Parting off

[old martParticipant @oldmart]

I buy blades in 26 and 32mm depths for 2 and 3mm inserts. I didn’t get on with the GTN style at all and use Kyocera, Kennametal and the double ended MGMN which are currently favourites. Insert blades have an advantage over one piece holders as they are double ended giving two lifes.

The size of lathe makes a huge difference and if possible part off under power. Rear inverted toolposts can help and a dedicated parting off toolpost fixed directly to the cross slide eliminates some of the flexibility of the top slide. Also locking of the carriage adds to the stiffness.

At home, my 7 x 12 mini lathe works well with a holder with a tapered 2mm HSS parting off blade in a little holder.

This is a regular subject on more than one forum.

[vintagengineerParticipant @vintagengineer]

If its an insert tool, they are design to be power fed into the work with lots of coolant. The tool design curls the chips width wise so they clear.

[bernard towersParticipant @bernardtowers37738]

Out of interest aquired this the other day and wondered if a design like this might be helpful, especially a smaller version for the lighter lathes. I has a well known chuck makers name on it so it was a commercial item.

[JasonBModerator @jasonb]

Clearly made for front tool post use if the writing is anything to go by. It would certainly stop the work riding up or the cutter getting pulled down on a flexible machine.

[interferencefitParticipant @interferencefit]

Thanks for the responses. I’m not quite grasping what the soft jaw concept is? I don’t have soft jaws so maybe a moot point for me.

The bearing idea… how do I grip a round bearing and also grip my part if they are different diameters?

I’m led to believe that HSS rather than carbide is the most appropriate for the Myford 7? Something to do with speed?

Are there any other parting off tools I should consider that would work with my current set up?

I really am a noob so please be patient if I’m not immediately grasping some of the terminology.

 

[egaParticipant @ega]

bernard towers:

You have a vintage gem there!

E T Westbury said:

“One of the most satisfactory parting-tool holders ever produced commercially was that made by Burnerd, which incorporated a special steadying device, by means of which the prevalent tendency to dig in, nearly always experienced with any form of parting tool, could be entirely prevented. So far as can be ascertained, this tool is not at present [1943] on the market.”

This approach reminds me of the tangential tools favoured by T D Walshaw where the downward force on the tool is directly transmitted to the cross slide.

[interferencefitParticipant @interferencefit]

If it helps, this is my current set up.

[egaParticipant @ega]

I see that you have a very nice-looking late model with power cross feed which should mean the longer cross slide and, hence, the practicality of a rear toolpost as, eg, sold by Hemingway Kits.

I  suggest you search this site for further information generally.

[interferencefitParticipant @interferencefit]

Thanks, it’s a nice machine that despite appearances, is not restored. I bought it, and the VMC fronm the original owner.

 

I had a rummage through the treasure trove of old oily cardboard boxes and plastic bags to see what smaller bits and pieces came with them, nd as luck would have it, there was a parting off tool in a custom made holder that nests perfectly under my quick heel clamp.

I just need to buy a thinner tool for it now.

[bernard towersParticipant @bernardtowers37738]

you may find that that parting tool has a far too aggressive angle on the top edge.

[egaParticipant @ega]

Those blue tools are the Myford Quick setting type I mentioned complete with boat at top left.

Two superb machine tools but you need more space for the mill! Where is the lathe’s switchgear?

[interferencefitParticipant @interferencefit]

No switch on the lathe, the motor is wired directly to the plug socket and I switch it from there.

The mill is tight, but it was the only place had room for them both. I get enough movement for the stuff I’ve needed to do so far.

If I need more, I have mounted it on polypropelene sliders, which with a good firm shove allow it to be dragged about a little without damaging the floor tiles.

[interferencefitParticipant @interferencefit]

I tried it on some aluminium (easy, I know) earlier and it cut a lovely long ribbon off almost effortlessly, but is too wide for what I need at circa 5mm.

I’ve ordered the RD Tools 3/32 one as an experiment as it appears to work with the clog heel clamp well from what I can deduce.

I’m very much still at the bottom of the very steep learning curve.

[Howard LewisParticipant @howardlewis46836]

Two comments, in the hope of not being thought pedantic.

Ideally, the lathe should be fed through a No Volt Release switch. Then if, for any reason, the power is removed, there is no risk of the machine starting up unexpectedly.

If you want to run the lathe in reverse, many use the old drum type switch (using this to switch the lathe on or off can cause the contacts to burn, so stoppong and starting with the NVT safegaurds this by ensuring that the drum contacts are only made/ broken with no current flowing).

Secondly, a parting tool with a large top rake is likely to be more prone to digging in, especially since you will be using it in effectively a front tool post. I fitted my ML7 with a Myford 4 way toolpost to make tool changing easier. (You could even make one from laminations of fairly thick plate, say 12 -15 mm)

My preference is to use a HSS parting blade, (Mine is 3/32″) with no top rake, and set on centre height. Usually moneral or soluble oil is drip fed with a brush to make life a lottle easier

Mine is mounted, inverted, in a rear toolpost. (I made one for my ML7, and it made parting off less fraught) Being inverted, the swarf is more likely to fall away, reducing the risk of jams.

