Hi Greg,
My ISP has had recent problems with their news server, which has caused me
to miss several posts. I read your inquiry through Google, however, which
I have copied below:

I have a few unhardened HRS studs with 1/4-20 LH threads on the end,
which I didn't turn down enough- they're big enough that they won't
fit in the holes I just threaded with a proper tap- the OD is not
unreasonable, but the threads aren't deep enough. Otherwise the studs
are fine, so I'd like to deepen the thread by maybe 3 to 5 thousanths
or so. I've tried re-chucking and threading a little more, but its
really hard to get everything set right and the consequences are a
wrecked thread.

Since its just a couple studs that need help, I was thinking I might
be able to build a cheapie die (avoiding paying McMaster's highway
robbery for such things) by drilling & tapping a short length of 1"
diameter stock, then slitting it to provide relief for the
swarf/chip/turnings (I still don't know the difference..)- and
hardening so the sharp edge of the slit will last long enough. Maybe
I could run the slit in at something less than perpindicular to the
tangent of the stock to give the edge a bit of rake. Maybe I could
also be clever and slightly ream the end of the hole to introduce the
edge more gradually.

Would this work, or is there a better approach?

Thanks,

Gregm

Hi Greg,

Studs have what is known in the industry as a class 5 interference fit
thread, which is intended to be a force fit in the mating part. The
government has published manuals on threads in which this subject is well
discussed. They are (or at least were) known as the Screw Thread Standards
For Federal Services H28 Handbook.

It is documented in the handbook that studs should NOT bottom out on the end
of the thread, but instead be the force fit mentioned. According to H28,
a much higher incidence of failure is attributed to studs that are tightened
against the end of the thread. I would assume that studs are generally
heat treated and lend themselves to the force fit installation, so in your
case it may not apply.

Did I manage to add yet another layer of confusion? (Hope not!)

Good luck

Harold

"Harold & Susan Vordos" writes:

Hi Greg,
My ISP has had recent problems with their news server, which has caused me
to miss several posts. I read your inquiry through Google, however, which
I have copied below:

The problem may have been with my isp- I had trouble sending it this
morning. Thanks for responding, though.


I have a few unhardened HRS studs with 1/4-20 LH threads on the end,
which I didn't turn down enough- they're big enough that they won't
fit in the holes I just threaded with a proper tap- the OD is not
unreasonable, but the threads aren't deep enough. Otherwise the studs
are fine, so I'd like to deepen the thread by maybe 3 to 5 thousanths
or so. I've tried re-chucking and threading a little more, but its
really hard to get everything set right and the consequences are a
wrecked thread.

Since its just a couple studs that need help, I was thinking I might
be able to build a cheapie die (avoiding paying McMaster's highway
robbery for such things) by drilling & tapping a short length of 1"
diameter stock, then slitting it to provide relief for the
swarf/chip/turnings (I still don't know the difference..)- and
hardening so the sharp edge of the slit will last long enough. Maybe
I could run the slit in at something less than perpindicular to the
tangent of the stock to give the edge a bit of rake. Maybe I could
also be clever and slightly ream the end of the hole to introduce the
edge more gradually.

Would this work, or is there a better approach?

Thanks,

Gregm

Hi Greg,

Studs have what is known in the industry as a class 5 interference fit
thread, which is intended to be a force fit in the mating part. The
government has published manuals on threads in which this subject is well
discussed. They are (or at least were) known as the Screw Thread Standards
For Federal Services H28 Handbook.

It is documented in the handbook that studs should NOT bottom out on the end
of the thread, but instead be the force fit mentioned. According to H28,
a much higher incidence of failure is attributed to studs that are tightened
against the end of the thread. I would assume that studs are generally
heat treated and lend themselves to the force fit installation, so in your
case it may not apply.

Did I manage to add yet another layer of confusion? (Hope not!)

Good luck

Harold


Heh. I guess I should have said "1/2 inch diameter rods with 1/4-20
threads turned into them, RH one end, LH the other". I certainly
didn't mean to invoke standard definitions of studs. The rods screw
into correspondlingly threaded holes, but have 1/8 inch or so of
bottom clearance. The thread length isn't a problem, I just didn't
turn the 1/4-20 LH threads properly- I want them to be loose enough so
they can be screwed in by hand.

Just normal newbie problems I guess. My dad urged me to try turning
them some more after careful setup, which I'll do after my new lathe
v-belts show up.

I'll hold off on manufacturing standards conformant studs until I get
a few more mistakes under my belt...

Gregm

Harold & Susan Vordos wrote:

Hi Greg,
My ISP has had recent problems with their news server, which has caused me
to miss several posts. I read your inquiry through Google, however, which
I have copied below:

I have a few unhardened HRS studs with 1/4-20 LH threads on the end,
which I didn't turn down enough- they're big enough that they won't
fit in the holes I just threaded with a proper tap- the OD is not
unreasonable, but the threads aren't deep enough. Otherwise the studs
are fine, so I'd like to deepen the thread by maybe 3 to 5 thousanths
or so. I've tried re-chucking and threading a little more, but its
really hard to get everything set right and the consequences are a
wrecked thread.

Since its just a couple studs that need help, I was thinking I might
be able to build a cheapie die (avoiding paying McMaster's highway
robbery for such things) by drilling & tapping a short length of 1"
diameter stock, then slitting it to provide relief for the
swarf/chip/turnings (I still don't know the difference..)- and
hardening so the sharp edge of the slit will last long enough. Maybe
I could run the slit in at something less than perpindicular to the
tangent of the stock to give the edge a bit of rake. Maybe I could
also be clever and slightly ream the end of the hole to introduce the
edge more gradually.

Would this work, or is there a better approach?

Thanks,

Gregm

Hi Greg,

Studs have what is known in the industry as a class 5 interference fit
thread, which is intended to be a force fit in the mating part. The
government has published manuals on threads in which this subject is well
discussed. They are (or at least were) known as the Screw Thread Standards
For Federal Services H28 Handbook.

It is documented in the handbook that studs should NOT bottom out on the end
of the thread, but instead be the force fit mentioned. According to H28,
a much higher incidence of failure is attributed to studs that are tightened
against the end of the thread. I would assume that studs are generally
heat treated and lend themselves to the force fit installation, so in your
case it may not apply.

Did I manage to add yet another layer of confusion? (Hope not!)

Good luck

Harold






I've used the following hack in a similar situation to make a solid die
cut deeper threads.

Start the die on the part and then stuff (I mean *really* stuff) wadded
up paper or cloth or (best) tapered wooden pegs in two of the die's
clearance holes. That will push the die to the side and make the
contacting cutting edge(s) chase the threads down a bit.

Try it...Like the guy who suggested the doctor try administering an
enema to his dying brother-in-law said, "So vot, it mighten not voik,
but it von't hurt to try!"

Jeff

--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"My luck is so bad that if I bought a cemetery, people would stop dying."