Grub screws

[ITAM805]

I need some of these to fit my 63' Watkins Copicat knobs. I don't suppose they're still available are they, so what do you folk do in such cases? I dont know what thread they are either but they might be BA seeing their pedigree?

Many thanks

[Alistair D]

Do you have access to a vernier(very near, sorry) or a micrometer to measure the diameter of the grub screw?

This link will help you identify what it is.

http://mdmetric.com/tech/thddat8.htm

Al

[Station X]

The thread looks far too coarse for BA to me.

If the machine is of US origin the threads are likely to be Unified types. If of UK origin Whitworth types.

If you can measure the diameter and count the number of threads per inich, it should be possible to identify the thread form.

[Refugee]

That is most likely to be UNF or UNC at a diameter very slightly larger than what you measure since the screw is made from a rod.

[ITAM805]

Many thanks for quick replies chaps!

Graham, the 'machine', if you mean the Watkins, was manufactured in London.

Since posting I've been rummaging around my junk screw box and found a couple of screws that fit (after trying loads of em'), but I think I'd have to splash out on a Dremel to cut the tiny slot into them. Has anyone had success using this method? Or will it be better (certainly cheaper!) to measure and track down the appropriate grubs.

.

[Station X]

You can cut a slot with a junior hacksaw.

If you decide to buy new, assuming you can identify the thread, I recommend grubscrews with internal hexagon heads. So long as you use the correct "Allen" key it's impossible to strip the head, unlike a slot.

[ITAM805]

OK, the diameter is 3mm, counting the threads wasn't so easy! I make it 9 or 10 per 5mm - if that makes any sense at all

[Station X]

M3 x 0.5mm pitch (approx 50 TPI) might do the job bearing in mind the material is plastic.

[ITAM805]

Originally Posted by Station X

M3 x 0.5mm pitch (approx 50 TPI) might do the job bearing in mind the material is plastic.

Thanks Graham, but when I google "M3 x 0.5mm grub screw" I get everything but, do they go by another description?

[Refugee]

I would try the screw in a known nut in order to check the thread type.
A nut from Japanese kit will be metric (M3) and so on.
It looks less likely to be a US thread if it is UK made.
It is likely to be an old British thread if it is a valve set though.

[kalee20]

I'd be surprised if they are metric M3. 4BA is more likely (nominal dia 3.6mm but probably slightly less).

Cutting a slot in a sawn-off screw is certainly possible - as Station X says, use a junior hacksaw.

Metric M3 grub screws are available from Farnell - google them! BA, rather harder, but try eBay.

[ITAM805]

Thanks guys

I think I'll use the screws I've found which fit but as far as sawing them, well I'm not so confident - they're only 3mm across. I'm not a total plank but I think it'll be tricky

ps Kalee20, I am aware of M3 screws, not ".5mm" bit though

[Station X]

You said that there were 9 or 10 threads per 5 mm. Given that an inch is about 25mm that's 45 to 50 threads per inch (TPI).

If we assume 50 threads in 25mm that's a thread pitch of 0.5mm. Pitch is the distance from one thread crest to the next. Looking at the spec for M3 screws, the pitch is indeed 0.5mm, hence my suggestion that you try them.

The spec for 4BA is diameter 3.6 mm with 38.46 TPI.

The spec for 5BA is diameter 3.2 mm with 43.1 TPI.

The spec for 6BA is diameter 2.8mm with 47.9 TPI.

I'll let you google the specs for UNF, UNC and BSW.

The problem is that DIY outlets only stock metric fasteners and often only in even sizes ie M4, M6 and M8. If you want BA, UNF, UNC or BSW you'll have to buy onlline or find a specialist "Fastener" supplier. I use these suppliers:-

http://www.suffolkfasteners.com/

http://www.emkaysupplies.co.uk/

Cutting a slot is easy if the hold the screw in a vice. Either use soft jaws or lock two nuts on the thread before you grip it. Otherwise you'll damage the thread.

[ITAM805]

Many thanks for the explanation Graham

[Mike Phelan]

Also, sometimes you need to stone the sides of the hacksaw blade to remove the "set" so the slot isn't too wide on smaller BA screws.

[60 oldjohn]

Adding to what Mike has said. To get the slot central make a Jig, easy. Set the screw low in vice use hacksaw with two pieces of metal one at each side of blade. A short piece of hacksaw blade might do if it will fit.
John.

[Radio_Dave]

Use the screw head slot as a cutting guide and then cut it off

David

[Alan Stepney]

Items Mail Order used to stock grub screws in all the BA sizes.
Might be worth asking them if they still do.

Even easier, if you can make (fairly) sure what thread they are, I'll pop a couple in the post.

[ITAM805]

Gents, thank you for your advice and suggestions.

Alan I'd like to take you up on your very kind offer. As they say - "a picture is worth..."


.

[M0FYA Andy]

Grub screws in all sizes -
http://www.modelfixings.co.uk/steel_grub_screws.htm
Andy