Recommend a threading tool for Warco WM250

Hi

I would like to get down to doing some threading on my lathe which I have had for a while, its a Warco WM250V. I usually use 12mm shank tool holders and inserts, though am not averse to grinding my own out of HSS! At this stage its just for practice.

I would be looking at threading on aluminium (I have 6082 at the moment) or mild steel mostly.

Do I need two separate tools for ally and MS, or can I do that with the same kind of tool? I know alu tends not to want to break into chips too readily after some... fun experiences with turning!

Is there a tool you have had good experiences with / specific supplier?

Cheers!

I've only ever ground my own from HSS. The last one I used was a Whitworth 55 degree tool I ground in 1975 from a 1/2" square HSS blank my father-in-law gave me, on 1" BSW steel bolt. I've used it for alli too - it's got about 10 deg. top rake on it so it works well enough for most stuff - I think it'd probably be OK on brass or suchlike too.

I guess I use 8mm square blanks mostly for screwcutting tools, and 1/4" square for most other work.

Other things about the setup - workholding and component design - are generally far more influential on the way you do a screwcutting op than the cutting tool itself. For example, threading a nut to an internal shoulder may be better done turning the chuck by hand than under power.

First thing is to decide between Imperial and Metric because the flank angles are different - 55° and 60°, and also internal or external threads or both.

As I mostly cut smallish internal and external metric threads I bought this set from RDG. The holder for internal threading is like a boring bar - designed to fit a hole. The shank size may depend on the size of hole you work with in that an 8mm holder will go places a 12mm holder won't. But 8mm has less reach and is more likely to chatter because it's thin. Apart from threading, I use 12mm tools in my lathe wherever possible because they are stiffer, but I have a fair selection of 10mm (compromise on size & price), and 6mm occasionally come in handy for tight work.

I use the same inserts on Aluminium, Steel and Brass. I don't know if a metric holder would take 55° Imperial inserts or not. I suspect not.

If you want to cut big coarse threads the inserts in the RDG sets will probably be too small. Look for holders taking larger inserts.

Provided the holder will take the insert and isn't cheap and nasty, I don't think there's much need for anything posh. The professionals pay extra for improved tool rigidity, I just experiment on the job to minimise chatter.

Two possibilities if you're having worse than normal bother with Aluminium

• it needs lubricating with paraffin or similar, OR,
• you have a type of Aluminium that won't machine well whatever you do. Pure aluminium and alloys intended for extruding are soft and tear easily. Sharp tools help, but when buying I always tell the man I want to machine it.

Dave

Edited By SillyOldDuffer on 29/07/2019 16:19:27