# My First Screw



## ProfessorGuy (Jun 30, 2015)

I made this screw with my thread cutting attachment on my Sherline tabletop lathe.




It is huge compared to the screws I'll need to make for my pocketwatch, but a credible first effort.  This brass screw is shown on a silver dollar.




I ground the 60-degree threading tool myself.  Now I have to make a slot cutter tool.

><gts


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## mikey (Jun 30, 2015)

Nice job! It's always exciting to learn a new skill and nothing encourages like success. Congrats!

By the way, a P1N parting tool makes a good thread relief tool.


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## JimDawson (Jun 30, 2015)

Wow!  That's small.  Good job!  Looking forward to seeing your ''real'' ones.


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## ch2co (Jun 30, 2015)

Great job! What size is it anyway? Looks about like a #6 or #4 by around 30 TPI??
And then the big question is how small do you really need to go?  6-32 is a size that
I can readily do, but 4-40 would be sorta a challenge.  Keep on turning.

Chuck the grumpy old guy


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## RJSakowski (Jun 30, 2015)

Nice job!  I look forward to seeing your "tiny" screws.


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## churchjw (Jun 30, 2015)

Really nice.  Next one you do take a picture of your setup.


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## brino (Jun 30, 2015)

Beautiful tiny parts.....WOW!
Do you have a microscope mounted to the cross-slide?!?!
I wouldn't be able to see the thing.

I would like to know size/dimensions of that part...and the real pieces.

Oh...and also those are nice clear close-up pictures. 

Thanks for sharing!
-brino


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## ProfessorGuy (Jul 1, 2015)

mikey said:


> By the way, a P1N parting tool makes a good thread relief tool.



Forgive my ignorance, but what is "thread relief?"


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## ProfessorGuy (Jul 1, 2015)

brino said:


> Do you have a microscope mounted to the cross-slide?!?



I use a simple 4x jeweler's loupe (with a wire harness) which I've always used for watchmaking.  Over the years, I've modified it with air holes to prevent fogging.  A loupe, with its 3-4 inch focal length, allows me to put my head right up close to the spindle.
If you look at the photo of me on the left, you can see my long hair and beard.  I have since gotten a crewcut and beard trim so I won't have problems getting my face so close to the machinery.  Also, I cut the threads by hand:  That is, the lathe motor is removed and a manual handwheel installed, so danger is minimized.


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## RJSakowski (Jul 1, 2015)

ProfessorGuy said:


> Forgive my ignorance, but what is "thread relief?"


An undercut below the shoulder of the screw.  Used where you need a full thread but but can't cut the thread up to the shoulder.  It also gives a nice clean break to the threads.


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## mikey (Jul 1, 2015)

As above. Another way to look at this is that it provides a run off area for your tool. You can cut until the tip of the tool enters the thread relief area, thereby avoiding gnarled ends on your thread. The depth of the relief is cut to the minimum diameter of the thread so you don't lose strength. Here is an example:


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## RJSakowski (Jul 1, 2015)

Further, on Mikey's info, if you cut your threads without the relief your last cut could go a tad further than the previous cuts, possibly causing some problems. The relief gives you a larger window to withdraw.  Since you are cutting manually, it is probably not an issue for you.


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## ProfessorGuy (Jul 1, 2015)

This screw is about 1/4" long.  I don't know the pitch, but it's about 50 TPI.

I understand the need for thread relief so the cuts don't have to end all at the exact same spot, but cutting by hand under a loupe made stopping at the "end" of the thread very easy.  But cutting the thread relief before cutting the threads was not an option for me!

That's because I had absolutely no idea where the bottoms of the threads would end up, so I didn't know the final minimum diameter.  I know the calculations are not difficult but I did all this work by eye!  I knew I hit the correct thread depth when the flat areas disappeared from between the threads as I cut them deeper.  But how deep?  Didn't know, and more important, didn't really care.  Since I can make my screws and holes all custom (non-interchangeable), what need have I of measurements?


