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Speed and threading chart?

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Aqua-Andy

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#1
Hi I'm new to this forum so mods please feel free to move this thread to the appropriate place if needed. I have been using a Jet 1440-3PGH lathe at work, the only problem is the feed speed/threading chart is missing. I have looked all over the net for a picture of this chart but I can't seem to find one. I have called Jet and they have been no help at all finding a replacement chart or even just a picture of one. For the feed speeds I have spent some time manually turning the chuck and measuring how far the carriage moves. As for threading this has proven to be more difficult. Any suggestions would be welcome.
 

Aqua-Andy

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#3
Thank you for the info. I have been searching for months, I guess I just needed to ask in the right forum. Now I can try to cut a thread.
 

Bob Korves

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#5
Welcome to the H-M.

Is this what you are looking for:



More can be found here. http://www.airlinebrats.com/lathe/
That chart is odd in that it shows straight gearing for metric threads, along with compound gearing for both metric and imperial threads. Is the chart for a metric lead screw or an imperial one? It appears to me to be correct for a metric lead screw. The OP did not say which lead screw he has, but it really does matter!
 

Bob Korves

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#7
Bob,

The bottom of the chart says 4TPI lead screw, 8TPI feed rod. That chart is kind of confusing to me.

Ted
Good catch, Ted! It looks like the entire box on the left is for feeds. But then they show compound gearing for both metric and imperial threads. I don't get it...
 

Aqua-Andy

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#8
Thanks for the help with the chart. I tried cutting my first thread today. Well the first did not work out so well, there is a lot going on and that carriage was moving much faster than I was used to. So I cut that part off and tried again. I actually came out with something that resembles a thread and a nut would also screw on to it. Was it pretty? No! But I think this is a good start, when I have more time I will try some more.
 

Aqua-Andy

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#9
Well I finally got time to play with the lathe today. I tried cutting a 12x1.75 thread. I made sure the bit was ground at a 60* angle. set the compound to 29.5* and squared the bit to the part. On this lathe you can't use the threading dial for metric threads so I just stopped the machine, pulled out the tool and reversed until I was at my starting point again. The problem I had was the threads came out looking more like arrows than a nice "V", as in the right side of the thread had a 90* angle and the left side sloped from the peak to the valley. After looking at things I tried again and instead of using the compound to feed the bit in I used the cross feed. So I would make a pass then pull out and then on the next pass turn in the cross feed to where it was plus what I wanted to take off. this last thread came out looking nice, it had a nice "V" shape and a nut fit very nice. All the videos I have seen show using the cross feed just to move the tool in and out but using the compound to dial in the amount to be cut. Not sure what I'm doing wrong.
 

higgite

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#10
Sounds like the compound is set at the wrong angle. It should be rotated 29.5* counter clockwise from perpendicular to the spindle axis. Or clockwise 60.5* from parallel with the spindle axis.

Tom
 

Wreck™Wreck

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#11
Sounds like the compound is set at the wrong angle. It should be rotated 29.5* counter clockwise from perpendicular to the spindle axis. Or clockwise 60.5* from parallel with the spindle axis.

Tom
Bloody Hell, there is a good deal of bull floating around on the web about this subject.

One may make excellent threads from the cross slide, contrary to what hundreds of Youtube "how to" videos will tell you.
No, this will not cause abrupt tool failure.
No, this will not render a thread unusable.
No it will not cause your machine to explode in a hail of shrapnel.

It will however **** off traditionalists in search of 1935 era copies of Machinery's Handbook.
Choose wisely
 

brino

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#12
Bloody Hell, there is a good deal of bull floating around on the web about this subject.
Perhaps, but let's try to clear up some confusion in this thread.

@higgite is totally correct that setting the compound to the wrong angle and then using the compound to feed the threading tool can give "off angle" threads. That is a very likely explanation for Andy's threading problem when using the compound.

One may make excellent threads from the cross slide
That is also absolutely correct!
In fact, this method only requires the tool bit to be ground to the proper angle and then set square to the work with a fish-tail gauge.
Since you then use the cross slide to advance the tool the angle of the compound has no consequence.
This is a very likely explanation for Andy's success when using the cross-slide.

What I have seen is that on my small, sloppy lathe I get better results when threading with the compound since I am only cutting on one side face of the threading tool, it seems to put less force on everything, reducing chatter and giving a better finish.

Here are a couple links to similar discussions to give some pictures:
http://www.hobby-machinist.com/threads/what-am-i-doing-wrong.54207/#post-449384
http://www.hobby-machinist.com/threads/threading-help.49488/

-brino
 

Wreck™Wreck

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#13
Perhaps, but let's try to clear up some confusion in this thread.

