Tool Post Holder

[extropic]

In addition to what francist wrote, there is very little chance (essentially zero chance) that four different tools in a 4WTP will have the same cutting height.
That's why you need to shim each cutter individually.

The comments that my earlier reply has motivated makes it clear that I made too many assumptions and also didn't specify a detailed description of what type of 4WTP we were discussing. Francisist referred to "An ordinary 4-way bolts straight to the compound without a central pillar (snip)". That's the kind I was talking about.

The ideas of using only indexable insert tooling and/or only new (not resharpened) brazed carbide bits and/or a custom design 4 Way didn't occur to me. I guess they should have. My reply was based on the use of various sizes and grinds of HSS bits which, in my experience, are very common.

Whether you call shims spacers or spacers shims, isn't the function the same?

 

[T Bredehoft]

Whether you call shims spacers or spacers shims, isn't the function the same?

I guess "shims" brings forth stacks of shim stock to make the correct height. My spacers are one piece of 4140 ht, .750 by .750 by 1.50 with a .187 by .187 (or whatever) relief to accept the proper tool and place it under the screws that hold it in place. I also have a spacer than holds a .090 wide hollow ground cut off tool at the correct height, ditto knurling tool.

 

[mickri]

I find everyone's comments interesting and educational. Thanks for sharing

In furthering my knowledge on tool post holders I came across several threads on how people had made their lantern's easier to use. Mostly by replacing the typical rocker and the spacer it sits on with a spacer machined to give the correct angle and/or height to place a cutting tool at centerline. As an experiment I put one of my craftsman tool holders in my lantern without the rocker and the spacer turned upside down and checked to see how far off it was from being on centerline. I was surprised to find that it was exactly on centerline. I tried a couple of others and they all were on centerline. The only one that wasn't on centerline was the parting tool. It was a little below center. In one of the boxes of tooling that came with my lathe there was a bunch of shims and spacers. I tried a couple and found a spacer that brought my parting tool up to being on centerline.

I only use my lantern for parting and threading and always dreaded these tasks because it was such a PITA to setup the lantern. While still not being as easy as a qctp it will be much easier now to use my lantern when I need it.

 

[mickri]

I have started making this tool post holder. In looking at my 4 way and a boring bar holder I have they both have a protrusion on the bottom that fits into the slot on the compound. One, I am concerned that I do not have the skill to make the protrusion precise enough to closely fit in the slot and be square with the slot, and two, that I will be able to get the hole for the "T" post precisely in the center of this protrusion. I am also going to drill holes in the base at 30 degree spacing so that the tool holder can be indexed with the height adjustment screw. Would 15 degree spacing be better? I will be making the base on my mill/drill. Here is a sketch of the base.

I am thinking about not having the protrusion. Without the protrusion each time I mount the tool holder on the compound I would have to square it to the face of the chuck. I think that this will be better for me. I am concerned that without a tight fit and if the holes aren't precisely inline with the protrusion the tool holder won't be square to the axis of the lathe. Am I over thinking this?

As for indexing off of the height adjustment screw my plan is to either bevel the end of the screw with a corresponding bevel in the index holes or turn down the end of the index screw to fit in the holes.

 

[T Bredehoft]

For years, I, as a professional Tool & Die maker, eyeballed square for the QCTH. In other words, it isn't critical.

 

[mickri]

The post is done and the only thing left to do on the base is to make indents for the height adjustment screw to sit in so the tool holder would be indexable. I was thinking of making the indents every 30 degrees. I think that I could also make them every 15 degrees. The only question I have on indexing concerns threading. Everything that I have read on threading says to have the compound set at either 29 or 29.5 degrees for threading. How would you achieve this if the tool post holder is indexed at 30 degree intervals. Do you square the tool post holder to the face of the chuck with the compound set at 29.5 degrees?

Another question. I have thought of drilling 1/8" holes in the base and turning the end of the height adjustment screw down to 1/8" to fit in the hole. Or should I use a drill to make a shallow dent in the base with the end of the height adjustment screw turned to match that angle? Or should I use a different angle say 60 degrees? Or a combination of both?

 

[homebrewed]

Early on I removed the indexing pin on my tool holder, and have yet to have a problem when I turn stuff. It may be this is partially due to the fact that I'm using a 7x12 lathe and don't take heavy cuts, so the cutter angle(s) are not as critical. The QCTP I made has no indexing feature.

For threading, the tool is square to the work. The tool path follows the 29.5 degree angle. You can do this by setting the compound to 29.5 degrees, or simulating that by setting the compound to zero degrees and using a combination of cross slide + compound moves. IIRC, if you move the cross slide by "x", you move the compound by "2*x". This IS an approximation--instead of the 29.5 degree path it's 26.6 degrees, an error of 2.9 degrees. Ideally you'd move the compound by 1.77*x but that's not so easy to do in your head. But if you insist on an indexing feature, this approach doesn't require anything special to accommodate the 29.5 degree angle.....and would be a piece of cake if you happen to own a CNC lathe.

 

[mickri]

Here is a picture of the base and post on the compound. I have not tried do make any dents in the base for indexing.



It is very solid and square to the compound.

The only reason I thought to make it indexable is because of comments above that this style of tool post holder was not indexable implying that it would be better if it was indexable. Making it indexable does add complexity because every tool holder you make has to be identical in all respects. To be honest I probably don't have the skill to do that. The main reason I am making this qctp is to not have to use the lantern tool post. I primarily use 4 different tools. RH turning, parting, threading, and boring. It will be very convenient to have a tool holder for each. I will probably make a separate holder for each of the 3 boring bars, 1/4, 3/8 & 1/2, that I use most often. And several separate holders for normal HSS and the altas/craftsman tool holders for a lantern tool post that came with my lathe.

Now on to making the holders.

 

[pacifica]

The post is done and the only thing left to do on the base is to make indents for the height adjustment screw to sit in so the tool holder would be indexable. I was thinking of making the indents every 30 degrees. I think that I could also make them every 15 degrees. The only question I have on indexing concerns threading. Everything that I have read on threading says to have the compound set at either 29 or 29.5 degrees for threading. How would you achieve this if the tool post holder is indexed at 30 degree intervals. Do you square the tool post holder to the face of the chuck with the compound set at 29.5 degrees?

Another question. I have thought of drilling 1/8" holes in the base and turning the end of the height adjustment screw down to 1/8" to fit in the hole. Or should I use a drill to make a shallow dent in the base with the end of the height adjustment screw turned to match that angle? Or should I use a different angle say 60 degrees? Or a combination of both?

I know it isnt the recommended way, but I lock the compound and thread straight in, no 29 degrees business.
With a retractable toolholder , I reverse the carriage and dont have to worry about finding my place for depth on the next cut,thread depth calculations are more straight forward since you are not advancing at an angle.. When you are doing 10 or more cuts it is easier for me.

 

[Winegrower]

I hope everybody considering a four way will check out the inexpensive wedge type QCTP and holders available from many sources, say for example,, CDCO tools. The capability and ease of use, coupled with the low cost of more holders and styles (boring, knurling, etc.) are hard to beat.