Replacable insert parting tool

[Roger B]

I purchased a 2mm wide replaceable insert parting tool from APT. I am hoping the deeper and more rigid blade will be better for machining crankshaft journals.

I can understand that the insert pushes into place and can be pushed back out with the screwdriver like thing. My question is how hard does it need to be pushed in? Is finger pressure sufficient or does it need a tap from a plastic hammer?

[Steamer5]

Hi Rodger,
Mines got a flat bar with 2 pins in it, one pin goes in the hole at the bottom of the blade, the other is used to push the tip in. Hope that makes some sense. To remove the tip one pin in the bottom hole , the 2nd pin goes into the pin size hole at the back of the insert, & used to push the inser out

Cheers Kerrin

[Jasonb]

I just push the holder against the side of the wooden bench to push the insert in, if it needs any more then the cutting force will push it back.

I don't have an ejecting tool so just twist a flat bladed screwdriver in the gap behind the insert to remove it.

[fumopuc]

Hi Roger, I do it in a similar way like Jason said.
Running this tool the Myford style (upside down), is for me the  best way to use it since a couple of years.
The parting of a 60 mm steel bar was no problem any more, so it will be a good choice to make crank shafts.
In Germany is a supplier, who offers the inserts in different cutting designs, straight, left and right.
https://shop.kobratec.com/public/catalog_xmlxslproducts.aspx?art=viewproduct&suid=13335&productid=122700335&zid=b31a898b-f7bc-4d5e-8b94-9ddd6af26e63&ln=de
The left or right ones are sometimes very useful for parting off operations only where you would like to determine a plane face. 

[Roger B]

Thank you all for the information    I was concerned that an insert coming loose during parting would make quite a mess 

[Roger B]

Having used the tool on a piece of 10mm silver steel the insert was pushed around 0.25mm deeper into the holder. Hopefully I can get it out later 

[Gas_mantle]

Hi Roger,

What is your first impression ?

I could do with a better parting tool and have considered something like the one you have.

[Roger B]

It is certainly more rigid than the two I have with 1.5mm wide HSS blades when used at a long overhang such as crankpin turning. I will need to look at other inserts as the ones I have seem to load the lathe much more when parting off (ok I only have a Hobbymat). I was surprised how much the motor slowed when parting a piece of 10mm silver steel compared to my 1.5 mm wide HSS tools.

[Firebird]

Hi

I have a similar tool to the one shown. I have had it for about 6 years now. I have it mounted upside down in a rear tool post on my Myford. It works exceptionally well and I would not go back to the old style parting tool. The only problem I have encountered is when parting off large diameter aluminium there is a build up of material on the tip which means withdrawing the tool to pick it off. Sometimes the tip would stay stuck in the material. A simple cure was a couple of drops of super glue when inserting the tip into the holder, it never came out again.

Cheers

Rich

[mcostello]

One thing I have found out the hard way was keep the speed up when getting near the center. Was running about 350 rpm on 1 " steel and the tool grabbed around the 3/8" left mark.
Lesson 1 learned- keep the speed up. Have to rethink things as I am a high speed steel kind of Guy.
Lesson 2 learned- make an upside down adapter for My Bxa tool post. When things go pear shaped the jam up tends to lift the tool holder up . Quick change tool posts seem to not have been designed to counter forces in the up direction saving things.

[Florian Eberhard]

Hi Roger

Im a bit late - however, those holders i know are normally designed to support the insert from the rear side aswell - just where you have a small gap between your insert and the holder.
But I have no Idea if all these holders work like that or if some (probably due to a design error?) won't all the insert to be pushed that far back until it is supported on the backside aswell??

What you found out with silversteel (load of your machine) is simply normal. Silversteel is pretty tough to machine, especially operations like parting off. I am not sure but I had the impression that it even gets a bit harder right at the spot your tool is cutting it (like most grades of stainless steel).

The insert you are using looks like one for general purpose with rounded edges? I would - for finishing only - try to get some inserts with ground edges which are usually sold for non ferrous-materials.

Florian

[Roger B]

Thank you for the thoughts Florian. I bought this tool specifically for finishing crankpins where rounded corners are a good idea but thought I would see how it performed when cutting a camshaft blank. I only used it for the final parting off as it was already in the tool holder. I was surprised at the extra load compared to my usual 1.5mm wide HSS blade which is normally ground without any top rake angle.

[Gas_mantle]

It is certainly more rigid than the two I have with 1.5mm wide HSS blades when used at a long overhang such as crankpin turning. I will need to look at other inserts as the ones I have seem to load the lathe much more when parting off (ok I only have a Hobbymat). I was surprised how much the motor slowed when parting a piece of 10mm silver steel compared to my 1.5 mm wide HSS tools.

Cheers Roger, I use 1.5mm HSS blades at the moment and I find they are ok parting off a small diameter but if I want to put a shallow grove in a large diameter I often get a lot of chatter 

[Florian Eberhard]

Hey Roger

I meant rounded cutting edges, not corners. (you will need to use a microscope to see that in detail!)

Peter: The problems you are having with chatter can have several reasons, so its not easy to give you a general answer what to do.
However, if your parting tool works fine with small diameters, then it could be an issue with speed. Do you have a vfd on your lahte? If so, start as slow as possible and then look what happens. Then increase the speed slighlty and see what happens then. That way you may find a speed that works for your task. But if there is there already chattermarks in the groove, you will find it difficult to get the tool cutting properly.
Sometimes chatter issues are also caused by feeding in the compound slide too slow!
Oh and the holder also has quite some influence on how good the parting tools perform!
This holder for example is rubbish: https://www.rdgtools.co.uk/acatalog/RDG-TINY-LATHE-PARTING-OFF-TOOL-8MM-X-8MM-1731.html
The blade of that one is held way too unstable to ged good results.
You can use that blade, but you have to make a better holder which supports the blade similar to this one:
http://www.garvintools.com/cutting-tools/535/parting-tool-holder-clamp-type

Oh and the blade overhang should be kept as small as possible. And usually not exceed the height of the blade, especially in this small size. (larger blades can stick out a bit more but that will require a rigid setup and a constant infeed!)

Cheers Florian

[Gas_mantle]

Thanks Florian,

To be honest I think some of the trouble I have is technique and some is the tool. I did start off with one of those cheap RDG tools you mention when I first bought a lathe, it was enough to put a beginner off parting for life - I still suffer the trauma   

The tool I use now is this one, it is a vast improvement but I do still have trouble with it sometimes.

http://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/Lathe-Turning-Tools/Parting-Off-Blocks-with-M42-HSS-Co-Blade

I'll take note of the comments you make and perhaps treat myself to something better at a model engineering show I'm going to shortly.

I really ought to try parting off with a rear mounted tool, one of the reasons for recently upgrading my lathe was I wanted T slots on the cross slide for this kind of thing but haven't yet tried it.