Taiwan lathe spindle runout

[Mike Bryant]

Nez, I started with a Jet belt drive lathe in a 12x36. Axial movement was about the same as yours originally. After I adjusted the bearings, it worked very well. Never could get rid of the chatter in the threads when cutting a thread in back gear, but I put a VFD on it and I could thread on the high speed side without any chatter. Something in the angled back gears was causing the chatter.

 

[NezRongero]

Nez, I started with a Jet belt drive lathe in a 12x36. Axial movement was about the same as yours originally. After I adjusted the bearings, it worked very well. Never could get rid of the chatter in the threads when cutting a thread in back gear, but I put a VFD on it and I could thread on the high speed side without any chatter. Something in the angled back gears was causing the chatter.

Mike,

Good to know about threading with the back gear with these belt drive Jet lathes. Thanks for the information. I am in the process of installing the VFD and a 2 HP 3P motor on this baby lathe, should be enough to run even at the lower RPM setting.


Nez

 

[Mike Bryant]

Nez, that was about what I put on mine. I put a 3 phase inverter motor and a Hitachi VFD on it. The inverter motor had a fan that ran all the time that power was going to the motor. The slowest it would run on the high speed side before the VFD was 300 rpm and I couldn't pull out of the thread at that speed at the time. The VFD let me slow it down where I could thread on the high speed side. Now 250 rpm to 300 rpm is about where I thread depending upon the pitch that I'm cutting. The faster the tool moves across the thread, the slower I thread. About 250 rpm is where I thread with a 16 or 18 pitch thread. Do you have trouble with chatter with your Jet when threading in back gear? Your lathe is probably about the same era as mine was. I tried everything I could think of to get rid of that chatter. Threading on the high speed side did it though.

 

[NezRongero]

Nez, that was about what I put on mine. I put a 3 phase inverter motor and a Hitachi VFD on it. The inverter motor had a fan that ran all the time that power was going to the motor. The slowest it would run on the high speed side before the VFD was 300 rpm and I couldn't pull out of the thread at that speed at the time. The VFD let me slow it down where I could thread on the high speed side. Now 250 rpm to 300 rpm is about where I thread depending upon the pitch that I'm cutting. The faster the tool moves across the thread, the slower I thread. About 250 rpm is where I thread with a 16 or 18 pitch thread. Do you have trouble with chatter with your Jet when threading in back gear? Your lathe is probably about the same era as mine was. I tried everything I could think of to get rid of that chatter. Threading on the high speed side did it though.

Mike,

The 1024 Jet is a new addition, a 1981 production, it replaced a similar, but older lathe of different badge, the Jet being a better machine condition wise. Lucky I was able to swap out for about even after I sold the much older one. Incidentally, the VFD I will use is also a Hitachi. When I get the lathe going, I will try threading with the back gear and without and see if this one exhibits the same characteristics as yours.

One feature I am incorporating in the system is a proximity sensor, hopefully it will allow me to thread at higher speed and stop the spindle and carriage precisely and accurately. With an external brake resistor on the VFD it just might do it. Will post some videos when the project is substantially complete.

nez

 

[TRA]

Nez, that was about what I put on mine. I put a 3 phase inverter motor and a Hitachi VFD on it. The inverter motor had a fan that ran all the time that power was going to the motor. The slowest it would run on the high speed side before the VFD was 300 rpm and I couldn't pull out of the thread at that speed at the time. The VFD let me slow it down where I could thread on the high speed side. Now 250 rpm to 300 rpm is about where I thread depending upon the pitch that I'm cutting. The faster the tool moves across the thread, the slower I thread. About 250 rpm is where I thread with a 16 or 18 pitch thread. Do you have trouble with chatter with your Jet when threading in back gear? Your lathe is probably about the same era as mine was. I tried everything I could think of to get rid of that chatter. Threading on the high speed side did it though.

You could try different threading methods. The style of cutter, be it inserts or ground tool bits can have dramatic results on machines with stability issues. The best quality threads are cut with machines that have belt driven spindles. Gear head lathes are prone to surface finish issues, both turning and threading.

What style cutters are you using? Light weight machines don't fair well with negative rake tooling. Most shops avoid high positive ground tooling due to it's higher cost.

 

[Butch Lambert]

Having .00005 bearings is no assurance you can hold .0002 either. Enlarging a rifled hole with a drill bit could cause runout even if you bore the chamber then ream it.

With that quality of bearings you have a much better chance of eliminating most of your runout. Doncha think?

 

[Mike Bryant]

You could try different threading methods. The style of cutter, be it inserts or ground tool bits can have dramatic results on machines with stability issues. The best quality threads are cut with machines that have belt driven spindles. Gear head lathes are prone to surface finish issues, both turning and threading.

What style cutters are you using? Light weight machines don't fair well with negative rake tooling. Most shops avoid high positive ground tooling due to it's higher cost.

I don't have that lathe anymore. I was using a Carmex partial profile tin coated insert. It worked well on the high speed side of the Jet. The lathe I use now is a Kent 1340V which is a Clausing Colchester copy. Weighs a little over a ton. Still use the same threading insert.

