Thank you for those pointers;

DC31k –

No, the machine and its components are not so sacrosanct that I cannot replace as you suggest, and it would be the most reliable solution. Usually I prefer to make new parts and especially any accessories fit existing mounting-points, edges, etc., rather than make the machine fit the new parts; but this would be replacing like for like with no significant change.

The wheel and its stub-axle / leadscrew carrier are cut in a single piece of bronze but there is enough metal available to mount a replacement on a shoulder.

The worm-wheel is not heavily worn, and there is a clue beyond missing drive, that it might never been used – the table lacks the T-slot carrying the feed off-trigger block. This is clearly visible in the lathes.co illustrations apparently taken from the Denbigh catalogues. Denbigh's other H-series mills had lever-operated tables, but the table on mine also lacks anything for lever-feed components. Perhaps it is an early version assuming through-milling or manual control analogous to turning to a shoulder.

Hence, since appropriate worms and wheels are readily available, I think your suggestion probably the easiest and certainly most reliable. After all, I would have to make all the other parts to my own design and with a reversed drive, reasonably in keeping but not original.

Imperial or Metric pair? Well, inch sizes would match the machine but not matter functionally, and any universal joints available now are likely to be metric only. It would not be noticeable and anyway the main drive to the spindle, with a massive reduction around 24:1, will probably have to use metric components!

The actual worm-wheel tooth-count is not critical within reason, and I wonder if changing it from 22 to 24, assuming clearance for it, may be an advantage because the lead-screw is of 6TPI (lead = 0.16r inch or 4.23mm). Or would that lose any "hunting" effect?

'

Andrew –

Thank-you for correcting my typo.

And for your machining offer, but given the difficulty in identifying properly a worm-wheel likely also to be a bit worn anyway, I think DC31k's suggestion of machining the component to carry an appropriate replacement, paired with its correct worm, better than trying to make a worm.

++++

Many moons ago I rescued a very old Hure (not Huron) Universal Mill from a local scrapyard, and installed it in the workshop our society rented at the time. One of the teeth of the bevel gear operating the knee-screw was broken, and I managed vaguely serviceable dentistry by welding pieces of steel rod in its place and filing them to shape! The mill, probably 1880s-1890s vintage, was later sold to Weston Zoyland Pumping Station Museum, and subsequently into private preservation.