask. It nearly doubles the chip
load,
and I can't see a good reason for it. There probably is one, but I don't
get
it.

I'll wait to have it explained.

I've floated this question a couple of times before. I never got a solid
answer, just possibilities.

I've think I remember you asking before.



Now if we were using cnc's we could get creative in how
we cut the profile. I seem to remember reading in the Sandvik book a
technique for
alternating between both flanks to reduce cutting forces.

Google is my bud.

D. Alternating flank infeed

This method alternately feeds the insert along both thread flanks, and
therefore it uses
both flanks of the insert to form the thread. The method delivers longer
tool life because
both sides of the insert nose are used. However, the method also can
result in chip flow
problems that can affect surface finish and tool life. This method is
usually only used
for very large pitches and for such thread forms as Acme and Trapeze.

http://www.cncinformation.com/cnc-wo...ing-on-a-lathe

This wouldn't work very well using engine lathes with screws with
backlash
which is about
all of them, mine for sure.

That's interesting, but, as you say, it isn't what the original
instruction
was about. We need someone who's even older than me to answer it. Most
such
people are dead. d8-)

There seems to be a problem with people winking out that have the old
skills. I'm reading
one of Tubal Cains books when I visit the reading room.

I wonder if John from amdinc has experience cutting acme? He repairs a
lot of big
machinery.

Wes

I can't think of who John is.

There are two old machining books handy, and I just looked in my 1940
edition of _American Machinist's Handbook_. Nothing there. I also looked in
Colvin and Stanley, _Turning and Boring Practice_ (1943). Nothing there,
either.

There are a few interesting bits about single-point turning of threads,
however, one of which relates to what you said above about CNC turning.
Colvin mentions a method that sets the compound perpendicular to the cross
slide, and then using the compound to cut one flank, and then run back to
cut the other. There is no detail; it sounds like it requires some careful
thought. The finishing pass(es) are taken by plunging straight in. He says
this is "said to be a common method used in English shops."

Apparently plunging straight in was the more common method in production,
even for conventional 60-degree thread forms. It's also interesting that
Acme threads derived from a group of miscellaneous flat-bottom threads known
as "******* threads." The 29-degree angle, says Colvin, probably was chosen
because Brown & Sharpe published a simple method for laying out cutting
tools with 29-degree angles.

Some time I'll dig into my other books to see what they say about cutting
Acmes. I have four or five others from that era.

--
Ed Huntress

[Robert Swinney]

Ed sez: " . . . . I've never seen an explanation of what you do that, Bob."

One reason is that going straight in avoids the difficulty of an angular feed in the bore which can
be a clearance problem if you're threading from left to right Double chip load, and chip
clelarance is reason to take it slow and easy. One of those options, hobby types like to worry
with.

Bob Swinney

[Ed Huntress]

"Robert Swinney" wrote in message
...
Ed sez: " . . . . I've never seen an explanation of what you do that,
Bob."

One reason is that going straight in avoids the difficulty of an angular
feed in the bore which can
be a clearance problem if you're threading from left to right Double
chip load, and chip
clelarance is reason to take it slow and easy. One of those options,
hobby types like to worry
with.

Bob Swinney

'Sounds reasonable, but why do they plunge straight in with *external* Acme
threads?

--
Ed Huntress

[Wes[_5_]]

"Ed Huntress" wrote:

I can't think of who John is.

John



There are two old machining books handy, and I just looked in my 1940
edition of _American Machinist's Handbook_. Nothing there. I also looked in
Colvin and Stanley, _Turning and Boring Practice_ (1943). Nothing there,
either.

There are a few interesting bits about single-point turning of threads,
however, one of which relates to what you said above about CNC turning.
Colvin mentions a method that sets the compound perpendicular to the cross
slide, and then using the compound to cut one flank, and then run back to
cut the other. There is no detail; it sounds like it requires some careful
thought. The finishing pass(es) are taken by plunging straight in. He says
this is "said to be a common method used in English shops."

Interesting. I suspect a lot of art was common knowledge, so common, no one wrote it
down.



Apparently plunging straight in was the more common method in production,
even for conventional 60-degree thread forms. It's also interesting that
Acme threads derived from a group of miscellaneous flat-bottom threads known
as "******* threads." The 29-degree angle, says Colvin, probably was chosen
because Brown & Sharpe published a simple method for laying out cutting
tools with 29-degree angles.

