Drilling jig

[Charles Lamont]

I am making a drilling jig to accurately locate the 6BA cylinder head studs, 8 per pot. The jig will be used for the cylinders, heads, and head water jacket covers. The cylinder is tapped and the other two parts have clearance holes.
Now, there seem to be two options: do I put tapping size holes in the jig and then open out the holes in the parts to clearance size, or do I put clearance size holes in the jig and use it just to spot the tapping holes in the cylinders?

 

[abby]

Hi Charles , when making drilling jigs I generally fit drill bushes , which I make from silver steel and harden , this gives the option to change the bushes so you can drill tapping or clearance and replace the bushes if worn through production use.

 

[Walltoddj]

Depending on the size of the jig and run to put them in, but could do both with a removable liner. With the liner in drill the tapped holes, with the liner out now you can drill the clearance holes. If the pattern is to small what I've done before is make a jig with bigger holes than you need then make a liner or as they are known a drill bushing for both then just insert the one you need for the hole you need. Drill bushings can be made to suit with drill rod then hardened. I've made a number of jig like that and some I'm still using.

Todd

 

[Swifty]

I would put tapping size holes in the jig, that way there will be no mistake by drilling the wrong size holes. Just use the jig to spot for the clearance holes then drill the right size.

Paul.