Quick Change Tool Post Indexing

[npalen]

I dn't get it. Any time you change the compound, the absolute the angle of this "Thingy" is GONE, so what does a "relative" change mean anyway?? :-(
...lew...

I normally run with the compound off to the left at 30. Just a habit, I guess, but it works for me and rarely change the angle unless cutting a taper or large chamfer.

I just want the capability of quickly changing the toolpost back to its "home" position if I do need to change its angle for any reason. I find myself sometimes just filing a small chamfer instead of cutting it correctly and want to get away from that by easily changing the tool post angle. Sure don't want to mess with changing the angle of the compound as I mentioned earlier. Would actually like to get rid of it and replace with a sold block as others have.

I appreciate what some of you are saying about having a tool for every type and angle of cut ready to use in a toolholder. Nothing wrong with that, really.

[Paul Alciatore]

J,

Engineering is about trade-offs. Remember the old adage: I can do it fast. I can do it cheap. I can do it well. Pick ANY TWO!

But back to the tool post. Although I can change holders with no tools, a great time saver; my post can be easily rotated to any angle with a single tool. In fact, that single tool is all that is needed for mounting the post and for all the adjustments. It is a unique shaped tool which makes it easy to keep it at the lathe at all times. I never have to go searching for it. It is right there. So for the few times when I do need to change the angle, it is a fast task.

The trade-off was the omission of accurate indexing at a number of different angles. That feature is probably responsible for half the sky high cost of the Multifix posts and holders. And it would likely cost a great amount of coin or effort in any other indexable tool holder. When you combine the price and the 9 degree indexing of the Multifix, I just can not see buying one.

As for having a lot of holders, as I said, many people do. There have been articles and web pages devoted to the making of the dovetail holders by the dozen - by people who already have over two dozen of them. So that concept is not new with me. On the other side of that coin, I made my QC tool post over 12 years ago and still have only about 6 or 8 holders. Two or three of them have the same tools in them for all or most of that time. The others can be changed for individual particular jobs. You say "all the angles", making it sound like a lot. But for 99.999% of the work I and most of us do, "all the angles" equates to 0, 30, 45, 60, and 90 degrees. That's not a lot of angles. Tools for all the alloys would be a bigger number, perhaps much bigger.

It may not work for you. It may not work for Doozer. Ditto for others here. But it does work for me. We can all choose our own mixture of features that are present and missing.

Vive la difference!

So............ that seems to be trading an easy post movement for needing a lot of holders. Each tool at all the angles ? That's a lot of holders, even though not all tools need moved..

Sure, if you needed to go get a wrench every time, yeah, but moving a lever, turning the post, and moving the lever back? Not an issue, and any angle you need is available.... you don;t HAVE TO use the detent positions if a different angle is better.

[BCRider]

If they slide in a hole they must have clearance, which equals a loss of repeatability. The taper can only take out the play on one of the mating parts.

That's true. But if the user twists back to remove the play between the pin, hole and, in this case between the center stud and the body of the QCTP then it should be pretty consistent.

Another option is to drill a hole with a little clearance so the pin easily enters. But then to mill an undersize partial cut so the hole is sort of pear shaped. When twisted to remove the play the pin would "wedge" into that narrower entry and should provide pretty good repeatability. This would ensure that the pin sets the same each time and that any and all play could be "twisted" out of the tool post.

Like.....

[npalen]

That's true. But if the user twists back to remove the play between the pin, hole and, in this case between the center stud and the body of the QCTP then it should be pretty consistent.

Another option is to drill a hole with a little clearance so the pin easily enters. But then to mill an undersize partial cut so the hole is sort of pear shaped. When twisted to remove the play the pin would "wedge" into that narrower entry and should provide pretty good repeatability. This would ensure that the pin sets the same each time and that any and all play could be "twisted" out of the tool post.

Like.....

I'm not sure that we need this kind of accuracy for the idea presented in post number 1 of this thread. I normally realign the tool post by bringing it up against the face of the chuck when tightening the nut/stud. This is plenty accurate for cutoff operations. I feel like the implementation of spring loaded ball/detents would do.

