Parting off brass

Thomas,

Having no text; your post is rather cryptic.

However; looking at your first picture, I would say that your parting tool is probably wrongly shaped, and not sharp.

Please let us have some more detail, so that folks here can advise.

MichaelG.

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

From personal experience, have you locked the lathe saddle?

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

I suspect it's a demo of how to get an elliptical curve in some part for a loco and that it has been parted off in a way that allows the front to be domed later.

Pity about the stub left because it broke off before being fully parted off - usually because the feed was too fast and is why I generally feed by hand. Using the narrowest available parting off blade helps too but in this case some size of pip breaking off is likely but this one looks a bit big. This area makes me wonder why 1/2in x 1/16in blades seem to have disappeared off the market.

John

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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

As has been sugested to get answers you must ask questions, a few computer generated images are usless photographs would be a lot more useful and give us all a chance at finding a solution for you when coupled with some questions.

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

I don't think that the person who posted wanted a solution. Pity they didn't mention that.

There isn't really any point on elaborating on the lack of a question aspect as that was pointed out on the first answer on this thread. That does waste thread space.

John

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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

Ahhhhhhhh I don't see any sub headings. Could be others don't as well.

I still feel though that if people do post they may as well make it constructive in relationship to the post that started it for the simple reason 652 people have read it and who knows even if we don't know what the question is some of those might gains something useful from it.

John

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

Steve

John you should be able to see it at the top of the thread.

Also as this was his first post he would not have been able to see it or go back and edit once he pressed "add posting" until it was approved and went onto the main forum.

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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LOL I can now - must have expected it to be under the title. Anyway this explains the lack of words. Here's me thinking he used fancy parting off to leave less material on when it's domed later or used the technique I just outlined to widen the groove rather badly.

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

I'm curious to find out what it is. Obviously it fits over the tyre, but why? And why the carefully made cut-out?

Neil

Jason

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

Ian P

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Ian,

The second image in the original post [note: I suspect they are presented in inverse order] appears to show a piece of bar, with a recess in the end ... immediately prior to the parting-off operation.

MchaelG.