Making studs

[Jo]

Thanks Bill, Steve & Dave,

I hope some of the other members also found it useful 

Jo

[steamer]

I am sure it will Jo!....I have a small fixed die head with a plethora of different dies....just haven't had a chance to make studding yet...though the die works very well.

I have a bed mounted turret and tooling for SB...but I need to learn the correct way or sharpening the cutting tools for them......some day before I kick off I suspect....

Dave

[IanR]

Ah but those were bolts not screws. Certainly BMC used studs. My current Ford has bolts as well.

JerryNotts

The main reason for us using studs is that the engines we're modelling used studs, because they are much more economical in metal and machining time. Making a 1/2 Whitworth bolt out of 59/64 hexagon or 1 1/16 round means most of it becomes swarf; with a stud and nut, there is little swarf. But these days bolts are machine forged, and Ford doubtless get them cheaper by not buying a few at a time, shrink-wrapped.

Jo, does the drill chuck you use for holding while doing the second end not chew up the thread you've already done?

[Ian S C]

When I rebuilt the Stuart S9, I cheated a bit, to get the correct amount of thread protruding through the nut I loctited the nut on the studs, and used them as bolts so that if anyone in future on removing them, could reassemble them correctly.   Ian S C

[Jo]

Jo, does the drill chuck you use for holding while doing the second end not chew up the thread you've already done?

  If you have machined them correctly the parallel bit in the middle is the same diameter as the major dimension of the thread. So if you graunched the thread you have already made a mess of the nice parallel part and it won't fit in the hole, so best make another one  .

Jo

[ozzie46]

   Thanks Jo. Nicely done and will help a lot of people here.

 Ron

[sco]

2. the nominal [minimum] depth of thread engagement is 1.5 x the thread diameter

No thread engagement is not how far the stud/bolt or screw is turned into the tapped hole.

It is the relationship between diameter of tapped hole to the major dia and is expressed as a percentage. eg how much flank contack there is not how far the stud is screwed in. If the commercially produced rolled studding is undersize then the percentage engagement will be reduced.

3. I simply noted that BA is a metric thread form

The term "form" relates to the shape of the thread and as BA is not shaped the same as metric it can't be the same form. It would have been better to say something like "BA is a metric based system"

J

In the industry I work in 'thread engagement' means the length of thread that is screwed into a tapped hole.  We use the same factor of 1.5xD with two exceptions; if space is extremely tight we use 1.2xD and for tapped holes into cast materials where we use 2xD.

Thanks Jo for taking the time to write this stud tutorial.

Simon.

[Jasonb]

Maybe this is where Model engineering and industry differ, ask most Model engineers about thread engagement and they will refer to the tapping drill dia to give a percentage engagement.

Take a look at something like "Model Engineers Handbook" and there are several pages and tables dedicated to % engagement and not once does it mention thread engagement length.

The BSI even produced a guidance document "Guidance on metric screw threads and fasteners for use by Model Engineers" which again deals with percentages of radial engagement not length.

These percentages are there to help Model engineers get a strong enough threaded joint using hand tapping methods and without the risk of breaking taps in too tight a hole. So as this is a forum of Model making these standards are far more relevant than a standard in industry where threads are machine cut to higher tiollerances which you may want if hanging the wings of an aircraft off the fuslage with the fixings.

J

[Steam Haulage]

As I seem to have started a thread which has found some interest with other members I have ought to pass on a link which I have just found and which has data  for almost every thread I have heard of, and more.
http://www.gewinde-normen.de/en/index.html

I am very appreciative of the information which has been exchanged and from which I have learned much.
My thanks especially to Jo for illustrating and describing the methods she employs

JerryNotts

[sco]

Well GHT talks about lengths of thread engagement in The Model Engineers Workshop Manual and recommends 1.25 to 1.5xD.

I guess if both the tapping hole is too small or the length too great the end result is the same - broken taps as I've recently found to my cost 

Simon.

[pgp001]

A very rough guide to a suitable thread length can be got by measuring the thickness of a nut in the size you are working with.

I said "rough" because it depends on various other factors as well such as materials etc.
It is quite common to find studs with course pitch threads on one end and fine pitch on the other, especially when they are fitted into something like a cast aluminium crankcase.

It always amuses me when we get new design engineers starting work straight from university and they start drawing up things with tapped holes M3 x 25mm deep in 303 stainless, and wonder why the guy from he machine shop throws a dickey fit 

Phil

[tel]

Where possible, I like to bury a stud into the parent piece by dx2.

[wagnmkr]

Thanks one and all for this info. Jo, excellent pics and explanations.

Cheers,

Tom

[Tennessee Whiskey]

Ok you studding gurus. My steam chest cover calls for 2-56 screws. If I wanted to impress Jo, what size stud and nut would I want to produce. It calls for a 3/32 thru hole in the cover as the prints are drawn now for the supplied screws. Sorry for these nasty old imperial measurements.

Whiskey

[Mosey]

OK, Eric, around our way, studs are born not rolled. I don't know about Tennessee!
Mosey