@higgite is totally correct that setting the compound to the wrong angle and then using the compound to feed the threading tool can give "off angle" threads. That is a very likely explanation for Andy's threading problem when using the compound.

-brino
Single point threading is a form tool operation, the included angle is fixed by the tool shape.
If the tool is square to the work moving either the cross or compound slides can not alter the angles of the tool form, this can only be accomplished by changing the angle of the tool itself which would require another axis of motion.

In other words the tool angle remains constant regardless of the approach angle, advancing the tool from the compound set at an angle alters the position in the X and Z axes not the tool angle itself.

 

brino

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#14
Sure the tool angle is constant.
But in the case with the compound set to the wrong angle that constant angle is also wrong.

I am NOT talking about a rotated tool. The tool gets fed in on a bad diagonal.

One edge of the cut thread is indeed controlled by how the tool bit angle meets the work.
However the other edge is controlled by a possibly bad angled compound.

Sorry, my CAD skills are not up to supplying a drawing.....and I don't even have visio on this computer.....

-brino
 

higgite

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#15
Bloody Hell, there is a good deal of bull floating around on the web about this subject.
.
Choose wisely
Yes, there is. But, discounting a widely accepted method of doing something in favor of another widely accepted method of doing the same thing doesn't do much to clear it up for beginners who might be interested in learning the proper way to apply both methods. Both of the forum threads that Brino posted links to above have illustrations of the proper angle vs the wrong angle for threading with the compound, for those who would like to compare both methods before they choose wisely.

Tom
 

Wreck™Wreck

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#16
Sure the tool angle is constant.
But in the case with the compound set to the wrong angle that constant angle is also wrong.

I am NOT talking about a rotated tool. The tool gets fed in on a bad diagonal.

One edge of the cut thread is indeed controlled by how the tool bit angle meets the work.
However the other edge is controlled by a possibly bad angled compound.

Sorry, my CAD skills are not up to supplying a drawing.....and I don't even have visio on this computer.....

-brino
The thread included angle CAN NOT be altered by the Approach Angle, it is fixed by the tool shape. A 60 Degree included angle tool shape will always produce a 60 Deg. included form on the part, the angle of approach does not change this relationship in any way.

I think that this makes the idea far more clear, a threading form tool produces a fixed included angle defined by it's shape, it will make a V at that angle regardless of the approach. One may advance the tool at any angle, this will not alter the form on a manual machine. The theoretical sharp point of the tool may move yet the form remains.

 

Dan_S

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#17
The thread included angle CAN NOT be altered by the Approach Angle, it is fixed by the tool shape. A 60 Degree included angle tool shape will always produce a 60 Deg. included form on the part, the angle of approach does not change this relationship in any way.
I'm sorry but this is wrong.

It is only a form tool when the angle of the compound is less than 30 degrees to perpendicular. When the angle is greater than 30 degrees, it will only be a form tool on the left cutting edge, because the right side of the tool has clearance.

The image below shows what would happen with the compound set to 45 degrees and 8 passes taken to get to depth. As you can see you are left with steps. As the number of steps goes to infinite, you get the black line. That would yield a thread angle of 75 degrees. This is why all the machinists I know take the last few light passes using the cross-slide, regardless of what angle they set the compound to. This turns the the toolbit back into a form tool.

https://drive.google.com/file/d/1uEs240xor_thckPBB5CpzwJbPBjjjkdk/view?usp=sharing

threadingAngle.png
 

Wreck™Wreck

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#18
Indeed, doing so will leave steps on one side but the angle remains unchanged.
Did not recommend doing so merely pointing out that the tool angle is constant.
Like so.

For practical purposes this will not work well for reasons that are obvious.

This has been one of the most entertaining threads that I have seen here, keep it going.
 
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higgite

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#19
This has been one of the most entertaining threads that I have seen here, keep it going.
What's the point in keeping it going? Looks to me like we have reached an impasse. Hopefully, the OP understands the various explanations well enough to choose wisely.

Tom
 

Aqua-Andy

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#20
Wow, thanks for all the info. My compound angle was not correct. I blindly set the compound to 29.5* and tried to cut threads. Well on our lathe the compound scale is set to 0* being parallel with the shaft. So today I played around some and set the compound to 60.5* and cut a perfect looking thread. This machine has been there for over twenty years and I'm the first to use it to cut threads. I was even told that the lathe is too worn out and inaccurate to cut threads. I found all the change gears to do the full range of threads the machine is capable of, they were packed away in a box and still had the cosmoline on them. every time I use this machine It seems like I learn something new.
 
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