Parting-off

[JAParticipant @ja]

On my Myford I use a rear mounted tool post with the parting off tool mounted up side down (chuck running in the usual direction). As long as a cut is being taken in a positive manner (without dithering) there are no problems. I did use the power cross feed, again without any problems, but ceased after being told on this forum that it was a real NO-NO. I note that Jason uses power cross feed.

I have a rear tool post on my Cowell whose chuck screws onto the headstock shaft. However, as yet, I have only used the normal toolpost for parting off.

Geo. H. Thomas used forced diagrams to explain why a rear tool post worked. They made absolutely no sense. I note the comments about the possiblity of lifting the carriage etc but I think the drop out of swarf from the kerf (thanks for the new word) is very important especially after looking at how quickly it filled up with bronze chippings with the Cowell.

I find parting off to a hole very much easier than to solid. Also I always try to use a rod up any such bore, from the tailstock, to catch the parted off item. I once had a largish item fall between the bed and four jaw chuck. Fortunately nothing was hurt.

So, for me, use rear tool post on Cowell and power cross feed on Myford.

JA

[noel shelleyParticipant @noelshelley55608]

As Andrew has said, Cut Off Slide, Myford made 2, a screw operated one (which I have ) and a Lever Operated one (more common). They were clamped to the bed in the required position and wound across to cut off. They were part of the repetition gear that turned a Myford into a production lathe. There were 2 capstans available, a cross slide mounted one or the very expensive bed mounted Proper capstan, add the lever operated collet chuck and your away ! Noel.

[peak4Participant @peak4]

Thinking purely Myford 7 here, another reasons I suspect some folk find a rear toolpost advantageous for parting with an inverted cutter;

You are pulling the tool towards you using the opposite side of the feed nut, using the distant end of the feedscrew, and the least worn farthest end of the top slide dovetails.
You are loading the dovetails upwards which reduces the possibility of vertical movement, as well as increasing the front to back friction.
All of this makes the setup slightly more rigid and less likely to allow a dig-in of the cutter.
It’s also loading a different area of the main bronze cone bearing on a Super 7, or a different section of the softer bearings on an ML7.

Bill

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