Carbide insert tools for lathes.

Hi Chris, we used to have tangential threading tools and parting tools. They do work great and are easy to resharpen. What I like about the carbide stuff is I can have the heights on the tools set, and then forget. I have 3 lathes all with dickson type toolposts and all tools will interchange on the centre heights. No need to adjust tools from one machine to the other.

Neil

Thanks for the advice. I bought a CCMT one and various tips from RDG in the end.

Usually I grind crazed carbide tools to how I want them, but it's not really a favourite job!

This arrived today and I've had a quick go with it. The CCGT are very good on aluminium, a very smooth polished finish.

Any advice for feeds and speeds on EN1A using CCMT?

> Any advice for feeds and speeds on EN1A using CCMT?

Flat out! The insert will be perfectly happy peeling off heat-blued chips. Depth of cut will be determined by your machine.

I've used 1200 rpm, 0.75mm depth of cut and 0.004" feed on 5/8" bar in my lathe, but it was a bit scary compared to what I'm used to.

Neil

It's a Harrison so fairly rigid!

Top speed is 2000rpm.

No coolant?

This talk of tangential tools has lost me .. anyone got a link to a picture?

Try the Eccentric Engineering advert on the right of the page

Hi JC

Have a look at the ads to the right of your post, up about 2.5 at the moment for Excentric Engineering .

Cheers Michael

My rule of thumb for ruffing is max depth of cut is 5 times the radius, and a feed rate of 1/2 the radius.

For finish cuts, I use 1/6 the radius for a fine finish, for general finish I use 1/4 radius as the feed rate, and depth of cut to being genrally 1/2 the tool radius.

Some lathes do not have the power or rigidity to run these ruffing numbers with anything bigger than an R0.2mm cutter.On my S7, I use R0.2mm TNMG tools, with 4340 or 4140, cut depth is 1mm on radius, 2mm diameter, but only a feed rate of 0.004 inches, about 0.1mm per rev. For finish passes , I use 0.2 to 0.4 mm on diameter. RPM wise, I think it is 690 rpm or so, the fastest on the slow pulley. As for a coolant, I use cooking oil.

Neil

There is an example of the tangential lathe tool on page 119 of volume one "Model Engineer and Amateur Electrician" July 1898

For many materials it's hard to beat a really sharp piece of HSS no matter what size lathe you're using. I guess its not an option though for Industry these days. It cost me nothing to make my Tangential tool and runs on a few pennies of HSS a year.

For really hard stuff though insert tooling comes into its own in the home workshop. I found this out trying to take the crust off Cast Iron. Solid carbide mounted in a Tangential tool is an option but I don't yet have a diamond wheel so trying to sharpen the stuff if problematic. The problem with insert tooling is the cost. Large three or four sided inserts used on industrial machines don't seem to work on hobby lathes very well even if you can get a holder for them. It's a shame as they are normally double sided as well giving you 6 or 8 cutting edges. Insert tooling aimed at model engineers only have two cutting edges and from what I've seen are a similar cost to industrial ones. In real terms then they're 3-4 times the cost and are much more fragile. As a result of this I've found the best compromise is to only use insert tooling when I need to.