Help required with threading inserts

[Blogwitch]

Another question again, this time concerning threading inserts.

Has anyone any experience with them?

I do know a few things from a bit of research. For what we do, basically there are two sizes, 11 and 16, then 60 degree and 55 degree followed by right and left hand and maybe internal and external, or can they be used for each type of threading?

There are other sizes available plus many different shapes including Acme, but I am just interested in the basic ones above and proceed from there.

The sort of info I am after is how they are used, by the looks of the holders they are used by swinging your topslide over to half the angle, do they cut nicely profiled threads? Are they robust or is it changing to a new tip after each main job?

There is a reason for this, it is getting much more difficult for me to sharpen cutters, I can't do it by hand any more and even grinding using my surface grinder has become a large chore, if I can get away with just dropping in a pre made tip, it will help me no end in the future. In fact, I already use a lot of tipped tooling and getting good results, if these will be acceptable, then it will be the icing on the cake.

I have got my milling cutters sorted, it is just lathe tooling now, and I will modify or make a new swing up tool to take any holders that I start to use for threading.

Thanks in anticipation.


John

 

[RM-MN]

Carbide threading inserts last a long time in a production shop. The are run until one tip gets worn, then turned to a new tip, and when the third tip get dull they are replaced. Unless you are a production shop you probably won't be able to dull one tip to the point that it needs replaced. Even high speed steel threading cutters last a long time unless used for something very hard or abrasive.

 

[Jasonb]

I don't do a great deal of screw cutting on the lathe but do find the insert tools work well.

There are two main types - "full form" which you need one insert for each pitch as they have the correct radius on teh tip to vut the vally of the thread, this can get a bit costly.

The other type are "partial form" which are basically a pointed Vee at the desired angle, each tip will cover a range of pitches so for example you may get a metric insert that does 0.5mm to 1.5mm pitch so that could be used from any standard thread from M3 to M12 plus any large dia but small pitch threads like M18x 1.0mm.

I have the 11 size on an internal bar as it will fit into smaller holes and it is also possible to use this bar at the rear of teh work running the lathe in reverse so you could get away with just one holder but would need to back it out of the cut rather than use a swing up. But handy if threading to a shoulder as you can work away from the shoulder at a ggood speed.

As they are partial form you may just need to chase along teh crests with a needle file but otherwise they give a good thread and seem to work OK hand turning the chuck as well as under power.

I tend to seed straight in but they do also work with an angled topslide. only issue you may have is they can be a bit bulky on small dia threads when using tailstock support so you may need a half ctr or make up a small dia ctr - this is a 16mm external insert

 

[Blogwitch]

That is a good bit of info gents, things are starting to look up.

Just two bits of info that I still require, can the same tip be used for both internal and external threading and what is the difference between the holding and use of right and left handed tips? This last bit has me rather confused, and I just hope it isn't anything to do with right and left hand threads, but the holders seem to be not just mirror images.

Attached is one of the charts I am looking at for info.


John

View attachment Thread turning inserts.pdf

 

[bazmak]

One will cut from the front and the other will cut from the rear to give both
options for internal and external threading.I have looked at these and if I was doing
more threading would definitely use them.For the little I do I can still
grind HSS ok.If you can no longer grind the form then its reason enough
to use them

 

[Jasonb]

On the coarser pitch inserts there will be more relief on one edge due to the steeper helix angle so you would have to use the correct insert depending if cutting from the front or back.

Also for the same reason the tip is placed on the left of the insert for external threading from the front but on the opposite side for cutting from the rear. This allows the tool to cut upto a shoulder.

As I have shown it is possible to use an internal tip to do external threads but it has to be held in a internal holder and used at the back and probably not ideal on a coarse thread such as a spindle for a lathe thread.

 

[rodw]

I'm not sure if I'm qualified to join in as I've only ever cut 3 threads in my life! But all of them have been cut with insert tooling. I purchased a set that does both internal and external threading. I have never used the internal tool but can confirm that both tools use the same insert.

This is the kit I purchased

https://www.machineryhouse.com.au/L456

EDIT:
OOPS I lie, they included different inserts for internal and external threads

 

[Blogwitch]

As far as I am concerned Rod, anyone can join in as long as it improves my knowledge about the subject somewhat, or maybe someone else has further questions that I haven't come up with yet.
All the replies that have been posted up to now have helped me in my quest for information about the system, and to reply to Baz about being unable to hand grind any more. I only have the use of thumb and forefinger on my right hand now, so I can't hold the tools rigid enough to grind any more, they bounce all over the place.