[J Tiers]

Good luck getting them apart.

It has never been a problem in any of the situations I have used it for yet. You don;t have to hammer the taper pin in, you know!

Because it is not going to do the "snap to position", you always have a knob to pull it out for movement.

Of course, unless you need very good accuracy, ther is no reason to go to the trouble to use the taper pin that way.

............................ I normally realign the tool post by bringing it up against the face of the chuck when tightening the nut/stud. This is plenty accurate for cutoff operations. I....................

I do the same thing for cutoff. More recently, I have taken to using a 1 2 3 block as an intermediate, so that interference with the tool or work is less of an issue. For other angles, eyeballing it is usually enough for any but maybe the four 90 degree points; one for each tool position

Unlike others, I do not use a QCTP, instead using a special type 4-way. So I alter the angles quite a lot, because it is just done by moving a lever.

No need to move a lever, pick up and move the tool holder, put it somewhere, locate, pick up, and move another, put it on the toolpost, and move the lever back. Just move lever, turn post, move lever back. Easy, no problem, far fewer movements than fiddling with racks of tool holders. *

Some common angles on detents would facilitate that, so long as it could also do angles other than those. If you are happy to be picking up and moving around tool holders all the time, fine. What suits you is what you should do.

With the 4 way, 4 stops at 90 deg angles, along with 45 degree would be good. If the 30 and 60 fit, that would be fine in addition. They might not fit. Most likely not all positions would need the 30 and 60.

* if you do many parts in a run, that require many different tools, then a QCTP is good, and worth the extra movements.

[JRouche]

I dont know? Missing the point or not?

[npalen]

I dont know? Missing the point or not?

In regard to?

[BCRider]

I'm not sure that we need this kind of accuracy for the idea presented in post number 1 of this thread. I normally realign the tool post by bringing it up against the face of the chuck when tightening the nut/stud. This is plenty accurate for cutoff operations. I feel like the implementation of spring loaded ball/detents would do.

I do the same for lining up the parting tools. And aside from that I just eyeball it.

But consider that one of your opening goals was to permit separate and totally repeatable operations so you can make multiple identical parts. Most folks manage that with one clamping of the tool post and after that rely on the tool holders to seat on the dovetails or other features the same way each time. And they do so to typically within .001 inch or .01 to .02mm.

The issue is that the post to center stud has a few thousandths of play. I just measured my own imported AXA style tool post and stud and there's 0.010 to 0.011 of play between the hole in the post and the diameter of the stud. And a spring pin will need about .002 to .003 of play to ensure smooth action. And if that pin also has a similar .002 to .003 of play in the index plate to permit it to find the hole? The possible source of inaccuracy is adding up rapidly. Of course when you load it back a lot of those will be reduced by working against each other. But I don't think we're doing anything here that will ensure a consistency in repeated positionings to within a .002 to .003 value. And if we're talking that much play now we're potentially looking at a .002 to .003 variation in shoulders and a possible .004 to .006" variation in diameters.

There's possible options for getting around some or most of this. But it means things like working with spit cones at the top of the tool post nut or similar in conjunction with your locking T nut idea to ensure self centering during tightening. Or we move the accurate positioning to the indexing pin via something like the trick I showed. But at some point there needs to be a locking out of variation to ensure consistent enough positioning to make the indexing project worth the time. Otherwise if it can't be relied on to permit repeatability to within .001 or less then what is the point?


Side note;
One of the options you mentioned for justifying the indexing was the ability to swing the post around to make chamfers. I went with another way. Rather than swing the post I did the a holder up with dedicated cutters for chamfering. In the first picture the cutter sticking out the left is 5/16 ground conically on the one side as shown in the second picture to give me the ability to chamber any diameter of bore. It works even for 1/8 holes. I've not tried it on anything smaller. The other three edges are just ground as per a normal lathe tool front clearance angles since those are always working with normal exterior edges. The tool is used as shown in picture 3 for the inside and outside corners of tubes or bores. Picture 4 is the setu for chamfering grooves or parting slots before finishing up.

