lathe turning taper toward headstock

[mike mcdermidParticipant @mikemcdermid41977]

Lathe has developed a habit of turning tapers

smaller at headstock end ,it did always cut 1 thou or so over 6 inch but was never bothered ,this seems to have grown to about 5 thou now over 3inches

doesnt matter wether using tailstock or not taper is the same which rules out the tailstock, in fact i can get a good result by setting over the tailstock to eliminate the taper

however its not the best option

any ideas

no crashes or bangs and wallops of late

[mike mcdermidParticipant @mikemcdermid41977]

[NobbyParticipant @nobby]

Hi Mike & Guys
What lathe is it ? are the bearing in the headstock adjusted ok ? if the job is held in a 3 jaw chuck the jaws may be worn at the front allowing the bar you are turning to push away. By the way Happy New Year to you & all the Guys on this forum
Regards Nobby

 

Edited By Nobby on 31/12/2013 18:57:22

[Thor 🇳🇴Participant @thor]

Hi Mike,

As Nobby says, has anything been done to the lathe? A wooden stand will not be as stable as a steel stand, what kind of stand do you have? Have you read Harold Hall's description on Lathe setup, turning paralell etc.?

Regards Thor

[mechman48Participant @mechman48]

Happy New Year to all the guys on the forum.

George

[mike mcdermidParticipant @mikemcdermid41977]

hi chaps its a boxford 280 industrial

brand new d1-3 chuck to be honest i had not noticed problems as i was using a 4 jaw and clocking everything

that got tiresome

spindle taper clocks at 0 if i put my finest clock on it and i probably am not as good as the clock

using a cheaper clock

i get runout on diameter of the chuck is less than 1/2 a thou

worst on face less than 1/2 a thou and if i put a

piece of bar in the chuck is 2 thou concentricity anything tighter i switch to the 4 jaw

if i shift the tailstock i can get ban on diameter over the length of 3"

even if i pu the old chuck on i get similar taper towards headstock

[EmgeeParticipant @emgee]

HiMike

Surprised you have that problem with such a lathe. Just ask if the taper on spindle and in chuck are absolutely clean, also of course the mating faces of chuck and spindle.

Is it better by using a particular jaw for tightening ?

Rgds, Emgee

[S.D.L.Participant @s-d-l]

Posted by mike mcdermid on 31/12/2013 19:40:02:

hi chaps its a boxford 280

i get runout on diameter of the chuck is less than 1/2 a thou

worst on face less than 1/2 a thou and if i put a

piece of bar in the chuck is 2 thou concentricity anything tighter i switch to the 4 jaw

if i shift the tailstock i can get ban on diameter over the length of 3"

even if i pu the old chuck on i get similar taper towards headstock

What make chuck is it?

if you put a true cylinder in the chuck (bit of silver steel) what is the runout along the bar to that you know is true?

ie are the jaws eccentric to the body of the chuck?

Steve

[mike mcdermidParticipant @mikemcdermid41977]

It’s a bison 125 mm
The spindle is spotless as is the seat
Concentricity on a ground 1 inch bar is about 2 thou over a foot

Can’t figure it as the headstock sits on a vee and the bolts are still tight

Edited By mike mcdermid on 31/12/2013 22:55:28

[blowlampParticipant @blowlamp]

Is this with carbide tooling?

If so, grind up a very sharp HSS tool and try that on some brass or aluminium.

Martin.

[NobbyParticipant @nobby]

Hi Mike
From you first post it seems as if you have done something different lately have you moved it ? is there a heat source you have put next to it . or another heavy machine next to it
Nobby

[Ady1Participant @ady1]

Any play on the saddle etc ?

Lock it to the carriage.

Then try locking the carriage at various points along your bar

[Author]

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