Anyone come across a 15/32 AF spanner?

Yesterday I decided to try and get the Taylor & Hobson Model C engraver going that's been sitting in the shed for 10-15 years. I made new drive belts from round PU belting and tried it out. There is slack in some of the pantograph linkages, although it looks like vertical play rather than radial play is the major culprit. As it happens the linkages involved are adjustable, But:-

They seem to have nuts that are 15/32" AF. This isn't a size that I've come across before and doesn't seem to match any series that I can find reference to.

I can use my smallest adjustable spanner and could mill a pair of fitting spanners out of gauge plate, then harden them, but I'm curious as to if anyone has ever come across this size?

would 12mm be too loose?

Here’s one on eBay. About £5.

My AF spanner set from the late 60s went up in 32nds and I still have them, Britool of course and the chrome is still on them!!!

Take a 7/16" or 11mm AF open end and file or use a grinding disc to increase it to 15/32" ! Done it with a 50mm to convert to 2" Good luck. Noel

12mm is a very sloppy fit, even though it's the closest that I had.

My mind had been working along those lines as an option. Possibly with the surface grinder or an endmill.

Hey, after I get the engraver working I gan grind off the original markings and engrave some new ones.

How about supergluing a shim in the jaws to tighten the sloppy fit? That's ought to be good enough for a few uses. A cheap set of feeler gauges is worth having for such jobs.

Or you could machine some new nuts to match other fittings on the machine. Which is a permanent fix.

Edited By Nicholas Wheeler 1 on 12/03/2022 23:43:19

15/32 is .469". And 12mm is .472".

How tight a fit do you want? Less than 3 thou?? Spanners are normally made five to ten thou bigger than the nominal hex size for easy use.

If a sloppy-fitting spanner risks rounding the ‘corners’ of the hexagon … try flank drive

MichaelG.

Given that it is an old English manufactured machine, the fastners are probably all whithworth, in whick case it will be 1/4" whit which requires a 3/16" whit spanner. Hexagon size is 0.454" and the spanner size is 0.445"

Steven

Edited By Split Pin on 13/03/2022 10:30:29

Agree - I use a metrinch set for most things.

I'll have a look when I get home it's possible I might have one.

It isn't a Whitworth size, or a 12mm metric size, or a BA size.

Mr Micrometer says its 0.467" AF.

From a Taylor Hobson engraver it is likely to be a 15/32" but I'm sure a 12 mm A/F will suffice.

Tony

Mark

In case you fancy making a pair of thin spanners … the basic geometry is here: **LINK**

https://worldwide.espacenet.com/patent/search?q=pn%3DGB1138546A

… and yes, it’s adaptable to open-enders

MichaelG.

Hi Mark, I don't think 15/32" A/F is a standard size in the UK, however 1/4" BSF / 3/16" Whit is supposed to be 0.445". I've just measured three 1/4 BSF / 3/16 Whit open ended spanners of mine, one is 0.452", one is 0.453" and the other is 0.459", so I would say one of those should fit your nut, which is a lot closer than a 12mm spanner that I have measuring 0.480".

Regards Nick.

Right:- update time.

I discovered that my only 12mm open ended spanner has got slightly sprung jaws. Doesn't normally affect it, since my normal reaction to a 12mm AF nut is to replace it with something else.

A 12mm hex (not bi-hex) socket fitted the outer, accessible nuts quite well.

A Bahco 4" adjustable spanner was thin enough to get to the inner, less accessible nuts.

The engraver produces far straighter lines once the play in the two joints is taken up. It isn't prefect yet, but it's better than it was.

Grip Master 12 mm spanner as used by ICI Instrument Artificers 60 + years ago will do the job as they grip the flats on the nut back from the corners on four places.

About 65 years ago I purchased a set of open end wrenches from Sears Roebuck. I contained a couple of wrenches with odd 1/32 openings. I never found anything they fit.

Old American cars used some of those sizes.