Metric Bolt pitch

[Mike_Berkshire]

Not sure where to post this but as Im rebuilding a CB550 I thought I would post the question here; apologies if this belongs somewhere else.

I have just bought a tap and die set and there is a set of thread pitch gauges in it. I haven't come across thread guages before. In the past when dealing with metric screws I have just worked on the basis that all M4, M3, M2 pitches are standard & the same; I haven't had much to do with larger screws and bolts. From the set of gauges there are obviously different pitches of metric screw threads made. If I am buying screws/bolts for the bike do I have to be careful I buy with the right pitch thread? I notice that if I randomly search for 'M8 Steel Bolts' using Google that there are multiple suppliers come up but they don't specify different pitches of thread; just 'M8'.

Cheers

[DomP]

Yes definitely be careful, quite a few bolts on Hondas are metric fine thread, from memory on a 550 the bottom yoke bolts are m10 metric fine for example as are the rear shock bolts and dome nuts.  Middletons stainlesscare a good source.

[taysidedragon]

Google t'internet to find a table of Metric Thread Pitches. Save it or print it out so you always have a reference  of Coarse, Fine or Extra fine thread pitches.
The common Metric pitch is coarse, that's usually what is sold by DIY stores if not otherwise specified.

[taysidedragon]

Link to previous topic.

https://www.sohc.co.uk/index.php/topic,24619.msg224177.html#msg224177

[Bryanj]

If they still do them Zeus tables are good

[davidcumbria]

A thread guage to measure the pitch of the bolts you are replacing is a very good investment and saves multiple wrong purchases. DAMHIK 🙂

[AshimotoK0]

I always go by this 1967 Threads Service Bulletin to check if there was a pitch change post 1967. All of the M8 fasteners I have come across on my bikes have been 1.25 mm pitch.

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[Matt_Harrington]

If they still do them Zeus tables are good

Yes, still available and I regularly refer to mine - mind you I mess about with BSW & BSF as well!

[SumpMagnet]

From personal experience, if it JUST says metric, then you are getting standard or coarse pitch. So an M8 would be 1.25.
Metric fine is 1.0 pitch for M8 and would normally specify.
Never come across extra fine in the wild. Or at least...I don't think I have!

If in doubt, message the supplier. If they don't know...buy elsewhere. If they DO know, they are usually pretty understanding.

Smaller sizes are hard to tell visually, but larger bolts are easy to tell by eye. Drop the pitch gauge onto the thread and see if it fits. A thread pitch chart just helps you choose the right pitch gauges to try.

[Mike_Berkshire]

Thanks all, really helpful information. I will use the pitch gauges I got with the tap and die set which I can cross reference with the tables.