Head steady bolts

Waiting on some new parts and had bike stripped down ‘74 850 and noticed I was missing 1 head steady bolt (06-7745). Checked the other 2 and they were tight but washer underneath was loose so bolt wasn’t seated. Removed bolts to find bad threads on center bolt and a cut bolt on the other with 1/8” sand filling bottom of hole. After cleaning out the holes with air everything looks in order. Have ordered new bolts but thinking I might need to chase out the holes. Bolts are 5/16” x 3/4” . Anyone know the thread pitch. Any advice on this would be great. Never chased a hole before so guess I need a 5/16” by whatever thread pitch. Looks to me to be a 5/16” x 22 BSF ??
Thanks, Corey.

kn0ck4times said:

Bolts are 5/16” x 3/4” . Anyone know the thread pitch. Any advice on this would be great. Never chased a hole before so guess I need a 5/16” by whatever thread pitch. Looks to me to be a 5/16” x 22 BSF ??

Click to expand...

Yes, 5/16" BSF.

L.A.B. said:

Yes, 5/16" BSF.

Motorcycle parts and spares for Norton motorbikes - Andover Norton Spare Parts - Andover Norton Motorcycles Parts - Original Andover Norton Parts

Motorcycle parts and spares for Andover Norton motorbikes: Andover Norton manufactures and supplies all Factory Spare Parts for Norton motorcycles built before 2002.

andover-norton.co.uk

Click to expand...

Is there a thread pitch I need though. No nothing about BSF threads. Do I just buy a BSF kit with 5/16?

5/16" BSF is 22 TPI.

L.A.B. said:

5/16" BSF is 22 TPI.

https://britishfasteners.com/threads-bsf

Click to expand...

Awesome, got it. Really appreciate it.

Often mistaken for 5/16" x 24 UNF unfortunately and why the head steady threads can be damaged or stripped.

If you're replacing the bolts and one of them is serviceable, cut a slit either side, with a dremel and run it in like you would a tap (oil and gentle). Will clean the thread, without enlarging it.

Mart UK said:

If you're replacing the bolts and one of them is serviceable, cut a slit either side, with a dremel and run it in like you would a tap (oil and gentle). Will clean the thread, without enlarging it.

Click to expand...

Out of the 2 that were left they both appear to be the wrong pitch. Luckly none of them were seated more than half way. May be able to chase them and get a good torque. Amazon has a BSF tap and die set that includes a 5/16x 22.

I have ran into a few heads over the years with these threads damaged - I have helicoiled them with 5/16"-24 inserts - yeah, not original, but at least readily available. FWIW

Derek Wilson said:

I have ran into a few heads over the years with these threads damaged - I have helicoiled them with 5/16"-24 inserts - yeah, not original, but at least readily available. FWIW

Click to expand...

Good to know, going to try to clean them up first.