M4 x 0.75mm pitch CSk machine screws

.

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

MichaelG.

.

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

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

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!

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

.

Neil's link included no tolerances

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:

**LINK**

Russell

Just found this on a French site:

**LINK**

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!

Russell

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?

Howard

Ooops.

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.

Andrew

Thanks for putting me right Andrew!

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

Howard

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

Adrian

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