Topic: drill and tap fork leg for caliper bracket.

[fayettebr]

My new project, '72 CB750 came with no front brake. After I gathered all the parts I needed to restore them I started mounting the caliper. I noticed one of the small 6mm bolts was broken flush on the fork leg.  The other 2  bolt holes were packed with gunk so I cleaned them out and ran a bolts in them to check the threads. One had stripped threads and the other bolt seized about 1/2 way in. @%$#&*. I know now why it did not have a ft. brake!
My plan is to  extract the broken 6mm bolt, drill the holes to 9/32 and tap for 5/16 bolts.  The 8mm hole I'll enlarge to 3/8 threads. Any downside to doing this? It doesn't appear to me I have many options other than replacing the fork leg. Advice please.

[burnoutking1971]

Hello
Did you use a bottoming tap to clean the holes or a starter tap? I don't know how much room there is for drilling larger holes could be a good idea if there is enough room to do so. I bet other forum members have had this issue before.

I had holes on my fork leg kinda gummed up and after a few passes with a well used bottoming tap and a good gleaning with WD-40 and some compressed air the threads were pretty good. I like to use well used taps for thread cleaning rather than new ones so I don't remove material and only remove dirt and oxidation.

[fayettebr]

I did use new bottoming taps as a last resort, but it was too late damage was done

[Bob3050]

I think that I would look into thread inserts (heli-coil or time-sert) to keep the original bolt sizes and actually gain strength.
Bob

[crazypj]

I would Heli-coil back to stock size.
 It ALWAYS looks 'tacky' when you start mixing inch and metric on Japanese bikes