Kenwood TS-50 Tuning control fixing nut - size?

[SiriusHardware]

Just lately the tuning control / encoder on my old Kenwood TS-50 has started to rattle around loose - it's done this once before and I took it apart far enough to tighten it up, and that was the point at which I should have measured the size of the nut. But I did not.

To tighten it up properly I really need what I believe may be called a 'box spanner' - a bit of metal pipe with the end stamped into a hexagon shape so I can slide it down over the tuning shaft to tighten the nut up properly. Nut drivers / nut spinners will not, as a rule, be deep enough for this job as the tuning shaft is quite long.

Does anyone with good knowledge of these know what size I need to order?

[Steve G4WCS]

3/8" generally and a drop of loctite or anti tamper lacquer/nail varnish on the threads.

Ive an RS components one in the toolobox if its still there, Ill measure it tonight.

If its a one off happy to lend it you provided I get it back. PM me if you want it posting

[SiriusHardware]

Steve, thanks for the info - I am surprised that it is an imperial size given that the Kenwood is Japanese made (I would expect metric) - maybe you're just quoting an imperial size which you know from experience is close enough?

Thank you for the kind offer of a loan of the tool, let me look around first to see if I can source one at a reasonable price, now that I know what size I need.

[Steve G4WCS]

Hmmm. This ones measuring in at 13.5mm.
Fits an old RS pot though. Japanese radio ones could be smaller, I’d googled pot nuts and it came up at 3/8”.

Is there room round the nut for a deep socket ?
Anyway if this ones suitable let me know 😁

[Steve G4WCS]

D’oh. Thinking about it again its probably 3/8 unf thread on the pot shaft

[SiriusHardware]

I've discovered that a branch of 'Toolshack' near me sells a metric set of box spanners, so I may just pick up a set of those. If one of those fits I'll report back here.

[G6Tanuki]

I've not come across 3/8UNF being used for Japanes pot spindles; 3/8-24 (3/8UNF) is the thread used on things like CB antennas.

Most of the Japanese pot-nuts I see are a significantly finer thread.

[SiriusHardware]

It's easy to get cross threaded when going into this sort of problem. I have the nut, it is not missing, it is merely loose.

My question, then, was: What size box spanner (in terms of the size of the nut) did I need. As mentioned, I'm going to buy a set of box spanners locally, I'll see which size fits best and report back here.

[SiriusHardware]

I picked up a set of box spanners from 'Toolshed' - not 'Toolshack' as I misquoted above, and I find that on this metric set at least the 11mm end of the 10mm / 11mm spanner is the best fit for this particular nut.

I went for those instead of a similar set offered by Screwfix because on Screwfix's set the holes into which the 'tommy bar' fits are heavily indented, severely limiting the diameter of any thread / stud / bolt over which they can be slid, which sort of defeats the point of a box spanner. The 'Toolshed' ones are very parallel sided both inside and out.

Unfortunately when I undid the grub screw to take the tuning knob off I found that the nut still could not be seen at that point as it was completely covered over by the front panel moulding, so it then became necessary to pull off the volume / squelch / RIT and IF Shift knobs, remove the top cover, the bottom cover, release the clips (two upper, two lower) which secure the front panel and ease it off to reveal the offending nut at last.

Even then, the nut was set deep in a depression with very little clearance at the top and bottom so the box spanner was still required after all that, as a normal open ended or ring spanner would not have been able to get onto the nut and very few 11mm sockets would be deep enough to absorb the full length of the tuning shaft and reach the nut.

I got it nice and tight - I don't use the radio as much as I used to, so by the time it comes loose again it will probably be someone else's problem.

At least the half-stripdown gave me the opportunity to measure the voltage of the tagged Lithium cell which retains the memory contents - still ticking over at 3+ volts, not bad considering it was last changed (by me) about 10 years ago.

[Herald1360]

11mm across flats is a fair fit for a 7/16 AF nut and vice versa....... and not far off 3/16 Whit either.

[M3VUV51]

i had the same issue with a ts-50,im sure i used a 12mm deep single hex socket.

[SiriusHardware]

That's possible, but the socket would have had to have very thin walls due to the limited clearance immediately above and below the outer edges of the nut.