tnmg inserts

The higher rake CCGT also work very well on brass and you don't get the shower of fine chips that a zero or very low rake tool gives, I use them on all non ferrous metals.

I must admit to using the DCGT intended for aluminium/non-ferrous on steel as well, 0.8mm radius tip.

Works a treat for me for finishing with swarf like dust (wouldn't risk a heavy cut with it though)

Paul

One of the reasons i brought this up was that i`m making a fly cutter ,along the lines of the suburban tools flycutter. Ive got most of it finished and attached to a MT4 arbor from my Alexander mill . I bought some negative inserts Walter TNMG inserts cheap off ebay (10 for a pound).

The hole through them is a straight hole ,not much  chamfer to the holes.BUT what type of screws do i need for fixing them to the bar i have to make the cutter. As far as i can tell the hole is around 3.5 to 3.6 mm??? Do i need pan head special screws or what ???

Thanks

Edited By mark smith 20 on 18/09/2017 15:56:42

Edited By mark smith 20 on 18/09/2017 15:57:25

Edited By mark smith 20 on 18/09/2017 16:04:26

Hi

Tools using inserts with a plain straight hole don't use screws for clamping, they have an internal and/or external clamp arrangement where a screw acts on a lever and the lever clamps the insert.

I would imagine the leading manufactures will have some information on their websites.

Nige

Edited By tractionengine42 on 18/09/2017 16:13:50

They're not intended to used with screws. Instead the hole fits over a post and the insert is clamped by a variety of methods, depending upon the holder. So you're on your own with a screw; whatever fits, but it'll need to be a precision fit, as will the holder, or the insert will move.

Andrew

Dammit, too slow

Edited By Andrew Johnston on 18/09/2017 16:07:42

Can't help thinking that the bottom edge of that insert will rub without any clearance unless you are swinging a very large arc. Probably better with a TCMG with 7deg clearance

If you look down around p142 of this reference work from Mitsubishi you'll see many options for triangular with hole. And note that the **GT inserts are not exclusively for non-ferrous work. They can also be used on steels etc.

For a flycutter you may benefit from a "wiper" insert. This would reduce the ridging and improve surface finish.

Murray

So they can be held by a screw ??? I have seen 3.5mm insert screws with pan head but dont know the thread details.

In case anyone hasnt seem this video , but this is the sort of thing ,im basing it on. Jason insert seating is tilted to give clearance. I dont know if my hodge podge will work but i can always try and see.

**LINK**

Thanks for your experience Dave!

If one has to have the lathe flat out with big cuts and lots of coolant. Then I will definitely stick to HSS. Simply because I would never land on the exact diameter required with a big cut! I am a "creep up to the required diameter" type of person. I suppose this separates the men from the boys in model engineering skill. I am definitely a boy!

Thanks,

Andrew.

Andrew and NIge, looks like i`ll have to find different inserts or different way of clamping. ,the hole though the insert is more around 3.75mm so m3.5 screws wouldnt work.

Well i decided to try the inserts ,using M4 high tensile caphead screws. I reduced the diameter very very slightly so that the screw would pass through the insert which happens to be 3.81mm for some reason. I managed to drill and tap for the screw accurately and when screwed down appears rock solid. I had to guess the lean back on the toolholder for clearance for the insert. The bar is an old 20mm Sq. lathe tool shank.

Some photos showing the flycutter adapted onto a morse taper 4 stub arbor the actual fly head is pretty heavy and around 3" x 3" steel. I read that a higher mass head puts less stress on the head bearings. It appears to work great with no shaking .juddering or noise. I made two keys to mate with the flats on the arbor .

I tried auto feed at first the aluminium block didnt seem to like the slow feed (i unfortunately at the moment cant really change the feed speed as i dont have the set of change wheels for the mill.)

I tried a slower speed and quite fast hand feed and this is the result. Not quite mirror finish but almost. This is my first attempt at flycutting and i dont know if i have the correct inserts .Maybe sharper polished ones specifically for aluminium would give a better finish. The suburban tools type specify tnmg 243 inserts but im not sure what they are . The ones i used are made by walter and seen above ,i think they have a 0.4mm radius, maybe a larger radius gives a nicer finish ,i dont know.

Edited By mark smith 20 on 21/09/2017 20:20:37