What was the method?



Some time I'll dig into my other books to see what they say about cutting
Acmes. I have four or five others from that era.

I took a look at K. H. Moltrecht's Vol. 1 Machine Shop Practice a hour or so ago before
going out to wack the grass. He indicated using the compound at 14.5 to cut one flank on
external threads and to use a follow rest, he didn't say anything about internal threads
but I would suspect the same technique would work. I do the 30 degree thing for external
and internal 60 degree threads.


Wes

[Ed Huntress]

"Wes" wrote in message
...
"Ed Huntress" wrote:

I can't think of who John is.

John



There are two old machining books handy, and I just looked in my 1940
edition of _American Machinist's Handbook_. Nothing there. I also looked
in
Colvin and Stanley, _Turning and Boring Practice_ (1943). Nothing there,
either.

There are a few interesting bits about single-point turning of threads,
however, one of which relates to what you said above about CNC turning.
Colvin mentions a method that sets the compound perpendicular to the cross
slide, and then using the compound to cut one flank, and then run back to
cut the other. There is no detail; it sounds like it requires some careful
thought. The finishing pass(es) are taken by plunging straight in. He says
this is "said to be a common method used in English shops."

Interesting. I suspect a lot of art was common knowledge, so common, no
one wrote it
down.



Apparently plunging straight in was the more common method in production,
even for conventional 60-degree thread forms. It's also interesting that
Acme threads derived from a group of miscellaneous flat-bottom threads
known
as "******* threads." The 29-degree angle, says Colvin, probably was
chosen
because Brown & Sharpe published a simple method for laying out cutting
tools with 29-degree angles.

What was the method?

It requires an illustration. The edition on Google Books (1948) doesn't
allow sufficient searching, but it's on page 70 and some previous page, if
you want to get tedious about it.

My scanner sucks but I'll see if I can do something with it some time.


Some time I'll dig into my other books to see what they say about cutting
Acmes. I have four or five others from that era.

I took a look at K. H. Moltrecht's Vol. 1 Machine Shop Practice a hour or
so ago before
going out to wack the grass. He indicated using the compound at 14.5 to
cut one flank on
external threads and to use a follow rest, he didn't say anything about
internal threads
but I would suspect the same technique would work. I do the 30 degree
thing for external
and internal 60 degree threads.

Hmm. That's the first recollection I have of someone recommending the
half-angle setover in print.

--
Ed Huntress

[[email protected]]

On Jun 26, 1:10*pm, "Ed Huntress" wrote:


It's also interesting that
Acme threads derived from a group of miscellaneous flat-bottom threads known
as "******* threads." The 29-degree angle, says Colvin, probably was chosen
because Brown & Sharpe published a simple method for laying out cutting
tools with 29-degree angles.

--
Ed Huntress

I think Colvin is wrong in this case. My understanding is that the 29
degree angle is the strongest angle. It is also the angle used for
gears (14.5 degree pressure angle. ). Brown and Sharpe came out
with involute gear cutters in 1858 so they are likely the source of
the angle. Brown and Sharpe probably published a method for laying
out tools with 29 degree angles as that would be what is needed to cut
a rack using a shaper to work with 14.5 PA gears.

This is just based on bits dredged up from memory and some guessing so
please correct me if I am wrong.

Dan

[John]

Ed Huntress wrote:
wrote in message
...
"Ed wrote:

I can't think of who John is.





There are two old machining books handy, and I just looked in my 1940
edition of _American Machinist's Handbook_. Nothing there. I also looked
in
Colvin and Stanley, _Turning and Boring Practice_ (1943). Nothing there,
either.

There are a few interesting bits about single-point turning of threads,
however, one of which relates to what you said above about CNC turning.
Colvin mentions a method that sets the compound perpendicular to the cross
slide, and then using the compound to cut one flank, and then run back to
cut the other. There is no detail; it sounds like it requires some careful
thought. The finishing pass(es) are taken by plunging straight in. He says
this is "said to be a common method used in English shops."

Interesting. I suspect a lot of art was common knowledge, so common, no
one wrote it
down.



Apparently plunging straight in was the more common method in production,
even for conventional 60-degree thread forms. It's also interesting that
Acme threads derived from a group of miscellaneous flat-bottom threads
known
as "******* threads." The 29-degree angle, says Colvin, probably was
chosen
because Brown& Sharpe published a simple method for laying out cutting
tools with 29-degree angles.

