Q about lathe tooling

[Old tool guy]

Everything i know about lathe work, i learned here and youtube. I like watching Cutting Edge Engineering, the australian guy. Here is a closeup picture of the tool holder on one of his lathes, can anyone explain the shape of the bolts? Threaded shafr with a square drive on top … got that. But why is there a spherical section in between?

 

[larry_g]

probably hot forged from round stock.. no other reason for the spherical section.

lg

 

[GeoBruin]

This cutting edge engineering videos always seem to follow me. I'm sure some algorithm suggested the first one, and then when I got sucked in, it just reinforced to the algorithm that I'm a sucker for watching big machines do big machine things, so they pop up all the time.

Anyway, I agree with Larry and beyond that, I have no idea why the shape. The bigger question in my mind is, why is he using a 4-way tool post? Do QCTPs just not come that big or are they less secure for big cuts or is it just cheaper?

 

[dutchgray]

This cutting edge engineering videos always seem to follow me. I'm sure some algorithm suggested the first one, and then when I got sucked in, it just reinforced to the algorithm that I'm a sucker for watching big machines do big machine things, so they pop up all the time.

Anyway, I agree with Larry and beyond that, I have no idea why the shape. The bigger question in my mind is, why is he using a 4-way tool post? Do QCTPs just not come that big or are they less secure for big cuts or is it just cheaper?

He does have one big Dorian ? QCTP, but they are less rigid, very expensive in the large sizes and in reality if you are organised and have your tools paired up with the correct shim there is almost no advantage to having one.

You rarely see QCTP fitted on large lathes that are actually used for heavy turning.

Those toolpost screws, that's just how they have been made.

 

[F-22]

I also think it is mainly just due to cost. A big QCTP is a big expense. Alternatively you can also have 2 or 3 of the 4-way tool posts and just get the nut off and pop it off entirely. Making the 4-way tool post with a manual mill is much easier than making dovetail joints (requires dovetail cutters), not to mention multifix grooves and holes...

 

[alfadan]

From what he shows, he really doesn't use that many different tool types so if they're all the same height there's no need to shim the insert holders, and he can hold at least two tools in the 4 way holder.

 

[2oolhound]

But why is there a spherical section in between?

If you used a square box end wrench the sphere would prevent the wrench from slipping down on the threads. It holds the wrench up where it's needed.

 

[isb cornbinder]

This cutting edge engineering videos always seem to follow me. I'm sure some algorithm suggested the first one, and then when I got sucked in, it just reinforced to the algorithm that I'm a sucker for watching big machines do big machine things, so they pop up all the time.

Anyway, I agree with Larry and beyond that, I have no idea why the shape. The bigger question in my mind is, why is he using a 4-way tool post? Do QCTPs just not come that big or are they less secure for big cuts or is it just cheaper?

I am subscribed.
In one of the CEE videos, Curtis explains the QC tool in one of the videos.
This is my favorite video channel. I do not watch the bloopers at the end. The bloopers are too childish.
It is very likely the tool-post bolts are forged.

 

[dutchgray]

From what he shows, he really doesn't use that many different tool types so if they're all the same height there's no need to shim the insert holders, and he can hold at least two tools in the 4 way holder.

You always need to shim the tool holders, unless you have holders that are too tall and mill or grind the underside until they are at the perfect height.

I use pieces of gauge plate for the purpose, it's best to only use one shim under the tool.

 

[alfadan]

You always need to shim the tool holders, unless you have holders that are too tall and mill or grind the underside until they are at the perfect height.

I use pieces of gauge plate for the purpose, it's best to only use one shim under the tool.

You are correct, I misspoke. I meant not having to change between a bunch of different shims.