Making studs

[smfr]

After making some studs for my Muncaster, a couple of questions popped into my head:

• Should the stud bottom out in its threaded hole, or be stopped by the limit of the threads on the stud shaft?
• Is it cheating not to screw the stud all the way down in order to get the perfect 1-1/2 threads above the nut?

Simon

[Jo]

The depth of the hole into which the stud is fitted should be twice the diameter of the stud, the stud should be threaded at the end for 1 1/2 times the diameter of the stud. ( noting that both hole and stud will have the final few threads tapered) The stud should be stopped by the limit of its threads.

There is no such thing as cheating... in the old days people were proud of the engines their companies created and would make sure that there was nothing for another engineer to pick holes in on their engines. The engine drivers were also very proud of their charges and would endeavor to ensure that nothing was a miss on their engines. Having the same number of threads sticking up on every nut (as well as for the reasons mentioned earlier) meant that it was quickly obvious to the driver if any of the fastners was amiss and needed attention... I am sure in the twilight years of the industries when money was tight  maintenance went down hill and as studs needed to be replaced what ever came to hand was used to do repairs, even  bolts.

Jo

[Mosey]

Yep, most car wheels have bolts these days as do cylinder heads and the like. Studs and nuts seem a much better idea to me though, not least because you don't have to replace studs but with these 'stretch' bolts you have to replace them every time a head gasket is replaced.

Perhaps because when they are inserted with a predetermined torque, it ensures the stress on the fastener is correct.
Mosey

[Steam Haulage]

Thanks Jason,

I had forgotten my earlier interest, now revived following my concern with fine threads for which you kindly gave me some starting encouragement.
The thread is older than I recalled.

Regards
Jerry

[kvom]

In past models I avoided making studs other than a few fake ones with threaded rod.  But with my current Muncaster engine it seems mandatory to make them.  If like me you're blessed with a CNC mill then then you can thread mill each end as long as there is a convenient way to hold them vertically on the mill's table.

I will be using drill rod and holding it in a collet vise.  Most of the studs are 1/4-20, 12 for the steam chest cover, 6 for attaching the chest to the cylinder, and 6 more for cylinder to base.

So my process will be to use the lathe to part off all the pieces to length and to chamfer both ends.  Then for each end it becomes a matter of inserting the stud into the collet, move it up to touch the bottom of the thread mill to establish Z0, tighten the collet chuck, and hit the green button.  A 1/2" thread length done in three passes takes a couple of minutes using conservative feeds & speeds.  One thing I did learn from my first few threads is to check it in a tapped hole.  I made pins on which a nut would screw nicely but was too tight for the fit of the tap I am using and/or the starter hole.

It's also possible to make threads smaller than the stock by adding extra passes; for example, 10-32 threads on a 1/4" rod.

For studs and pins smaller than 1/4 I use model scale nuts from American Model Engineering.  I have used their nuts for screws as small as 2-56.  I think that for a 2-56 stud I'd just use threaded rod or cut the head off a screw.  They also can provide model scale screws with hex heads  that look much better then socket heads.