Lathe rear parting tool

[Pescadora]

Not mine, and no comment by someone unqualified to make one.

 

[mikey]

Good job! Those of us who have this tool love it.

 

[Pescadora]

deleted

 

[Manual Mac]

I’ve been trying to come up with an idea for making one for my SB9.
Been thinking for years, & nothing’s happening.
But…I just remembered, I have this table I made years ago before I bought a mill.
it’s 4”x 8”x 5/8”, with a spigot on the bottom so it will bolt to the cross slide with the compound off. It’s as accurate as i could make it.
Thanks to you guys, I will now make one, roughly adapt those plans, bolt it to the table & Bob’s yer Uncle.
Cheers

 

[Wheat.Millington]

Someone help me out here as a beginner - I can't get my head around why a rear mounted parting tool makes a difference??

 

[Zertsman]

Every connection between parts from the Ways on the lathe bed up to the tip of the parting tool can have some sort of flexibility or movement. On their own, they are small or possibly unmeasurable. Add them all together and all sorts of strange things can happen.

Making a solid connection with no adjustment, (center height is guaranteed) removes all the other parts and their connections, lubrication and things from the equation. many problems go away and you likely will have a larger operating envelope in some other areas for parting.. more materials, bigger/smaller diameters..

on a machine tool, stiffness and rigidity is everything.

 

[Pescadora]

deleted

 

[mikey]

Someone help me out here as a beginner - I can't get my head around why a rear mounted parting tool makes a difference??

Have a look here. It might answer some of your questions.

 

[SLK001]

It is clear to me now that all the problems with parting stem from the flexibility in the tower of moving parts that held the tool. Take most of them out of the equation and the difference is profound.

Yeah, but this method takes none of them out. The cutting forces with this contraption is UP, away from the ways - and the apron isn't tightly held down against up-lift, so rigidity isn't what this is giving you.

Also, this design is likely to give you fatigue cracks at the flexure point over time, faster for aluminum, slower for steel.

 

[Pescadora]

Yeah, but this method takes none of them out. The cutting forces with this contraption is UP, away from the ways - and the apron isn't tightly held down against up-lift, so rigidity isn't what this is giving you.

Also, this design is likely to give you fatigue cracks at the flexure point over time, faster for aluminum, slower for steel.

I yield to a superior opinion. I should not post on a forum where I know so little.