Carbide parting tool for 250-000 toolpost.

[Rowan Sylvester-BradleyParticipant @rowansylvester-bradley37244]

I have fitted a 250-000 cuneiform toolpost to my Portass PD5 lathe. I need to fit a grooving/parting tool to it, preferably with replaceable carbide inserts. What is the best way to do this? One of the problems is that the 250-007 toolholder that is designed to hold parting tools already has a 5 degree back rake built into it. The carbide inserts and holders that I’ve found also have the back rake built in, so if i use one of these, there will be too much backrake. Why doesn’t someone make a 250-000 series parting toolholder without the backrake? Do I really have to make it myself? I surely can’t be the first person to have this problem?

Thank you – Rowan

 

[bernard towersParticipant @bernardtowers37738]

Cant you use a MGEHR holder in an ordinary toolholder?

[JasonBModerator @jasonb]

These holders will fit a standard tool holder and ar ewhat I use in my Dickson, slightly more overhang but not found that to be a problem myself

[DC31kParticipant @dc31k]

The parting tool sold by Greenwood Tools for many years was just a standard Sandvik item, cut in half and bolted to a length of square stock with two countersunk screws.

The advantage of this is that a deeper blade can be used for more stiffness than the Glanze holder, which has some material below the blade.

That could be an option and would fit in a standard holder with less overhang than the dedicated parting holder above.

[JasonBModerator @jasonb]

Though the ability to slide the Glanze type holders forward does allow you to part larger diameters than the Greenwood one with it’s fixed blade.

Still plenty of blade in the holder here parting a 70mm dia casting of not the nicest iron, holding by a 15mm dia spigot.

Measured the thin disc that I wanted afterwards and less than a thou difference in thickness from edge to middle so must be reasonably stiff, not a new insert either.

[Rowan Sylvester-BradleyParticipant @rowansylvester-bradley37244]

Those are all good suggestions thank you.
It seems that Greenwood Tools doesn’t exist any more.
Are the SPB226 Glanz style holders very hard and therefore difficult to drill and countersink? Are the Chinese ones which you can buy from Temu or AliExpress comparable to the Glanz ones? Maybe I’ll just try drilling one of these and screwing it to a 12mm square piece of steel stock (which is  the biggest that will fit in my 250-001 holder). Have to make sure I can get it lined up with the centre line of the lathe first.

Thank you – Rowan

[DiogenesParticipant @diogenes]

Screwing a piece of 12mm bar to a blade will leave it inadequately supported and liable to wander and twist.

Worth checking Warco & Amadeal both sell SLTBN holders that are cheaper than the Glanze ones.

 

[JasonBModerator @jasonb]

How do the warco holders grip the tool? The”Warco” branded image does show the usual top screws but the holder with the SLTBN code on it is not the same as the branded one. So maynot grip the blade as well. I like to suggest what I have used.

[JasonB]

On JasonB Said:

Though the ability to slide the Glanze type holders forward does allow you to part larger diameters than the Greenwood one with its fixed blade.

The Greenwood one was geared towards Myford-size lathes, and as above, maximised the seller’s revenue by cutting a standard blade in half. A full length blade could be used with more than two mounting holes, to give variable projection.

Non-Sandvik, generic GTN2 blades are very economic so could be a good basis for experiment.

[Diogenes]

On Diogenes Said:

Screwing a piece of 12mm bar to a blade will leave it inadequately supported and liable to wander and twist.

So are you suggesting that Greenwood were selling snake oil for many years? Their many satisfied customers might have a different opinion to your own.

[JasonBModerator @jasonb]

Maybe that is why the Greenwood one could only part upto about 40mm dia, not rigid enough for a longer tool projection?

[Rowan Sylvester-BradleyParticipant @rowansylvester-bradley37244]

I can’t see any screws at all in the Warco image. Not clear how it grips the blade.

[DC31k]

On DC31k Said:

On Diogenes Said:

Screwing a piece of 12mm bar to a blade will leave it inadequately supported and liable to wander and twist.

So are you suggesting that Greenwood were selling snake oil for many years? Their many satisfied customers might have a different opinion to your own.

I was responding to the OP’s most recent suggestion at the time – but is that really all the Greenwood ones were?

..I thought they were fixed to a more substantial ‘cheek’ for support.. ..weren’t the screws disposed in a vertical arrangement? – memory’s a little treacherous these days..

 

 

[DiogenesParticipant @diogenes]

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