chuck, thread cutting and turning

[naughtyboy]

been drilling some 3mm holes using drill press with 16mm chuck.
want to make adaptor to hold spare 10mm chuck ive got both to make it easier an get bit of practice on lathe.
are chucks left or right hand thread?

need to make some double ended bolts using 24mm hex bar.
they need to m14 one end and m10 other with hex bit in middle as nut.

do i need to turn m14 sect to 14mm rd to thread it as cant seem to find info on what size rd to start with for making bolts.

lastly how do i turn hex bar into rd?
worried about breaking cutter with corners on hex bar hitting it.

sorry if long winded.

 

[MattF]

Chucks: If it's not an arbor type, right hand thread on chuck, left hand thread on the retaining screw, (if there is one).

Bolt: M14 bolt needs outer diameter of 14mm on rod. Same outer diameter when making bolts, smaller inner diameter for tapping.

Hex bar: Turned the same way as anything else.

 

[brightspark]

2 ways rough grind the edges off first. or take shallow slow cuts till it gets rounder then increase and dont use tip tools just a hss tool will do

 

[naughtyboy]

cheers for that.
will hav play on sat.

 

[the artfull-codger]

cheers for that.
will hav play on sat.

I'd cut the bar to length,turn down the larger size 14mm first then thread cut it & finish off with a die if you like, then turn it round & put the 14mm in the chuck & turn to 10mm & thread cut that & jobs done, not the other way round as 10mm dia will turn in the chuck with the 14mm threading forces & the first cut can be just below the af hex size steady away then you won't have it bouncing across the corners, [unless it's a flimsy lathe!!] if you're just threading with a die only you might have trouble slipping in the chuck for the 2nd thread.

 

[MattF]

if you're just threading with a die only you might have trouble slipping in the chuck for the 2nd thread.

An appropriately sized nut held in the jaws, with the piece secured into that rather than held in the jaws, would sort that.

 

[the artfull-codger]

An appropriately sized nut held in the jaws, with the piece secured into that rather than held in the jaws, would sort that.

Or 2 or 3 nuts to get the length in the chuck so the jaws are not just gripping on the outer edge as the holding powers too short & it can move & ruin the job.

 

[Lawnmowerboy]

I wouldn't ever attempt it like that. the holes in the centre of the nuts are never concentric. they are punched and the thread will never be cut perfectly centrally either. i would do it by having enough for the flats to grip and both threaded sections out of the chuck plus 20mm or so. Centredrill one end then turn the OD to 10mm for the M10 end then use a normal turning tool to do it the other side of the chuck so you do it all in one op then part off and chamfer the other end. You can use a piece of brass shim wrapped around one end to protect it.

 

[MattF]

I wouldn't ever attempt it like that.

If you're running a die down the piece of stock, it doesn't really matter if it's off centre. It'll be centred against the die when the die is initially offered up via the tailstock, provided the jaws are left slightly loose initially, and from then on things will be done by hand. You're only holding the piece stationary against rotation and backwards movement, to be able to rotate it by hand. Same as it doesn't matter whether there's one nut or three locating the threaded portion.

If screwcutting was being done in the traditional way by using the changegears and the lathe itself, it would be a different matter entirely. In the case I replied to, as long as the piece can't rotate in the jaws or shift backwards through the spindle, job sorted. End of the day, a die is never going to achieve a precision alignment thread.

 

[naughtyboy]

going to be using die as no confident enough to try thread cutting on lathe yet.

 

[hareng]

Using the two drill chucks in tail stock?
If so just buy an arbor.

 

[Lawnmowerboy]

It does. The thread will be massively over or undersized with up to a 1mm of runout (quite possible using a normal nut. Different story if you drill and tap a round piece of bar. If you use a die think about when you whack it in reverse and the thread begins unscrewing it'self from the chuck!

 

[naughtyboy]

It does. The thread will be massively over or undersized with up to a 1mm of runout (quite possible using a normal nut. Different story if you drill and tap a round piece of bar. If you use a die think about when you whack it in reverse and the thread begins unscrewing it'self from the chuck!

wont be using it in lathe its to use in drill press only so i hold smaller bits.

 

[Lawnmowerboy]

No I mean when you are cutting the thread and you reverse the lathe to wind the die off. If you have wound the previous thread into a nut which you are holding on it will try and unscrew it instead of breaking the swarf and unscrewing the die?

 

[MattF]

It does. The thread will be massively over or undersized with up to a 1mm of runout (quite possible using a normal nut. Different story if you drill and tap a round piece of bar. If you use a die think about when you whack it in reverse and the thread begins unscrewing it'self from the chuck!

This is threading with a die. There will be negligible or no runout because the threading will be done by hand. For goodness sake, how do you think people have been threading using dies for years? If someone wants powered screwcutting and ultimate precision, (within the scope of the lathe), use the lathe as intended. The lathe, in this instance, is nothing more than a fancy vice. No feed or powered rotation. If the die happens to jam when unwinding, (likely crap threading or die if it does), it ain't rocket science to take the threaded rod out of the chuck and pop another nut on the other end against the existing nut to lock it.

You're envisaging/creating a problem which doesn't exist. Just because a lathe is present doesn't mean people have to turn off their gumption and stop thinking.

 

[Hitch]

I'm no machinest, but last time I did a little job like that, I made a holder to suit. In this case, a spare bit of the hex bar, drilled and tapped for the m14 to screw into. tighten it up using a spanner, and it won't come undone easily on reversing.

 

[hareng]

Depends how accurate the thread needs to be and what you can get away with by using dies.
Have seen 100's of cockups where a die was rammed down a turned down shaft with runout to be ashamed of. Its not accurate by any means with barely a few that are tolerable.