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## mikey (Jul 1, 2015)

Understood but it is well to keep in mind that without a thread relief you may need to take the thread very nearly to the shoulder in order to have the screw tighten deep enough. In addition, oftentimes the thread form near the end is not neat and will require some cleanup if you cannot run it off into a relief; it isn't about having them end in the same spot. You don't have to cut one but its good to know about them and how to cut them.


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## coolidge (Jul 2, 2015)

That's quite nice, we need to see some action photos of these being turned.


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## RJSakowski (Jul 2, 2015)

ProfessorGuy said:


> This screw is about 1/4" long.  I don't know the pitch, but it's about 50 TPI.
> 
> I understand the need for thread relief so the cuts don't have to end all at the exact same spot, but cutting by hand under a loupe made stopping at the "end" of the thread very easy.  But cutting the thread relief before cutting the threads was not an option for me!
> 
> That's because I had absolutely no idea where the bottoms of the threads would end up, so I didn't know the final minimum diameter.  I know the calculations are not difficult but I did all this work by eye!  I knew I hit the correct thread depth when the flat areas disappeared from between the threads as I cut them deeper.  But how deep?  Didn't know, and more important, didn't really care.  Since I can make my screws and holes all custom (non-interchangeable), what need have I of measurements?


If you know the pitch and profile of the thread, you can calculate where the bottom of the thread will be.  If you under-cut or over-cut the relief slightly, it won't matter much.  Under-cutting will leave marks from the root of the thread, over-cutting unnecessarily weakens the screw; neither of which is likely to be a problem for you.  If your depth of cut is about .8/P, you should be fairly close.


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## RJSakowski (Jul 2, 2015)

ProfessorGuy said:


> but I did all this work by eye!  I knew I hit the correct thread depth when the flat areas disappeared from between the threads as I cut them deeper.  But how deep?  Didn't know, and more important, didn't really care.  Since I can make my screws and holes all custom (non-interchangeable), what need have I of measurements?



If your screws are all custom and noninterchangeable, what do you do when you lose or damage a screw?  Reverse engineering something of that size would be a real problem!


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## ProfessorGuy (Aug 2, 2015)

RJSakowski said:


> If your screws are all custom and noninterchangeable, what do you do when you lose or damage a screw?  Reverse engineering something of that size would be a real problem!



My plan: just drill the hole to the major diameter and make a slightly bigger screw next time.  How much bigger?  About *this* much (I do them by eye).


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## ELHEAD (Aug 2, 2015)

ProfessorGuy said:


> My plan: just drill the hole to the major diameter and make a slightly bigger screw next time.  How much bigger?  About *this* much (I do them by eye).


So do you make a matching tap for each new screw of unknown thread count?


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## ProfessorGuy (Aug 3, 2015)

ELHEAD said:


> So do you make a matching tap for each new screw of unknown thread count?



I'll make each screw too long, cut the end into a tap (I file slots in the end), use the tap to make a perfect mating hole, cut the tap off (with its stressed and ruined threads), finish and polish the end, leaving the short screw with perfect, unused high threads.  And it is perfectly mated to the hole.

All with no measurements!


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## savarin (Aug 4, 2015)

Would this custom thread making by eye have been the usual way years ago?
The reason I ask I've had to make a bolt for an old clock fixing for a friend and the closest I could measure the thread came out at 3/16" dia, .75mm pitch and around a 50 degree profile.
I cant use the nut for a trial fit as the clock is 4 hours away.
I've made it but wont find out if it fits till the weekend when he takes it away for a try.


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## Eddyde (Feb 23, 2016)

Someone started a thread a few of weeks back asking "what is a seat of the pants machinist" I think this is the answer:


ProfessorGuy said:


> I'll make each screw too long, cut the end into a tap (I file slots in the end), use the tap to make a perfect mating hole, cut the tap off (with its stressed and ruined threads), finish and polish the end, leaving the short screw with perfect, unused high threads.  And it is perfectly mated to the hole.
> All with no measurements!



Amazing!


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