Making studs

[Steam Haulage]

This is not really a new subject but I need to understand the methods used by other members of the forum. There is a lot of mentioning of studs, and often Jo's name come into the discussion. However after a read through nearly every occurrence of the word found from the search box nobody has actually described in detail, as far as I can see, a method of making them!
If anyone has done this I would appreciate a note of where I can find a description, or a link.
It may seem obvious but making M3 - M6 sizes is new to me. I am content with 1" Whit and similar but I reckon there must be some challenges at the smaller sizes.

Thanks
JerryNotts   

[Tennessee Whiskey]

I agree Jerry. I think Jo, the master of studding, should start a tutorial thread. And also, how do you determine the size of stud as opposed to a ( God forbid ) a screw or bolt.

Whiskey

[Jo]

 

I use two techniques depending on the size of said beasties (actually there is a third but I don't "go large"  often) . But it is late and I really need to set up a set of photos to explain the processess.

So not tonight boys  .

Jo

[vcutajar]

Looking forward to it.  Maybe I will stop using threaded rods instead of studs.

Vince

[maury]

Y'all, I'm looking forward to this too. I have been using SST ground threaded rod. Would like to make real studs. This method may also be able to be used for making pipe nipples too????

maury

[derekwarner]

Guys....pre threaded rods in many applications do have the advantage of being a rolled thread ....so irrespective of the parent material...the actual tensile strength of a rolled thread is far superior to that of a stud with a machined thread.....

The determination on the number or size of threaded studs is the same as that for bolts....& is based on the UTS of the parent material x the nominated factor of safety.........Derek

[Jasonb]

In the majority of our uses the strength is not such a big issue. Far better to have an equal length of thread on the end that screws into the hole so all studs fit leaving the same amount sticking out which ensures all your studs show the right amount of thread above the nut.

Rolled studding can also be a bit undersize which can allow the part to move about slightly whereas a properly dimensioned stud not only resists the tension on it but also locates the part better in shear.

The fact its also undersize reduces thread engagement so it may be stronger but will be more likely to pull out.

And finally have you seen the price of BA studding.

J

[Jo]

A few basics:

Size of parent material:

Irrespective of the size of the stud you are making never use parent material that is smaller than 3.2 mm (1/8”) diameter. The problem is that as the material gets thinner it bends so even when making the 1.4mm 12BA studs for the DTC I started with 3.2mm material.

Material:

I know some kits come with steel, others with “bronze”: I in the main use 303 Stainless as it does not rust and cuts nicely. Rarely am I using studs in applications where the tensile strength of the stud is an important factor.  (Just in case you are wondering 303 has a better tensile strength than that horrible 304, but only a ¼ of the strength of a high tensile steel – but my models are not expected to be subjected to the sort of high stresses in modern high performance engines)

Stud length

Now for some maths, the length of the stud consists of:

• The material in the thing we are fixing to.
• The gasket thickness (so easy to forget  )
• The cover we are bolting on.
• The washer thickness (if fitted  )
• The nut thickness (this needs to be checked as some manufacturers don’t make to the published standards)
• Plus an additional one and a half threads to make it look right and to take into account that the last thread will not be full hieght as it will be slightly curved.
  

The thickness of the cover plus the gasket should be left unthreaded in the middle of the stud. A piece of threaded material which is threaded all the way is  horrible.

I have a couple of quick look up tables I use to speed things along, sorry  I normally use BA threads, hopefully someone will have a similair table set for American & French (metric) threads.

Jo

[Steam Haulage]

Hi All,
Now I'm glad I asked the question, seems there is some general interest in this subject. I suppose we all need studs at some time in our lives.

Jo: thanks for the tables. It may be obvious but can I assume  that although TPI are imp. that the other dimensions are all mm? We all know the warning phrase about assumptions!

I hope somebody will chime in with some production methods, especially for the type where covers and such like are held by studs which are un-threaded through the cover.

Thanks to all who have commented

JerryNotts

[Jo]

Yes Jerry, TPI are imperial but I work in metric as all my machines are metric 

I did say last night that I was going to go through the processes of making studs. I could provide a written description now but was going to knock up a couple this evening so that I could provide photos to go with it.

Jo

[derekwarner]

Guys....

1. despite the crazy dimensions....BA is a metric thread form 
2. the nominal [minimum] depth of thread engagement is 1.5 x the thread diameter

Jasonb...

3. a stud threaded [or bare] diameter is not designed to provide alignment or concentricity......... but simply to secure a bolted attachment
4. the purpose of a bolted joint is to retain or constrain energy ..............the calculation of strength is critically important

Derek 

[Jo]

Sorry Derek I do not agree with you:

1. The BA thread form is 47.5 degrees, metric is 60 degrees, you cannot use a metric thread cutting tool to cut a BA thread. It is however based around metric measurements.


3&4.

Studs are carefully shaped / designed with gasket and cylinder alignment in mind: This means that it is easier to assemble an engine using studs. If you think about the differences between using studs and bolts for an application it comes down to the means of installation:

A bolt is installed by rotating it into place, this causes both twisting and vertical clamping forces which are increased when the engine’s cylinder comes under load. Because a bolt is having to simultaneously respond to the stretching and twisting moment its ability to secure the head is slightly reduced.

A stud is tightened into place without any direct clamping force applied through the tightening. It can be threaded up to “finger tightness,” and afterwards, when the item it is securing is installed the nut is torqued into place against the stud. The result is that the nut torque provides the clamping force, causing the stud to stretch along the vertical axis without the simultaneous twisting moment.

So a stud provides a move evenly distributed load distribution (and if you are torqueing up your nuts, accurate torque) than is possible with a bolt.

Jo

[b.lindsey]

Good stuff Jo !  Am looking forward to the next chapters too

Bill

[derekwarner]

Jo...
1. With respect I offer the following..............
2. I was not suggesting that BA & any metric thread forms were interchangeable....
3. I simply noted that BA is a metric thread form & based upon "exact multiples of the metric system units" .........Derek

British Association or BA screw threads are a largely obsolete set of small screw threads, the largest being 0BA at 6 mm diameter. They were, and to some extent still are, used for miniature instruments and modelling.

They are unusual in that they were probably the most "scientific" design of screw, with a basis in metric size (the 1 mm pitch and 6 mm diameter of 0BA) and with a mathematical relationship between the 'number' (e.g. 2BA with K=2) and the corresponding pitch, major diameter, and then spanner size. Though originally defined in terms of the imperial units then in use in the United Kingdom, this was deliberately set to be exact multiples of the metric system units, rounded to the nearest thousandth of an inch. This anticipated worldwide metrication by about a century. The design was first formulated in 1884, following a study of Swiss practice and was standardised in 1903.

[Steam Haulage]

I hope I have not opened a can of worms.

All of the answers so far have been most interesting.

To me a stud has 2 threads, one at each end but the middle section is plain round bar, otherwise if it's threaded full length it's 'studding', a Mickey Mouse device.
 As Jo has told us the purpose of the stud is to provide location and clamping force parallel to the axis of the stud itself. When we use studding we are providing a relatively inaccurate location and the 'stud' with its many unnecessary threads is weaker, and tends to stretch both under the tightening torque and in service. It also provides a thinner section at the point where the two faces meet. A correct length stud ensures that no sharp edges are contacted.
Those of us old enough to have maintained their own cars will recall how the cylinder head studs were unthreaded through the head and the washer not only allowed the nut to turn without twisiting the bolt but also would not tighten down unless the washer was in place.

JerryNotts