lathe toolholder rotation





    While I also use an Aloris style, and I keep it locked down with one dovetail parallel to the chuck face, and the other parallel to the workpiece axis.
    If you are putting two tools in a single holder (I don't, as this usually requires re-adjusting the tool height when you swap between ends), put one turning tool and one facing tool in the holder, so when you switch from the side dovetail to the front dovetail the tool is already at the proper angle -- no need to shift the toolpost. And shifting it defeats the indexable tools idea, where you always have the tool at the same projection from the post. If you use one tool to do something, and zero the dial with that tool, then shift to another which does not require you to re-zero the dial (e.g. facing the workpiece), if you have not shifted the toolpost, when you go back to the first holder the dial is still correct for the next part to be turned to the same diameter. If you have shifted the toolpost, you will have to re-establish the zero for that tool when you come back to it.
    As I mentioned in an earlier (slightly earlier) followup in this thread, the only time I loosen the toolpost is when I'm resetting the compound for threading at other than 60 degree threads -- or when putting the toolpost back on after using something like a toolpost grinder.
    Different ways for different people. :-)
    Enjoy,         DoN.
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On Sat, 29 Mar 2014 16:45:11 -0500, Pete S wrote:

Well, I was thinking about the contrast between the Aloris-style square posts which are apparently intended to almost never rotate, and the various round-post designs that apparently consider rotation as a feature. I was wondering how each style worked out in practice and whether people often wanted to rotate the non-rotating style, or never rotated the rotating style.
I was also curious what would happen if there was an in-between style of post that (for whatever reason) only allowed limited rotation; would it be useable. That's why I was asking about the "requirements" rather than the capability.
Certainly the popularity of the square-post style suggests that rotation is not vital as long as the toolholders come in varieties that include popular angles.



Wow, tools out both ends; that's one that I never heard of. I recall reading about people who have tools on all four sides of a rotating turret, and reading that they tend to acquire scars.
Bob
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    The tools which I use benefit from having one face of a quick-change toolpost (e.g. Aloris) parallel to the face of the chuck, and the other parallel to the axis of the workpiece.
    This assures that the insert tooling for threading is in the proper position, and that turning and facing tools (e.g. the Aloris BXA-16N) have their working edge almost at right angles to the direction of travel during the cut. For turning, the tip very slightly leads the rest of the side, so when you halt at a given location and switch to cross-feed from lateral feed, you get a nice finish cut on the face left by the previous cuts.
    Also, the knurling tool is sensitive to angle, and is best used with the faces of the knurls parallel to the axis of the workpiece.
    This also means that a boring bar holder will have the boring bar parallel to the axis, so if the tool tip is touching to cut, the rest of the boring bar will clear the workpiece -- assuming that it is not too large for the hole in question.
    I have, in addition to this, two holders which hold the inserts at about 60 degrees, so they look like an oversized threading tool. These are useful for breaking (beveling) corners after the main work is done -- without ever needing to shift the toolpost itself.
    The only time I need to shift the toolpost (other than when it has been removed to replace it with a toolpost grinder or something else) is when I shift the compound angle from 29.5 degrees (normally 60-degree V threads) to something else, such as 14 degrees for Acme threading, or other angles for weird threads, e.g. the 55 degree Whitworth threads.) So -- when I shift the compound angle, I reset the toolpost to again be parallel to the chuck face and the workpiece axis.

    Selected by the bit and the holder, not by rotating the toolpost. Aloris has some insert holders in which the insert part can be set in 15 degree increments to produce a reasonable tool angle for whatever you want to do. Again -- without having to move the toolpost.

    Agreed -- assuming that you need the rotation at all. I find that I prefer the tool holder to stay in the same position. If it were not for the occasional adjustment for the weird threads, I would drill the compound and the toolpost for a dowel pin, so it would always go back on at the same angle.