HTH

Howard

[egaParticipant @ega]

In addition to Howard’s point, it looks as though you would have to reach over the chuck to switch off in an emergency which could well be awkward.

Good tip about the polypropylene tabs!

[interferencefitParticipant @interferencefit]

Thanks both – can you recommend or link to what switch I should buy as it is something I ought to set up. Would prefer period/Myford correct, but will go with the flow.

I’ve ordered a RDG tools 3/32 parting off tool to see how I get on.

[Howard LewisParticipant @howardlewis46836]

You may be able to buy a No Volt Release switch as an aftermarket spare replacement from suppliers of bandsaws, such as WARCO or Chester, or possibly from someone like Home and Workshop Machinery.

If you want to run the lathe in reverse, the reversing switch should wired between the NVR switch and the lathe, so that it can only be operated when the lathe is stationary.

Either of these set ups should move the “On/Off” function way from the lathe so that you do not lean over rotaing parts to switch off.

Howard

[interferencefitParticipant @interferencefit]

Just updating this for completeness. I ordered a NVR switch and a diecast aluminium enclosure to house it. I had some original Myford Green enamel paint that the original owner bought with the lathe back in 1989 that had never been opened, so I used that to paint the box for a more cohesive look.

I’m quite pleased with how it turned out.

 

 

[Howard LewisParticipant @howardlewis46836]

Very neat!

Howard

[egaParticipant @ega]

And you have taken the trouble to let the forum know!

Where did you get it from, please?

[old martParticipant @oldmart]

Soft jaws when new are just square blocks of a machinable steel alloy which fit in place in the chuck body exactly the same as hard jaws. They can be set up and be bored to make holding difficult and delicate work exactly. With care they can be used many times before they are worn out. Even then they can be milled and drilled to accept shop made tops and that will extend their life pretty much indefinitely. Here are pictures of soft jaws and of an old chuck with aluminium tops held onto worn out soft jaws with SHCS ready to have an extended life.

[ega]

On ega Said:

And you have taken the trouble to let the forum know!

Where did you get it from, please?

Yes indeed, thought it might be appreciated.

Die Cast aluminium enclosures are available from most electronics distributors – in this case, RS.

The switch came from Amazon.

[Alan JacksonParticipant @alanjackson47790]

A good while ago I made my version of a vertical parting tool, just to try it out and it worked very well for the small testing I gave it. Here is a youtube link.

In order to clarify the operation of a vertical parting tool here is my rather primitive description of how I think it works.

Imagine that you are the parting tool holder whereby your two hands are held straight out from you body. Your hands are gripped together and your fists are the cutting edge. You have a friend who represents the metal being cut and he (If you are a front parting tool) pushes down on your hands while you do you best to resist him pushing down. You can see that he can quite easily push your arms down. If you want to now become a rear parting tool you can turn round 180 degrees and your friend would now push your hands upwards still he can easily overcome your resistance to him pushing up.

So in order to stiffen you up, say you are frozen solid or have rigor mortise and are wearing a large pair of lead diving boots to anchor you down. When your friend (or should I now say de-parting undertaker) pushes down on you hands he will not be able to move your arms down because they are rigidly fixed to your body and he have to apply more force until you tip forward on you toes. Note that as you tip forward you rotate about your toes moving your cutting tool hands deeper into the metal being cut.  If you are now rotated 180 degrees to become a rear parting tool your friend (some friend) now has to apply more upward force until you tip backwards on your heels. Also note that your cutting tool hands now move away from the metal being cut as you rotate backwards on your heels.

Now you have to play the part of a vertical parting tool as I am proposing, so you now can be thawed out or de- rigor mortised. So lay flat on your back and push one arm vertically upwards and clench your fist to form the cutting tool. Your friend now has to apply considerably more force to overcome your vertical arm. Your arm will be in direct compression and until your elbow or wrist give way you will have much less a problem resisting his downward cutting force. It will also not matter if you are a front or rear vertical parting tool as long as the rotating force is pushing down on your hand. You can now get up and go back to your work or whatever you were doing. I apologise for being so flippant but I hope it does explain my reasoning.

 

Regards

Alan

 

[egaParticipant @ega]

It was very much a “step ahead”!

I think the idea is similar to the tangential tool I mentioned.

[martin haysom]

On martin haysom Said:

On John Haine Said:

I am amazed just how often this topic comes up – an annual event?  I know this site is hungry for content but surely there must be a case for posting a permalink to an edited summary of the best advice?

but who decides what is “best advice” and what is bad advice

AI ?  Look where that gets us!

Martin

[Author]

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