Full profile threading insert

Remember:

With a full profile insert your tool contact with the part increases significantly as your depth of cut increases. Tool rigidity and work holding rigidity are very important when using these inserts.

Chatter, chatter, chatter. . .
 
I thought all full profile tools put a radius top and bottom. Are there some that don't? Doesn't that preclude the need for a file? Meaning, once you hit the PD, the OD is already trimmed to something less than the nominal, and there is a radius (however small) at the root and crest.

Unless I'm mistaken...
 
4Mesh....yes it does. I was trying to relate to what Jim said about cutting the pitch dia too small to compensate for crest interference. There would not be any, but. Read what he said.

Profile tooling is a common in production work, and using it for casual work is a little overkill.

There is a lot of tool pressure in threading and using sharp pointed v thread tooling with CNC's is counterproductive.

There was even a comment that tooling couldn't tell if it was in a cnc or not, I beg to differ. Tooling not designed for the environment it's used in will definitely know.
 
Gotch'a TRA.

I was sorta thinking the same thing. The OD would not need cut to size if you used a full profile insert, since the OD would get reduced as soon as you got close to the PD. (The insert 'files' the tops for you!) :D

I tend to agree on the tooling knowing where it is at its best.
 
My point was if you use a full profile insert and use thread wires or thread mic to tell when you are at spec, a problem can still occur with crest interference and in MHO a file is sure not the way to take care of that. I have watched folks use full profile inserts and turn a thread until an action screws on easy instead of using thread wires or thread mic to tell where they were. After adjusting OD of tenon to 1.058, they then had a loose thread and could not understand what happened. I know two action makers that use full profile inserts (i am one of them) to cut the threads in the actions and control to PD with a PD gauge. Crest limits will allow a shallow thread root in internal thread when pd is still within limits. So--if a 1.0625 od was used and a 1.025 pd was reached (paired for most inserts), then crest to root interference could occur.

3A specs for an ID thread allows a minimum major diameter to be 1.0625. Turning a tenon to 1.062 to 1.0625 is asking for trouble particularly with stainless against stainless.

I love the full profile inserts, I was just issuing a caution on the use of them for barrel tenons.

Jim
 
Last edited:
Jim,
Did you mean to start off by saying that "If you use FP inserts and do NOT use wires/mic" ????

Then, I guess you could be right that if the action manufacturer leaned on the tolerance pretty hard, that there could be an interference situation with too large a tenon, but, A, the action maker should not do that, and B, the gunsmith should not do that! Hhehe. I'd agree, it's easier to cut the blank tenon to 1.055 first, then thread, rather than file it off when the threads are done.
 
Phil

That is what I meant to say--the mics or thread wires need to be used to determine the pitch diameter (PD) which is the target number. As for pushing the specs--I ended up targeting the ID PD to 1.0264 to 1.0275 based on the samples of many other custom actions that used the 1 1/16x18 thread. Did not want to hit the middle of the spec and be larger and be "perceived" as having loose threads. With that said-look at insert specs and you will find that controlling to a PD of 1.0264 to 1.0275 results in a major od for the ID thread of 1.0625 to 1.0636.

The tests of many samples of two other brands of custom actions using thread gauges showed that they are using the same target I adopted (based on a large sampling of their actions). That is why I mentioned the caution about turning the tenon OD to 1.058 to 1.055

Jim
 
I see what you're saying now Jim. Personally, even if I went a little under on the tenon it wouldn't bother me, but I'm sure there are others who would think it was the end of the world. You have it right when you say "Perceived". Unfortunately, that's true.

Still, even if a person did cut the tenon to 1.0625, Lets assume you've made an action that was dead on the low limit of the tolerance (probably unlikely). But IF, they were to use a FP insert on the external thread, would it not reduce the OD before it hit the PD that would work for a manual test fit in the receiver? In other words, Isn't the crest of the external thread a non issue, due to the insert profile forcing the smith to get the major OD right? I could easily see where this would be a problem with a V insert, (thus the file).

