Left Hand Laydown Threading Bar Question

LEEQ said:
I recently went through the same thing. After much looking I felt like there was a fair amount of evidence that an internal left insert is the same as an external right insert. I bought the internal left and internal right threading tools as well as the external right and external left. I purchased some internal right and external right inserts. I have used internal right inserts in a lefthand external tool upside down to cut a right hand external thread away from the chuck. I used the same method to make a plug gauge. I then threaded internally as you suggest( in reverse, tool upright, cutting the far side of bore, feeding away from the chuck) with the external right insert in the internal left tool. All of my threads seem to be great. I can't find anything wrong with them. I used these methods to produce a 1/2 20 external thread finding my desired over the wires number with the machinery handbook 23. I then purchased a nut and tested the fit. All was well. These experiences suggest to me that I am getting away with what you're contemplating. I might be cutting a misshapen thread, but they seem to fit commercial stuff when cut to a class 2 with the inserts and methods mentioned. I would love to hear from an authority. I couldn't find mention of any IL inserts most places I looked either. I also use the threading tool to find my over the wires number and set my handwheel to zero when threading away from the chuck externally. I just use the threading insert to make my undercut and measure with one or two wires. When I am at the proper number I set the cross slide to zero and know how deep to go. I read up on these methods, but my confidence in trying them came from watching it in action thanks to Joe Pie. All of my measuring methods and threading tricks come from him. I just took a leap on the bangood threading tools and the insert guess. Good luck and keep us posted
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I started using the same method after watching a Joe Pi video and being able to thread at high speed really gets the best out of Carbide inserts plus it is just hassle fee in 99% of what I do.
 
Finally found an answer!! After months of research.

Thank you all for a timely post. I have been looking at this series of inserts for the last couple of months, trying to figure out what I need to do reverse turning. What is more confusing is that there are several Ebay sellers the have both LH & RH internal tools, but come with ER inserts. Even more confusing I ran across an insert manufacturer that shows using a RH insert in LH threading in a "pull out" direction. Joe Pie style. I didn't bookmark it and went looking for the picture to post which basically supports the above discussion. Didn't find it BUT I did run across this Carmex reference which I didn't see before. The difference is 10 degrees on ER and 15 degrees on IR inserts. Got to love the internet. Run the same search every couple of days and come up with different information. With this answer, you can easily run IR threads with an ER bit up to the point where it rubs. Depends on diameter.
Now I know to get a bunch of ER bits for most use and 1-2 IL bits for insurance.

Thanks guys! Am glad to know that I wasn't the only one getting a headache with this problem. Charles
 
There are differences in both the insert profiles for internal and external use and also different anvils, so if using an internal left hand threading tool to cut a right hand thread away from the chuck is uses a different anvil. This makes sense because of the angle of the thread into cutting direction is opposite. The major difference is probably the thread tool holder and the inserts available for that design. Some of the holders do not have an anvil and the inserts are more generic. I have the Carmex threading holders for both external and internal right hand thread cutting and they work well and give very clean thread finishes. Although it may seem that they are more expensive, I am still using the same threading insert for both over the last 2 years. I am sold on lay down inserts, before this I would break the insert every couple of threads, and the finish was poor.

thread inserts.jpg
 
mksj said:
There are differences in both the insert profiles for internal and external use and also different anvils, so if using an internal left hand threading tool to cut a right hand thread away from the chuck is uses a different anvil. This makes sense because of the angle of the thread into cutting direction is opposite. The major difference is probably the thread tool holder and the inserts available for that design. Some of the holders do not have an anvil and the inserts are more generic. I have the Carmex threading holders for both external and internal right hand thread cutting and they work well and give very clean thread finishes. Although it may seem that they are more expensive, I am still using the same threading insert for both over the last 2 years. I am sold on lay down inserts, before this I would break the insert every couple of threads, and the finish was poor.
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@ Chewy + @mksj: Thanks so much for posting the link to the thread turning PDF. They (Carmex) really went to town on the graphics and clarity. Pretty much educational, even if it is primarily a catalogue.
 
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I use laydown for internal and external. Pretty sure my LH internal bar is using 16ER inserts. This is a cheap import from Shars of course. Cuts great!
 
mksj. Which insert are you using? You say you are using one insert for both. Are you using the anvils? Are you using the same bit for steel aluminum and brass? With all the options available, I would prefer to go with a combination that somebody knows will work well. I spent a lot of time trying to figure out what I should get in insert tooling and gave up before this thread.
 
I'll have to make time to try to find some left hand carmex inserts to try out. I'm guessing I'm getting by but may not on a different pitch. Seeing if I can figure out that relief angle on my Mitsubishi inserts sounds like a good idea too(as well as the holder). I for one want a warm fuzzy that I have the tool on hand to cut the thread. Finding out while making a part that I have to order inserts would be a bummer. Thanks for that perfect graphic. I've been crawling along in the dark trying to figure this out by gosh and by golly.
 
I have two separate threading holders, one for external right hand thread and one for internal right hand thread. The holders come with their respective anvils, but others are available. I use the respective inserts for each holder 16ER AG60 is an external and 16IR AG60 is an internal, I thread at ~250 RPM in steel, aluminum/bronze... ~400 RPM. I take 4-7 passes to cut a thread depending on the depth, the maximum depth fo the AG60 0.07" (I have gone deeper) and a TPI of 48-8. Both inserts are made by Carmex, each insert has 3 cutting tips. I have been using the same insert for both steel alloys and softer metals like bronze and aluminum. The discussion is that there is a difference between the different inserts, and in some cases you need to use a different anvil for reverse threading. I am still on my original cutting tip for both right hand internal and external inserts, so although the inserts are more expensive, they last a long time.

I use an automated lathe stop system so I thread toward the headstock for both external and internal threads, I only use the cross slide and do not dissengae the half-nut until the thread is finished. Carmex is an off brand of Iscar, they also use to be sold be Hertel but they brand just about anything, their latest Hertel holders are now from China.

7/8-14 bronze and M16-2.0 O1 steel, these are the finished cut finish. I take only one spring pass when at the target depth, additional passes can result in chatter. The cutters are sharp.
Thread cutting .jpg
thread cutting M16-2.0.jpg
 
The thread pictures are fine. Just what most of us are looking for. Do you know the grade of insert? Carmex lists 5 grades and non are listed for non ferrous. Guessing that you have the partial profile, 8-48 tpi. Thanks for helping us!
 
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