Theading away from the head stock.

[uscra112]

Exactly how I do it. ^^^^^^

[M-Tecs]

You want a bed stop that clamps to the bed vee solid, You also will find this useful for turning shoulders and facing to length.

The lead screws/half nuts on most lathes do not have a clutch. Using a hard lathe stop while threading is a recipe for disaster on most lathes unless you are threading away from the spindle. Lathe stops are designed to be used with the power feed that have a clutch. Bad things happen when you hit the hard stop while the half nut is engaged. If you are lucky you will only break a shear pin. Some of the cheaper lathes use the lead screw for the power feed and they don't like lathe stop much either.

Some manual lathes do have auto disengage (half nut knockout) for the half nut or you can make your own like here.



Some plans here

https://books.google.com/books?id=xi...0lathe&f=false

My Hardinge HLV-H doesn't even have a thread dial due to a unique and wonderful design feature. The half nuts stays engaged thru the complete threading operation. The lead screw rotation is controlled by a carriage control lever. The Hardinge uses a single-toothed dog clutch which preserves the rotational relationship between the leadscrew and the spindle. Most lathe don't have this feature.

Hardinge has a set of adjustable dog stops on the bar immediately below the lead screw. So you can literally be threading at 1,000 RPM (max recommend) up to a shoulder, and when the apron hits the dog clutch stop, the leadscrew disengages from the spindle.

https://www.practicalmachinist.com/f...d-stop.150848/

[uscra112]

Who suggested running the carriage under power into the stop?

[PopcornSutton]

I have turned many barrel tenons to the shoulder and never hit the shoulder. A lot of people cut a groove to make it easy to just run the tool into and disengage. I just don't like the look, and if you ever want to set a barrel back to freshen the throat, there is that groove.

For years, I used a 2" travel dial indicator on a mag-mount, and set it to zero at my stopping point. Works great and watching the dial run to zero is easy, unlike trying to watch a bunch of flashing number on a DRO. I set the cross feed to zero with the handle up, and cut the thread feeding the compound in. When I get to zero, I pull the half-nuts and back the compound at the same time. This gives a nicer thread finish I think. The other method that is simple, is to set the carriage where you want to end, and use a sharpie and make a mark on the ways. Pulling the half-nuts when you get to the mark is very easy and amazingly repeatable. If you like you can leave the cross feed alone and let it cut the circle next to the shoulder. It looks better than a groove, and if you want to set it back, that one thread will hardly be noticed.

[country gent]

I suggested using a hard mounted dial indicator as a travel dial readout leaving .200 on the 1" travel indicator. While in one line I said bed stop it was in reference to the indicator mount. As attaching with a magnetic base it can be bumped or move loosing your zero. The bed mounted indicator make turning a shoulder or threading to a set point easier.

I have this type mount made up for my small lathe and normally use a 0-1" indicator on it. But I also have a 3" travel .oo1 indicator in the tool box.It gets trickier to read as there is the .001 dial a revolution dial ( .100 ) counter and 1" dial.

The travel dial was a great addition to a lathe but I dont think they are made now. Digital readouts are inexpensive and common now. A battery operated one can be purchased for a few hundred dollarsm then its the time to make the mounts and mount it to the machine.

[uscra112]

I remember Trav-A-Dials. Never owned one. They're bringing some breathtaking prices on evilBay now.

[M-Tecs]

I remember Trav-A-Dials. Never owned one. They're bringing some breathtaking prices on evilBay now.

Back in the day I never much cared for them all that much. What they are getting for them on fleaBay is beyond silly.

[country gent]

The trava dials were decent but the wheel that rolled down the flat of the ways would pick up ships and swarf changing diameter and its accuracy. they had to be cleaned occasionally. we had the same issues with the brigeports with the southwest Proto tracks the readers were a traveling wheel and chips would affect them.

[slughammer]

Another little thing that helps, is a 1 inch dial indicator on the bed. Set it so that 0 is the start and .800 is the stop point then watch that and when it touches you can count down to disengage point.
I do this milling to a shoulder with the readout I watch the readout counting down the .1 then the last .01 the stop with in .010 easily.

You want a bed stop that clamps to the bed vee solid, You also will find this useful for turning shoulders and facing to length.

I do it a little different.

I set the carriage at my stop position and then set the 0-1 indicator so it contacts the carriage and moves the needle only .020.

I can run the carriage and see it getting closer to the indicator tip, then the needle JUMPS to life! I wait until I'm about .005 away from zero and disengage.

I only have a brief moment that I'm seeing the needle move, its kind of like a light turning on as a visual signal.

I don't have a lot of experience counting the .1's, so this works very well for me.

[Ernest]

Thanks for the responses. Lots of idea's to mull over. I think that I will try to thread away from the head stock next time to see how it works for me. Everything in life is a gamble it looks like with small cuts it can be done safely.

[country gent]

Same technique, just different numbers but it does work. When an apprentice started single pointing threads I showed them this starting out. even if you dont hit the shoulder over running a almost threaded end can chip the tool or cause problems.

Another help is to grind the threading tool off center making the cutting side just deep enough to cut the thread this leave a lot more room.
You want a sharp tool with a clean edge and point. Hone the tool sharp and a smooth edge, I have a block made to grind and sharpen threading tools in the surface grinder. The better the tool the better the thread.

If you have to recatch a thread a piece of clean white paper or small flashlight under the tool helps to see the alignment.