 

[TRA]

With that quality of bearings you have a much better chance of eliminating most of your runout. Doncha think?

No not really. The tolerance of the ways, carriage, compound, the type of tooling and their setup. Machine rigidity, flat and true of the X&Z axis. All machines have twist, and parallel issues. Any time you use a tailstock you throw out the window most of the accurate setup you though you had. Tools with less than stable setup and tool pressure will allow a boring bar to run all over the place. Drill a hole with a drill mounted in a tailstock, with a drill chuck and a MT shank, then use a boring bar with upwards of 10-1 overhang and you will never true that hole back up. After you bored the hole which is still out of round a tenth or more and the reamer will telegraph that runout into the finished chamber.

You can have the best bearings in the world and the runout of the chamber will be the result of the unstable tooling practices, ,,,not the spindle bearings.

A lathe is not a grinder. what I hear being claimed about budget import equipment is quite a stretch.Every time you move the carriage, compound and heaven forbid the tailstock,,, you could have easily put the TIR into the .000+ range, not .0000.. It's not an easy task running parts and keeping them all under .0002 As the machine warms up you really start chasing ghosts as everything moves. Then there's the issue of the cutting tools inconsistency.

Nothing that has motion whether its rotary, linear.... Will move without some clearance, and that all adds up.

Chambering PPC or 6BR cases with a ~1.625 length is child's play compared the long chambers for some of today's Magnum calibers.

Look At the guys that claim accuracy in tenths, with old flat belt lathes and sleeve bearings.

 

[JerrySharrett]

No not really. The tolerance of the ways, carriage, compound, the type of tooling and their setup. Machine rigidity, flat and true of the X&Y axis. All machines have twist, and parallel issues. Any time you use a tailstock you throw out the window most of the accurate setup you though you had. Tools with less than stable setup and tool pressure will allow a boring bar to run all over the place. Drill a hole with a drill mounted in a tailstock, with a chuck and a MT shank, then use a boring bar with upwards of 10-1 overhang and you will never true that hole back up. After you bored the hole which is still out of round a tenth or more and the reamer will telegraph that runout into the finished chamber.

You can have the best bearings in the world and the runout of the chamber will be the result of the unstable tooling practices, ,,,not the spindle bearings.

A lathe is not a grinder. what I hear being claimed about budget import equipment is quite a stretch.Every time you move the carriage, compound and heaven forbid the tailstock you could have easily put the TIR into the .000+ range. It's a not an easy task running parts and keeping them all under .0002 As the machine warms up you really start chasing ghosts as everything moves. Then there's the issue of the cutting tools inconsistency.

Nothing that has motion whether its rotary, linear.... Will move without some clearance, and that all adds up.

Chambering PPC or 6BR cases with a ~1.625 length is child's play compared the long chambers for some of today's Magnum calibers.

Look At the guys that claim accuracy in tenths, with old flat belt lathes and sleeve bearings.

FINALLY, some facts!


.

 

[Rflshootr]

Not to hi-jack the thread, but what oil do you guys use in the headstock? My jet has been sitting for years and before I fire it up, I'd like to change it.
Are you running hydraulic or a way lube type oil?

 

[TRA]

hearstock oil

Not to hi-jack the thread, but what oil do you guys use in the headstock? My jet has been sitting for years and before I fire it up, I'd like to change it.
Are you running hydraulic or a way lube type oil?

A lot of lathes call for Mobil DTE Light. It's actually is hydraulic oil but works great for high pressure gear and bearing applications.

Although I've never done it, I would not hesitate using John Deere Hy Trans oil, that they use in most,if not all gear train and hydraulic systems., It's Available any where and is usually referred to as "Trans-Hydraulic" fluid. IT's usually ISO 32.


http://www.practicalmachinist.com/v...tween-mobil-dte-light-mobile-dte-24-a-194032/

 

[jackie schmidt]

This is what we use in just about everything. Thr R O stands for Rust and Oxidation inhibitor.

Years ago we called this Turbine Oil.

http://benchrest.com/attachment.php?attachmentid=18213&stc=1&d=1471095927

 

[Rflshootr]

Thanks guys. I did a bit of searching, and I think the 68w is what most recommend. And better yet, I have some.

 

[Butch Lambert]

No not really. The tolerance of the ways, carriage, compound, the type of tooling and their setup. Machine rigidity, flat and true of the X&Z axis. All machines have twist, and parallel issues. Any time you use a tailstock you throw out the window most of the accurate setup you though you had. Tools with less than stable setup and tool pressure will allow a boring bar to run all over the place. Drill a hole with a drill mounted in a tailstock, with a drill chuck and a MT shank, then use a boring bar with upwards of 10-1 overhang and you will never true that hole back up. After you bored the hole which is still out of round a tenth or more and the reamer will telegraph that runout into the finished chamber.

You can have the best bearings in the world and the runout of the chamber will be the result of the unstable tooling practices, ,,,not the spindle bearings.

