tool bit/inserts for turning

[Jonnyofalltrades]

I have a precision Matthew’s 1236t lathe with a BXA tool post. I need an inside left hand thread tool for truing up receiver threads in reverse.

What do you recommend with carbide inserts?

Even if you do decide to run your lathe in reverse for truing threads, you would still want a right-hand insert.
But before you do the upside-down boring bar/reversing spindle setup, just try threading a blind hole in a conventional manner. Do air passes if you must. It really isn't as scary as you think.
10 minutes practice and you'll be a pro.
If someone like me who is all thumbs can do it, I'm sure you can too.

 

[ELR LVR]

I have a precision Matthew’s 1236t lathe with a BXA tool post. I need an inside left hand thread tool for truing up receiver threads in reverse.

What do you recommend with carbide inserts?

Maybe use one of these?
If you wanna go reverse, flip the tool over in the holder

Pardon Our Interruption...

 

[tonyben]

I already have a threading tool for right hand. If I turn it upside down, the cutting tip will be on the right side and I'll have to move the cross slide in to cut on the opposite side of the threads. But this wont' work because the cutter will be upside down and when the chuck is turned to the reverse it advances on the non-cutting side of the insert.

I want to do it like this guy. At the 24:08 mark you can see the chuck as it's slowing down and it's actually turning in revers and he's got a left hand cutter with the cutting surface on the top. When the chuck is turning full speed the camera frame rate makes it look like it's turning forward but as it slows down you can see it's actually turning in reverse.

 

[ELR LVR]

I already have a threading tool for right hand. If I turn it upside down, the cutting tip will be on the right side and I'll have to move the cross slide in to cut on the opposite side of the threads. But this wont' work because the cutter will be upside down and when the chuck is turned to the reverse it advances on the non-cutting side of the insert.

I want to do it like this guy. At the 24:08 mark you can see the chuck as it's slowing down and it's actually turning in revers and he's got a left hand cutter with the cutting surface on the top.

Sorry the tool I showed you, would have to have the point sticking out the opposite side to do what you want.
But - Instead of going in reverse
Thread as normal BUT
Can you cut a relief groove where to stop at, at the end of your cut
Since if you fudge a little bit into the relief groove it wont hurt anything.
Come in with the threading tool as normal
Trusting your numbers
and stop/disengage when you hit the mark? (cutting with your compound set at 0 deg instead of the usual 29 so that when you hit your stop number it will be the same every time)
Also this sort of operation is one reason we have the slow speeds
---
to set your tool, have it loose in the holder, fit it into a thread groove while the half nut is engaged and feeding in the correct direction
then lock your tool down
it should now follow your threads and you can make deeper cuts
I'd do a practice piece first to be sure you got everything down (Piece of pipe or something)

 

[tonyben]

But then that would cut a left had thread, no?

 

[ELR LVR]

But then that would cut a left had thread, no?

Ro Scratch going in reverse,
You would have to advance in the Y plane like a normal threading operation,
advance the tool outward only in the X direction each cut
but stop/disengage the halfnut at your relief groove
---
Edit:
To go in reverse like you are wanting - and feed left to right, I just turned my insert upside down
looks like it would work
although my set screw to hold the insert in, only engages maybe 3 threads,
If you can use a longer screw for your tool in the holder (Boltdepot.com)
Maybe turning the insert upside down will work to do what you want
You would run the lathe in reverse / Chuck in CW direction
and be able to feed L to R

 

[LVLAaron]

Thread like "normal" - Go slow. Set up a dial on the way closest to you. Hit zero, spin the wheel lift the lever. Easy peasy.

 

[WSnyder]

I already have a threading tool for right hand. If I turn it upside down, the cutting tip will be on the right side and I'll have to move the cross slide in to cut on the opposite side of the threads. But this wont' work because the cutter will be upside down and when the chuck is turned to the reverse it advances on the non-cutting side of the insert.

I want to do it like this guy. At the 24:08 mark you can see the chuck as it's slowing down and it's actually turning in revers and he's got a left hand cutter with the cutting surface on the top. When the chuck is turning full speed the camera frame rate makes it look like it's turning forward but as it slows down you can see it's actually turning in reverse.