For longer conical features this is no good of course. But for any sort of chamfering it works from the same "squared up" position as needed for my parting tool. And that same squared up position works for all my normal turning tools. So I've got the big majority of work covered from the one tool post position.

It's not a single long cutter either. The internal end is an old short length 5/16 square and the other end sticking out the right in the first pic is a short old end of 3/8 square. A nice final use for cutters that are mostly too short for anything else.

[Doozer]

Hot tip for both ID and OD chamfering...
Use a D-bit or a graver bit in the toolholder. The round ones.
You can angle the D-flat a little below center for OD work
and the other side is naturally a little above center for ID work.
It just works so well.

--Doozer

[Paul Alciatore]

When I designed my QC tool post I wrestled with this very question. I wanted better than 0.001" repeatability at the tip of the tool, which is where the action takes place. Preferably a lot better than that. Why? Because I sometimes make identical parts which also need good accuracy for good fits. If you analyze the geometry you will see that the errors increase in direct proportion to the distance from the effective center of action. In the case of a rotating (indexable) tool post, that center is probably the center of the mounting stud. And any indexing pin will be closer to that center than the tip of the tool will be; probably by a factor of two or more. This means that any errors in repeatability at the pin will be doubled or worse at the tool tip.

If you are making a number of identical parts, repeatability is a very serious concern. The lack of it translates into more time spent checking and correcting the dimensions you are cutting. For professionals, time is money. And for hobby machinists like me, time is precious. Seems like I am running out of it faster every day. And sometimes even I make things for profit.

So if you want +/-0.001" at the tool tip, then you need less than +/-0.0005" at the pin. The pin may achieve that when new, but after some use it will become looser and looser. And the repeatability at the tool tip will become worse and worse.

I looked at pins and keys for my tool post but rejected them because they will inevitably become worse with time and the day-to-day wear from the intended use. Yes, you can always remember to install the holders with a twist in the same direction, but what a PITA. Oh, and be sure to carefully clean off all chips and even grains of dust first. I looked for and FOUND an indexing method that was self compensating for wear and to a great extent, self cleaning. So I can just drop a tool holder on the post and tighten the nut, all in one downward motion, and I am ready to go. And the tool's tip will be in the same position as it was when it was last removed.

So NO, I do not recommend pins or keys. I believe the Multifix posts draw surfaces covered with gear tooth like ridges into intimate contact. This is also self correcting for wear. I don't know how effective it is in cleaning those surfaces. And it involves a large area of contact so the wear is minimized, also like my design. A small pin or even a key is a bad choice for long term use.

I'm not sure that we need this kind of accuracy for the idea presented in post number 1 of this thread. I normally realign the tool post by bringing it up against the face of the chuck when tightening the nut/stud. This is plenty accurate for cutoff operations. I feel like the implementation of spring loaded ball/detents would do.

[npalen]

When I designed my QC tool post I wrestled with this very question. I wanted better than 0.001" repeatability at the tip of the tool, which is where the action takes place. Preferably a lot better than that. Why? Because I sometimes make identical parts which also need good accuracy for good fits. If you analyze the geometry you will see that the errors increase in direct proportion to the distance from the effective center of action. In the case of a rotating (indexable) tool post, that center is probably the center of the mounting stud. And any indexing pin will be closer to that center than the tip of the tool will be; probably by a factor of two or more. This means that any errors in repeatability at the pin will be doubled or worse at the tool tip.

If you are making a number of identical parts, repeatability is a very serious concern. The lack of it translates into more time spent checking and correcting the dimensions you are cutting. For professionals, time is money. And for hobby machinists like me, time is precious. Seems like I am running out of it faster every day. And sometimes even I make things for profit.

So if you want +/-0.001" at the tool tip, then you need less than +/-0.0005" at the pin. The pin may achieve that when new, but after some use it will become looser and looser. And the repeatability at the tool tip will become worse and worse.

