# Metric Grub Screws



## niagra (22 Nov 2014)

Hi all,

Anyone know where I can get hold of some M4 x 0.75mm thread pitch grub screws? They all seem to be 0.7mm TP.

Thanks,
Dario


----------



## marcros (22 Nov 2014)

M4 is 0.7mm pitch so I doubt that you can. Will they not force fit?


----------



## niagra (22 Nov 2014)

Dunno, I haven't ordered any as assumed not. The screws I have are from Germany, I wonder if 0.75mm pitch is more standard there?

I guess I could always make my own?


----------



## dickm (22 Nov 2014)

... or re-tap the hole to the standard pitch, if there's enough metal there for it not to be too weak?


----------



## RobCee (22 Nov 2014)

I believe that the metric coarse thread M4.5 has a 0.75 pitch. Could it be that size?
Good luck finding them though...


RC - Tapatalk


----------



## Myfordman (22 Nov 2014)

Is it possible (from the age of the application) that it could be an imperial thread?

4mm is almost exactly 5/32" 
5/32 whitworth pitch is 32 tpi or 0.79mm

All depends on the accuracy of your measurements. If you have a sample grubscrew, check the fit of English and metric allen keys.


----------



## niagra (22 Nov 2014)

I checked with the seller when I bought the screws, he said they were 0.75mm pitch. I've tapped the holes to 0.75 and the screws fit perfectly. 

I could just cut down the screws and make the grub screws like that or just do my own. As I got them from Germany I can only assume they are M4 and not 5/32 WW.

I'll get by in the end! Thanks for the responses, great to know I'll always get helpful advice.


----------



## pcb1962 (24 Nov 2014)

If the pitch really is 0.75 then the screws are M4.5, not M4


----------



## woodpig (24 Nov 2014)

These folks will sell you a M4 x .75 Tap but I've never seen fasteners with that pitch.

http://www.tap-die.com/contents/en-uk/d ... _taps.html


----------



## pcb1962 (24 Nov 2014)

woodpig":1xf9c2th said:


> These folks will sell you a M4 x .75 Tap



That's bizarre, I wonder why anyone would make such a thing when the standard pitch is 0.7mm


----------



## niagra (24 Nov 2014)

pcb1962":3q9d3x94 said:


> woodpig":3q9d3x94 said:
> 
> 
> > These folks will sell you a M4 x .75 Tap
> ...



My set of taps and dies have two pitches for each diameter - a coarse and a fine. Coincidently, they are German made (as the screws I've been using are also) which makes me wonder if the standard in Germany is 0.75?


----------



## CHJ (24 Nov 2014)

http://www.gewinde-normen.de/en/index.html


----------



## dickm (24 Nov 2014)

CHJ":1bwt1w0u said:


> http://www.gewinde-normen.de/en/index.html


........... and that's called standardisation!!


----------



## Inspector (24 Nov 2014)

pcb1962":2y8o6pdv said:


> woodpig":2y8o6pdv said:
> 
> 
> > These folks will sell you a M4 x .75 Tap
> ...



There are manufacturers that use propriety threads so you can't interchange with a competitors product or to keep you returning to buy their parts.

Pete


----------



## Myfordman (24 Nov 2014)

According to my Machinery's Screw Thread handbook 13th ed.
The French series of metric threads align with the ISO metric series above 6mm however diameters between 0.3 and 5mm can be different.
One of the original French threads is 4mm x 0.75

Furthermore the thread angle can be either 50 or 60 degrees!

Now why does this not surprise me about the French??

MM


----------



## Hemsby (24 Nov 2014)

Not that this helps you much but the M4x.75 pitch is an old German DIN standard


----------



## Hemsby (24 Nov 2014)

Depending on what the application is could you not use Helicoil or similar thread inserts and change the thread to M4x.7

Repair kits containing drill, tap & inserting tool and some inserts (depending on the length you need) cost £20 or less. All you need to do is drill out the old threads 4.1/4.2 diameter. :idea:


----------

