I have no preference at the moment but looking at your set up I have now got to make something like that. I am waiting for a casting to be done for making a new cross slide with provision for the rear tool post set up, once that is finished I will have the centre height to make the boring bar set up. Thanks for showing it.

Ramond if you hold all your boring bars like that what do you do when you want a tapered bore?

Also is there some way of stopping the sleeves rotating or do you have to twist the sleeve/tool about each time you fit one to get the tip on ctr height?

Edited By JasonB on 24/01/2016 16:53:32

You're a firm believer – but on what basis? Are you promoting the notion of sleeves as a sort of quick change system or you don't think they should be gripped directly? Why do baring bars (even carbide ones) come with flats on top and bottom?

I always try to minimise overhang anyway and if that isn't possible, put a piece of flat stock underneath to add rigidity.If you have a big beefy boring bar for a demanding job, does it really need further support?

It appears that some of the OP's boring bars (shown in the picture) are clamped in the sleeves by set screws anyway! Though TC boring tools sometimes have brazed-on tips, I've never seen one that is solid TC, though I am sure they would be better held with a "collet" style split clamp if it was. However the finish obtained looks exceptional.

Hasbean, The indexable bars with a solid carbide shanks are more rigid so you can have more overhang for a given diameter of bar.

I am aware of at least one manufacturer that makes the following distinction on the set screw issue. The http://www.ultradexusa.com catalog offers, "Use the right set screw! Flat point, not cup point!"  

Personally, I use a QCTP in a few ways to hold my boring bars.  1) A collet tool holder 1/2" shank and under.  2) A split sleeve in a bored tool holder. 1" shank and under.  3) A standard tool holder with a vee on the bottom slot. 3/8" shank and under.

Edited By MyrtleLake on 24/01/2016 21:58:30

(yawn). Haha, the first 3 I looked at use clamping screws direct to the bar, inc Sandvik. That's 3 out of 3? Over to you to show where it says not to clamp directly?

It seems most likely that the cause of breakages would be clamping to a non-flat surface, in which case it won't matter whether the screw contacts directly or not. That's just good housekeeping.

The sleeves and the large solid toolpost make sense. Much of the surface finish problem with boring is often vibration. I've seen old timers clamp a pair of vice-grips onto the toolpost end of the boring bar to "soak up" the vibration and give a better finish, and seen others wrap straps of rubber bands cut from old inner tubes around the boring bar to dampen vibration. It seems like the all-surrounding sleeves and that big square block of a toolpost might do a better job of soaking up any vibration/ dampening harmonics etc.

I use a big solid toolpost mounted direct to the cross-slide for most of my turning except tapers that require the topslide. Gives a better finish and allows heavier cuts too.

I agree for some jobs like bigger bores on awkward materials a toolblock would be more rigid than a bar held in a QCTP but for most model size machining the resulting  surface finish on a bore is more to do with the material , angles and tip radius of the cutting edge than it is with how the boring bars clamped at the toolpost . for my solid carbide bars with shanks from 3 to 10 mm dia i use bits of of 1/2-3/4 square steel bar bored out a good fit on the shank and a couple of grub screws to hold them in place , made them after snapping a small bar in half when i put it in a vee block.

regards Geoff

Edited By Kettrinboy on 25/01/2016 09:23:33