[Scrounge]

Ever see the old turret lathes with the back cut toff post ( some had turrets even) tools were upside down and ran fine I think the cut offs ran even better than in the front position. When the gibs are properly adjusted there is little to no chatter.

I have a block of steel set aside to make a rear tool holder for my Nardinni lathe as it already has the mounting slots in the cross slide for one. ( its a 14/18 X 40 ). My smaller lathe dosnt have the slots id Im leaving it as is. Since I dont want to disassemble the cross slide and machine them in to it.

Last threading project for my class was a 1-1/2x4tpi Acme Stub thread matching external and internal threads. The internal thread was cut with the lathe in reverse, and the feed to right, towards the tailstock. Their lathes don't have threaded spindles, but somewhere in my info stash I have a copy of a patent to lock down threaded chucks from the South Bend company. It will be a while yet before my SB Heavy 10L is operational, but I plan on implementing that change on my Atlas lathe chucks, too. Basically, you drill and tap a hole or two or three, as you like, into the collar on the back of the chuck, and put a set screw in there with a shoe to protect the spindle threads. Lock it down when you need it not to move, and unlock to change chucks.

Bill

[country gent]

Both my lathes are cam lock d series spindles. the smaller is a d 3 and the bigger a d 6 so chuck rotation isnt an issue for me. But it is a consideration on some machines. Another is if your using insert tooling it is designed for force in a certain direction

[Ernest]

Last threading project for my class was a 1-1/2x4tpi Acme Stub thread matching external and internal threads. The internal thread was cut with the lathe in reverse, and the feed to right, towards the tailstock. Their lathes don't have threaded spindles, but somewhere in my info stash I have a copy of a patent to lock down threaded chucks from the South Bend company. It will be a while yet before my SB Heavy 10L is operational, but I plan on implementing that change on my Atlas lathe chucks, too. Basically, you drill and tap a hole or two or three, as you like, into the collar on the back of the chuck, and put a set screw in there with a shoe to protect the spindle threads. Lock it down when you need it not to move, and unlock to change chucks.

Bill

That is what I had in mind! I think that would be a very good solution. I am not sure what is meant When you say "with a shoe to protect the spindle threads" I am not sure what is meant by a shoe. I wonder if three brass screws would work. Loosen when not needed and tighten when running in reverse.

[alfadan]

Ive daydreamed about an arrangement to automatically kick out the halfnut lever when the carriage gets to a set point like a relief groove.

[Willbird]

Ive daydreamed about an arrangement to automatically kick out the halfnut lever when the carriage gets to a set point like a relief groove.

Another idea I had was to use a hydraulic tracer attachment , you could just run the cut towards the chuck and the tracer would move the tool away enough that it did not ever touch the 1.2" diameter barrel shank. Not a good reason to buy and setup a hydraulic tracer but the tracer could be used to profile barrels too. We had a hydraulic tracer in vocational high school, used it to make small cannons as a shop project.

My grizzly has a spindle jog button, it's slowest speed is pretty fast too, 70 RPM, I just leave half nuts engaged, use jog button to run towards chuck, release at the magic moment....pressing a hand onto the lathe chuck OD when stopping helps, then back cross slide away, and reverse spindle to move the tool back to the right, half nuts stay engaged the whole time.

Mauser threads make you pucker a little lol. Been meaning to swap in a 3 phase motor and use a VFD to get a slower spindle speed when wanted.

[uscra112]

By "shoe" I want to assume a brass tip on the setscrews that would not mar the threads.

For the SB 10 Heavy you might set up an air cylinder to operate the flat belt tension. Releasing the pressure would stop the spindle pretty quickly when you're using the back gear. That would of course also stop the feed.

[Willbird]

By "shoe" I want to assume a brass tip on the setscrews that would not mar the threads.

For the SB 10 Heavy you might set up an air cylinder to operate the flat belt tension. Releasing the pressure would stop the spindle pretty quickly when you're using the back gear. That would of course also stop the feed.

Getting deep into the drive train redesign ideas here but ....could use an air conditioning clutch on the motor output shaft...actually in industry a device we use quite a bit is a clutch-brake....when power is supplied, typically 24VDC the clutch engages and drives the load, when you remove power a brake is applied. at high speed that could make a threaded lathe chuck unscrew, but as you say in back gear it would work fine.

When we use them typically the motor stays running all the time.

A toolroom lathe as they refer to it often has stops built in that will drop out the leadscrew drive. There is a lever that can be raised to go left, when the carriage hits the stop on the rod it pushes the lever to the center which is neutral, it will drop an Acme threading tool into a 1/4" undercut really nicely even with spindle running say 200 rpm, one backs out the cross slide which often has a thread stop included then pushes the lever down...and the carriage moves right, and hits another stop which again bumps it to neutral. One runs cross slide back in to the stop, cranks in the compound, and runs another threading pass.

The lever is setup so it can sync things up without messing with the half nuts or a thread dial, they stay engaged the whole time.

I did hundreds of acme screws for milling machine vises this way, you can chase that thread nicely moving compound in .02" or more per pass and no fear of the tool crashing into anything.

Bill

[Cap'n Morgan]

So putting upward pressure on apron, cross slide, compound slide and tool holder,, four things all designed to rigidly support downward pressure only,, dosent cause chatter like crazy ?

On older lathes with glide bearings you can minimize spindle chatter by running the tool upside down. This prevent the cutting force from lifting the spindle (especially useful when parting off)

Modern CNC lathes create the same effect by moving the tool to the backside of the part. This makes good sense as the tool turret is rock-solid compared to the rotating chuck.

[BS2]