Grub screws

[Humber67]

Can anyone give me the definitive answer to the size of the Centre pin slotted grub screw used to set the end float.
I’m in need of ones for AA sea Aerial and 3in 7950 T3
Regards Martin

[Crucian]

6BA, I would think.

[Wallyboy Rob]

If it's the same as a C815 or match aerial it's 6BA as Crucian suggests. If it is pm me your address and I'll pop a couple in the post (6BA x 1/4") for you

[Dave Burr]

If it's the same as a C815 or match aerial it's 6BA as Crucian suggests. If it is pm me your address and I'll pop a couple in the post (6BA x 1/4") for you

I always figured you'd have a few loose screws Rob

[Wallyboy Rob]

You know me well Dave

[Humber67]

If it's the same as a C815 or match aerial it's 6BA as Crucian suggests. If it is pm me your address and I'll pop a couple in the post (6BA x 1/4") for you

That’s very kind of you will pm.
Thanks
Regards Martin

[Nobby]

We need Leszek on this as apparently it isn't 6BA after all, it's a model engineering thread I think he said!

[Watermole+]

We need Leszek on this as apparently it isn't 6BA after all, it's a model engineering thread I think he said!

Many thanks for your trust Nobby; I did read this “thread” and deliberately held fire on answering because I honestly don’t know in this particular case.
I can definitely say that the centre boss thread of the 1960s Rapidex reels that I looked at is 5/32” x 40 ME, but that’s because I had examples to measure, even to the point of buying a new HSS tap of that size to make new bosses with!
However, 5/32” is a lot bigger than 6BA and would be an obvious mis-fit.

I have seen a pre-war Sea Aerial reel, even worked on one, but never had cause to check this thread. Looking at online pictures of both the reels in question however, it does appear that they are apparently smaller than 5/32” diameter and might well be 6BA, but would not take that as being the case or for granted. Both Allcock’s and other pre-war makers used a lot of sizes no longer in common usage such as Cycle threads, which have a generally finer pitch (number of threads per inch) than BA, finer pitches being preferred for adjustment.
They certainly would not be modern iso-metric as these threads were not in use then.

I think it would be prudent to be very cautious when trying a 6 BA for fit-and if a screw thread of that size doesn’t want to go in, to not force it and risk damage to the thread in the centre hub.
If the owner has the original screws-no matter how worn they are-they can easily be checked for size. Failing that, I can check the sizes here.
Send a PM if you get stuck..

wm+

[Humber67]

Up date thank you Rob screws arrived. Fit fine if a little long 1/4in not 1/8in but easy to shorten. Will put in with a tiny amount of silicone to keep them still.
Thanks for all comments
Martin

[Wallyboy Rob]

You're very welcome Martin