I now have a 'bit' more spare time to myself between repaying my DIY debt that i racked up when i was building my car!
I want to begin to experiment with my lathe.
lathe
I noticed that when i put something in the 3 jaw chuck and move the tailstock up to meet it then centre on the tailstock is quite a bit off centre (by
eye) of the work piece.
How do i overcome that!
Cheers
hi there
there should be facility to adjust the tailstock backwards and forwards.
if the tailstock is too low you may have to raise with shim
keith
i dont like the look of that drive belt.
make your first job a guard
[Edited on 30/1/08 by gy351100]
There are opposing screws in the tailstock one front one back, usually recessed, which are used to move it backwards and forwards, also used for
offsetting the tailstock to turn tapers. You centre the stock by loosening both, then screwing the front screw in - move the stock towards you, or the
back one to move the stock away, once centred lock both up. There may also be a pinch screw to prevent movement which needs loosening. Be sure the
clamp lever is tight and the stock foot cannot move on the ways during centering.
Rgds.
Pete.
[Edited on 30/1/08 by r1_pete]
Just to clarfy. Are you saying you find the tailstock to be offcenter when you bring it upto the spiing chuck.
- Or are you saying that when you bring the tailstock upto it you find the chuck to be off center?
Becuase its possable for both to be out, and should be possably also to adjust both.
- This is why quick release chucks have marks on them to allow you to put them back on in the same origentaion (otherwise you might but in on with
the adjusment working the wrong way for you).
But yeah, it should all be dead line. Headstock bearings, chuck body, tailstock.
I was also once told by one technition that as an apprentice he spend most of a day alining and realining the tail stock on this lathe, only to find
out eventually that he had been given (deliberatly?) a slightly bend center. So everytime he took it out and put it back a diffrent way, the alinement
was to cock!
*I was told this story after being caught trying to center a work peice using the tip of of a drill rather than a center. Although ofcause when
centering the work peice, the fact that the dril/tail might have been of center wasnt relivent
Daniel
[Edited on 30/1/08 by dhutch]
Ok i got to think its been years since i have been a apprentice.
Machine a dead center in the 3 jaw chuck
Get a round bar Sin bar is best (has center drilled holes on both faces)
fitted a center to the tall stock.
trap the bar between the two centers.
Put a Dti on the lathe saddle run the clock from left to right along the bar.
this will give you the run out.
Adjust away
Obviously the accuracy of the bar will be what sets how good the results are.
Hope that helps
Another way is to get a piece of round steel bar as big as the lathe can handle, put it in the 3-jaw and drill a centre hole in each end.
Put this bar in the lathe between centres (you'll need a driving plate and dog) and take a sliding cut along the whole length until it's
running true. Measure each end and adjust the tailstock until both ends can be turned to identical diameters without adjusting the cross-slide.
This can be made much easier by making a deep cut for the middle 90% of the bar, just leaving a collar at each end. You only have to do a small cut
across each collar to achieve the same result.
If you do this, keep the bar safe once you've got both ends identical - it can be used to set up the lathe the next time you have to reset the
tailstock.
Note: this only works if the tailstock is off-centre horizontally (e.g. after turning a taper). Fixing a vertical error is a BIG issue on a typical
lathe!
David
[Edited on 30/1/08 by David Jenkins]
If it is a LONG way out at the chuck make sure that the jaws are in the correct slot, they should be numbered and in the correct order.
[Edited on 30/1/08 by Schrodinger]
3 jaw chucks dont always hold things central. Do you have a 4 jaw and a dti? This might help to check if tail stock is aligned first, then you can use tail stock to check the 3 jaw alignment. or use the dti to confirm the 3 jaw is OK.
The only certain thing to give you a true centre is a centre (strangely enough!).
I remembered a quick and dirty way to roughly check the tailstock alignment. Put a centre in the headstock and another in the tailstock (remembering
to clean both the centres and the holes they go in). Hold a steel rule vertically between the two and very gently bring them together. If
they're prefectly aligned then the rule will stay vertical and at 90 degrees to the bed. If they're not then it will tilt one way or
another.
As I said - it's a crude check, but it is quick and easy. Not too precise, but at least you'll know if you've got any gross errors,
and in which direction.
The fact you machine the dead center after its been put in the 3 jaw removes the 3 jaw chuck run out as a issue.
first check your chuck jaws are in the right slots, probably aren't.
Failing that adjust the tailstock if its got taper turning adjustment (but many havent)
Depends on your required accuracy and skill level but for most DIY use I would:
Centre drill a hole in a piece of bar
Put your centre in the tailstock
Move the tailstock close to the workpiece and lock
Wind the tail stock in to the centre drilled hole
See which way you are out and adjust
The above method will get you close enough for DIY use, after that you will need a dial test indicator and lots more patience.
Misalignment can be both vertical and horizontal, and adjustment may be screws or worst case shims. You may also have different misalignment along
the length of the bed.
I quite like the centre to centre idea from David Jenkins, I haven't used it myself but it would work. If you haven't got a centre for the
headstock you can turn one (60deg included angle) yourself to guarantee concentricity.
Oh yeah, mind your willy in those gears, they take no prisoners.
quote:
Originally posted by Mansfield
Oh yeah, mind your willy in those gears, they take no prisoners.
