Parting off help!

[Howard LewisParticipant @howardlewis46836]

With regard to chatter, if it chatters, and the tool geometry is right, and set on, NOT above, centre height, reduce the speed.

It sounds as if you will not be able to make and fit a rear toolpost.

However, with a flange mounted chuck, you can safely run in reverse., with the parting tool mounted inverted in the front toolpost.

I do not use any top rake, leaving the HSS blade as is, just grinding a clearance on the front, and ensuring that the cutting edge is not, in the case of an inverted blade in the front toolpost, below the centreline. (So that the blade cuts, but does not rub ) having an inverted blade above centreline will encourage the work to try to climb over the tool, probably to the detriment of both.. Again an argument for maximising rigidity and setting the cutting edge on centre height.

Apart from weakening the cutting edge, and reducing the area to conduct away heat, a lot of top rake will encourage the tool to wear or dig in, hence my preference for Zero top rake.

Lubrication will always improve matters. I have rigged up a gravity feed, with a valve to control the flow to a jet mounted on a small magnetic base on the Cross Slide. The reservoir is just a plastic soap dispenser bottle, with a piece of plastic windscreen washer tube rammed onto the spout of the pump, and sited on a shelf above the lathe. Nothing fancy there! Crude but effective.

If you use blades either with a groove on the top, or T section blades, jams are less likely, since the swarf is narrower than the groove being cut..

HTH

Howard

Edited By Howard Lewis on 03/09/2021 17:56:54

[SillyOldDufferModerator @sillyoldduffer]

Posted by Chris Crew on 03/09/2021 14:19:56:

Apologies in advance if I come across as a little sharp but we have been through all this so many times. There is plenty of parting off advice on this forum already ,,,

What I like about the forum is it's willingness to answer questions – enormously valuable when I was a raw beginner, less now I'm no longer a virgo, but I'm still learning new tricks.

The forum isn't an organised reference source like Wikipedia, and it doesn't have a first class search either. It has a Question and Answer format, which can be repetitive. Inevitably the same subjects come up again and again. I don't mind – helping people get started by answering their questions keeps the hobby alive! Newbies arrive on the forum, are educated, and move on to greater things.

Sad state of affairs if a primary school teacher like William told new classes to use their common sense just because he was fed up teaching the same material year after year! William may get bored repeating himself, but his job benefits different children every time. Although a river looks much same day by day as it rolls to the sea, the water is different: just like life.

By the by I strongly suggest there's no such thing as common sense. Everything has to be learned…

Dave

[Nick WheelerParticipant @nickwheeler]

Posted by SillyOldDuffer on 03/09/2021 20:18:28:

By the by I strongly suggest there's no such thing as common sense. Everything has to be learned…

Common sense was used here to mean something I learnt(or was taught, they're not the same) so long ago I've forgotten how ignorant I was.

[JourneymanParticipant @journeyman]

Posted by Mick B1 on 03/09/2021 13:05:20:

I see the article involves sacrificing the compound slide complete, with its entire functionality, in order to fit a QCTP. It might reflect the sort of stuff I make, but myself, I'd never do that…

I think the point of the article has been a tad missed. The idea of making the cross-slide toolpost was to enable turning the compound slide to remove the cast in boss. Perhaps *** Page 2 *** makes thing clearer.

Once finished as described the top-slide can be re-fixed but you end up with an extra bit of interchangeability:-

• A cross-slide toolpost using the 4-way or QCTP
• A top-slide toolpost using 4-way or QCTP
• A rear toolpost using 4-way or QCTP

The modification would needs re-working to fit the WM180 though and of course fitting a QCTP is unlikely to improve rigidity for parting off.

John

Edited By Journeyman on 04/09/2021 08:21:15

[Howard LewisParticipant @howardlewis46836]

IF you can make and fit a rear toolpost, I would urge you so to do.

I made one for my ML7 and never looked back.

When i got my larger lathe, I made a four way rear toolpost. This allows work to be Front, or Back chamfered as well as parted off, leaving the last op to be just a skim to clean up to length.

Pity that I have yet to find a means of fitting one to the original Cross Slide on the mini lathe!

Might be worth doing a bit of drilling and tapping to extend the Cross Slide (although it would then reduce the travel by fouling the splash back. Thinking cap on!

Howard

Edited By Howard Lewis on 04/09/2021 17:32:12

[William Harvey 1Participant @williamharvey1]

Posted by Howard Lewis on 03/09/2021 17:55:10:

With regard to chatter, if it chatters, and the tool geometry is right, and set on, NOT above, centre height, reduce the speed.

It sounds as if you will not be able to make and fit a rear toolpost.

However, with a flange mounted chuck, you can safely run in reverse., with the parting tool mounted inverted in the front toolpost.

I do not use any top rake, leaving the HSS blade as is, just grinding a clearance on the front, and ensuring that the cutting edge is not, in the case of an inverted blade in the front toolpost, below the centreline. (So that the blade cuts, but does not rub ) having an inverted blade above centreline will encourage the work to try to climb over the tool, probably to the detriment of both.. Again an argument for maximising rigidity and setting the cutting edge on centre height.

Apart from weakening the cutting edge, and reducing the area to conduct away heat, a lot of top rake will encourage the tool to wear or dig in, hence my preference for Zero top rake.

Lubrication will always improve matters. I have rigged up a gravity feed, with a valve to control the flow to a jet mounted on a small magnetic base on the Cross Slide. The reservoir is just a plastic soap dispenser bottle, with a piece of plastic windscreen washer tube rammed onto the spout of the pump, and sited on a shelf above the lathe. Nothing fancy there! Crude but effective.

If you use blades either with a groove on the top, or T section blades, jams are less likely, since the swarf is narrower than the groove being cut..

HTH

Howard

Edited By Howard Lewis on 03/09/2021 17:56:54

Quick one on inverting a parting off tool. I have a 250 series QCTP (Which I need to modify to fit correct and I will go back and update one of my other threads to sort that out).

I have bought a T Shaped Blade from Chronos Here is an image of the bladed mounted in it's holder.

To invert it, can I simply turn this one upside down, like so?

[Howard LewisParticipant @howardlewis46836]

IF you are going to mount it in the front toolpost and run the lathe in reverse, yes., as long as inversion does not cant the tool over from the vertical.

The tool holder already provides top rake, so don't grind any on the tool, just front clearance, and set on the centre height.

Since you will be changing tools easily (The purpose of a QCTP ) it may be worth making a Centre Height gauge with two blades. The upper one will be for tools mounted normal way up, which touch the underside of the blade, and the lower one for inverted tools, such as your parting tool, which will just touch the upper surface of the lower blade.

Have a look at my albums.

Either that, or spend time experimenting with, and adjusting, every tool, facing the end of a bar until there is no central pip. But you may still need a gauge for setting boring tools.

Howard

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