Whitworth bolt help required please

[Nick67GT]

I’m repairing an old treadle sewing machine for my wife and have discovered that 1 of the 4 bolts holding the frame together has gone awol.

It matches up nicely to a 5/16-18tpi Whitworth form:



But the o/d is 0.364” which is confusing me



The length is 1-1/4”



And it has a slotted pan head or whatever the nearest was at the time



Before I adopt the ‘drill out & re-tap’ approach to accommodate a metric or UNF hex head bolt, does anyone have anything kicking around in their useful spares box that would look more in keeping with the original?

Thanks for taking the time to have a look - beer tokens etc available as usual.

 

[Morris]

11/32 18tpi is a thread, taps are available. Finding matching screws may be a problem.

 

[Agroshield]

11/32 18tpi is a thread...

...which has a major diameter 20 thou. smaller than he has measured.

Maybe find a 3/8" screw of the correct head style and having at least a 1 1/4" plain shank and get someone to screwcut it for you.

 

[colnerov]

Or get a hex head bolt and modify the head.

 

[Rudi McAnichal]

Probably 3/8" x 18 tpi, a thread size included in this list for Singer sewing machines (first column Simanco No 506):

Singer sewing machine screw threads and taps

Screw threads and tap sizes used on Singer sewing machines.

www.singersewinginfo.co.uk

 

[Morris]

...which has a major diameter 20 thou. smaller than he has measured.

Maybe find a 3/8" screw of the correct head style and having at least a 1 1/4" plain shank and get someone to screwcut it for you.

There's 20 thou gone from the crest of that thread looking at the photos.

 

[Agroshield]

There's 20 thou gone from the crest of that thread looking at the photos.

See bottom of page here:

https://www.mitsubishicarbide.com/application/files/5314/7191/5783/tec_threading_depth_external_en-us.pdf

18tpi has 35 thou. depth of cut. I think you would notice if more than 50% of it had disappeared.

 

[Morris]

See bottom of page here:

https://www.mitsubishicarbide.com/application/files/5314/7191/5783/tec_threading_depth_external_en-us.pdf

18tpi has 35 thou. depth of cut. I think you would notice if more than 50% of it had disappeared.

Fair point, didn't think it through

 

[keithski122]

Sounds like a bolt from the british car industry.