What was the method?

It requires an illustration. The edition on Google Books (1948) doesn't
allow sufficient searching, but it's on page 70 and some previous page, if
you want to get tedious about it.

My scanner sucks but I'll see if I can do something with it some time.


Some time I'll dig into my other books to see what they say about cutting
Acmes. I have four or five others from that era.

I took a look at K. H. Moltrecht's Vol. 1 Machine Shop Practice a hour or
so ago before
going out to wack the grass. He indicated using the compound at 14.5 to
cut one flank on
external threads and to use a follow rest, he didn't say anything about
internal threads
but I would suspect the same technique would work. I do the 30 degree
thing for external
and internal 60 degree threads.

Hmm. That's the first recollection I have of someone recommending the
half-angle setover in print.



Plunging straight in or cutting on one flank is determined by the
stiffness of your machine. Every old time machinist I know with a good
lathe will plunge straight in. They cut in to the double depth and then
check it with a profile gauge, looking for any light coming under the
gauge and then try the thread gauge. It's easier because you just cut
to the double depth of the thread that is stamped on the back of the
Starrett fishtail gauge. With inserts and the tool holder set properly,
your thread angles will be correct.
CNC machines can cut alternate flank threading as well as single flank
or plunge cut. A good machine will cut either way with no problem. Some
of the special acme threads we do we plunge cut to the depth and then
shift the tool a couple of thousandths in the Z axis to widen out the
acme profile because of certain tolerances that are required on the
parts we do.

What it comes down to is if your machine can handle plunge cutting that
is the way to go, if you run into problems then go to flank cutting.



John

[Paul K. Dickman]

"Ed Huntress" wrote in message
...

"Robert Swinney" wrote in message
...
That worry kinda goes away if you grind an accurate Acme profile and feed
straight in, slowly.

Bob Swinney
"Ed Huntress" wrote in message
...

"BillMe" wrote in message
...
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

There are such taps. I have one, 1/2" x 10 Acme.

Boring a female Acme thread is something I've never tried. I still
scratch
my head over single-point turning of *external* Acme threads. Some of the
old books tell you to cut both flanks at once, but I've never figured out
why. I made a couple of Acme threaded shafts in 1/2" x 10, and cutting on
one flank, just scraping the other, seemed to work Ok.

--
Ed Huntress

I've never seen an explanation of what you do that, Bob. Why plunge
straight in, nearly doubling the chip load, rather than feeding in on an
angle and cutting on one flank, as with conventional threads?

There must be some simple reason that I've just never come across.

--
Ed Huntress


The fallacy in the argument is the assumption that feeding straight in would
double the chip load. This is true with vee threads because you are in fact
cutting twice as many sides.

I am too lazy to do the trig, but I drew the acme thread on a cad program
and found that the difference in chip load between the two methods is pretty
small.

Feeding at 14.5 deg for each unit of depth of cut at the root of the thread,
I get .499 units on one flank and 0 units on the other.
1+.499+0=1.499

Feeding straight in, I get .252 units on each flank
1+.252+.252=1.504

Paul K. Dickman

[Phil Kangas[_3_]]

"Wes" wrote in message
BillMe wrote:

I need to cut an acme thread in a steel block. Roughly
5/8" X 6. I
forget what I measured! Is that done with a tap or a
boring bar?
Friends have not heard of an acme tap. Thought someone
might know.

Thanks,

Bill A

Serial tap. A series of taps that work you up to an
agressive thread form.

Wes

This looks like a good place to add my attempt at making
such a tap.
There is a problem with fire hydrant gate valves. What
happens is that
when the valve is closed there is only a very short thread
engagement
between the gate and the actuating screw and after some wear
the
threads lose engagement and the valve cannot be opened. Not
good!
So I came up with a repair that involves a longer threaded
portion on the
gate. I've repaired several of them now with this tap. I
have posted a
pic to the dropbox, the text file has not appeared yet for
some reason
so I'll include it he

http://www.metalworking.com/DropBox/...ead_tap_01.jpg

This tap is a 1/2-4 double helix left hand thread used to
cut a thread to repair fire hydrant gate valves. It has
been used several times to cut threads in aluminum. Six
previous attempts were failures due to the wrong heat
treatment procedure. The last few threads are the only
ones that cut the final profile. The thread profile of
the actuating screw is definately a square thread. The
tap is made from W-1 drill rod and was done on a 9"
South Bend Model A workshop lathe. The flutes were cut
on a milling machine. Tap drill size is 25/64.

