GHT Rear Toolpost 8deg milling cutter

Salty

When I made mine it was made on the lathe only before I had the luxury of a mill. The flutes were cut using a 1/4" milling cutter in the chuck and holding the embryo cutter in the tool post. The centre was relieved using an form tool ground on the end of a tool bit plunged into the end. The relief allows the cutter to cut more freely without rubbing in the centre.

John

Edited By John Purdy on 03/01/2021 22:05:27

Just for completeness here is the information on my other parting tool holder that takes a conventional HSS blade which is retained with a wedge.

These have given trouble free service for a few years now.

Phil

Just for completeness (from my experience), - my advice would be to avoid those ‘cutters at an angle’ designs like the plague. I have one (bought as part of a set when I bought a QCTP but I only used it a couple of times. I know overhang with parting tools needs to be kept to a minimum. Changing the extension of the blade needs the tool height resetting every time the cutter is moved. No thanks, that type is not for me. I’ll stick to a parallel holder!

I made the rear tool post nearly 30 years ago. From memory once I had machined the dovetail the cutter was then filed the cutter before hardening. One good thing at the time was I had access to a heat treatment shop who hardened it in a salt bath.

The cutter worked with light cuts. Saw it in the last 12 months, took a while to remember what the cutter was.

My rear toolpost is a QC one that has height adjustment so the extension of the tool blade can very easily and quickly be set to the correct height.
I find having the tool blade at an angle gives me an automatic top rake which certainly cuts better, and means the blade is very easy to keep sharp by cleaning up the end face only.
Each to their own though, if you find a horizontal blade suits you best, then I am not going to try and convert you.

Phil

PS.

I just noticed on your profile you are into Moggie Minors, what do you have ?.... I have a 1969 Traveller
I always fancied a "Black Bomber" as well, but still have my 1972 XL250.

Edited By Phil P on 04/01/2021 12:09:33

Edited By Phil P on 04/01/2021 12:10:33

Hmm! I missed that & I've already hardened it. I could relieve it with the Dremel & a small burr.

Yup, I'm Mill-less too, everything has been done on the lathe with 4jaw/3jaw & angle plate. I used the Dremel with a greenstone burr clamped to the angle plate to cut the flutes. I had the cutter in the 3 jaw & used the bullwheel & backgear as a makeshift indexing system. A lack of toys certainly makes you think out of the box, which is half the pleasure tbh. I'll have a look at relieving the centre of the cutter.

All my parting off is done with a 3/32" wide tool set to horizontal in the back toolpost, and with Zero top rake. This removes the need to reset the tool height after every regrind, and reduces the risk of a dig in.

This arrangement works so well that I am now brave enough to use power feed (0.0022"/rev ) for the job.

To give some confidence:

Normally long tool extensions are avoided, but, with lubrication, it has successfully parted off a 4" diameter Aluminium bar!

Howard