Top Notch threading inserts and tool holder

[LVLAaron]

When I did things on a manual machine I knew when to start checking the fit by the width of the flat on top. I could get to within a pass or two before checking.

Bingo.

 

[gunsandgunsmithing]

What they're telling you about the BXC inserts is right on. They do a great job at low rpm on stainless. Still, they do better if you can run them at about 200rpm or so. Same with BMA inserts but they like a little more speed, still. Both do well though, even down to 70rpm or so but that's slower than ideal, for sure. The closer you can get to ideal speed/pressure, the better the finish will be. You have to look at carbide differently than hss. Hss cuts where carbide, for lack of a better way of saying it, kinda melts it off and is dependent on heat at the contact area for best results. Not the best way of stating it but it's apples and orages when comparing carbide inserts to hss. You just have to keep in mind that heat is a big factor in how well carbide will cut vs hss. You can cheat it a little with using a little heavier cuts with carbide to get that heat at the point of contact. Most of that heat goes away in the chip so it's not a huge deal but that heat is exactly why hss is best when talking about inducing or relieving stess in the part being machined. This is why I almost always use a very sharp hss cutter for crowns, fwiw.

Bottom line, the bxc grade is the best choice for most bbl work with bma being another good option if need be. Just play with speeds/feeds and pressures to get a finish that you're happy with.

Check out this chart

Carmex - Inch Catalog 2022

Carmex - Inch Catalog 2022

212.235.101.239

 

[gunsandgunsmithing]

Bingo.

Yes, full profile is really handy if doing many identical parts too or for brakes/tuners with a very consistent thread on the female part. Just play with the od before threading and when the cutter just kisses the tops of the threads, you're there. You can be remarkably close just by eyeballing it this way.

 

[urbanrifleman]

Left insert is flat on top. Middle insert has a K chip breaker, the right insert also has a K chipbreaker. It is just adding positive rake in these inserts.
View attachment 1467046

Wow Walt thanks!!!

Yes, I see it!!! Now I get it.

 

[eddief]

I have Carmex BXA and MXC coated inserts. They work great as all said, but the Iscar laydown with IC908 coating do even better. Slow or fast they cut phenomenal. For slow manual speed, it's all about the coatings. I also have HSS and the Warner stuff, but I will take the good carbide inserts all day long, manual or CNC.

https://www.mscdirect.com/product/details/88341946

 

[urbanrifleman]

In fact you had better turn the OD smaller. If you don't you're depending on the mating threads to be perfect.

Savage threads are always way undersized on the OD but they actually always fit great. They are very flat top looking. I have measured some that were 1.048 OD for 1.0625 x 20 threads.

So you are saying that a flat top thread properly fit is actually a better fit? Any explanation you could provide would be great. I've never completely understood this.

 

[urbanrifleman]

I have Carmex BXA and MXC coated inserts. They work great as all said, but the Iscar laydown with IC908 coating do even better. Slow or fast they cut phenomenal. For slow manual speed, it's all about the coatings. I also have HSS and the Warner stuff, but I will take the good carbide inserts all day long, manual or CNC.

https://www.mscdirect.com/product/details/88341946

Iscar 16ERM A 60 IC908 Carbide Laydown Threading Insert (5921206), 1 Piece | eBay

Iscar 16ERM A 60 IC908 Carbide Laydown Threading Insert (5921206), 1 Piece. TiAlN Finish, RH External Partial Profile 60� Thread, 48-16 TPI, 3/8" Inscribed Circle, 0.143" Thick

www.ebay.com

Here is the MSC eBay link if someone wants to try one.

 

[SKWERLZ]

Savage threads are always way undersized on the OD but they actually always fit great. They are very flat top looking. I have measured some that were 1.048 OD for 1.0625 x 20 threads.

So you are saying that a flat top thread properly fit is actually a better fit? Any explanation you could provide would be great. I've never completely understood this.

CNC threading insert – partial vs. full form - Cadem

CNC threading insert: When would you use a partial profile insert and when a full profile insert ? What is the difference between them ? An explanation.

cadem.com

Add in correct root flat/radius for individual TPI’s allowing tighter fit with less work compared to universal 60 degrees cutters.

 

[gunsandgunsmithing]

Savage threads are always way undersized on the OD but they actually always fit great. They are very flat top looking. I have measured some that were 1.048 OD for 1.0625 x 20 threads.

So you are saying that a flat top thread properly fit is actually a better fit? Any explanation you could provide would be great. I've never completely understood this.

To a point, clearance is clearance. Threads should never be left full sharp. The flat width is specified and can be found in machinery's handbook. Full sharp can only cause problems and is, in every way, incorrect machining practice.

 

[urbanrifleman]

To a point, clearance is clearance. Threads should never be left full sharp. The flat width is specified and can be found in machinery's handbook. Full sharp can only cause problems and is, in every way, incorrect machining practice.