[Ed Huntress]

"Paul K. Dickman" wrote in message
...

"Ed Huntress" wrote in message
...

"Robert Swinney" wrote in message
...
That worry kinda goes away if you grind an accurate Acme profile and
feed straight in, slowly.

Bob Swinney
"Ed Huntress" wrote in message
...

"BillMe" wrote in message
...
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

There are such taps. I have one, 1/2" x 10 Acme.

Boring a female Acme thread is something I've never tried. I still
scratch
my head over single-point turning of *external* Acme threads. Some of
the
old books tell you to cut both flanks at once, but I've never figured
out
why. I made a couple of Acme threaded shafts in 1/2" x 10, and cutting
on
one flank, just scraping the other, seemed to work Ok.

--
Ed Huntress

I've never seen an explanation of what you do that, Bob. Why plunge
straight in, nearly doubling the chip load, rather than feeding in on an
angle and cutting on one flank, as with conventional threads?

There must be some simple reason that I've just never come across.

--
Ed Huntress


The fallacy in the argument is the assumption that feeding straight in
would double the chip load. This is true with vee threads because you are
in fact cutting twice as many sides.

I am too lazy to do the trig, but I drew the acme thread on a cad program
and found that the difference in chip load between the two methods is
pretty small.

Feeding at 14.5 deg for each unit of depth of cut at the root of the
thread, I get .499 units on one flank and 0 units on the other.
1+.499+0=1.499

Feeding straight in, I get .252 units on each flank
1+.252+.252=1.504

Paul K. Dickman

I don't do math on Sundays g, but are you measuring "chip load" in terms
of metal volume being removed? That's the common definition of the term, and
I shouldn't have used it. What I meant was cutting force, rather than chip
load.

I'm rusty on that but the primary factor determining cutting force in
turning, IIRC, is the depth of cut, with the feedrate being a relatively
minor issue. The depth of cut, or the effective equivalent in terms of
cutting force, in the case of a turning insert plunged straight in, is twice
the actual depth, multiplied by the secant of the flank angle. Add the
length of the flat at the tip of the cutter, if you want to get it all.

Right? I'll try it again on Monday. d8-)

--
Ed Huntress

[Paul K. Dickman]

"Ed Huntress" wrote in message
...

"Paul K. Dickman" wrote in message
...

"Ed Huntress" wrote in message
...

"Robert Swinney" wrote in message
...
That worry kinda goes away if you grind an accurate Acme profile and
feed straight in, slowly.

Bob Swinney
"Ed Huntress" wrote in message
...

"BillMe" wrote in message
...
I need to cut an acme thread in a steel block. Roughly 5/8" X 6. I
forget what I measured! Is that done with a tap or a boring bar?
Friends have not heard of an acme tap. Thought someone might know.

Thanks,

Bill A

There are such taps. I have one, 1/2" x 10 Acme.

Boring a female Acme thread is something I've never tried. I still
scratch
my head over single-point turning of *external* Acme threads. Some of
the
old books tell you to cut both flanks at once, but I've never figured
out
why. I made a couple of Acme threaded shafts in 1/2" x 10, and cutting
on
one flank, just scraping the other, seemed to work Ok.

--
Ed Huntress

I've never seen an explanation of what you do that, Bob. Why plunge
straight in, nearly doubling the chip load, rather than feeding in on an
angle and cutting on one flank, as with conventional threads?

There must be some simple reason that I've just never come across.

--
Ed Huntress


The fallacy in the argument is the assumption that feeding straight in
would double the chip load. This is true with vee threads because you are
in fact cutting twice as many sides.

I am too lazy to do the trig, but I drew the acme thread on a cad program
and found that the difference in chip load between the two methods is
pretty small.

Feeding at 14.5 deg for each unit of depth of cut at the root of the
thread, I get .499 units on one flank and 0 units on the other.
1+.499+0=1.499

Feeding straight in, I get .252 units on each flank
1+.252+.252=1.504

Paul K. Dickman

I don't do math on Sundays g, but are you measuring "chip load" in terms
of metal volume being removed? That's the common definition of the term,
and I shouldn't have used it. What I meant was cutting force, rather than
chip load.