    So -- look at the Aloris holders which have the adjustable insert holders -- and (almost) never touch the toolpost itself.
    Just my own preference here.
    I think that the habit of rotating the toolpost comes from the old days of the Lantern style toolposts -- where every time you changed a tool, you had to re-adjust all the angles prior to clamping it down again.
    Enjoy,         DoN.
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wrote:

Interesting. I always thought that a knurling tool was used at a very slight angle to the work piece so that the teeth gradually cut in as you advanced the Z axis feed.
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    [ ... ]

    O.K. My knurler (an Aloris scissors style knurler with arms on dovetail slides and a single leadscrew adjusting both symmetrically around the set height), happens to be fitted with knurling rollers with a slight rounded bevel, which handles that part.
    And it is often used in the middle of a workpiece (where the knurl happens to be needed) just by positioning it there and either clamping it down at that point, or (if already set for the depth of knurl desired) by using the cross-feed to remove it from the first workpiece and then advance it into the second.
    I certainly agree that a bump style knurler would benefit from the slight angle, but I think that a scissors style does not need it.
    Enjoy,         DoN.
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On 30 Mar 2014 02:19:17 GMT, DoN. Nichols wrote:

Thanks DoN for the clear explanation of the "no rotation" approach. It sounds like "small rotation only for unusual threading, and everything else handled by specialized holder". I suppose that if you did the odd-angle threads often enough you could even make or buy a holder for that angle, and never move the toolpost at all.
I can see that the Aloris-style holders and the carbide insert holders seem to have undergone mutual evolution to work well together.
It looks like most of the same things could be done with HSS bits, except for the 15 degree indexing insert holder trick.
Bob
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    [ ... ]

    [ ... ]

    [ ... ]

    Well ... not really -- because the adjustment for the odd-angle threading involves shifting the angle of the *compound* for the correct infeed angle (typically a half degree less than one-half the thread included angle). When you shift the compound, since the toolpost is mounted on it (unless you have a lathe like a Myford where the compound itself is an option), you will change the angle of the tool mounted in the toolpost (along with the toolpost itself). So, when I shift the compound, I have to shift the toolpost in the opposite direction so the dovetails are again parallel to the chuck face and the workpiece centerline. This assumes a proper ground HSS tool bit for the thread angle being cut. (Last time I did this was for an Acme thread when helping a friend make a new nut for his log-splitter.) I actually had to make two -- one for external threads, and one for internal, since I did not have the leadscrew available for test fitting. :-)
    This also applies if I am using the compound to cut an angle, though usually when I want to cut an angle I use the angle attachment on the lathe bed, so I don't have to adjust the compound. The adjustment of the compound only happens if I am cutting an angle beyond the range of the angle-turning attachment (+/- 10 degrees or so, IIRC).

    Yes. In particular, Aloris makes tool holders which directly hold the inserts (I like the BXA-16N -- there are other sizes of course), which holds two inserts on the two ends -- one for turning and one for facing.
    I've looked at the clone maker's offerings, but they tend to provide angled tools only (triangle point towards the workpiece), not with the triangle oriented so one edge is almost square in the direction of cut). The 'N' in the part number says that the pockets are angled for negative rake inserts (thus giving three working points on the top, and three more on the bottom), and with a proper chipbreaking groove, you have the effect of a positive rake anyway.
    And Aloris also has the swivel insert holders, both in single-ended and double-ended versions. I may eventually get that, but my straight shank holders give the angles I commonly need, so that purchase is not particularly urgent. :-)

    I understand that you *can* find HSS inserts to fit the holders for carbide inserts. (No, I don't know where.)
    Normally, a good HSS can get a sharper edge than the typical carbide -- especially the carbide inserts which have been TiN coated, which tends to round the edges a little. I have some small diamond-shaped carbide inserts which are ground quite sharp, without a TiN coating, which I prefer when I want a really smooth finish, and feel too lazy to grind a HSS bit to size. (Besides, I have a large bag of these inserts, and not that many remaining HSS bits. :-)
    Enjoy,         DoN.
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wrote:

<big snip>

I use Arthur R. Warner Co http://www.arwarnerco.com/ . They are expensive, but work well.
<snip>

Pete Keillor
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On 31 Mar 2014 04:24:43 GMT, DoN. Nichols wrote:

Thanks again, yes I had forgotten about rotating the compound requiring rotating the tool holder.
I gather that you seldom use the compound rotation for anything but threads and the rare fast taper, is that correct?
Bob
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You can set the compound to 5 or 6 degrees off parallel to the ways and gain a decimal place of control over the cutting depth, that is, 0.001 of compound travel moves the bit 0.0001" toward or away from (boring) the centerline axis. I haven't found this precise enough to try to set the compound to the angle whose sine is 0.1000, 5.739 degrees. 5 degrees cuts slightly less than indicated, which is safer, and it's easy to remember.
With the compound parallel to the ways you can control the feed into a recess in a face, such as an o-ring groove in a pipe flange, or the width of a shoulder if you don't have an indicator displaying carriage travel or a micrometer carriage stop.
The proper groove angle for a vee belt pulley varies with its diameter, since the belt grabs by expanding sideways against the groove walls when it wraps around the pulley. http://shopswarf.orconhosting.net.nz/vee.html I made a vee belt drive for a heavily loaded hydraulic pump on my tractor that needed everything done by the book to survive. jsw
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    [ ... ]

