Live centre screw

[Stigmorgan]

So yesterday I noticed the bearing retainer at the back of my live centre had come loose, I cleaned the thread off, used a little bit of plumbers tape and screwed it back in, then I noticed the retaining screw for the point was missing, I've spoken to the manufacturer and apparently the screw should be checked regularly so is my fault, they have said that the screw is M6 X1.5 and can be found on ebay but I can't find them, can anyone here point me in the right direction?

 

[rob1693]

Is it just an m6 grub screw quite a few in various materials on the bay

Example

 

[Inspector]

Try adding grub screw, set screw or Allen screw after the thread designation.

Looks like Rob types a little faster than I.

Pete

 

[Phill05]

Stig PM me with the length you need and your details I'll drop you 1 or more in the mail.

 

[J-G]

If that screw really is 6mm x 1.5 then it is NOT M6 - ie a 'Special' M6 is 1mm pitch.

1.5mm pitch on a 6mm dia is VERY coarse, it would normally only appear on a 10mm Ø or larger.

I would be very surprised if the information from the maker is accurate though so the standard M6 grub screws ought to be OK. I'd certainly try the standard and then castigate the maker (for the wasted time trying to find 6 x 1.5) if it does fit!

 

[Phil Pascoe]

Try a normal 6mm bolt to ascertain the thread

 

[Stigmorgan]

Is it just an m6 grub screw quite a few in various materials on the bay

Example

View attachment 129169View attachment 129170

The missing one had a flat head screwdriver slot, ive now also dropped the centrepoint, if I can't find it I'll have to just buy a whole new live centre

 

[Stigmorgan]

Stig PM me with the length you need and your details I'll drop you 1 or more in the mail.

PM sent, thanks Phil

 

[Stigmorgan]

If that screw really is 6mm x 1.5 then it is NOT M6 - ie a 'Special' M6 is 1mm pitch.

1.5mm pitch on a 6mm dia is VERY coarse, it would normally only appear on a 10mm Ø or larger.

I would be very surprised if the information from the maker is accurate though so the standard M6 grub screws ought to be OK. I'd certainly try the standard and then castigate the maker (for the wasted time trying to find 6 x 1.5) if it does fit!

It's about 4 or 5mm long and there's only 3 threads that I can see so 1.5 would be about right I think

 

[Robbo3]

Try Phil's method of a standard M6 thread first as it may save you searching for a harder to find thread.
When you have it sorted please report back with the correct information to help anyone else in the same situation.

 

[Stigmorgan]

Try Phil's method of a standard M6 thread first as it may save you searching for a harder to find thread.
When you have it sorted please report back with the correct information to help anyone else in the same situation.

Managed to find one in my box of bits and the thread is way too fine on the bolt, at least double the number of threads.

 

[J-G]

It's about 4 or 5mm long and there's only 3 threads that I can see so 1.5 would be about right I think

If you have measured the thread in the hole and compared that to a 'normal' M6 grub screw which is too 'fine', you will have great difficulty in finding any commercial fastenings supplier with 6mm x 1.5mm 'on the shelf'. Do not bother with anyone who offers you 'M6' -- that designation is specifically reserved for the standard 6mm x 1mm, even the 'fine' pitch version (0.75mm pitch) will always be specified as 6mm x 0.75mm.

Today, virtually all grub screws are made by 'thread rolling' and in the case of a 6mm x 1.5mm 'cutting' a thread would be the least sensible way to manufacture, so getting someone with a metal-working lathe to make one for you is also a no-no.

I have to assume that this 'special' has been created to make sure that any replacements are sourced from the OEM at a 'captive audience' price!

 

[Fergie 307]

You could try Helicoiling it to M6x1 and then use a standard M6 grubscrew, although if the hole is only 5mm deep there might not be enough depth to do it. Any local engineering firm or engine reconditioner should be able to do this for you.

 

[Fergie 307]

If it's not that hard you could even just drill and tap it to say M7. Dare say you can probably get M7 grub screws, but if the original just had a screwdriver slot, then you can make a new one from an M7 bolt. M7 isn't a common size so a tap will be more expensive than the run of the mill sizes, but still a lot cheaper than buying a new centre. I assume since you asked the question that the manufacturer can't supply a replacement for their weird sized grubscrew?

 

[kinverkid]

Maybe you could get away with drilling and M6 tapping a fresh new hole in the opposite side to take an off-the-shelf type grub screw.

 

[Phill05]

Stig it sounds like you have a BSW 1/4 inch this has 26 Teeth per inch a 6mm is a smaller dia it has 1mm pitch so 25.4 teeth per inch I can send you one of each that way you should get it working that is so long as you find the missing centre.


Edit: no need to go drilling or helicoiling.

Edit X 2 " so getting someone with a metal-working lathe to make one for you is also a no-no." Oh yes it is.

 

[Fergie 307]

Stig it sounds like you have a BSW 1/4 inch this has 26 Teeth per inch a 6mm is a smaller dia it has 1mm pitch so 25.4 teeth per inch I can send you one of each that way you should get it working that is so long as you find the missing centre.


Edit: no need to go drilling or helicoiling.

Edit X 2 " so getting someone with a metal-working lathe to make one for you is also a no-no." Oh yes it is.

1/4 BSW is 20 tpi. If his thread is genuinely M1.5 pitch then that is a whisker under 17 tpi. The nearest imperial thread is 1/4 NPT at 18 tpi, but it's tapered so not much use. The valid point made about not cutting one is that rolled threads, as used in pretty much all commercially made bolts and grubscrews, are much stronger than cut threads. Very unlikely a cut thread that size, and such a short length, would last any time atall.

 

[Stigmorgan]

Thanks @Phill05

 

[Phill05]

If the centre is old stock it could be 1/4 BSW I looked close at the image of the threaded hole and thinking it looks coarser than 1mm I put a Whitworth form against the image and it looks like 1/4 BSW, I might be wrong I have been known to according to my wife.

Stigs threaded hole.


Top screw is 1/4 BSW, Mid screw is 1/4 BSF (too fine), Bot screw 6mm coarser than BSF, finer than BSW.

So have said I will send over 1: 1/4 BSW and 1: 6mm with domed slotted head.

 

[Stigmorgan]

If the centre is old stock it could be 1/4 BSW I looked close at the image of the threaded hole and thinking it looks coarser than 1mm I put a Whitworth form against the image and it looks like 1/4 BSW, I might be wrong I have been known to according to my wife.

Stigs threaded hole.
View attachment 129225 View attachment 129224

Top screw is 1/4 BSW, Mid screw is 1/4 BSF (too fine), Bot screw 6mm coarser than BSF, finer than BSW.

So have said I will send over 1: 1/4 BSW and 1: 6mm with domed slotted head.

You're an absolute Phil