Boring Bars.

[Raymond AndersonParticipant @raymondanderson34407]

During a recent thread concerning boring bars which included a discussion on methods of holding the bars. I am a firm believer in sleeving all bars. Solid sleeves for steel bars, and Split sleeves for Carbide bars. The reason for split sleeves for Carbide is that no screws are to bear directly on the Carbide because that really is a "no no ". This is a picture of my method of holding all me boring bars. The steel in shot is En 24t and is for thick washers for slitting saw arbors. All the sleeves are made from EN24t

What are fellow members preferred method of holding their boring bars.

[Raymond AndersonParticipant @raymondanderson34407]

[JasonBModerator @jasonb]

You can't beat a good G cramp or two

6" long bore in CI, 25mm bar with 1/4" dia HSS bit, no measurable taper.

Rest of the smaller bars go into the QCTP and held by the screws, I don't have any with carbide shanks. Bars with flats in a flat bottomed holder, round bars in a holder with a "V" bottom.

Edited By JasonB on 24/01/2016 16:33:59

[Chris Evans 6Participant @chrisevans6]

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.

[Thor 🇳🇴Participant @thor]

I use sleeves like you Raymond, except for one boring bar made from square bar.

Thor

Edited By Thor on 24/01/2016 16:35:55

[JasonBModerator @jasonb]

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

[Michael ToppingParticipant @michaeltopping17870]

I use a QCTP for all boring bars, never had any problems. Seems to me to be a lot of work making up the sleeves etc for what advantage?

Michael

[Raymond AndersonParticipant @raymondanderson34407]

Hi Jason, The toolblock in the photo is En 19 and it is "split " Once the sleeve is in, the cap heads on top are tightened up that stops the sleeve from moving. It results in a very rigid set up. All is machined so every bar is at exact ctr height. I did think about making an index pin, but often its a good thing if you can slightly turn the bar [depends on the Material and the insert ] so decided against the locating pin. If I ever needed a tapered bore I have a toolholder for the QC toolpost that accepts the sleeves to allow me to use the top slide.

Chris, I will post a pic of the toolblock It is straight forward to make, Just make sure that the bore is a very precise fit to your sleeves { what ever size you decide to make them ] and it pays to have a very smooth surface finish on the bore of the tool block and the external / internal dia of the sleeves. Achieve those 2 critical areas and you will have a very rigid set up. Me biggest Carbide bar is 32mm and me biggest STEEL shank one is 40mm . I have the same set up for those {just bigger } The one in the pic accepts up to 25 mm dia.

[Raymond AndersonParticipant @raymondanderson34407]

Michael, The advantage is in "Rigidity " If your method keeps you happy then thats fine.

The toolblock and sleeve method is far, far, more rigid than any QC tool holders. and that is reflected in the surface finish. Prior to me toolblock, I used the normal method and, like you was very pleased.. Then it was pointed out to me about the toolblock /sleeve style and It is chalk and cheese.

[MuzzerParticipant @muzzer]

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?

[HasBeanParticipant @hasbean]

Can I ask what are the advantages of a carbide boring bar?

Paul

[John HaineParticipant @johnhaine32865]

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.

[Raymond AndersonParticipant @raymondanderson34407]

Hi Muzzer, On the basis that me brother [who is a foreman turner ] pointed it out to me, and I think he knows a bit more about it than me. Re, the flats on Carbide bars,. I cant answer that, but Sandvik ,Walter,. Arno, et al, all say NO screws should bear directly on a "CARBIDE " bar and prior to knowing about that I broke a Carbide bar by having the screws directly on the bar [ broke right at the middle screw ] That was an expensive lesson that I have no intention of repeating. A lathe is no different from a milling machine in respect of Rigidity, the more the better. If you were to try the normal style over the sleeve / toolblock style then you would see the difference. [It would probably make no difference to what most of us make ] but the difference is apparent.

[JasonBModerator @jasonb]

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

[Raymond AndersonParticipant @raymondanderson34407]

Hi Muzzer, On the basis that me brother [who is a foreman turner ] pointed it out to me, and I think he knows a bit more about it than me. Re, the flats on Carbide bars,. I cant answer that, but Sandvik ,Walter,. Arno, et al, all say NO screws should bear directly on a "CARBIDE " bar and prior to knowing about that I broke a Carbide bar by having the screws directly on the bar [ broke right at the middle screw ] That was an expensive lesson that I have no intention of repeating. A lathe is no different from a milling machine in respect of Rigidity, the more the better. If you were to try the normal style over the sleeve / toolblock style then you would see the difference. [It would probably make no difference to what most of us make ] but the difference is apparent.

[Raymond AndersonParticipant @raymondanderson34407]

Sorry for the double post I got way laid . John, The bar seen on the lathe is a Carbide one and is held in a split sleeve [shown in another pic ] The other bars in the pics are steel shank ones not Carbide and can have screws bearing directly on them. All me carbide bars are held in split sleeves.

The finish you see is typical of what I get now. Prior to the sleeve /toolblock style, I used the normal style and although rhe finish was nice it was nothing like what I get now. Even on EN3 [ which is usually a swine to get a great finish on ] the finish is much the same as in the pic. the correct insert also helps.

HasBean, Normal steel shank bars can go out to around 3 x bar diameter. Carbide up to around 7 x because Carbide is more rigid [ there's that word again ]

[MuzzerParticipant @muzzer]

Posted by Raymond Anderson on 24/01/2016 18:35:05:

Hi Muzzer, On the basis that me brother [who is a foreman turner ] pointed it out to me, and I think he knows a bit more about it than me. Re, the flats on Carbide bars,. I cant answer that, but Sandvik ,Walter,. Arno, et al, all say NO screws should bear directly on a "CARBIDE " bar and prior to knowing about that I broke a Carbide bar by having the screws directly on the bar [ broke right at the middle screw ] That was an expensive lesson that I have no intention of repeating. A lathe is no different from a milling machine in respect of Rigidity, the more the better. If you were to try the normal style over the sleeve / toolblock style then you would see the difference. [It would probably make no difference to what most of us make ] but the difference is apparent.

That's funny. When I look at the brochure for the carbide shank boring bars I bought recently, the sleeves they sell for them have grub screws to hold the bar in place. Perhaps your brother should write to them to tell them where they are going wrong? When he's at it, he should also get in touch with Simtek who also don't seem to know what they are doing.

If it really is necessary to avoid contact with the set screw, I would use a "packing piece". I often do this if I'm concerned about damaging the top of the tool. Much less palaver than making up a vast system of sleeves and holders?

Merry

[MyrtleLakeParticipant @myrtlelake]

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

[Raymond AndersonParticipant @raymondanderson34407]

Muzzer, Try reading the post correctly ,it is Sandvik, Walter, Arno, ect that recommend that no screws should bear directly on the Carbide bar. Maybe once you break one, then you will understand why !! You stick with you're set up, I will certainly stick with mine. In fact, if you could bore a piece of EN3 with the "normal set up and stick up a pic I will do the same using a Toolblock This post was originally intended to see what other members use nothing else., and certainly not to get into the technicalities. And if you can find the time, check with messers Sandvik / Walter / Arno

[MuzzerParticipant @muzzer]

(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.

[Michael GilliganParticipant @michaelgilligan61133]

Muzzer,

I think Myrtle makes a very significant point.

… by emphasising the importance of not having any stress-raising ones!

MichaelG.

[HopperParticipant @hopper]

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.

[GoCreateParticipant @gocreate]

[KettrinboyParticipant @kettrinboy]

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

[egaParticipant @ega]

tractionengine42:

Interesting, but what is the source of the posted material, please?

[Author]

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