Quick Change Tool Post Indexing

[BCRider]

I like the way you're thinking!

.....My lathe uses a t-nut with a stud that can be screwed down tight to the bottom of the t-slot locking it in place. ......

That is not a feature. It is a VERY risky problem area!!!! You're risking the stud tightening enough that it ends up levering up and snapping the edges of the T slot.

Very seriously, you need to stake or peen the bottom edge to stop the stud from screwing down against the bottom. It's one thing to use set screws to lock the T nut in position with some carefully used torque. It's another for the stud to be left to lever itself under those ears with the full torque you can apply from up top.

[npalen]

Some people try to do it by the book
and some people do what is shown to have results
and realize the book is just to get you started and
anyone who understands the scientific method of
cause and effect reasoning will graduate their mind
and exceed the knowledge contained in the book.
People who follow the book exactly, will never be
smarter than their book. Be it the machinery bible
or the holy bible.

-D

I actually "learned by the book" about 60 years ago attending a 600 hour machinist course. Even had to make our own "rocker" on the shaper to use with the "lantern post" on the lathe. Since then, I've been trying to think outside of the box and doing things "my way". (Frank Sinatra) I'm only 77 so perhaps I'll come around when I get a little older and understand the correct way of being a machinist.

[npalen]

That is not a feature. It is a VERY risky problem area!!!! You're risking the stud tightening enough that it ends up levering up and snapping the edges of the T slot.

Very seriously, you need to stake or peen the bottom edge to stop the stud from screwing down against the bottom. It's one thing to use set screws to lock the T nut in position with some carefully used torque. It's another for the stud to be left to lever itself under those ears with the full torque you can apply from up top.

I'm planning to machine a 60 degree point on the bottom end of the tool post stud to engage a shallow center drilled hole at probably three different positions in the bottom of the t-slot. The stud will be screwed in hand tight to center it and then the hexnut tightened to secure the tool post.

I've had to tighten the hexnut extremely tight a time or two to keep the tool holder from rotating when trying to knurl. I've since built a clamp type knurling device that doesn't rely on cross slide force to produce the effect. The t-slot lips are not going anywhere soon.

[npalen]

I think your idea is promising. Soon after I got my lathe I tired of the lantern toolpost, so I made a four-way toolpost. I had seen a catalog photo of a Royal four-way which indexed, so I emulated that in my design. It indexed in 15° increments and was quite repeatable. It served me well for many many years. Eventually I upgraded to a shop-built QCTP, but I wanted to keep the indexing feature, so I kept what I could of the four-way and made a new body to fit it, with a dovetail clamp. I can use it exactly as you propose, swing it around for a quick chamfer, then return to normal position. However, I find it just as convenient, if not more so, to change to a chamfer tool holder and back to a turning tool, because I don't have to crank the cross slide a couple of inches and back, which turning the toolpost requires. One place it really does help is when using the tailstock center. I find that the toolpost body will often clash with the tailstock or the live center itself when using the center with a small diameter workpiece, so turning the toolpost cw one ot two steps solves that problem. Also, I needed to build my QCTP with only one dovetail rather than the usual two, since I can swing it to both turning and boring positions.

But is indexing really that helpful? Well, with a four-way I think indexing is essential, in order to be repeatable. So I got fixated on it. But for a QCTP with two dovetails, not so much. Don't get me wrong, I like the indexing feature, it's a nice luxury, but I rarely use any but the two normal positions. The tailstock clearance issue is real, but sticking the tool out a bit farther works, too.

Indexing might be a bit of a gimmick, but I kinda like gimmicks. And I use it, though less than I anticipated.

Yeah, I run into the interference (pun?) problem sometimes when running a live center so have to rotate the tool post. That is another reason I like the indexing feature-so the toolpost can be rotated and then easily brought back to the home to a true 90 degree position.

I try to use tools with the needed angle also, like to do 45 degree chamfers but seem to run out of quick change tool holders quite frequently.

Edit: Forgot to mention that one of the prime reasons for wanting indexing back to the home position is for the cutoff tool. Seems like I'm always reluctant to change the rotation angle of the QCTP is that it then has to be realigned exactly for the cutoff blade.

[thin-woodsman]

Wow! Tough crowd around these parts! You never have the need to briefly change the angle of your cutting tool?

...versus how much time do you want to invest in something like this when you can just use the $5 angle gauge you probably have near the lathe already. Machine the parts, remove and machine the compound and the QCTP, then true the angles that were off just a hair in the previous steps. But hey, have at it, it's your time not mine.

