Inverted parting tool

[Andy SprouleParticipant @andysproule22368]

Hi,I have a boxford 280 lathe with a Bison dickson type toolpost.I was going to try parting off with the blade upsidedown and the chuck running clockwise but the holders can't be risen to centre height any ideas how this could be done?

[Andy SprouleParticipant @andysproule22368]

[JasonBModerator @jasonb]

Probably have to see if you can drill and tap the underside for a new height adjuster and then mount the whole thing upside down. Holders are quite hard so not easy to drill & tap.

[EmgeeParticipant @emgee]

I suppose another toolholder designed for the inverted tool is required,

Emgee

[Nigel Graham 2Participant @nigelgraham2]

Is there a particular reason for this approach though?

Usually, parting with an inverted tool is from a rear tool-post and the lathe running in the normal anticlockwise direction. It tends to be a more rigid set-up; but obviously needs a cross-slide capable of holding the tool-post.

[Speedy Builder5Participant @speedybuilder5]

What will stop the saddle lifting off of the bed ?

Is the chuck a screw on one ? if so, what stops the chuck unscrewing ?

[old martParticipant @oldmart]

You need to make a rear toolpost, then you can use any size blade in any size lathe.

[David George 1Participant @davidgeorge1]

If you have a screw on chuck just make the rear toolpost with the blade upside down.

David

[John ReeseParticipant @johnreese12848]

Inverted parting tools in a rear toolpost work so well because if rigidity an the fact that deflection tends to pull the tool out of the cut. When parting from the front toolpost, which is less rigid, deflection pulls the tool into the cut and tilts it to the left, both of which tend to cause jamming.

[Tony Pratt 1Participant @tonypratt1]

Old mart, I like your sturdy rear toolpost design, better by far than some of the flimsy 'designs' I have seen!

Tony

[Ady1Participant @ady1]

upside down rear post is the best and simplest solution

[HopperParticipant @hopper]

The Boxford 280 has a camlock chuck so parting off in reverse with a front mounted parting tool would be easiest. You can buy side-mount holders for parting blades that would then be clamped in the regular QC holder. Otherwise you might have to buy a QC holder made specifically to hold a parting blade. Use carriage lock to prevent lifting while parting.

Edited By Hopper on 27/02/2021 08:55:20

[Howard LewisParticipant @howardlewis46836]

Rear toolpost and inverted parting off blade gets my vote.

IF a rear post can be fitted, it is safe for lathes with screw on chucks and without securing dogs.

Works so well, that I am now brave enough to part off under power, with a fine feed..

Keep the tool overhang to a minimum, so that rigidity is maximised. having things that flex is ma recipe for problems.

Howard

[old martParticipant @oldmart]

Some more pics of my effort, the top part turns round to make use of both 26mm and 32mm industrial blades. I have blades 1.6mm, 2mm,3mm, 4mm and 6mm. The larger ones are too big to use for parting on the Smart & Brown model A, but could be useful for grooving. I also added a rear saddle lock to complement the front one to make sure the rigidity id not compromised by the upward forces. An advantage of inverted parting is that the swarf falls away better.

 

Edited By old mart on 27/02/2021 15:39:12

[Chris VParticipant @chrisv]

David George, just sent you a PM.

Chris.

[Andy SprouleParticipant @andysproule22368]

Thanks for all the replies tried to drill the underside of the tool holder drills including cobalt hardly marked it.

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