I looked at pins and keys for my tool post but rejected them because they will inevitably become worse with time and the day-to-day wear from the intended use. Yes, you can always remember to install the holders with a twist in the same direction, but what a PITA. Oh, and be sure to carefully clean off all chips and even grains of dust first. I looked for and FOUND an indexing method that was self compensating for wear and to a great extent, self cleaning. So I can just drop a tool holder on the post and tighten the nut, all in one downward motion, and I am ready to go. And the tool's tip will be in the same position as it was when it was last removed.

So NO, I do not recommend pins or keys. I believe the Multifix posts draw surfaces covered with gear tooth like ridges into intimate contact. This is also self correcting for wear. I don't know how effective it is in cleaning those surfaces. And it involves a large area of contact so the wear is minimized, also like my design. A small pin or even a key is a bad choice for long term use.

"And any indexing pin will be closer to that center than the tip of the tool will be; probably by a factor of two or more. This means that any errors in repeatability at the pin will be doubled or worse at the tool tip."

Looking at the picture in the first post of the thread, you will notice that the distance from the center of the tool post to the indexing holes is quite a bit more than from the center to where a tool tip would normally be.

Edit: The above is not correct on my part. The two distances are somewhat close to the same. That is one advantage of the index quadrant being outside of the tool post. Lots of space there to make use of on the top of the compound.

I rarely do multiple parts so really not looking for extreme repeatability. Just want to be able to swing the turning tool around to do a chamfer and then return it to home and switch to a parting tool that is reasonable straight with the world. Simple as that, nothing more nothing less.

[garyhlucas]

I set the toolpost straight with a parallel against the face of the chuck. If 30 or 45 degrees is something you use all the time make a spacer block with that angle. Takes just seconds to angle and straighten the toolpost that way.

[BCRider]

In that case set your post using the parting tool and then leave it alone. Set all your other tools in other holders so you can do all you need to do from that same tool post position. Case in point is my chamfer cutting tool. It was set up so the angled cuts are at 45 plus or minus about a degree. It doesn't require me to alter the tool post. Nor do most of my other tools, including boring bar holders. Another good example is the carbide insert tooling that I'm now starting to use more often. The cutting edge is dead nutz parallel to the long edge of the tool shank. But I get the lead angle I need by just slightly skewing the tool shank within the room I have in the slot of the tool holder. It's only about 3 or 4° but it's enough that I can face the ends of a work piece. And that's all I need.

About the only time I ever need to move my tool post around is when I alter the angle of the compound slide for a conical cut. But that's the "special case" where I actually need to swing it so the tool is aligned correctly for that conical pass. For the other 95% of the time I rarely need to loosen and swing the tool post away from "square" as set by the parting tool.

Clearly, unless you go to great lengths as we're discussing in this thread, you would not be able to repeat your original "parting tool" position anyway. Using the play in the T nut and between the stud and tool post body is enough to permit pressing the parting blade up against the front of one of the chuck jaws. And that's going to be way more consistent and easy than trying to use any sort of externally located gauge that has to deal with existing and other parts clearances.

Consider too that the accuracy also relies on the compound rest angle. And given the small degree divisions found on most lathes I'm thinking that bringing the parting blade up to the front face of the chuck jaw and pressing it to the jaw while tightening the tool post is far more accurate and consistent than almost anything else.


Doozer, that's a slick idea! But in the end for me without the T&G grinder or an easy way to hold the round HSS tool for grinding back the face I just found it easier to grind the short squares I had. But for others with the stuff to make it easy to do that's super slick!

[npalen]

"But consider that one of your opening goals was to permit separate and totally repeatable operations so you can make multiple identical parts."
I don't recall saying that.

[J Tiers]

"But consider that one of your opening goals was to permit separate and totally repeatable operations so you can make multiple identical parts."
I don't recall saying that.

You did not say it as far as I know. People read into posts whatever they want, and that's if they bother to read past the title. Don't worry about it.... Some of us "get it".