Garden Railway Forum

Could be 3/32 (2.2381mm) or 7/64 I guess (2.778)? I don't have any of those to offer I am afraid

ge_rik wrote: ↑Mon Jan 11, 2021 5:26 pm Hmmmm ..... I've tried fitting metric screws into the hole. It's too small for M3 but too large for M2. I suspect it might be Imperial. I've lost track of my diddy Allen keys, but when I track them down I'll see what fits.

Welcome to the wonderful world of thread 'standards'..........

It might be quicker to wait for Ivan to reply, so let us know what he says.

With an OD between 2mm and 3mm, the easily available candidates in the UK, would be either 6BA, or maybe M2.5.

If you have a 6BA screw available try it and if it fits then 6BA grub screws are still available. I usually get mine from the local ME suppliers, but have also bought them from BA Bolts in the UK and I think EKP Supplies would have them.

If you want to play around and measure things while waiting for Ivan, 6BA uses a 0.050” key and M2.5 uses a 1.27mm key. The same size key actually, if you do the calculation. If you manage to remove one to measure, a 6BA grub screw will have an OD of 2.8mm and M2.5 will have an OD of 2.4mm.

I keep some M2.5 grub screws, but they are fiddly to use and I only keep them as spares for a couple of locos that use them. They are even harder to find on the workshop floor than a 10BA nut.........

Less likely candidates would be the US threads, #3-48UNC or #3-56UNF, which have an OD of approx. 2.5mm. Presumably available in the US, but as rare as rocking horse manure here in Oz, and also the UK I should think.

Small 'imperial' fasteners below 1/8” BSW and 3/16” BSF have been obsolete since Adam was in short pants, with BA sizes being the recommended alternatives.

Just to make life interesting, a 6BA screw will fit into an M3 threaded hole, but an M3 screw won't fit into a 6BA hole, which is why I think you might be looking at a 6BA grub screw in this case. Maybe.........

Regards,
Graeme

Thanks Graeme
I'll await Ivan's response in the first instance, but if nothing is forthcoming, I'll have a go at figuring it out using your guidance. My problem is that I have a container full of miscellaneous nuts, bolts, washers and screws and have no idea what they are. Whenever I need one, I dip into it, find a bolt of about the right dimensions and then fish around trying various nuts until one fits (a Cinderella moment!).

The metric ones are easy, they are the silver ones - the brass ones are Bassetts Allsorts. I'm afraid I'm not very systematic when it comes to keeping tabs on my fixings collection.

Rk

ge_rik wrote: ↑Tue Jan 12, 2021 10:24 am My problem is that I have a container full of miscellaneous nuts, bolts, washers and screws and have no idea what they are. Whenever I need one, I dip into it, find a bolt of about the right dimensions and then fish around trying various nuts until one fits (a Cinderella moment!).

I have one of those as well, well actually I have two. A small one with all sorts of small modelling size nuts, bolts and screws and also a 2 litre ice cream tub with larger, mostly BA brass but also steel Whitworth and other odd threads, plus washers, bits of stud and strange things that I can't imagine what they were for. I inherited it from my dad who worked for the MOD and was a bit of a kleptomaniac!( I do know that some bits originated in German V2 rockets which he worked on after WW2!)

philipy wrote: ↑Tue Jan 12, 2021 11:08 am I have one of those as well, well actually I have two. A small one with all sorts of small modelling size nuts, bolts and screws and also a 2 litre ice cream tub with larger, mostly BA brass but also steel Whitworth and other odd threads, plus washers, bits of stud and strange things that I can't imagine what they were for. I inherited it from my dad who worked for the MOD and was a bit of a kleptomaniac!( I do know that some bits originated in German V2 rockets which he worked on after WW2!)

I've still got a box inherited from my dad with all manner of rust and grease encrusted nuts and bolts. I have no idea where they originated but some of them must go back to when he worked at Stansted aerodrome or when he used to repair mowers for Atco.

Rik

Presumably, Atco were working on an early form of hover mower!?

Phil.P wrote: ↑Tue Jan 12, 2021 8:05 pm Presumably, Atco were working on an early form of hover mower!?

Too subtle for me, Phil

Rik

ge_rik wrote: ↑Wed Jan 13, 2021 11:04 am

Phil.P wrote: ↑Tue Jan 12, 2021 8:05 pm Presumably, Atco were working on an early form of hover mower!?

Too subtle for me, Phil

Rik

I think he has conflated "he worked at Stansted aerodrome" with " mowers for Atco."

philipy wrote: ↑Wed Jan 13, 2021 12:33 pm

ge_rik wrote: ↑Wed Jan 13, 2021 11:04 am

Phil.P wrote: ↑Tue Jan 12, 2021 8:05 pm Presumably, Atco were working on an early form of hover mower!?

Too subtle for me, Phil

Rik

I think he has conflated "he worked at Stansted aerodrome" with " mowers for Atco."

Oh ..... I geddit now ....

Rik

BTW - Just heard back from Ivan. He says they are M3 grub screws. I'll try again. Maybe what I thought was an M3 was something else when I tried putting one into the hole.

Rik

ge_rik wrote: ↑Wed Jan 13, 2021 1:11 pm BTW - Just heard back from Ivan. He says they are M3 grub screws. I'll try again. Maybe what I thought was an M3 was something else when I tried putting one into the hole.

There are two ISO 3mm threads, coarse and fine, but the coarse one is the common one and so just termed M3. I've only seen the coarse thread on grub screws.

A squizz at this site will show you why a jam jar full of fasteners of indeterminate origin could contain a lot of screws that look much the same........

https://www.gewinde-normen.de/en/index.html

One of my brothers inherited my father's shed contents and I'm fairly sure some of the jam tins of fasteners had come from my grandfather's shed, certainly some of the hand tools went back at least that far.

Regards,
Graeme

To identify threads accurately you need three things:

1) A set of thread gauges preferable 55 degree and 60 degree.
2) A Micrometer of vernier calliper
3) And most important something that will identify the measurements: My Zeus is a little older but invaluable.