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M4 x 0.75mm pitch CSk machine screws

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Michael Gilligan23/08/2019 09:44:38
15885 forum posts
693 photos
Posted by Neil Wyatt on 23/08/2019 09:33:37:


Not a cheap option with shipping, I guess.



I wonder what the tolerances are, on those rather impressively specified dimensions



M4-0.75 Screw as used on Hispano Suiza J-12.

Material: Steel
Finish: Natural
Thread: M4-0.75 x 15.75
OAL: 27.59mm
Shoulder: 8.5mm
Length under head: 23.84mm

not done it yet23/08/2019 10:19:28
4746 forum posts
16 photos
Posted by Michael Gilligan on 23/08/2019 09:40:01:
Posted by not done it yet on 23/08/2019 08:56:48:
Posted by KWIL on 23/08/2019 07:24:35:

Yes is the answer, it all depends upon how many items you need.

I know what you mean.smiley “Ally Barber” would gladly supply a million from China. Not so good a price, or availability, if one only wanted four or five!


I may be wrong, but I think KWIL was answering the question by Nicholas Wheeler 1

[quote] Is anyone really going to screwcut such a thread when they can buy taps and die?. Anyone who gets work done, that is. [/quote]


Mine was just a tongue in cheek reply referring right back to the start of the thread, there being no reference for anything else.smiley

Just shows how things can easily be misconstrued - like three separate suggestions (in three separate sentences) all being assumed to be intimately connected when they were most certainly not!smiley

JasonB23/08/2019 10:27:31
18321 forum posts
2024 photos
1 articles

If there are more than you fancy making yourself then someone like Historicthreads may be able to run a small batch, expect their CNC machines would also hit the tolerances of the screws Neil linked to and would actually be CSK too.

Edited By JasonB on 23/08/2019 10:28:42

Michael Gilligan23/08/2019 10:32:47
15885 forum posts
693 photos
Posted by JasonB on 23/08/2019 10:27:31:

If there are more than you fancy making yourself then someone like Historicthreads may be able to run a small batch, expect their CNC machines would also hit the tolerances of the screws Neil linked to and would actually be CSK too.


dont know Neil's link included no tolerances

Russell Eberhardt23/08/2019 10:33:35
2595 forum posts
85 photos

It would almost certainly be French Automobile Thread, a slightly different spec. to the old French Metric Thread. I still have a few taps and dies for it from working on vintage Morris cars which used French Automobile thread on their engines but with W.W. hexagon sizes so that UK garages could use their existing spanners. Unfortunately I don't have a 4 x 0.75 die - sorry.

For reference the spec for French Automobile Thread can be found about 2/3 of the way down this page:



Russell Eberhardt23/08/2019 10:45:41
2595 forum posts
85 photos

Just found this on a French site:


It is a bit expensive but if you need a number of screws . . .

The interesting thing is that the dies are made by Dormer to BS1127:1950!


Howard Lewis23/08/2019 16:21:08
3394 forum posts
2 photos

Purely as a comment re fasteners for switch patresses. I thought that with metrication, the threads had changed from BA to 3.5mm diameter x from memory 0.5mm pitch?


Andrew Johnston23/08/2019 16:38:02
5558 forum posts
650 photos
Posted by Howard Lewis on 23/08/2019 16:21:08:

............ from memory 0.5mm pitch

Ooops. embarrassed

When my electrician said he'd leave it to me to fix some of the old sockets in my replacement kitchen I bought M3.5 x 0.6 taps.


Howard Lewis23/08/2019 17:04:26
3394 forum posts
2 photos

Thanks for putting me right Andrew!

Moral: don't trust to memory. Should have looked at Tracy Tools brochure, as they sell them!


AdrianR17/05/2020 08:48:01
486 forum posts
25 photos

Last August at the Lincolnshire Steam Rally I picked up some taps. I recently came across them again, and popped the M4 in my metric set. Yesterday I used it for the first time to tap holes for the DRO on my new mill. It puzzled me for while why the screw would not go in very far. Took me a while to notice the pitch on the tap!

Live and learn


Clive Hartland17/05/2020 09:12:28
2575 forum posts
40 photos

try stainless steel M4 x .75 c/sunk screws.

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