As MG says looks like your tool is being deflected by the cutting tip angle. Or could be the tool is not set truly at 90 degrees to the workpiece.

Emgee

The tool should be flat topped, and SHARP, The cutting edge is probably best at right angles, and run the lathe fast, and wear a face mask because the chips fly.

Ian S C

This thread has all the hallmarks to develop into another long saga!

OK we have only had five 'replies' but since the OP did not actually ask a clear question it seems to me that there is really little point in offering solutions when we are so in the dark about the subject.

I know by replying I am adding to the tally, but looking at the pictures again and again just leaves me in confusion as most do not seem be anything to do with parting off. I also wonder whether the first picture is actually a render as the shadow look iffy.

Ian P

The sub heading would seem to indicate what the problem is:

"Problems keeping a right angle cut with the parting off tool."

As Emgee says your parting blade is probably not quite square to the lathes axis or is blunter on the right hand corner. Judging by the pip that is left the tool is ground straight across so that is unlikely to be the reason for deflection as an angled cutting edge can throw the tool off line.

J

Give him a chance. Many people don't expect forums to be as 'real time' as this one, he may not check in again for a day or two!

But seriously bad drift, an angle is wrong somewhere, the saddle isn't locked and something else may be loose…

Neil

Parting off blade is too thin for the diameter of the work and set too low? I've seen that somewhere else

Steve

I use the chuck to square up my parting of blades. This does assume that the face of the chuck is square with the axis of the lathe and doesn't account for the fact that lathes usually face concave. I just wind the saddle along while feeling for when the holder is flat on the chuck and then lock the tool post. I generally don't lock anything else but always have the slides on the compound set fairly tightly and most definitely not loose.

The groove can be widened with the blade. The brave way involves flexing the blade back and forth very very slightly with the saddles rack feed. Really this is just a case of feeling slight resistance to movement via the saddle wheel so isn't as bad as it sounds. The other way is to take full width cuts with the blade itself or leaving a very narrow section. This way the depth the tool is into the "rigid" part of the work can be controlled.

Some times it's just a case of having to leave a little bit of extra material to face off afterwards. Depends what it is.

John

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Just thought it may not be the blade that is deflecting, the part could be quite thin and being pushed away from the cut, you can get this when cutting things like thin cooling fins on engine cylinders.

If the "Disc" is as thin as the sides shown on the sketch then quite likely. Maybe we will never know.

If that is the case then turn up a plug to go in the recess with a ctr drill hole and use that to support the work with tailstock pressure until the cut is almost complete then remove while you cut teh last bit

Edited By JasonB on 06/08/2015 21:00:22

Jason

My confusion knows no bound, where is the sketch you are referring to?

Ian P

I would suspect it's for the front of a loco and the cut out fits around what I would call the chimney. No idea what steam train people call it.

John

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As the wheels are included in teh photo I wonder if teh part was to be cut up to make "wheelarches" or whatever you loco boys call them, the angled cut would clear the boiler