a 1/8″ HSS cutter is more appropriate + cheaper (I have a Perris v similar to a ME90) – buy a cheap grinder and grind your own eg buy a ?20 one from Screwfix etc but make a better table that the flimsy one provided tho you don’t need to go to great trouble just more rigid square onto wheel with a very small gap between wheel and table – you can make up a few spacers to raise the HSS up the wheel to adjust cutting angle – once you’ve done it once or twice all the descriptions in various guides will make much more sense – make sure however that the cutting edge is at centre height when you mount it on the lathe

Edited By Frances IoM on 04/08/2018 17:37:52

Edited By Frances IoM on 04/08/2018 17:38:45

You could try making the tool a little narrower than the groove that you require, and move it from side to side as the groove deepens. Also, I had a similar problem a while ago on some rather "odd" brass, and found that a little negative rake helped a lot.

On enlarging the pic it looks as though the 1.5 mm blade is dull / has a radius on the cutting edge which is where I assume you mean …​'

…'gave a slight hone, which didn't help a great deal'…

​It needs to be really sharp on the tip otherwise you are 'rubbing' rather than cutting. I assume that you have the tip dead on centre height ( no insult intended ) otherwise you will be 'rubbing' just under the tip if the tool height is high, conversely if the tool height is 'low' then the tool will be 'dragged under' as the work tries to climb over the tool tip… broken tool / work / both.

​Once you start to 'cut' continue to feed the tool in at a steady feed, iirc your machine is too small to have a power x feed so you will be feeding in by hand, keep it steady & constant & you'll be ok. As with all of us at some time or other we have been frightened by parting off, gingerly feeding in then immediately withdrawing the tool as soon as it chatters, don't! keep the in feed going, with practice you'll soon get to 'feel' the cutting action & know when to increase / decrease the in feed.

As for lubrication…
Brass / Cast iron … dry.
​MS & other ferrous material… Neat cutting oil or similar applied with brush works fine, ( for me )
​Aluminium… WD40 does fine for me, other members use a variety of mixes so…

Enjoy

George.

I think you've got too much protrusion on your parting tool in pic 1.

The game is usually to set it accurately to centre height, minimum tool protrusion to reach depth or cut the piece off, as close to the chuck as you can get away with, about half nominal surface speed for starting, a sharp tool kept well into the job and maybe a spot of oil.

I would blame the parting tool holder, with that overhang there looks nothing much to stop the cutting edge pivoting on the front and lifting the back edge as the clamp looks very flimsy.

Side rake is to give clearance

It looks like you need to touch it on the bench grinder, not a hone stone. Edge should be about sharp enough to cut your finger.

It helps a lot, too, to lock the carriage and top slide while parting or grooving.

you definitely don’t want blood on cast iron milling tables – you can’t get rid of the stain – I know thanks to (mis)handling a milling cutter!

.

Steve,

Going by your photo … Yes that is a metric screw: The proportions of the heads differ noticeably between Metric and Imperial.

If it's M3 then the socket should be 2.5mm a/f … So I guess you were using a 3/32" a/f wrench.

Buy some better quality screws

MichaelG.

Edited By Michael Gilligan on 05/08/2018 16:33:49

0.5 pitch in my book for M3

Could also be UNC or even Whit as you often find odd sizes and poor screws on these type of holders