TOPIC:

Oh, and 7tpi makes it BSF "fine" thread form, the standard BSW 2" thread is 4.5tpi

Scan from " 'The Scientific' The Story of the Cambridge Instrustrument Company" by Donald J. Unwin, ISBN 0 904355 07 1 - note Boxford Precision Plain lathe with collet drawbar, no counter pulley assembly, and motor on tower to rear of lathe, plus long belt (& partial cover).

The short spanners that came with the lathe have proved to be barely adequate for tightening the most often used nuts (top & side of the toolpost, 7/16ths Whitworth & 1/4" Whitworth) & sometimes not able to deliver the torque needed to undo them.

These sizes are available new, but I wanted vintage British made spanners - and one brand in particular is funnier than the rest

The large Thor brand thwacker is probably too heavy at 560+g, but "helpfully" they are sold by head diameter (64mm) not weight.

Jonny wrote:

These sizes are available new, but I wanted vintage British made spanners - and one brand in particular is funnier than the rest

Love it

I found the tool slide was tending to precess inwards, meaning that unless you held on to the dial the lathe wanted to cut make slightly cone shaped cut ... and once things got warm, the belt would ping off the motor spindle at inopportune moments

A bit of tighening on the gib strips & angling the motor very slightly seem to have fixed things

Today is Thor's day so time for some hammering.

I wasn't quite sure where to put this - to a certain extent it's a tool, it's also a tip that could go under scratchbuilding, but in the end I put it here because it's not something I could make without a mini lathe...



If you’ve worked with EMA Plastic Weld straight from the bottle (or even bulk Dichloromethane in a Tamiya 10ml glass jar), if you knock it over you’re likely to destroy your cutting mat and whatever you happen to be working on at the time.



I already made an untipperoverer on the Unimat a while back & it does help – but I wanted to make an even bigger one to improve stability. The problem is that round bars get really expensive once they get up to any meaningful size. This 70mm OD, 165mm offcut of POM (PolyOxyMethylene, aka Acetal or Delrin - Dupont’s trade name for it) was 16 GBP & therefore a bit of a bargain as these things go…






First setup was to face the ends, skim the required length of side, then use a parting off tool to finalise the length of the 1st part and give an edge to work up to for the required outer diameter – giving a solid “top hat” shape for the bottle holder.



2nd setup was basically the same, but with a smaller OD & height for the smaller jar.





With the parts sawn off, they could be reversed in the chuck & the bottom tidied up.




4th setup (not shown) was drilling & counterboring to make the things actually useful.

POM turned out to be (like other engineering plastics) quite a nice material to machine, with cuts of up to 100 thou (2.54mm) possible. Shallow cuts of just a few thou tend to just score the surface… 60 was about optimum for roughing, and 20 for finishing – which is a little problematic. The bottle is pretty loose, but the paint point part is spot on.

I have seen some 3d printed ones on Thingiverse for such task..

Bet you could make one faster with styrene than one being printed

I've been keeping an eye out for the taps needed to doing the nose protector & possible backplate for a 4-jaw chuck - this 2nd & plug tap were (relative) bargains at 30 and 25GBP respectively. 

Note the Tamiya 1g AG Thread Lock pot for size comparison - these weigh around 2kg each

I still need a tap wrench big enough to hold them, and a 1st tap as I really don't fancy trying to drive that 2nd tap as a first pass, even through "soft" metal. 



 

That's massive.

If you need training, there is no need to buy handlebars, just use those