Expensive bit of kit there BTW. If I do eventually go that way I am hoping not to spend that much.

John

 

[bazmak]

Just buy the inserts ,the holders can be made easily

 

[kvom]

The inserts and holder I use can be used for either external or internal threading as long as the hole is large enough for the holder to enter. Of course it's for 60-degree threads.

I've never used it for internal threads, and in reality I'd be more likely to threadmill any internal thread for which I don't have a tap.

 

[rodw]

Expensive bit of kit there BTW. If I do eventually go that way I am hoping not to spend that much.

John

John,

I bought that kit because I needed to cut a thread. I've never used the internal tool.

I would recommend you look further afield. I have bought a lot of tooling from CTC Tools in Hong Kong. They have some much cheaper options for threading.

http://www.ctctools.biz/threading-tool-holders/

When I was setting up my shop, every few months I'd order between $500-$800 worth of tooling at a time to make the freight worth it.

 

[Blogwitch]

I wasn't criticizing you Rod, everyone has their own ways of doing things, I have spent at least a couple of thousand UK pounds over the last couple of years, and haven't actually got to use any of it yet, I just hope to get to use it all before I snuff it.

I had already looked about for some items and the one you showed caused me to have a sharp intake of breath, so I do know that things can be had a lot cheaper, what I am after is finding out exactly what is required for the things I suspect I will be needing to be done, right hand and left hand threads in both external and internal in basic two major sizes, both fine and coarse threads.

John

 

[MachineTom]

The carbide inserts are great, beware when threading to a shoulder, or just retracting the tool. The carbide is brittle and snaps off instantly when overloaded. A runoff groove will be needed on most threads to prevent that from happening.
For internal threading I like solid carbide from Micro 100. Form ground they last until you break it. You can buy all different sizes, but I only single point threads larger than 3/8" or odd sizes like extra fine. Two cutters would be all you really need one for 8tpi up, the other for 16 up, depth of 1" and 3/4".

 

[rodw]

I wasn't criticizing you Rod,

I had already looked about for some items and the one you showed caused me to have a sharp intake of breath.

John

No offence taken, your sharp intake is due to the Australia tax that we pay every day for the privilege of living in this country.

I may be fortunate as we use metric in this country as it means we only need 60 degree tooling and there is no difference in form between coarse and fine threads. I do think that kit I bought also included 55 degree inserts for some of the imperial threads. I have cut a couple of fine threads (M12 x 1.0) with the same tool I use for M12 x 1.75 coarse threads.

 

[Chiptosser]

Just some food for thought, Have you thought about grinding a broken tap to make a internal threading tool?
:thumbup:
Grind all, but one cutting edge.

Yes, you will be limited to depth, and the size of tap that you modify will limit you to thread depth.

As you may have noticed by looking at the different tooling, there are single point, double ended, and tri angle tipped threading inserts.

I would not recommend the full form inserts to anyone, unless you want to spend a ton of money for every thread that you want to cut.

 

[Blogwitch]

Chip,

I can no longer hold tooling tight enough to grind myself, otherwise I would.

John

 

[mc_n_g]

I have used the stand up style threading inserts (TNMC and TPMC) both carbide and HSS for threading on a manual lathe.
The lathe has slop in it from 55 years of use.
The tools work nicely to thread parts.
I have not used the lay down style inserts.
I know you need to buy different inserts for different profiles and tooth size.
The stand up style are mainly for 60 degree thread styles but you can probably get others.

 

[Blogwitch]

Thanks to everyone's good info, I now think I have it under my belt.

Except for the two different size issues that I want to use, for small and large thread forms, and the 55deg and 60 deg types for form shape, there are basically two types, one for internal and one for external threading.

So basically eight different tips and four different holders will cover almost everything that I will ever need.

Many thanks gents for all your hard work.

John

 

[stragenmitsuko]

You'll have to use

 

[stragenmitsuko]

You'll have to use a higher rpm when threading with inserts.

Just like any "regular" insert tool , using to low a cutting speed will dull the
tip quite fast .

So threading to a shoulder or threading a blind hole can be demanding .

Other then that , they cut just as good or even better then an hss tool


Pat