I suppose I was meaning making a thread MORE flat top. Which appears to be what Savage does.

 

[LVLAaron]

for you full profile insert guys... compound or straight in?

 

[WillyTP]

Straight

 

[gunsandgunsmithing]

I suppose I was meaning making a thread MORE flat top. Which appears to be what Savage does.

I don't know what else to say really. If you remove more material from the tops than specified for a given thread, you quickly start removing flank area, which is the area that carries the load. The size and pitch of the savage nut is overkill, though and wouldn't typically cause issue with a wider flat. It's normally 1/8 of the pitch, iirc. But removing flank rapidly weakens the thread. I've never seen a print of the thread specs of a savage nut. It may or may not require more flat than is "standard" based on the specs they use but otherwise, I can't imagine a scenario where using a wider flat than needed is a good thing. But again, that nut would typically be way stronger than necessary, assuming everything is machined and torqued properly. But yes, we've all seen what you're referring to. It does seem like they use a very wide flat on the bbl threads, for whatever reason.

 

[DaveTooley]

Not a better fit. It's still about pitch diameter. It just precludes any interference between the root in the action and the crest on the barrel. I once had a custom action which was threaded with a broken insert. You could not fit the barrel but just going deeper. Once it screwed on it was too loose. And I like loose fitting threads. I finally chased the action threads with a tap. And like I said I could see when I was getting close to the correct depth. Saved a lot of trial and error.

Savage threads are always way undersized on the OD but they actually always fit great. They are very flat top looking. I have measured some that were 1.048 OD for 1.0625 x 20 threads.

So you are saying that a flat top thread properly fit is actually a better fit? Any explanation you could provide would be great. I've never completely understood this.

 

[DaveTooley]

for you full profile insert guys... compound or straight in?

I don't remember the G code and the exact feed angle but I know it's compound with the last pass straight in by the way chips come off.

 

[Judd]

These posts are why I love this place…so much to learn. Thank you all for sharing. I knew most of this because we’ve talked or I’ve talked to others but it seems there is always something else to try. I’m using the BXC inserts, not the thread specific ones. I think I finally switched to a second edge but I can’t tell you how many I’ve done on that last one. Threads still looked good but edge looked beat up a little in a lope. I’ll order the Iscar to try.

I used to do compound but I’ve switched to straight. You should’ve seen the look on my face when my mentor said ”Why the hell are you doing it that way with that insert? Just go straight it, that is what it’s for and it’ll be way faster”. He ain’t been wrong yet

 

[gunsandgunsmithing]

These posts are why I love this place…so much to learn. Thank you all for sharing. I knew most of this because we’ve talked or I’ve talked to others but it seems there is always something else to try. I’m using the BXC inserts, not the thread specific ones. I think I finally switched to a second edge but I can’t tell you how many I’ve done on that last one. Threads still looked good but edge looked beat up a little in a lope. I’ll order the Iscar to try.

I used to do compound but I’ve switched to straight. You should’ve seen the look on my face when my mentor said ”Why the hell are you doing it that way with that insert? Just go straight it, that is what it’s for and it’ll be way faster”. He ain’t been wrong yet

I usually start out with a heavy plunge cut, straight in. As you get closer to finished size, the chip load on the tool gets heavier and I go to the compound for the last couple of passes. But more than one way works, especially with modestly fine threads vs something really course, like a 4 tpi or so. Lots of area in a deep, coarse thread like that and hence, a lot of load on the cutter. It'll work but is more likely to chip or break the insert, ime. I tend to get a little better finish using the compound for the last passes as well.

 

[Alex Wheeler]

Machines are all different, you will need to experiment. Insert types and grades will not work for everyone. My old lathe did not like laydown inserts, the top notch worked great. New lathe works with the lay downs great. I have not found the speed to be all that important. I can get the same finish at 50 rpm as 400. The grade and edge prep of the insert is the main thing. Figure that out and everything gets happy.

 

[gunsandgunsmithing]

Machines are all different, you will need to experiment. Insert types and grades will not work for everyone. My old lathe did not like laydown inserts, the top notch worked great. New lathe works with the lay downs great. I have not found the speed to be all that important. I can get the same finish at 50 rpm as 400. The grade and edge prep of the insert is the main thing. Figure that out and everything gets happy.

A heavier machine does well with some negative rake inserts at times, where a lighter machine typically doesn't do negative rake well.

 

[jackieschmidt]

To a point, clearance is clearance. Threads should never be left full sharp. The flat width is specified and can be found in machinery's handbook. Full sharp can only cause problems and is, in every way, incorrect machining practice.

We use 10% of the thread pitch.

As an example, a 18 tpi has a pitch of .0555 inch. That means your tool should have a .0055 flat on the nose, and if all goes well, the flat on the OD should be about that.