Any way a guy looks at it, you're right in that it pays to simply measure twice and cut once.

As an aside, for those wishing to look up the numbers we're talking about, here's an excel sheet with the values in it for this thread. If you look at the tolerances for the part OD and internal thread OD, at the limits, they are the same, which means an interference fit. (not very desirable in stainless)
 

Attachments

  • ReceiverThreads.xls
    14.5 KB · Views: 308
No one suggested anyone cut threads without utilizing proper measuring tools. I don't know how that got started. Having od problems when using profile tooling just does not make sense, you can have it with V tooling threads when mixed with threads that are profile cut.

IE....ID threads, profile cut and OD threads, V cut. The crest of the OD threads will need altered.

The best advice is to learn the proper way to machine threads, and to understand what to look for.

This whole fitting a barrel to a receiver thing is getting blown way out of proportion. No need to make it any more difficult than it needs to be.
 
TRA

I am not sure what is wrong with sharing a caution to others based on what I have seen. There are in fact many gunsmiths that buy actions or just put on barrels that do NOT use thread wires or a thread mic. They use the thread and test method-which works for them. I do not agree with doing things that way-but that is the way they do it. Just tried to point out there are a number of actions out there that have pd within specs-but major od of the internal thread is under spec-maybe you are not sure how it happens. But, it does happen and it is not hard to understand how the use of ID full profile inserts can have it happen. Should it technically happen--NO--but they are out there. I have seen actions with the PD at 1.0274 (min pd) and an internal major od at 1.060 (.0025 under min). Both of the above were measured with ID thread gauges.

The internal full profile thread inserts wear faster on the nose than on the shank-so what I have related is not that difficult a thing to happen.
Certainly not trying to blow anything out of proportion-just shared a simple fact so others can watch for it and not end up galling a barrel to an action or having a fit that is on crest versus flank.

Guess we have gotten enough beating on this horse :)

Jim
 
Awe Jeeze,

I just called Production Tool. They are all out of thread wires, they said some gunsbuilders must be discussing threading online. They've been buried in thread wire orders for three days.

Glad I have mine.

Paul
 
I have been following this thread, and I am finally going to ask because I am not getting it.

If you pay good money for full profile inserts, why would you ever need a thread micrometer or thread wires?

I thought that once the insert clips off the top (crest) of the thread, the root of the thread is done. This means the thread form is perfect, does it not? At that point it is the major diameter or outside diameter you are concerned with, and a regular micrometer will tell you everything you need to know. Isn’t this the reason you turn the part a little large and bring the part to specifications using the full profile insert to reduce the diameter to the proper major diameter of the thread you are looking for?

If you continue the in feed with a full profile insert, this will reduce the outside diameter, but the relationship between the crest and the root will not change. So why would you need to measure this relationship?
 
Ron of Va said:
This means the thread form is perfect, does it not?
Click to expand...

Yes the threads you just cut may per perfect but as Jim Borden suggested the thread form on your action may not be perfect.

You have to watch for problems everywhere. I've had a few issues with a couple of custom actions to know that not all is necessarily perfect out of the box.

Paul, need thread wires? Try Fisher Machine. http://www.fishermachine.com/
 
Ron, you are completely misunderstanding the concept of pitch diameter.

Consider this. Threading a 1.450 barrel, and need 1.0625-16 threads. That's 1-1/16"-16.

If you begin threading while the barrel is at 1.450, you will hit the place where the crest of the thread is a full cut somewhere around 1.335 or so. Now, no matter how hard you try, that is not going into a hole that is threaded for 1.0625-16.

Even if you turn the tenon to 1.0625 and then start, again, when the crest is a full cut, you are WAY over the tolerance on Pitch diameter. Remember, there is only about .003x of tolerance from high to low. You are missing by probably .010 right there. Maybe .020. There is a radius at the top of the thread on the external (tenon). Just cause that hit, does not mean the threaded portion is down to size. If you are taking my original contention here and being misled by what I said, I'm sorry. But, what I said still is probably true. Jim pointed out where the possibility exists for things still to go wrong if you do not measure.

