Gallery, Projects and General > How to's

parting of made simple

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stirling lad:
I saw this video from latheman on utube...
I thought his explanation about the blade being knocked clear of the work piece seemed wrong if he was cutting dead on centre but i gave it a try anyway,,,,,,, and it was AMAZING!!!!  i've never parted of anything so quickly,,, ok, ive only tried brass so far but what a difference... just by turning the cutter up-side down...


has anyone else done this ?? ..

...mike...

wheeltapper:
seems to me just the same effect as a rear mounted toolpost.

Roy.

DavidA:
Mike,

I can't watch the video at the moment,  problem of some kind. Getting error messages.
But from what is written it seems like you turned the tool upside down and ran the machine in reverse.  Is this correct ?

Problem is that if you do this on a machine with a screw on chuck then there is a very real risk of unscrewing the chuck during the operation.

Dave.

Arbalist:
Thanks for posting that Mike. I've been meaning to try one of these on my Lathe.

http://www.eccentricengineering.com.au/index.php?option=com_content&view=article&id=31&Itemid=45

Roy, many of us can't easily fit a rear toolpost on our Lathes so this is a good option.

Good point Dave but I think most mini lathes like mine don't have screwed on chucks. One to look out for though.

I'll certainly be trying this as soon as I can Mike, thanks again.  :thumbup:

BillTodd:

--- Quote ---I thought his explanation about the blade being knocked clear of the work piece seemed wrong if he was cutting dead on centre but i gave it a try anyway
--- End quote ---

He is right. The problem is that a parting-off cut requires considerable cutting force, enough to bend the machine (tool post top-slide cross-slide etc.) . The geometry of the machine means that as it bends it pushes the tool further into the job creating even more cutting force - a vicious circle that, with a parting blade*, usually results in a stall ,broken blade or worse.

Changing the direction of the cutting force, either by cutting in reverse (watch that chuck!) or using a rear mounted tool-post will bend the tool away from the job.

There are parting-off versions of the ancient spring-tool design that can do the same automatic backing off task.

Bill

*Chatter is caused by something similar.  Chatter occurs when the tool springs back out of the work as the thicker chip breaks. The combination of springiness and mass of the machine parts, means that is plunges back into the work and so the cycle starts again  - only reducing the cutting force will stop the cycle so oil, reducing cutting speed, changing cutting edge etc, will help to stop the chatter.

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