Thread identifacation

[Mark P.Participant @markp]

Hi all can anyone tell me what thread this maybe? As far as I can tell the OD is 0.134" and it has a 32 TPI pitch it doesn't appear to match up with anything. They are from a Simat 101 I don't suppose that they made their own threads for this lathe. All the grub screws are chewed up and I would like to replace them with good quality ones. I know that I could make my own but I really don't have the time or inclination to do this,especially at this size.

Regards Mark P.

[Mark P.Participant @markp]

[Keith LongParticipant @keithlong89920]

Try 6-32 UNC, Zeus lists it as 0.138 in. od.

Keith

[Mark P.Participant @markp]

Hi Keith,have tried that size but no go I'm afraid.To tight,but I suppose that I could run a tap down the holes.Wouldn't have thought that size would have been used but I stand to be corrected.We used 6-32 on Boeing aircraft.

Thanks Mark P.

[Brian WoodParticipant @brianwood45127]

Hello Mark

They do seem to be a strange size, but since Simat lathes were made as 'el-cheapos' in Sheffield in the late 1940's for a while, I hardly think they would have used their own thread pattern. Common sized grub screws from that era were the BA series, 4BA seems to be the closest to the size you quote. UNF and UNC were still to be adopted in the UK while BSF and BSW still held sway.

I don't think they would have beem Metric either; M3.5 is closest but doesn't match 32 TPI being 0,6mm pitch. Don't forget BA threads have a thread angle of 47.5 degrees which would feel tight on broader angles like UNC

visit http://www.lathes.co.uk a most useful mine of information on all manner of machine tools, the Simat is listed in the lathes section

If all else fails I would be inclined to retap the holes and fit hexagon wrench size grub screws as replacements, hardly likely to detract from the rarity value I wouldn't think.

Regards Brian

[David JuppParticipant @davidjupp51506]

4BA may be closest to measured dia, but the tpi doesn't match

5/32 BSW (32tpi, 0.156" dia) might be possible. If you are measuring the existing male thread it may be quite a bit under nominal size.

2BA (31.4 tpi) and 3/16 BSF (32 tpi) are both OK for tpi, but major dia. larger than measured.

Good luck…

[John Stevenson 1Participant @johnstevenson1]

I'd go with Brian and retap the holes to something you can get off the shelf like 4mm

Chances of managing to buy new grub screws in somthing like 5/32 or 3/16" BSF / W is akin to winning the lottery.

 

End of the day as Brian says it's not about rarety that being able to use it.

 

Lets face it even Myfords, [ pause for hand on breast, bugle call and flag lowering ]

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Sorry long pause, changed from 2BA to 5mm

 

Edited By John Stevenson on 05/05/2013 12:02:17

[JasonBModerator @jasonb]

I'd just run a 6-32 tap through the holes to clean up the threads and buy new UNC grub screws which are easy enough to get hold of.

Quite possible they got hold of some US army surplus after the war.

J

[LambtonParticipant @lambton]

Mark,

If you are sure that you have measured the pitch accurately then it is almost certain the grub screws are 6-32 UNC as nothing else is near to the sizes you quoted.

I have some 6-32 UNC cap headed set screws x 1” long. The measured diameter is 0.135”. These could be easily adapted to you needs if they fit.

If you want to try one I will send you a sample if you send me a private message with your address.

Eric

[Mark P.Participant @markp]

Thanks for the replies,I think that I will go for the metric option.

Regards Mark P

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