Info needed: Rethreading nuts and bolts

[DaveBuckle]

Thankyou folks - all that info very helpful and much appreciated.

[Mike K]

Dave

A possible trap to be aware of is: Morris used metric threads on their engines , your CS8 engine has metric threads all over it. William Morris had an arrangement with Hotchkiss of France for engine manufacture back prior to WW1 I think so it goes , Morris eventually bought out a Hotchkiss factory that was setup in the UK making armaments during WW1 thus he inherited metric tooling

[rob love]

Sounds like you are going to need to order a couple of sets of pitch gauges, a caliper, and google some thread charts. After a time, you will start to recognize the threads on he bolts at least, but much harder to do on nuts.

Generally, these days you can tell the thread type by the head markings (but not always...I have seen standard bolts with metric grade markings), but those rules did not apply to the WW2 time period. The Hotchkiss name brings up another anomaly that I recall. Didn't they use standard threads but with metric heads on their M201 Willys engine production?

[Lynn Eades]

Ford did a similar thing in the 70s. With a Kent designed engine and German gearbox design in Escorts and Cortinas, meant a mix of both standards, and hybrid bolts.
Identifying from a bolt head has become far more difficult in the last 20 or so years with many new manufacturers.
The Australasian standard doesn't help.
Now that I think about it, even Ford of Canada made hybrid bolts and nuts for carriers with BSF threads and American (unified) standard heads.

Then there are the tool sets intended to cover all possibilities (eg 19/32", 25/32", and 29/32") made to fit British standard heads, as an extension of an American standard tool set.

[B. Harris]

A very handy and inexpensive tool(s) are Thread Files.
These are similar to a regular machinist file but will recut burred or damaged threads on bolts. One ore two pass's with one usually does the trick. A Google search is your friend for pics and descriptions.
Harris

[Matthew P]

Originally Posted by rob love

Sounds like you are going to need to order a couple of sets of pitch gauges, a caliper, and google some thread charts. After a time, you will start to recognize the threads on he bolts at least, but much harder to do on nuts.

I'll second the thread gauge. Handy little device. I have one that folds up similar to feeler gauges.

Matt