Solid Toolpost and Rear Toolpost

[Ian Moss]

Well..... How did it work? Or did you chicken out like I did the first time around?

I recall that I was initially afraid of lifting the cross-slide off the bed. But in practice that doesn't happen because the geometry is biased to let go instead of digging in. Digging in is bad even when directionally toward the bed. So all in all it was an awesome experience once the dust cleared.

Given a choice, I'll prolly always try to part properly. However, when the going starts to fall apart - as it often does - I'll flip the tool and cut in reverse in a heart beat! It has always worked!

Didn't see your post and question until this morning. I had not tried it before, but since you asked, I chucked up a piece of 1.5" mild steel bar and parted it off with the rear post and an insert type parting tool at a fairly high rpm and it cut beautifully without any hint of lifting or chatter. Remounted the tool in the front position and it cut just a well ......so maybe mostly useful if doing repetitive turnings and partings without having to change tools.

 

[Tom O]

 

[RobinHood]

That is a very good diagram @Tom O. It illustrates well what is going on.

 

[Susquatch]

For those who don't have the opportunity to put the tool at the rear, it works the same way mounted on the front if the tool is flipped upside down and the lathe is run in reverse.

I tried to find the photo that someone posted that showed the inside of a pipe gouged out from a runaway parting blade. The photo that @Tom O posted above shows why that can't happen parting from behind or in front in reverse.

 

[YYCHM]

@Susquatch This one?

 

[Susquatch]

Yup, that's it!

It's absolute proof of what happens when the tool digs in.

That's the reason I like to part upside down in reverse. That cannot happen!

 

[YYCHM]

Yup, that's it!

It's absolute proof of what happens when the tool digs in.

That's the reason I like to part upside down in reverse. That cannot happen!

A big part of that episode had to do with my x-slide screw and nut being worn out and having a lot of x-slide slop, that and the funky tool holder I was using.

 

[PeterT]

Not for screw on chucks or short height tool posts, but maybe just flip the tool & run lathe in reverse.

 

[Susquatch]

A big part of that episode had to do with my x-slide screw and nut being worn out and having a lot of x-slide slop, that and the funky tool holder I was using.

Prolly so. The angles would have loved the slop and yanked it in. But still, it wouldn't have happened in reverse or from behind.

I took a good look at my cross-slide. I'm pretty sure I can add another tool holder at the rear. Just not sure if it makes sense to allow for angular adjustment.

 

[Susquatch]

Not for screw on chucks or short height tool posts, but maybe just flip the tool & run lathe in reverse.

Yup. Exactly.