I'm rusty on that but the primary factor determining cutting force in
turning, IIRC, is the depth of cut, with the feedrate being a relatively
minor issue. The depth of cut, or the effective equivalent in terms of
cutting force, in the case of a turning insert plunged straight in, is
twice the actual depth, multiplied by the secant of the flank angle. Add
the length of the flat at the tip of the cutter, if you want to get it
all.

Right? I'll try it again on Monday. d8-)

--
Ed Huntress

I think it will still come out to less than you would think.
By either method, the big flat nose of the tool takes the deepest cut with
each pass and, unlike the flanks, it cuts the same width every time. The
result is that it swamps the numbers.

However, in the spirit of full disclosure, I have to admit that I do not
believe that I have ever cut an acme thread that I did not have to take a
file to.


Paul K.Dickman

[Wes[_5_]]

"Phil Kangas" wrote:


"Wes" wrote in message
BillMe wrote:
[snip]

Serial tap. A series of taps that work you up to an
agressive thread form.

Wes

This looks like a good place to add my attempt at making
such a tap.
There is a problem with fire hydrant gate valves. What
happens is that
when the valve is closed there is only a very short thread
engagement
between the gate and the actuating screw and after some wear
the
threads lose engagement and the valve cannot be opened. Not
good!
So I came up with a repair that involves a longer threaded
portion on the
gate. I've repaired several of them now with this tap. I
have posted a
pic to the dropbox, the text file has not appeared yet for
some reason
so I'll include it he

http://www.metalworking.com/DropBox/...ead_tap_01.jpg

This tap is a 1/2-4 double helix left hand thread used to
cut a thread to repair fire hydrant gate valves. It has
been used several times to cut threads in aluminum. Six
previous attempts were failures due to the wrong heat
treatment procedure. The last few threads are the only
ones that cut the final profile. The thread profile of
the actuating screw is definately a square thread. The
tap is made from W-1 drill rod and was done on a 9"
South Bend Model A workshop lathe. The flutes were cut
on a milling machine. Tap drill size is 25/64.


Nice bit of work. I searched the drop box, I can't find your .txt file. I hope our
benefactor keeps it in the box.

Obviously you have a taper attachent. Wish I did.

Wes

[Phil Kangas[_3_]]

"Wes" wrote in message
"Phil Kangas" wrote:


"Wes" wrote in message
BillMe wrote:
[snip]

Serial tap. A series of taps that work you up to an
agressive thread form.

Wes

This looks like a good place to add my attempt at making
such a tap.
There is a problem with fire hydrant gate valves. What
happens is that
when the valve is closed there is only a very short thread
engagement
between the gate and the actuating screw and after some
wear
the
threads lose engagement and the valve cannot be opened.
Not
good!
So I came up with a repair that involves a longer threaded
portion on the
gate. I've repaired several of them now with this tap. I
have posted a
pic to the dropbox, the text file has not appeared yet for
some reason
so I'll include it he

http://www.metalworking.com/DropBox/...ead_tap_01.jpg

This tap is a 1/2-4 double helix left hand thread used to
cut a thread to repair fire hydrant gate valves. It has
been used several times to cut threads in aluminum. Six
previous attempts were failures due to the wrong heat
treatment procedure. The last few threads are the only
ones that cut the final profile. The thread profile of
the actuating screw is definately a square thread. The
tap is made from W-1 drill rod and was done on a 9"
South Bend Model A workshop lathe. The flutes were cut
on a milling machine. Tap drill size is 25/64.


Nice bit of work. I searched the drop box, I can't find
your .txt file. I hope our
benefactor keeps it in the box.

Obviously you have a taper attachent. Wish I did.

Wes
Actually I don't have a taper attachment, but I do have an
offset center device for the tailstock. Somewhere in the
past
I saw a pic of this thing so I made one. It is not the most
secure
thing in the tailstock so means must be made to sprag it in
place
to prevent movement. Shall I post a pic to the dropbox?
Maybe
I should as others may copy it.
Tomorrow.......maybe.....phil

[Wes[_5_]]

"Phil Kangas" wrote:

Wes
Actually I don't have a taper attachment, but I do have an
offset center device for the tailstock. Somewhere in the
past
I saw a pic of this thing so I made one. It is not the most
secure
thing in the tailstock so means must be made to sprag it in
place
to prevent movement. Shall I post a pic to the dropbox?
Maybe
I should as others may copy it.
Tomorrow.......maybe.....phil


Heck yes, post a picture.

Wes