Let's fight about lathe toolpost setups

[rslaback]

A guy at work was peeved the other day because someone (or multiple someones) keep messing up the lathe setup. He insists that the compound of the lathe should be set primarily at 90 and the QCTP aligned to that. Most of the guys at work, like myself, have always set up the compound at a 29.5 and then aligned the QCTP to the chuck face.







I never learned to put the compound at 90 by default but it does seem popular with a quick Google search. I can see that it might be just the tiniest bit more rigid if the corners of a QCTP overhang the platform on the compound but it also would definitely always be in the way if you were trying to do tailstock work and is a redundant motion in that you already have an X travel adjustment with the carriage. One would assume that the point of a third axis would not be to duplicate either the carriage or cross slide travels.

I've always left the compound at 29.5 because in the event that I need it, which is rare, I need it for threading. The tailstock on the other hand gets used a lot and moving the compound and then the QCTP every time would annoy the **** out of me.
So what is the big benefit of aligning to the bed direction that I am missing?

 

[dutchgray]

I keep mine at 90° to the cross slide and have a 4 way toolpost, no qctp yet on my current lathe. It doesn't get in the way of the tailstock most of the time.
Threading you can go straight in with modern carbide tooling most of the time, I don't do a lot of single point threading though.

 

[cmandp]

It really depends on the lathe, how the compound sits on the carriage, what the lathe can do and what operation you are working on at the time.

On the Hardinge TFB at work it doesn't have a lead screw and cannot single point thread. So 29.5° is useless on the compound. With the lack of attachments (no steady rest or travel rest) you often run into clearance issues between the carriage and tailstock when using a center. It's a toolroom lathe so the carriage is particularly long compared to an engine lathe. In that case the compound parallel with the carriage travel helps you move away from the tailstock. So usually I set the compound parallel to carriage travel and square the toolpost to the spindle face. It's a Aloris quick change toolpost.

I usually have to move the toolpost from whatever someone else was doing so it doesn't bother me. What does bother me is when I can't find the darn toolpost wrench because the last person to use it put it somewhere else in the shop!

 

[CallumRD1]

On the lathes I typically work on, I can't stand using them with the compound at 90˚ because it will inevitably interfere with the tailstock at some point, forcing me to adjust the compound mid-part which can cause other issues. I don't single-point thread often enough to prefer 29.5˚ as a default, so I normally just keep it near 45˚ for making quick large chamfers, often done in reverse on the back side of the lathe with a boring bar.

 

[47chevy COE]

I keep mine at 29.5, and sometimes at 45. I can’t stand it being at 90.

 

[dr_clyde]

I leave mine at 29.5 for two reasons. Primary one is threading, it’s just easier to have it ready to go whenever I want to thread. Secondary reason is the compound interferes with the tail stock lock wrenches if the angle is too steep.

I adjust it regularly to machine tapers tho. It’s not like it takes long to loosen the screws and set it up.

 

[G-ManBart]

I set mine at 29.5 as a general practice, but there are times when I'm doing something oddball that I'll use another setting. It's certainly nice for threading, or if you want to dial in a really light skim cut.

 

[tdkkart]

One of those things that really, really, REALLY doesn't make a damn bit of difference, put it where you like it and move on.

45* makes a lot more sense than 29.5 for me, or 90 sometimes too.........

 

[zmotorsports]

I'm not a machinist so I didn't realize there was a certain way it had to be. I just leave mine @ 29.5 degrees as that seems to be where it's out of the way of the tailstock as well as for single point threading. I've had mine that way for so long I don't know if I could even change now if I had to.

 

[slowtwitch73]

Doesn't matter. Obviously if you are threading alot, 29.5 is good.

 

[mikegt4]

I put mine where ever it works best for the job at hand. I have a German made Weiler lathe, the instructions always seem to show the compound at 90*, maybe it's a European thing.

 

[vanapplebomb]

If I am not turning a taper, I leave mine at 29-30 degrees for threading, or 14.5 degrees for fine diameter control. 14.5 degrees means that for every 0.001” I advance the compound, the the diameter of the part decreases 0.0005” which is really handy for fine work.

 

[alfadan]

30deg for me to keep it out of the way. Also keep the gib tight when not using it to add a little rigidity.

 

[no704]

I almost always have mine at 90 deg. Can use the dial on it as 1:1 Z travel.

 

[RoninB4]

I have mine set to whatever the last job required but generally have it swung out of the way of the tailstock. I also single point thread at 29.5 degrees and use it at 90 only when the task requires it.

 

[LXCam]

If I am not turning a taper, I leave mine at 29-30 degrees for threading, or 14.5 degrees for fine diameter control. 14.5 degrees means that for every 0.001” I advance the compound, the the diameter of the part decreases 0.0005” which is really handy for fine work.

That’s a really great tip. I’ve always kept mine at 90 simply for the occasional extra reach and when needed, used a tailstock extension to clear it. But I think I’m going to change my ways now after reading everyone’s reasoning

 

[APEowner]

I leave mine wherever it needed to be for the last operation where it mattered until I setup for something else where it matters.

 

[txvwnut]

Put it where ever you want it is what I say. I usually leave mine wherever I had it last set until I need it at a different angle. I have Multifix tool post so I can pretty much get the tool square to the chuck no matter where the compound is.

 

[mechcsu]

I agree with APEowner, that is unless someone (or multiple someones) is breaking his setup in the middle of a job. If that is the case then they deserve to be beat with a large heavy object.

I leave mine wherever it needed to be for the last operation where it mattered until I setup for something else where it matters.