I initially thought the piece of paper in the pic was a 3D-printed gauge for setting the compound. That might be much faster and more accurate than what you initially proposed: the gauge would register on the sides of the compound, and the angle cutout would line up the QCTP to where it's supposed to be. If you only have a few angles, you'd keep a few of these on a magnetic hook stuck to your lathe, and grab em as you need em.

As for threading, I thought 29.5 (and 30, and "30 minus a gnat's fart") degrees was the angle of the *compound*, because that is what you want to feed at (so as to only cut on one side of the V as you get deeper, instead of both).

[npalen]

...versus how much time do you want to invest in something like this when you can just use the $5 angle gauge you probably have near the lathe already. Machine the parts, remove and machine the compound and the QCTP, then true the angles that were off just a hair in the previous steps. But hey, have at it, it's your time not mine.

I initially thought the piece of paper in the pic was a 3D-printed gauge for setting the compound. That might be much faster and more accurate than what you initially proposed: the gauge would register on the sides of the compound, and the angle cutout would line up the QCTP to where it's supposed to be. If you only have a few angles, you'd keep a few of these on a magnetic hook stuck to your lathe, and grab em as you need em.

As for threading, I thought 29.5 (and 30, and "30 minus a gnat's fart") degrees was the angle of the *compound*, because that is what you want to feed at (so as to only cut on one side of the V as you get deeper, instead of both).

Yep, that's the way I've always done it. Guys will argue that its crazy until the cows come home, however. Its just what you get used to doing.

As far as "investing time", at my age that is part of the motivation for fun projects like this. It just drives people nuts!

[npalen]

I think your idea is promising. Soon after I got my lathe I tired of the lantern toolpost, so I made a four-way toolpost. I had seen a catalog photo of a Royal four-way which indexed, so I emulated that in my design. It indexed in 15° increments and was quite repeatable. It served me well for many many years. Eventually I upgraded to a shop-built QCTP, but I wanted to keep the indexing feature, so I kept what I could of the four-way and made a new body to fit it, with a dovetail clamp. I can use it exactly as you propose, swing it around for a quick chamfer, then return to normal position. However, I find it just as convenient, if not more so, to change to a chamfer tool holder and back to a turning tool, because I don't have to crank the cross slide a couple of inches and back, which turning the toolpost requires. One place it really does help is when using the tailstock center. I find that the toolpost body will often clash with the tailstock or the live center itself when using the center with a small diameter workpiece, so turning the toolpost cw one ot two steps solves that problem. Also, I needed to build my QCTP with only one dovetail rather than the usual two, since I can swing it to both turning and boring positions.

But is indexing really that helpful? Well, with a four-way I think indexing is essential, in order to be repeatable. So I got fixated on it. But for a QCTP with two dovetails, not so much. Don't get me wrong, I like the indexing feature, it's a nice luxury, but I rarely use any but the two normal positions. The tailstock clearance issue is real, but sticking the tool out a bit farther works, too.

Indexing might be a bit of a gimmick, but I kinda like gimmicks. And I use it, though less than I anticipated.

I like your idea of the dovetail mount on a four-way with 15 degree indexing and that is basically what I will be ending up with but not quite as convenient as spring loaded ball detent. May have to rethink the pin in favor of actual detents. Thought about detent "dimples" in the bottom of the QCTP but it is a bit hard to machine.

[npalen]

...versus how much time do you want to invest in something like this when you can just use the $5 angle gauge you probably have near the lathe already. Machine the parts, remove and machine the compound and the QCTP, then true the angles that were off just a hair in the previous steps. But hey, have at it, it's your time not mine.

I initially thought the piece of paper in the pic was a 3D-printed gauge for setting the compound. That might be much faster and more accurate than what you initially proposed: the gauge would register on the sides of the compound, and the angle cutout would line up the QCTP to where it's supposed to be. If you only have a few angles, you'd keep a few of these on a magnetic hook stuck to your lathe, and grab em as you need em.

As for threading, I thought 29.5 (and 30, and "30 minus a gnat's fart") degrees was the angle of the *compound*, because that is what you want to feed at (so as to only cut on one side of the V as you get deeper, instead of both).

Good idea on the 3D printed gauges!

[BCRider]

I'm planning to machine a 60 degree point on the bottom end of the tool post stud to engage a shallow center drilled hole at probably three different positions in the bottom of the t-slot. The stud will be screwed in hand tight to center it and then the hexnut tightened to secure the tool post.

