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Chris Gunn

I think JA wanted M3.5 Chris?

Quite a few suppliers of M3.5 screws come up on Google but hex head don't.

JH, you are right, I searched for 3.5 hex head, and mistakenly believed Google took that on board, should have looked closer at the results. I thought it was too easy.

Chris Gunn

Why not use 4BA?

I’m not sure what size Hexagonal bar (metric/imperial) is available but it shouldn’t prove too time consuming to make your own?

JA wants hex head not cap head. Though I have used m3.5 cap heads on models I reserve them for the modern aero and ic engines rather than anything period.

When I have made hex head bolts in M3.5 to keep them in keeping with the other model hex heads which are smaller than the usual ISO sizes I mill the hex to 5mm A/F which fits in about right with M3 with it's 4mm hex and M4 with it's 5.5mm hex. For the few I make it is not worth sourceing 5mm hex stock and the spin indexer makes machining quite quick.

No sure what engine martin is making but when doing others in metric I often find the suggested BA size a bit large for example the 2BA ones on the Stuart Voctoria, beam, etc are on the big side so use M4 rather than M5 which would be closer.

Edited By JasonB on 22/11/2021 13:30:52

The model ones tend not to use standard hex, see my comment above and this table Similar to many people using one size smaller BA fixings.

They are also taller so more in keeping with a period engine.

Yes, edited it now.

First part of my reply was to Juddy.

Though grub screws may be a bit limited on length depending on what is needed or if studs are being used for the majority of fixings.

Edited By JasonB on 22/11/2021 13:33:33

Yes, sounds good Bill.