02-22-2012, 09:46 AM
The 3 equals - from my 1st year apprentice days
1) Equal Angles - As you hold the drill in front of you the two sloping edges must be equal about the centre of the drill bit.
2) Equal length - the cutting edges must be equal in length.
3) Equal backing off - the part that slopes away from the cutting edge, clearance if you like. The amount that slopes away must be equal on both sides.
The most common problem in hand grinding drills is it becomes too pointed.
The second common problem is there is no enough backing off - clearance.
It is one of these things that needs some one to show how it is done and to point out any mistakes. ( show me again) Then it is just a case of practice.
:)
DaveH
1) Equal Angles - As you hold the drill in front of you the two sloping edges must be equal about the centre of the drill bit.
2) Equal length - the cutting edges must be equal in length.
3) Equal backing off - the part that slopes away from the cutting edge, clearance if you like. The amount that slopes away must be equal on both sides.
The most common problem in hand grinding drills is it becomes too pointed.
The second common problem is there is no enough backing off - clearance.
It is one of these things that needs some one to show how it is done and to point out any mistakes. ( show me again) Then it is just a case of practice.
:)
DaveH