Thread: Is my Mandrel bent?

Or is it

Caused while drilling - slow is best removing every now and again to clear the flutes.

The lathe are the centres in line - slide the tailstock up to the spur-drive and see if the points meet up.

The mandrel take the nuts and spacers off hang the M2 over the edge of a bench which is flat and roll it, if the tail whips round its the mandrel

Are you over tightening the tailstock??

Pressing to hard with tools??

I don't think it is drilling, i turn it with the brass inserted and the bushes fit in snugly with no space all around.

My lathe center is dead on.

I will try to roll my mandrel later and see if that is the culprit... I may also be over-tightening the tailstock... i'll have to keep a better eye on it next time.

As you said try rolling it and if it is bent you can buy replacement bars so you do not have to buy the whole thing again

Good luck

If your blanks are not perfectly square with the tubes ,when you tighten on the mandrel will tend to kick off centre . Try loosening your locknut before you get right down to bushes and turn the blanks a half turn on the bushes ,retighten ,but just enough to nip up and finish turning ,you may find its now eccentric till you clean it up but should be okay to your bushes at this point. Good luck ! cheers ~ John

Put your mandrel in the lathe bare and tighten tailstock up as per usual. Have it spinning fast and slowly edge in a black texta to the centre of mandrel till it barely leaves a mark. Then stop lathe and check to see if it left a line all the way around. I bet it doesn't. This will show you if its bent or not. Also try loosening tailstock so live centre is just turning and make another mark just next to first one. This could tell you if you are over tightening Check in inch increments all the way a
long. After two mandrels and lots of mucking about I went to getting close to size on mandrel and then finishing between centres without bushes. Digital calipers are worth ever cent. Its also a good habit to check each kit with calipers as they can vary a little and spoil a well turned blank.
Just my thoughts.
But then sometimes thoughts are better left unthunked.
Kim

Or give up on the mandrel all together, I use a dead centre and the standard bushings between that and a live centre.

Take the bushes off for a final check and turn and sand down to size using vernier.

I found I was having trouble with off centre turning, but don't have a problem with the method used above.

Just my 2 cents worth.


Mike

Yeah, lot of folk don't use a mandrel.

If your mandrel is the standard"one piece" Morse #2 taper with a rod extending from it, the end of the rod threaded ¼ fine…then you can un screw the rod from the Morse taper…it is screwed into the Morse taper with appox. ½” of ¼” fine thread also.
Take the rod off, then roll the rod on a flat surface, such as a pane of glass or a granite counter top, any surface you know to be perfectly flat.
Listen, and if you hear a slight ticking sound as the rod rolls, then yes, the mandrel rod is bent.
The rods are quite easily bent with over tightening of the tail stock.
Keep in mind you only need enough pressure from the tailstock to let the headstock drive the mandrel, the bushings and brass knurled knob provide the pressure to hold the blank on the mandrel.
Replacement rods are available at most dealers on on line, I am sure one of this sites sponsors sells them.
The trick about turning between centers offers the best solution for perfectly true turnings.

Has anyone found that even when rod is straight that when mounted in lathe its not so good. I had one morse taper that was out . Can't be picked up by rolling on flat surface. I even had a morse taper machined on the working end to slide inside a 7mm tube and then stepped out to a slimline bush. It accomodates all bushes and works well. Still go to live and dead centres for final sizing and finishing.
Kim