Post by dickdastardly40 on May 6, 2008 13:14:09 GMT
Possibly a whole thread's worth in both eccentric turning and trepanning with a multitude of differing techniques.
A method for an eccentric outcome without a dti is to drill a hole offset to your centre axis in the drill press, tap and fit a threaded rod to suit.
Using the 4 jaw you can 'suspend' a dead centre into the centre mark (providing it's bang on)with another dead centre up its chuff which is in the tailstock. This method is sometimes known as the 'wobbly centre' As you rotate the 4 jaw you would normally have a DTI bearing on the suspended centre and you adjust to bring the runout to zero. With no DTI you could use a scribing block or a point held in the tool post. Gently rotate the chuck until the dead centre is closest the point. Move the point until is just touches the centre, rotate the chuck half a turn and adjust the jaws so that the job moves the dead centre approx half the distance closer to the point. Half a turn back and check, then 1/4 turn adjust to the closest etc etc. When it seems good nip up all jaws and recheck, spin by hand and watch for runout. Clear as mud?
Trepanning is really only boring but without removing the centre section, grinding a specialised tool is required for narrow grooves but you can do it with a boring bar and a couple of different tool positions for a wide slot such as yours. I'd drill afterwards so that I wasn't cutting intermittently.
I Still think it looks good despite you saying where the inconsequential flaws are.
A method for an eccentric outcome without a dti is to drill a hole offset to your centre axis in the drill press, tap and fit a threaded rod to suit.
Using the 4 jaw you can 'suspend' a dead centre into the centre mark (providing it's bang on)with another dead centre up its chuff which is in the tailstock. This method is sometimes known as the 'wobbly centre' As you rotate the 4 jaw you would normally have a DTI bearing on the suspended centre and you adjust to bring the runout to zero. With no DTI you could use a scribing block or a point held in the tool post. Gently rotate the chuck until the dead centre is closest the point. Move the point until is just touches the centre, rotate the chuck half a turn and adjust the jaws so that the job moves the dead centre approx half the distance closer to the point. Half a turn back and check, then 1/4 turn adjust to the closest etc etc. When it seems good nip up all jaws and recheck, spin by hand and watch for runout. Clear as mud?
Trepanning is really only boring but without removing the centre section, grinding a specialised tool is required for narrow grooves but you can do it with a boring bar and a couple of different tool positions for a wide slot such as yours. I'd drill afterwards so that I wasn't cutting intermittently.
I Still think it looks good despite you saying where the inconsequential flaws are.
