Pre-war Italian thread ?

[Tim StevensParticipant @timstevens64731]

I am working on a pre-war Marelli Magneto, and it has several screws 5.5mm diameter x 0.9mm pitch. My references cover UK, French, German and SI metric and I cannot find a match. Some of the screws have been attacked with screwdrivers which did not fit, and the heads are butchered.

Can you help with exact identity, or replacements (about 20mm or longer, domed countersunk heads) or even tap & die? – thanks

And happy Valentines Day to you all.

Tim Stevens
Welsh Marches – UK

[David JuppParticipant @davidjupp51506]

Could it possibly be 1BA?  Without knowing the history, it’s a bit of a guess – but the design could have been licensed in from elsewhere.  Hence may not have been an Italian thread at all.

[noel shelleyParticipant @noelshelley55608]

5.5 x .9 is a metric size and taps an dies are available from Tracy tools, or it may be 1 BA at 5.3 x.9. Good luck. Noel.

[Howard LewisParticipant @howardlewis46836]

1 BA is 5.3 mm dia and 0.9 mm pitch, as already intimated.

Being Magnetti Marelli, and so electrical, quite a possibility, IMO

Howard.

[JasonBModerator @jasonb]

5.5 Loew is 5.5 x 0.9

Close to 7/32″ x 28 BSF or #12-28 UN

 

[NimbleParticipant @nimble]

Hi Tim,

Perhaps you could contact “The Magneto Guys”  https://www.themagnetoguys.co.uk/  .

They seem to be pretty good about giving out information.

Good luck.

Nimble Neil.

[Tim StevensParticipant @timstevens64731]

It could indeed be 1BA, except that the measured od of the screws is a bit larger. So, properly speaking, 1BA is what I need, as the profile of the thread is unique with angles of 47.5 degrees between the flanks. So, who makes or sells 1BA screws – preferably in stainless steel?

Thanks David – I never thought to check if BA was used, as it is only found (in my experience) in models, and old electrical plugs etc.

Tim Stevens

[bernard towersParticipant @bernardtowers37738]

If you only need a few it would be simpler to make them yourself.

[noel shelleyParticipant @noelshelley55608]

In answer to who makes/sells 1 BA try EKP Supplies. Good Luck. Noel.

[Author]

Posts