Hi Bill,
I was taught to dr
Hi Bill,
I was taught to drill the guide itself with a step drill 75% of the lenght of the guide (basically 90% boss depth) first leaving only about .20 -.30 thousanths wall thickness left. Then heat, and press or drive out with a drift. The drift sits on the internal ledge left by the under drilling.
By drilling all the center material out of the guides it releases the compression fit and prevents the guide from expanding the boss on it's way out. It is important to drill striaght to prevent going into the boss material.
The best type drill bits for this operation have a stepped tip to aid in alignment and to keep things centered to avoid going thru the guide wall as the cut coes deeper. It's nice to start on the seat side so the guide is removed out the way they go in. But sometimes on well worn guides the drill bit won't center well enogh for the long cut.
If you need a better explanation of the procedure we can talk on the phone.
Regards, JRV
I was taught to dr
Hi Bill,
I was taught to drill the guide itself with a step drill 75% of the lenght of the guide (basically 90% boss depth) first leaving only about .20 -.30 thousanths wall thickness left. Then heat, and press or drive out with a drift. The drift sits on the internal ledge left by the under drilling.
By drilling all the center material out of the guides it releases the compression fit and prevents the guide from expanding the boss on it's way out. It is important to drill striaght to prevent going into the boss material.
The best type drill bits for this operation have a stepped tip to aid in alignment and to keep things centered to avoid going thru the guide wall as the cut coes deeper. It's nice to start on the seat side so the guide is removed out the way they go in. But sometimes on well worn guides the drill bit won't center well enogh for the long cut.
If you need a better explanation of the procedure we can talk on the phone.
Regards, JRV