    [ ... ]

    Start using your machine more -- it will remind you of these things. :-)

    That is correct. One other possible use of the rotation is when you are using a toolpost grinder on the lathe (in which case the toolpost is off anyway), and you want to get extra-fine diametric infeed. In that case, you want the compound rotated as close as you can get it to either 84.28 degrees or 5.71 degrees -- whichever gets your compound closer to the axis of the workpiece. This trick gives you 0.0001" infeed for each 0.001" on the compound's dial. You're not likely to get much benefit from that trick with normal turning, except with a *very* rigid lathe, and a *very* sharp tool edge, but the forces involved in toolpost grinding are quite low, and the possibility of removing in "tenths" is there, while usually with normal turning tools, the spring in both the lathe and the workpiece means that a very fine infeed will probably just spring things until you build up to a certain level, at which it will cut it all at once -- and likely overshoot your target dimension.
    Enjoy,         Don.
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On 3/29/2014 21:32, Bob S wrote:

The problem in all machines, whether it is a mill or a lathe, is that if you have adjustable angle part, it can be off from 90 degrees (or whatever the normal setting). Perhaps it went off last time you took a rough cut? You have to always check it.
In my early days with machinetools I though it is nice to have adjustable things for doing those odd jobs, but I have changed my mind regarding that. A two axis tiltable vice is just never 90 degrees, unless you spend a lot of time adjusting and measuring it. Sure, it is nice when you need to machine the odd angled surface, but all the other time it is a compromise compared to normal vice. Same for bridgeport J head - it could have moved - while a sturdy mill head with fixed angle is always at correct angle (or it is broken). If at all possible, I nowadays have several vices etc. with different degrees of rotation freedom - and use the one with minimum freedom that does the job. Keeps me sane at reasonable cost. :)
My opinion: rotation is nice, but install some mechanism that keeps the holder definitely at 90 degrees, when you don't want to rotate it. (With reasonable accuracy for the job, nothing is precisily 90 degrees).
My quick-change holder has a long pin for that. After rotation (for threading or whatever) install pin back to index it, and then tighten the big-ass M20 nut that holds the quick-change holder body. The pin prevents it from rotating when not wanted. The pin and its hole have good enough fit that it really is quite close to correct angle.
Kristian Ukkonen.
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On Sun, 30 Mar 2014 13:40:54 +0300, Kristian Ukkonen wrote:

Yes, I agree; an adjustable angle is likely to be a wrong angle...
A good mechanism for resetting it would be very helpful.
Bob
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    Agreed.
    [ ... ]

    Not all J-heads are adjustable. The Bridgeport used in their early CNC machines had a choice -- rigid ram, or adjustable one. The rigid ram is normally set up *once*, and taper pins used to lock it once you have it right. (Before pinning there is a very small freedom of adjustment if the bolts are lose.) And yes, that machine *did* have a J-head.
    Enjoy,         DoN.
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On Sat, 29 Mar 2014 15:32:32 -0400, Bob S

Greetings Bob, I've read the other responses and thought I'd contribute, since it is metalworking afterall. I own a machine shop and make my living with it. I have an Aloris tool post on one lathe. It mostly sits square with the X and Z axes. Sometimes I rotate it a bit for one job or another. But even though it is mostly normal to the axes it is almost never square with the compound. The compound gets slewed over to different positions on a regular basis. For example, I might need to use the compound to machine a taper or a large chamfer. It might be set at 29.5 degrees for threading 60 degree threads. And then it will need to be rotated again to cut some Acme threads. And then maybe the next day rotated again for clearance. But no matter what angle the copmound is set at the tool post will still probably be square. So having 360 degree rotation of the tool post is really nice. Eric
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On Sun, 30 Mar 2014 17:22:55 -0700, snipped-for-privacy@whidbey.com wrote:

Thank you Eric for pointing out so clearly what I had completely overlooked. Its not just the tool angle. The post system has to be able to rotate enough to compensate for whatever angle the compound slide is at. It might not matter much for turning a slight taper but it would matter a lot for half-angle threading.
Bob
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<SNIP>>>>

You're welcome Bob. That's part of what this group is supposed to be all about. Eric
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