Wadkin grub screw for DM morticer... how much!!!

[RobinBHM]

The grub screw thst holds the augar bit has rounded off, so Ive just had to order a new one.....


£15.00 delivered :shock:

Bargain!

Before ordering, I thought, Ill find out what the size is and find one on the internet.

Dimensions are 13.2mm major diameter 19 tpi.

After spending ages searching through thread charts, such as UNC, UNF, BSW I was having no luck so had a search through the manual, which says 1/4" gas x 1/2"

and yes, it turns out the grub screw is British Standard Pipe Thread! -any engineers on here know a logical reason for that?

 

[Steve Maskery]

History, probably. The guy who made the first prototype had a box of odds and ends and pulled that out.
Drill it out and tap it M8 and you are good to go.

 

[Jake]

Could it be taper/parallel for an interference fit to help stop it undoing it itself with vibration?

 

[RobinBHM]

Could it be taper/parallel for an interference fit to help stop it undoing it itself with vibration?

I did wonder that, but the taper would have to be well worked out so that the tapering threads started to tighten at the same time as the end of the grub screw started to bite on the auger. Also we have always ground a flat on the auger bit is done by hand and different each time, Ive never noticed the grub screw getting tight before locking the bit. I shall check my new grub screw in the morning but I think its parallel. From memory the taper is 1 in 16 so should be able calculate what size each end should vary by.

 

[Cheshirechappie]

It's a bit uncommon these days, but sometimes when a fine thread was demanded in something that (for example) had to resist vibration, or provide some sensitivity of adjustment, a variety of BSP threads were used known as 'British Standard Pipe Fixing' (BSPF) to distinguish it from BSP (parallel) and BSPT (Taper). They were specified when something even finer than BSF (British Standard Fine) was desired. The tolerances to which BSPF threads were machined were slightly different to standard pipe threads, I think, but I can't remember in what way. I'm pretty sure BSPF threads are obsolete and have been for at least a couple of decades. I only know about them from fiddling about with old steam locomotives - they throw up some real oddities of obsolete threads and sizes from time to time.

If push came to shove, you could probably find a machine shop able and willing to make one up, but the cost for a one-off would in all probability be more than £15. Finding a fastener stockist with any would be like finding a timber merchant with a never-ending supply of prime Cuban Mahogany and wide, clear boards of yew.

 

[Stormer1940]

History, probably. The guy who made the first prototype had a box of odds and ends and pulled that out.
Drill it out and tap it M8 and you are good to go.

That's what I did on my cooksley.