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Threading Question

A lot of good info in this thread. I haven't read through it all but has anyone recommended checking the change gears if it has any? If they're meshed too hard together it adds a lot of vibration and noise to the whole system.
Mounting the motor on isolators and removing any slop from the cross slide and compound will also help.
 
Positive update: The belt from the motor was somewhat loose and I tightened that to spec. I also pretended like I was brave (fake it 'till you make it?) and threaded at the next available RPM which was 200. MUCH better results! Threads no longer look like a record with peaks and valleys. I did crash into the shoulder on the last pass and had to clean that up but flipped the barrel around and threaded the muzzle for a tuner with my newfound bravery. Huge improvement. Thank you all!

Hank

Pic with crash cropped out.
IMG_8609.jpeg
 
Positive update: The belt from the motor was somewhat loose and I tightened that to spec. I also pretended like I was brave (fake it 'till you make it?) and threaded at the next available RPM which was 200. MUCH better results! Threads no longer look like a record with peaks and valleys. I did crash into the shoulder on the last pass and had to clean that up but flipped the barrel around and threaded the muzzle for a tuner with my newfound bravery. Huge improvement. Thank you all!

Hank

Pic with crash cropped out.
View attachment 1459080
Much better
Nice leade in ramp as well.
For me speed was the key, I was scared and nervous so was too slow.
Sped rpm’s up a lot and it was a huge difference.

Try reverse on lathe and upside down tool or inside inserts on the back side and thread out for worry free threading
Joe pie has an excellent video on that.

Also get a medium cratex and polish the threads with it
Looks super nice and threads in like glass on glass.
 
Positive update: The belt from the motor was somewhat loose and I tightened that to spec. I also pretended like I was brave (fake it 'till you make it?) and threaded at the next available RPM which was 200. MUCH better results! Threads no longer look like a record with peaks and valleys. I did crash into the shoulder on the last pass and had to clean that up but flipped the barrel around and threaded the muzzle for a tuner with my newfound bravery. Huge improvement. Thank you all!

Hank

Pic with crash cropped out.
View attachment 1459080
Hell yeah those look nice I figured it was the belt!!! My loose belt cost me a frequency drive in a three phase motor lol
 
I have a bunch of them, I'm pretty sure the one sitting on my lathe is an extra course. I hit any sharp edges on shoulders with it, and one or two passes over threads really smooth things out.
 
I have quite a few of the sticks as well. I can’t remember if I’m using a course or extra course along with the fine. I use them all the time touching up, deburring or finishing. I also have a bunch of cones and points for the Foredom in a range of grits. They work great (and fast) for polishing up cocking piece noses, cocking cams and many other things. Glock trigger parts too. Very useful to have around.
IMG_1165.jpeg
 
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I have quite a few of the sticks as well. I can’t remember if I’m using a course or extra course along with the fine. I use them all the time touching up, deburring or finishing. I also have a bunch of cones and points for the Foredom in a range of grits. They work great (and fast) for polishing up cocking piece noses, cocking cams and many other things. Glock trigger parts too. Very useful to have around.
View attachment 1459783
Those are the two I use most
 
I use kennametal top notch kc5025 and kc850 profile cutter and threading tool and on my g0554 lathe I thread at 45 rpms and it looks and works great best cutters I've ever used and I know of other smith doing the same too I trun the shank down around 500 rpms then thread I also ream chamber at 45 rpms and have never experienced chatter or any other problems yet know on wood
 
I was going to look for this post this week. I decided to spend the time and take a look at my belt this weekend. It was loose, tightened it up and I too saw an improvement. Thanks for bringing up the topic Hank, both originally and now.
 
I have quite a few of the sticks as well. I can’t remember if I’m using a course or extra course along with the fine. I use them all the time touching up, deburring or finishing. I also have a bunch of cones and points for the Foredom in a range of grits. They work great (and fast) for polishing up cocking piece noses, cocking cams and many other things. Glock trigger parts too. Very useful to have around.
View attachment 1459783

When the ends get raggedy and full of oil like that... run them over some 220 grit sand paper. (I use a belt grinder) - quickly takes them back to new.
 
I am sure you are all ready to be done talking about this,
but wanted to say thanks again for all the help. Tightening up the gibs and the drive belts and 200 RPM speed are giving me much better looking results.
View attachment 1464699

View attachment 1464700

Thank you again,
Hank

Glad it's improved.

Only let your material stick out as far as you need it to. Keep that shoulder as far inboard as you can. It will make a big difference.
 
Well, maybe I’m about to open a can of worms, but if I keep the workpiece close to the headstock, then I am clamping down on the chamber or, worse, the throat. Seems like that could be bad?

Thank you,
Hank
 
I have a G4003G and it does the job fairly well. I don’t see the issues you are having though. Obviously setup rigidity is important and through spiders isn’t exactly “rigid”.

I thread upside down in reverse so I never run into the shoulder. I use a standup HSS insert (Arthur Warner) on a left hand standup tool holder. I thread straight in (no 29.5 degree deal). I thread @ 200 rpm using high sulfur oil. I always take time to make a spring cut about half way through and 2 at the end.
 
I’m just a hobby machinist, but have spent way too much time troubleshooting large swing, light weight lathes, and only read this thread once so forgive me if I missed something important. I‘ve had two old, lightly used lathes - seldom used because they had never cut correctly and so many things were partially to blame it was more economical to pass them off to the next guy.

It helped me to think of the whole machine as being rubber - everything flexes, every part between how it’s held and the cutter is working against you. Avoid incremental mental creep - allowing a little extra flex here and a little there…a jaw or spider bolt tightened a little light, a gib slightly loose, tool stick out a little far, material stick out a little too much, not moving the tailstock quite as close as it should, etc.

Every place two metal surfaces come together should be suspect and checked for flatness. Regular use of precision stones to highlight and eliminate burrs on every flat surface is often thought of as standard practice. A properly leveled machine cuts better - a sensitive machinist level doesn't have to be expensive. Know what your spindle preload should be and what it is.

Every dovetail and gib should be checked for good contact and even wear. There are acceptable times gibs can be adjusted tighter than normal and later loosened for general machining. If your compound is worn out try locking it up tight and threading without it, or replace it with a solid block. Keep the cutting tool as close to the cross slide dovetails as possible - avoid big cantilevers. Mounting a long boring bar and measuring deflection of all the parts between the bed and tool shows the week links in the chain - it’s all rubber.

In lathes that aren‘t blessed with stiff spindles and the best spindle bearings, every fraction of an inch away from the spindle greatly increases chatter.

Using a center is a really good idea as long as it’s a quality center with good rigidity and the tailstock is actually centered and rigid. Experiment with different amounts of pressure - it’s very subjective so what’s described as light or heavy pressure means different things to different people. I‘d think the center isn’t doing much unless it’s somewhat tight, but keep in mind it is also adding to preload to the spindle bearings so once the threads are started you don’t want to fiddle with it.

Once chatter has started on a thread, even a proper change in technique that would have prevented it, may not clean up the chatter that’s already there.

It‘s funny that thousands of dollars in replacement parts and measuring equipment, a couple thousand hours of head scratching and rebuilding could be summarized in one short page. :-)

Glad to see you’re headed in the right direction.
 

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