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270669 Erik Levin 2020‑04‑29 Threading die for 0.108-50
A truly odd size that some may recognize, it is a Brown and Sharpe size from
early 1900's. I need to replace several adjusting and lock screws that have this
thread. I have several screw in hand, and they measure 0.106 to 0.108" OD, so
the nominal may be 0.110-50.


What I do not have is a die. If I needed to make one, I would single point it on
the lathe. I need enough of them that a die is preferable if I can find one. I
have 3/32-50. 0.120-50. 0.066-50. 0.250-50. but nothing that quite makes it
here.


If I must, I can make the die or single point the threads, but I figured I'd
take a shot here to see if anyone has such.


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270672 John Ruth <johnrruth@h...> 2020‑04‑30 Re: Threading die for 0.108-50
Erik,

You deserve more than the sound of the crickets after posting this “juicy”
obscure question.  So, in the interest of at least attracting more attention to
your quest:

Given the diameters you’ve measured, how did you eliminate size #4 and size
7/64ths as possible “nominal sizes?”

Sellers proposed/listed standard pitches for tiny fractional sizes including
7/64ths, but 50 tpi is not among them.

Have you considered the remote possibility that it’s Metric?  It’s “almost” a
pitch of 0.5mm.

IIRC, you have access and expertise on an Optical Comparator, which has become
an old tool in its own right.  And, your post certainly shows ability to perform
precision fine measurements.

“Grasping at Straws:” Can the thread profile be recognized as any particular
standard system?

Erik certainly provided impetus for wandering far out into the tall grass beyond
left field:  the 1959 re-definition of an inch was considered when pondering the
question of whether 50tpi is a round decimal in metric...no, that change only
shortened  the old US inch by two millionths of an inch!

John Ruth
“Of threads, and threading systems, there is no end!”
270677 Erik Levin 2020‑04‑30 Re: Threading die for 0.108-50
Thanks to those that got back to me with bits of info. To address John's
questions:


They are lock screws for long-reach internal micrometers (fixed range type. One
screw remains for the entire set), and two screws for a vernier caliper (24". It
also came with only one screw), all WW-II vintage. Metric is unlikely, as even
the metric B&S tools, in my experience, had imperial fasteners and fittings at
that time. The diameter is also not close enough to a metric to be a match,
either in standard or miniature. This is, obviously, not critical, but as I have
needed to swap these around a few times for use, I know I will eventually lose
one. These are user tools, and see life in the field, though they don't live in
my fieldwork kit.


I haven't eliminated 7/64, per se, but I think #4 is definitely too large at
0.112". The 0.108 screw is quite a neat fit, and there is little play in the
0.106. There are 10 holes for these screws, and the fits are pretty much the
same for all.


Most assuredly 50TPI. B&S, like Starrett, used their own sizes and pitches for
many things, especially smaller sizes. For example, the 0.110-52 screws Starrett
has used in the #154 adjustable parallel for many many years (not a match. I
tried one just to see). Measured the pitch with thread gauge, confirmed on the
optical comparator. 50 matches, 48 and 52 decidedly don't. 60 degree vee. I
didn't check the pitch diameter with wires, though will when I get the time. I
don't have 0.016 wires (0.020 is just too large) so will need to find my spare
gauge pins.


Yup. The comparator is most assuredly old-tool status at this point, but not as
old as the traveling microscope.


There are many threads I don't mind single pointing. These are small enough I
really don't want to deal with them, and 50TPI is not a standard thread on my
lathe. Some of the Stanley threads are pushing it, but at least they are more
accessible pitches.



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     On Thursday, April 30, 2020, 10:48:31 AM EDT, John Ruth 
wrote:
 
 Erik,

You deserve more than the sound of the crickets after posting this “juicy”
obscure question.  So, in the interest of at least attracting more attention to
your quest:

Given the diameters you’ve measured, how did you eliminate size #4 and size
7/64ths as possible “nominal sizes?”

Sellers proposed/listed standard pitches for tiny fractional sizes including
7/64ths, but 50 tpi is not among them.

Have you considered the remote possibility that it’s Metric?  It’s “almost” a
pitch of 0.5mm.

IIRC, you have access and expertise on an Optical Comparator, which has become
an old tool in its own right.  And, your post certainly shows ability to perform
precision fine measurements.

“Grasping at Straws:” Can the thread profile be recognized as any particular
standard system?

Erik certainly provided impetus for wandering far out into the tall grass beyond
left field:  the 1959 re-definition of an inch was considered when pondering the
question of whether 50tpi is a round decimal in metric...no, that change only
shortened  the old US inch by two millionths of an inch!

