Wedg1e
They call me Mr. Bodge-angles
- Messages
- 7,718
- Location
- Teesside, England
I've seen a few threads around the internerdle on this and I'm keen to put together a collet set for mine, but not at the silly prices I've seen the last couple being advertised for
Starting point is an adapter that slots into the spindle to accept 5C collets, and the first thing to get right is the outer taper of the adapter, i.e. the bore taper of the lathe spindle.
Opinion seems to be divided: some say its a 5MT, others say it's 4.5MT, someone else reckons it's a Jarno #8 or whatever.
Well, going out on a limb, I think they're all wrong
I measured the adapter from my lathe which feels a perfect fit (it steps down to 3MT for a live centre) and found that over the 2.375" of contact, its taper works out at 1.438 degrees wrt centreline.
Which is not a kick in the pants off the 1.4377 taper of a 3MT, but the adapter dimensions are obviously larger. So I drew a 3MT taper in AutoCAD, then extrapolated it a few inches towards the larger end, superimposed the adapter dimensions on it and it's within a midgie's todger of identical.
Tried the same thing with a 5MT and although you can get it close, the 5MT's 1.507 degrees wrt c/line shows up quite clearly against the superimposed adapter - put another way, the adapter would have the wrong small end diameter for its length if it was trying to be a 5MT (or a 4.5MT come to that).
If I'm right, and there's only one way to find out, but I do want a collet closer so it'll have to be done, then setting up the tool to cut a 3MT but moving further 'up the ramp', so to speak, should do it...
Starting point is an adapter that slots into the spindle to accept 5C collets, and the first thing to get right is the outer taper of the adapter, i.e. the bore taper of the lathe spindle.
Opinion seems to be divided: some say its a 5MT, others say it's 4.5MT, someone else reckons it's a Jarno #8 or whatever.
Well, going out on a limb, I think they're all wrong
I measured the adapter from my lathe which feels a perfect fit (it steps down to 3MT for a live centre) and found that over the 2.375" of contact, its taper works out at 1.438 degrees wrt centreline.
Which is not a kick in the pants off the 1.4377 taper of a 3MT, but the adapter dimensions are obviously larger. So I drew a 3MT taper in AutoCAD, then extrapolated it a few inches towards the larger end, superimposed the adapter dimensions on it and it's within a midgie's todger of identical.
Tried the same thing with a 5MT and although you can get it close, the 5MT's 1.507 degrees wrt c/line shows up quite clearly against the superimposed adapter - put another way, the adapter would have the wrong small end diameter for its length if it was trying to be a 5MT (or a 4.5MT come to that).
If I'm right, and there's only one way to find out, but I do want a collet closer so it'll have to be done, then setting up the tool to cut a 3MT but moving further 'up the ramp', so to speak, should do it...