A lathe is not a grinder. what I hear being claimed about budget import equipment is quite a stretch.Every time you move the carriage, compound and heaven forbid the tailstock,,, you could have easily put the TIR into the .000+ range, not .0000.. It's not an easy task running parts and keeping them all under .0002 As the machine warms up you really start chasing ghosts as everything moves. Then there's the issue of the cutting tools inconsistency.

Nothing that has motion whether its rotary, linear.... Will move without some clearance, and that all adds up.

Chambering PPC or 6BR cases with a ~1.625 length is child's play compared the long chambers for some of today's Magnum calibers.

Look At the guys that claim accuracy in tenths, with old flat belt lathes and sleeve bearings.

You are learning! tra, you need to read my post as posted. I made no claims other than the 50 millionths bearings. I think you know that to have an accurate machine, you have to start will an accurate spindle. I made no comments saying it is now a 50 millionths machine.
Now, let me ask you this. If you have a machine with good bearings, but unfortunately the ways are badly worn, can you or anybody do what it takes to create a great chamber? What adjustments would you have to make and why?

 

[TRA]

With that quality of bearings you have a much better chance of eliminating most of your runout. Doncha think?

You are learning! tra, you need to read my post as posted. I made no claims other than the 50 millionths bearings. I think you know that to have an accurate machine, you have to start will an accurate spindle. I made no comments saying it is now a 50 millionths machine.
Now, let me ask you this. If you have a machine with good bearings, but unfortunately the ways are badly worn, can you or anybody do what it takes to create a great chamber? What adjustments would you have to make and why?

I have no desire to engage you in a protracted discussion about the obvious.

If you have a work piece with zero run out, ( which is next to impossible) and unstable tooling.. the tooling will take any path it sees fit. Once that happens any operations after that will be affected by the inconsistent tool pressure a crooked hole will have. All very similar to why a gun drilled and reamed barrel is seldom straight.

If you have very stable tooling and runout in the work it makes the bore larger, seldom does it cause it to be crooked or out of round. Unless the spindle is bent, then you got problems.

I think the biggest mystery is.........Is perfect really necessary?

 

[JerrySharrett]

I have no desire to engage you in a protracted discussion about the obvious.

If you have a work piece with zero run out, ( which is next to impossible) and unstable tooling.. the tooling will take any path it sees fit. Once that happens any operations after that will be affected by the inconsistent tool pressure a crooked hole will have. All very similar to why a gun drilled and reamed barrel is seldom straight.

If you have very stable tooling and runout in the work it makes the bore larger, seldom does it cause it to be crooked or out of round. Unless the spindle is bent, then you got problems.

I think the biggest mystery is.........Is perfect really necessary?

A good, reasonable fit on the threads that are within a FEW thousands of being concentric with a chamber that has a near perfect mergence of the leade and the bore is about as good as man (or woman) can expect. A result like this and the barrel stands a better than 99% chance of being accurate with a properly tuned load.

If at this point one should have an accurate barrel capable of winning or placing very high if the shooter knows how to handle it.

Why are some barrels winners and some are not with todays barrel making technology? Ask the question, why do they all seem to belong to the same shooters?


.

 

[cloudrepair]

You are learning! tra, you need to read my post as posted. I made no claims other than the 50 millionths bearings. I think you know that to have an accurate machine, you have to start will an accurate spindle. I made no comments saying it is now a 50 millionths machine.
Now, let me ask you this. If you have a machine with good bearings, but unfortunately the ways are badly worn, can you or anybody do what it takes to create a great chamber? What adjustments would you have to make and why?

Through my time as a machinist I have learned setup is a large percent of a job to get closest to a nominal result in the part .now what adjustments would you make? Are you referring to something specific in relation to spindle bearings?

 

[cloudrepair]

Then there is the method used to get those nominal results. I chamber thru the head stock because I can dial in a barrel within .0002 and I don't have a steadyrest yet for my machine. And I'm not sure I would use that method but I will try it when I can.
Before I got my lathe I wanted an action that at least had the face perpendicular to the bore for the bolt so I made a jig to hand lap this in the same way you would dial it in on a lathe with a ground rod and bushings. I got very good results.

 

[Butch Lambert]

tra, you skirted my question.

 

[TRA]

Mike,

The 1024 Jet is a new addition, a 1981 production, it replaced a similar, but older lathe of different badge, the Jet being a better machine condition wise. Lucky I was able to swap out for about even after I sold the much older one. Incidentally, the VFD I will use is also a Hitachi. When I get the lathe going, I will try threading with the back gear and without and see if this one exhibits the same characteristics as yours.

One feature I am incorporating in the system is a proximity sensor, hopefully it will allow me to thread at higher speed and stop the spindle and carriage precisely and accurately. With an external brake resistor on the VFD it just might do it. Will post some videos when the project is substantially complete.

nez

FWIW, If you try to stop the spindle without withdrawing the tool it will break the tool. With carbide that has multiple cutting edges it trashes the whole insert. When it absolutely must be done this way, the thread is cut into a hole at the end of the thread. You may be able to pre machine a relief between the thread and the shoulder and stop it there. The tool will have to be clear of the thread when you stop the spindle. That's one of the cons to CNC machinery. When the power causes the relays to drop out, or total loss of power, things get broke, parts get trashed.