John Ruth
“Of threads, and threading systems, there is no end!”
270684 John Ruth <johnrruth@h...> 2020‑05‑01 Re: Threading die for 0.108-50
Erik,

Here’s a response from one of my correspondents:

“ I think it is 7/64” -50, that was a size used back in the day. I looked and I
have a .109”-50, it is #12 gauge Stubs IRON WIRE GAUGE, a bizarre set of sizes
that were used for bicycle spokes a[bout] 120 years ago. “

Before that, he’d suggested:
“...since these are for lock screws couldn’t he just use an adjustable jam die?
Or even a little giant type? I have often fudged a little with those.”

John Ruth
Reminded of his “non-buyer’s remorse” for passing up a very Antique jam die tool
at the Avenel Flea back in its heyday. I put it down because of the price. As I
changed my mind, the guy right behind me bought it!!!
270685 Erik Levin 2020‑05‑01 Re: Threading die for 0.108-50
Thank you for the follow up.

Another day, another piece of useful trivia I learn. 7/64-50 is reasonable, and
if once standard, likely. I measured the pitch diameter at 0.0954, which would
be consistent with this. It amazes me how often I still run across new, outdated
"standard" threads, in particular that I can't find in references.

I conjecture that, no matter what the size, between one millimeter and one inch,
and thread pitch, within a factor of two of the current closest imperial or
metric standard, there will be a historical standard size that is, for all
practical purposes, indistinguishable.


Why I haven't gone to an adjustable die? I have nothing quite close enough to
make the size in the right pitch. The thread engagement is deep enough that
going off pitch (48TPI) won't do the job, and might damage the tools.


For reasons having to do with practicality, I am going to borrow time on an
unmentionable device to make these. As much fun as the hunt for the proper die
is, current circumstances make the unmentionable method most practical (the
machine time is free)


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On Friday, May 1, 2020, 11:21:59 AM EDT, John Ruth  wrote: 


Erik, 



Here’s a response from one of my correspondents:




“ I think it is 7/64” -50, that was a size used back in the day. I looked and I
have a .109”-50, it is #12 gauge Stubs IRON WIRE GAUGE, a bizarre set of sizes
that were used for bicycle spokes a[bout] 120 years ago. “



Before that, he’d suggested:

“...since these are for lock screws couldn’t he just use an adjustable jam die?
Or even a little giant type? I have often fudged a little with those.”



John Ruth

Reminded of his “non-buyer’s remorse” for passing up a very Antique jam die tool
at the Avenel Flea back in its heyday. I put it down because of the price. As I
changed my mind, the guy right behind me bought it!!!
270686 John Ruth <johnrruth@h...> 2020‑05‑01 Re: Threading die for 0.108-50
Erik,

The knowledge that 7/64-50 is an obsolete Stubs Iron Wire Gauge bicycle spoke
thread is a clue to where a die might be found.

There are antique bicycle hobbyists just as there are hobbyists for any sort of
antique vehicle including motorcycles, which also have spoked wheels.  Start
searching for their suppliers!  Very likely, some supplier is making your die!

Stubs Iron Wire Gauge is associated with Birmingham, England.  Check British
cycle repair suppliers

As always when searching for oddball taps & dies, check with gunsmith suppliers.
Again, look to Britain for a solution.

Consider “chasing” the thread.  Only the visible parts of the screw have to
“look nice.”  The buried parts just have to be a safe fit that will not damage
the tool itself.

Regards,
John Ruth
Sent from my iPhone
270967 Erik Levin 2020‑05‑21 Re: Threading die for 0.108-50
Well, follow up time:


I borrowed a little time on an unmentionable machine with a brain of sorts, and
made up some test parts.


Things I was sure of:


-Thread pitch is 50TPI
-Thread for on the screws I had in hand was 60 degree vee. I don't have an
appropriate profile measuring way to accurately profile an internal thread this
small, so will figure it is as well.
-The OD is within a few thousands of an inch of 0.108", and the thread may be a
7/64-50.


I ran test pieces in sizes from 0.105"OD to 0.112"OD (#4), with sharp root
(0.001" or less, by the tool and by inspecting after) to avoid binding, and ran
with the nominal 1/8 of pitch flat at the top (0.0025")


For most of the tools, the 7/64" threaded in snugly, but in a couple, it
wouldn't start (no burrs on the female threads) 0.108" started in all but was
too tight in one, but the 0.107" ran in all of them fine. A tad loose in a
couple.


So, I went with 0.107 for the final parts. 


Manual work (Fine Arkansas stone) to lightly round the tips, and I used a manual
knurling tool (looks like a tubing cutter) to knurl the stock, as the the
unmentionable machine was not set up to do it and it is about half a day to
reconfigure.


Picture of one at: https://
i.postimg.cc/zXn211p4/IMG-1720.png


This one I tried knurling at the end, thinking that holding the material to cut
and thread would damage it, and it was a mistake. The rest were done at the
beginning on raw stock.


Thanks for the input on this. 

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