I've had to tighten the hexnut extremely tight a time or two to keep the tool holder from rotating when trying to knurl. I've since built a clamp type knurling device that doesn't rely on cross slide force to produce the effect. The t-slot lips are not going anywhere soon.

This is still a terrible idea. Even worse and more risky that you're thinking to rely on such a setup for positioning. You're setting yourself up to pop off one or both of your compound's T slot lips.

Take a lesson from why T nuts on milling table clamp sets are not done that way. It's due to how when torquing the nut on the top of the stud can result in more friction in the upper nut than on the T nut. Without the staking the stud can screw through and hit the bottom of the slot and force the T nut upwards and burst the ears of the T slot. This is a very real and fairly commonly found issue in old shool lathes and milling machines. Don't set yourself up to be one of those.

You always want the ears of the T slot to be pinched between the T nut and the bottom of the tool post by means of a captured stud that is solid in the T nut. There must never be a situation where you are pushing the stud down through the T nut and against the bottom of the slot.

It's a grand idea to ensure that the T nut on your tool post cannot move. But you do NOT want to use the center tool post hold down stud to do double duty.

[npalen]

This is still a terrible idea. Even worse and more risky that you're thinking to rely on such a setup for positioning. You're setting yourself up to pop off one or both of your compound's T slot lips.

Take a lesson from why T nuts on milling table clamp sets are not done that way. It's due to how when torquing the nut on the top of the stud can result in more friction in the upper nut than on the T nut. Without the staking the stud can screw through and hit the bottom of the slot and force the T nut upwards and burst the ears of the T slot. This is a very real and fairly commonly found issue in old shool lathes and milling machines. Don't set yourself up to be one of those.

You always want the ears of the T slot to be pinched between the T nut and the bottom of the tool post by means of a captured stud that is solid in the T nut. There must never be a situation where you are pushing the stud down through the T nut and against the bottom of the slot.

It's a grand idea to ensure that the T nut on your tool post cannot move. But you do NOT want to use the center tool post hold down stud to do double duty.

Sorry, Guess that we will just have to agree to disagree on this one. Could put a setscrew in from the side of the t-nut if that was an issue.

Pic shows a t-nut and stud from my mill clamp set. Must be thousands of people out there breaking chunks out of their mill table. A bit of common sense goes a long way

[Randy]

Pic shows a t-nut and stud from my mill clamp set. Must be thousands of people out there breaking chunks out of their mill table. A bit of common sense goes a long way

Most T-nuts I've used are either staked or not threaded through so as to stop the stud. But you're aware of the issue, and clearly smart enough to deal with it. 'Nuff said.

[Doozer]

Then there is "do it like the print says", which is required in order to get paid. "Innovation" and "creativity" are not welcomed when the print says "the feature is to be like this".

Does your mama know how special you are Jerry ? ? ?

-D

[npalen]

The indexing posts lock the t-nut position so it's not going to slide. And they usually have minimal slop and/or a means to locate the post relative to the holding post, so that the indexing works repeatably.

Adding that stuff seems likely to add significant height. There is no room to add it inside the toolpost, which is also hardened. So it has to go below.

What I see as nice about really positive indexing is the ability to set at a dead-on 90 deg whenever a parting-off operation is needed (and nice for threading as well). The other angles are nice, but not really "required".

The point about the 9 degree indexing is well taken on the Multifix. It DOES do a reliable 45 degree, but no 30 and no 60. I'll agree that 45 is the most commonly needed angle for chamfering, but.....

The other thing is that aside from 90 deg, no other angles are good for much aside from a chamfer, since there is no other angle to move the tool along a slide beside 90 or the typical 29.5 deg threading angle. To get any of those, you need to turn the compound, and most machines are not like a Rivett, where the compound is locked by a convenient lever.

"Adding that stuff seems likely to add significant height. There is no room to add it inside the toolpost, which is also hardened. So it has to go below."

The index plate represented by the paper in the picture will mount to the side of the QCTP, not underneath.
Yes, need a convenient way to bring the tool back to 90 for parting.

[J Tiers]

The index plate represented by the paper in the picture will mount to the side of the QCTP, not underneath.
Yes, need a convenient way to bring the tool back to 90 for parting.

Not the way I'd 'a done it, but whatever floats your watch..... Maybe you have a better idea than it seems like from here.

[npalen]

Not the way I'd 'a done it, but whatever floats your watch..... Maybe you have a better idea than it seems like from here.

Tell us how You'd 'a done it!