M10 DOME Cylinder NUTS HEX

[mo goldie]

do anyone know what the thread is on the cylinder head on the black bomber...... as trying to get some to replace the old rusted  steel domed Nuts with stainless steel ones ?

I got 8 domed ones and they don't fit seems as if they are a more of course thread as I tried one and it wanted to cut a new thread so must be some other thread on the studs. if it is the ones I got they only seem to do one size of thread on Ebay so if you know where I can get some would be great help.

Mo     

[Oddjob]

Depends on the age of the bike. Threads changed around 1966-67.

Most M10 nuts you find in the UK are 1.50 pitch, Honda used 1.25 pitch after 1967 ish. Also called metric fine.

Something like these may do. https://www.ebay.co.uk/itm/204483946909?hash=item2f9c31699d:g:DaQAAOSwLURgL-Ep&amdata=enc%3AAQAIAAAA4ErnCunwyYv0cQ%2FD4GvwbxJttqFKNFBKu96PPzSgtxXaphHoNtkYzfhwy%2FRv8juSOJELPcE3xX%2F2XUg7OEV3oobzPIHegFV%2FSqu%2Br%2FmDU%2Bvl0h4IDziZA5u%2FFJTxJIeiea9AsmElmuqytO8KUANJ59yuzpCNpxy1OkkO0h0NhCqKtmrQSxnlbrF9IgzXa7G0trfNOg0hrdfVOCuL65jzn65Y0c83bGANQxKvXhH%2FD35OGQsCKKLX7MJJGrWINPLlJ57mDSTAUBwvsYUy1zaoX2g6FfHFHD6ZlLy57%2Fw213%2Fa%7Ctkp%3ABk9SR4DYgbfwYg

[AshimotoK0]

M10 x 1.5

[Oddjob]

If that’s so Ash, then why does he say the nuts he bought have a rougher thread than the studs.?

I’m not sure what the bomber uses as I’ve never worked on one or owned one, my reply was pure logic, if the nuts he bought had a coarser thread then the studs must be metric fine and an M10 metric fine is 1.25. My logic wrong?

[Orcade-Ian]

I have to go with Ken on this one, OP says those nuts he bought are coarser, not finer and I have never seen or heard of an M10 coarser than 1.5mm pitch, only the 1.25mm finer version.  The domed rear damper top nuts on 350,400 and 550 fours are M10x 1.25 - I have some in stainless.  It wouldn't make engineering sense to clamp a cylinder head down with coarse threads where the wedge angle is greater and more prone to loosening.  I've never worked on a Bomber either and I've been wrong before though - just ask Christine 🤓

Ian

Just a thought - the stainless ones I bought are next size up across the flats compared with Honda - check there is clearance for your application.

[K2-K6]

Count ten threads on stud and then measure in mm.

1.25x10= 12.5......1.5x10=15.......well you get the picture  should be easily seen what pitch they are in situ.

Or try the bought nuts onto  rear shock mount to verify.

[AshimotoK0]

Yea you are right slapped wrist naughty boy Ash

https://www.zed-parts.com/product-page/m10-1-25-dome-nut-low-top-zinc17mm-spanner-a-f-jis

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[K2-K6]

Its a good bet because Soichiro was an aircraft man with many influences from that arena incorporated into the design, the "waisted head and barrel studs one of the most prominent in balance of load distribution, material elasticity and torque requirements. Fine pitch threads being an intrinsic part of accurately setting torque for such a design. 

[McCabe-Thiele (Ted)]

As folk here will know I am always confused by Hondas metric threads so reassuring to know I am not alone.

[Orcade-Ian]

Ah, Soichiro, my hero!

Mo,
A great asset to any restorers toolbox is a set of thread pitch gauges and if you can still get them - Zeus charts, although Mr Googly has most of that latter info these days. 
I've restored many offerings from BMC and Jaguar where there is often a 'from the factory' mix of fine/coarse Metric, UNF/ UNC and even BSF/Whitworth/BA on the same car - having gauges and charts takes any guesswork out of the game.

Ian

[AshimotoK0]

As folk here will know I am always confused by Hondas metric threads so reassuring to know I am not alone.

All explained here:- I was getting confused with M12 which DID change from 1.5 in 1967 to 1.25 pitch.

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[Orcade-Ian]

As always,
That's great info Ash,
I just checked availability of Zeus charts and they are still about but better still, someone has published them in PDF form.  No need for jig boring coordinates (except maybe Trig - maybe that's short for trigonometry  ) and other pages but it's all here:

http://www.moonshiners.org.uk/MZ/zeus.pdf

Ian

[Oddjob]

I knew about the JIS thread bulletin Ash, hence why I mentioned the year of the bike may be of note, before 67 he may have had the old JIS threads and after he may have the modified JIS thread. I took the chance he had the new.

Glad to see we got to the bottom of it in the end, which is the priority, not how we got there.

[AshimotoK0]

I knew about the JIS thread bulletin Ash, hence why I mentioned the year of the bike may be of note, before 67 he may have had the old JIS threads and after he may have the modified JIS thread. I took the chance he had the new.

Glad to see we got to the bottom of it in the end, which is the priority, not how we got there.

M10 never changed though . It's M12 that's the confusing one ... e.g.  the C110 has both M10 and M12 domed nuts on the rear shock mounts and the M12 changed in '67 from 1.5 to 1.25 pitch. Another one is the M3 screw that mounted the emblems  onto 'toaster' tanks, as that changed in '67 too.

[Oddjob]

I didn't have access to the bulletin though Ash, so I made the assumption that as most of them changed it was likely that so did the M10. As it turns out that was the wrong assumption but seeing as I was possibly asking him to spend money on something I thought I'd best hedge my bets so to speak. No harm done, we got there in the end.