Some like to part off that way. I don't have too much trouble in the normal rotation (and the Raglan could only be used in reverse if a collet and drawbar were in use). I think it is more to do with how rigid the set up is, particularly the cross slide position on the saddle.

I built a rear tool post from a Hemingway kit & it does very well, especially on steel, I won't go into all the geometry as Geo Thomas, & others have explained it very well. I haven't used it for some time as with the small stuff I'm doing at the mo' the conventional front position works well. look in my album 'Rear tool post' for pics…

​Looks nice but too much overhang for centre alignment…

So modified for a more rigid set up… lovvly jubbly…

George.

I made a similar vertical parting tool and it worked very well. It was described in Thread: Parting Off MEW225.

Alan

Thanks Michael, I do appreciate that, I actually use an inverted tool in the rear toolpost of my Myford and also it's Warco clone.

One advantage of that is that the whole slide is lifted against the dovetails, rather than being pressed away from them, which surely helps improves rigidity as well.

I was clearly half asleep when I posted, and was thinking more of using the tool set lower in the toolpost as a shallow grooving tool, rather than for parting off.; then extrapolated to parting without thinking it through.

Down here in the West Country we talk just like Vicky in Little Britain. 'Yeah, but no, but yeah but no but yeah…'

I use a rear tool-post with a carbide insert parting tool and run the lathe in reverse. I do so because the geometry of the post and my tool-holder won't hold the upside down tool at centre height. Zut alors!

For me success in parting-off came from both rigidity and keeping swarf out of the slot. On my lathe the problem parting off using the front too-lpost is that the thing towers above the saddle and has many wobbly joints and adjustments.

The leverage involved in this lanky set-up means that a parting-off tool cannot be really rigid.

So, my experience is that a rear tool-post is a much more better arrangement even if the lathe is running in reverse and the parting tool is the right-way up. It's simply more rigid than the alternative.

In practice reverse cutting with a rear tool-post works well, though I accept that cutting forwards against an upside down tool should be even better. Although my 'to-do' list includes making a suitable rear tool-post, I'm not rushing because what I have is easy and produces acceptable results.

I've experimented with upside-down cutting and an HSS tool that does fit my rear tool post. I wasn't able to convince myself that gravity helps clear swarf out of deep slots. Whichever way up the tool is orientated, swarf jamming and/or welding to the tip is my big problem, even with generous lubrication by hand. Am I doing it wrong (again!) ?

Dave

More thoughts on RTPs + parting in general

Two types:

Inverted ones that run with lathe in normal rotation, benefit from pulling cross-slide up on to the vees and eliminating top slide

Non-inverted ones used with lathe in reverse that are very rigid.

The benefit of carbide tools? the 'scoop+break' shape generates relative short swarf that is also slightly v-shape in cross-section and so is less likely to jam in the cut. GHT's top-grooved tool worked in the same way.

Overall?

One of my observations is that people who part off under power-cross feed rarely report problems! Could it be that, as well as being a spur to eliminating obvious problems (like poorly set or blunt tools, or obviously felxible setups), task-specific tool-posts and specialised parting tools give the operator greater confidence, leading to a less cautious approach to the work and therefore improved results?

Neil

Dave, you need to get rid of the wobbly bits! Get one of these:

Very rigid and can be used anywhere on the cross-slide of my WM250. Can even be used as a rear toolpost with the normal topslide fitted as well. Details **here**

John

There's a lot in that I think. Watching a carbide parting off tool at speed really opened my eyes – I didn't think it was possible. Now I do it all the time and it gets easier the less I worry.

A big problem for beginners, especially us self-taught types, is getting a feel for how hard to drive our new toys. There have been many posts about stripped gears in small milling machines not to mention those reporting burned out lathe motors and fried electronics. Perhaps this is down to over-confident he-men thrashing their hobby kit? My novice errors were at the other extreme: tentative, erratic light cuts causing rubbing, chatter, disappointing metal removal rates and many dig-ins whilst not parting. For a while I convinced myself that my new mini-lathe couldn't cut steel at all; actually driven with appropriate confidence it was rather good at it.

Internet videos help but for quick learning there's no substitute for a tutor who knows the ropes.

I'd be encouraged if MEW issued beginner certificates:

• Bronze – Often mangles metal and/or breaks tools and machines.
• Silver – Eventually produces work more-or-less to size but can't guarantee a good finish.
• Gold – Works accurately and quickly with a predictably good finish. Isn't embarrassed by showing the results!

I'm about half-way to getting my Silver…

Dave