Nick Mueller
Titanium
- Joined
- Jun 12, 2006
- Location
- Munich / Germany
Hi!
I have been asked to turn some tappets. Their problem is the bore:
Hole starts with ø7 mm, 3 mm deep. Then a conical part 9 mm long with the small end being ø 3.4 mm. So 12 mm deep with ø 3.4.
Material is AIS 4137 / 42CrMo4
Now I could buy some P. Horn minis + a holder and break a few along the work.
Or, I could grind my own D-bit (reamer). Grinding one is not the problem. The problem is a geometry that actually works good. Unitl now, my experiments failed more or less.
The primitive and general wisdom is to grind the cone and then split the bit to a tad more than half. These never worked too good, except in brass or soft material.
I think, I need a relief on the (9 mm long) cutting edge. And at least one surface that helps in guiding the bit. Yes, I will pre-drill to 3.4 and 7 mm
So the question is:
Has anybody got a sketch (of the cross-section) or description of it of a conical reamer that actually does makes a nice finish? I won't cut at the front (I'll drill the small diameter)
TIA,
Nick
I have been asked to turn some tappets. Their problem is the bore:
Hole starts with ø7 mm, 3 mm deep. Then a conical part 9 mm long with the small end being ø 3.4 mm. So 12 mm deep with ø 3.4.
Material is AIS 4137 / 42CrMo4
Now I could buy some P. Horn minis + a holder and break a few along the work.
Or, I could grind my own D-bit (reamer). Grinding one is not the problem. The problem is a geometry that actually works good. Unitl now, my experiments failed more or less.
The primitive and general wisdom is to grind the cone and then split the bit to a tad more than half. These never worked too good, except in brass or soft material.
I think, I need a relief on the (9 mm long) cutting edge. And at least one surface that helps in guiding the bit. Yes, I will pre-drill to 3.4 and 7 mm
So the question is:
Has anybody got a sketch (of the cross-section) or description of it of a conical reamer that actually does makes a nice finish? I won't cut at the front (I'll drill the small diameter)
TIA,
Nick