Much further on the subject is a topic for another thread. You have a basic idea of threading misunderstood. Or the geometry, whichever.
 
No I have the wires, and have had them... I was making light of the fact that we have beaten this dead horse to death.
 
It sounds like it needs beat a little more, as they're some that still do not understand the process.

Threads MUST be cut and MEASURED to the proper PITCH dimension. If some wish to ignore that concept, they should reconsider whether they are proficient enough to be working on firearms.

All a profile insert does is keep the crest at a consistent height, in relation to the pitch, IT has nothing to do with the pitch being of the proper dia for the application. They were designed for production use and they are more durable and reduce the need to de-burr the thread when finished. Usually a V tool thread is sharp and needs a file to knock off the sharp edges.

I posted a link to a Sandvik Manual.......again I would suggest everyone read it.

Ron,

What you say sounds reasonable, until you consider that the mating thread may have been cut with a different type tooling. IE, as Borden is saying. The problem lies in any interference that may exist with the crest and root of the mating thread. That's why he recommends that the OD be cut smaller than standard. so the crest of the barrel does not gall up in the root of his action threads.

Your right about the profile being correct, but measuring the OD is not the preferred method for fitting threads. In a production setting, and in a pinch.....but never as an acceptable practice.
 
Last edited by a moderator:
As it applies to fitting a barrel to a receiver the receiver effectively becomes the gauge. It either fits well on the tennon or rattles around like a marble in a can.

Wires, micrometers, etc. become rather pointless. This is only amplified if the action has been chewed on by the smith. Full profile inserts are great when running a pile of parts that need to go to a specific thread quality/class. This is what I use when I'm turning a muzzle for a can for instance. The suppressor manufacturers often use a 1/2-28 pitch thread machined to a 2B standard. I'll use the corresponding insert to cut a class 2A on the barrel. So far so good. No bitching from clients. I'd really like to have the suppressor in my hand, but the paperwork involved makes it unrealistic to do all the time.

With regards to being competent enough to work on guns, we (as gun plumbers) exist in a foggy environment when it comes to tolerances. All too often I'm presented with a receiver, be it std production from Remington or a boutique custom action, and the threads are not what the Machinery handbook says it should be. I have the gauging to check 2B threads for Rems, Winny's, and the 1-1/16x18 stuff used by many boutique makers. So I'm left with a decision. Reject 60% of what comes through the door in the interest of being a purest, or make it work. Making it work is far more lucrative.

Man visited the moon in the 1960's-70's. I'm betting at some point some machinist had too much to drink the night before and goofed at least one thread on the Saturn V rocket.

All the astronauts that made it off the pad returned safely so I can accept a receiver thread that's less than ideal in most instances for I know how to bump things around and make the tennon feel like the thimble on a B/S micrometer when I'm done. I'm betting I'm not alone on this. I just do it with code and offsets instead of a compound.

FWIW to date the nicest/most accurate threads I've ever seen are on Jim Borden's stuff. Exceptional in fact. :)

When in doubt, turn a sample tennon on a piece of scrap first. This is what I do when proofing out a new tennon program for something I've not run before.

Measure twice, cut once.

C.
 
Last edited by a moderator:
In my limited work, the only action that will take a full 1.0625 OD tenon is a Remington. Most every custom action I've fit a barrel to requires the tenon to be .005 to .007 smaller that the nominal measurement. As others here state, the major diameter is not what matters, it's the PD. I turn the tenon undersize right off the git-go, use a 60 degree threading tool, and thread the old fashioned way. When the action fit feels right, I measure with wires and record that measurement. It's repeatable and has never failed me.

I know of others that use the full profile inserts, turn the tenon big, and keep threading until the action screws on. To each his own.
 
You must log in or register to reply here.
Back
Top