Depends on the job. Small parts hand feed but say 20mm+ then normally power feed. Start by hand to make sure nothing feels untoward and then engage the power feed. This is on a Boxford

Nearly always

Almost always, my lowest available feed rate is 0.03mm/rev, (or 1⅙ thou per rev in old money) so there's never a reason not to.

I will sometimes use manual feed on the first few parts if I'm if I'm making multiples of something small but with a high length to diameter ratio, but that usually means I'm trying to work out how fast I can feed without the part deflecting to select a feed rate.

Edited By Jelly on 23/03/2023 13:04:14

Nearly always, rear post 40mm EN1A diameter 800RPM feed 0.05/rev works well if the lube is plentiful. Nervy pussying around is a disaster.

Almost always on the BL12 – 24.at 0.0025"/rev mubricated by brushing onand ordinary engine oil or soluble oil controlled feed through a needle valve.

On the mini, it has to be hand feed, but have just made and installed a rear toopost, so hope for betterb things.

Howard

Edited By Howard Lewis on 23/03/2023 18:35:38

Actually the thing I forgot to mention is matching the parting blade geometry to the material. It's something we think about all the time for other toolbits, but sometimes gets disregarded for parting blades.

I once did a job for a friend which involved lots of parting off in copper and some stringy horrible grade of brass, it was all a bit grabby unless I used a really slow feed, having quite a few to do, I specifically ground a parting tool with a small negative rake, and like magic I could suddenly feed at a much higher rate.

Similarly I have a brazed carbide parting tool which is preserved for stainless which is much wider (about 4.5mm) with a reasonably positive rake and chip breaker ground into the top face of the brazed insert, the shape helps reduce cutting pressure when taking the more aggressive feed rates needed to successfully cut stainless, whilst the thicker tool gives sufficient support for such heavy cutting forces.

Power feed (CNC), upside down parting tool and lubrication is my way using a SP200 2 mm wide insert, 800 RPM (max to keep the lubrication on the part) and 0.02 mm/rev.

After parting off years at these conditions on both my lathes, I recently started parting off steel dry to allow higher RPM (higher speed). I am not sure if this is a better condition, will try it for several weeks.

No you are not. Hand feeding can do the job also and if you are experienced and have good results why not.

Some times I also use a 1.2 mm HSS parting blade in normal position and manual feed. When I have time, I will make a tool holder for a 2 mm HSS Co8 blade that I want to try.

"The opinion was that the practice was an absolute no-no. So I went back to using a hand feed."

And that's exactly what it was, i.e. someone else's opinion. My own view is that there are no 'absolutes' in the privacy of your own workshop. If a technique works for you and produces a result that is acceptable to you, then you must be doing something right no matter how much 'inspector meticulous' may think otherwise. I have easily parted 5" noggins to make back plates for the Myford.

My own approach to parting-off is to use a combination of both hand and power-feed. I don't have the luxury of choice on the Myford but on the Colchester I use both hand and power feed. I always part from the rear tool-post, which should be as large and rigid as the lathe will permit, I keep the tool kept as sharp as possible and I always pump coolant in to the cut. I accept that some people can't tolerate the thought of something containing water being allowed anywhere near their cherished machines, and I understand that to a certain extent and also that it can be a little messy if the stream hits the chuck, but to me it makes any cut so much smoother and it was standard practice in the machine shop where I was once an apprentice. I use a cheap soluble oil diluted about 25:1 with a squirt of Rocol coolant disinfectant that kills the black algae in the sump when the machines are not used for a while.

By hand here too – because that's how I was taught in college at the start of my apprenticeship back in 1973!

Fortunately I'm blessed with a steady hand and pretty good "feel" so don't seem to suffer with some of the problems others have described. Think I might have a go with power feed now though particularly as I have been very impressed with the insert parting tool I now have – never too old learn a new trick after all. Having said that I seem to mostly work with stainless or aluminium which often sticks to the tool.

If I recall correctly it is the G H Thomas workshop manual book, where he describes a rear toolpost, that recommends parting off using power feed. Apparently he used to gives demos on a Super7 at exhibitions.