Sandvik has always had the best catalog IMO showing the tooling options for lathe work. Pay attention to the helix angle when you start swapping tool holders and threading inserts around. The note below mentions using a negative shim, this is to correct the helix angle with some setups.


Full catalog:

https://cdn2.sandvik.coromant.com/files/a53b485b-be0f-019d-8100-3f0d1619b9fa/5370939c-6de5-4b34-a938-2fa290a42316/c-2920-031.pdf

 

[WSnyder]

 

[El Matador]

Helix angle shouldn't be an issue with a 16 TPI action thread. The large diameter and fine pitch make for a fairly shallow angle and the inside threading inserts have quite a bit of clearance. There's not much you can do about it anyway since interchangeable anvils are only available on threading tools 3/4" or larger, which is too big for getting inside an action. Use left hand, internal threading tools and inserts for making right-hand threads in reverse. SIL is the boring bar type and 16IL or 11IL inserts, depending on which size your tool accepts. For example:

SIL 0500 L11 (Internal left hand tool, 0.500" forward shank diameter, size 11 inserts)
11 IL 16 UN inserts (size 11, internal left hand, 16 TPI Unified National thread full profile)
11 IL A60 inserts (size 11, 60 degree partial profile)

My lathe has an 8 TPI lead screw with some wear on the half nuts. This setup makes it a bit tricky to get positive engagement of the half nuts 100% of the time. Once in a while I get poor engagement and have to disengage, then try again. If this were to happen while threading in reverse it would be a disaster since there is zero room for error once you engage. So even though I like the concept, threading in reverse is not a viable option for my machine. If you have a 4 TPI lead screw and don't have issues engaging perfectly every time then it may work nicely for you.

 

[ELR LVR]

But then that would cut a left had thread, no?

Here ya go man
This is what ya want then

Lathe Boring Bar 1/2" Left Hand Internal Threading Holder 3/8" Carbide Inserts | eBay

About the threading inserts. 1 piece threading tool holder (with wrench). 10pcs Threading inserts. Pitch: 0.5--3.0mm. Boring Bar Size: Internal left hand holder, 5.9"/150mm long, 0.51"/ 13mm high, Screw size : M3.5 x 10, T15 wrench.

www.ebay.com

 

[tonyben]

Here ya go man
This is what ya want then
View attachment 1710265

Lathe Boring Bar 1/2" Left Hand Internal Threading Holder 3/8" Carbide Inserts | eBay

About the threading inserts. 1 piece threading tool holder (with wrench). 10pcs Threading inserts. Pitch: 0.5--3.0mm. Boring Bar Size: Internal left hand holder, 5.9"/150mm long, 0.51"/ 13mm high, Screw size : M3.5 x 10, T15 wrench.

www.ebay.com

Thanks! I assume the inserts work well for the typical steel that receivers are made of? I've found Kennametal KCU25 carbide inserts work very well for me, but this is a different brand and I'm not sure of what kind of inserts I'd need.

 

[tobnpr]

I have a precision Matthew’s 1236t lathe with a BXA tool post. I need an inside left hand thread tool for truing up receiver threads in reverse.

What do you recommend with carbide inserts?

Just curious, what's the TIR on the receiver threads that you need to true them?

 

[LVLAaron]

Easy button: https://www.micro100.com/products/tool-details-idlt-61

 

[tonyben]

Just curious, what's the TIR on the receiver threads that you need to true them?

I’ve never done one yet. I’m getting ready to do my own and build the skill. I have the GRE TAN receiver fixture as well as the bushings and the indicator rod for aligning the receiver in the lathe.

 

[tobnpr]

I’ve never done one yet. I’m getting ready to do my own and build the skill. I have the GRE TAN receiver fixture as well as the bushings and the indicator rod for aligning the receiver in the lathe.

To each, their own.
IMO, it's one of the highest risk, lowest reward ops in bolt gun smithing and rarely needed.
But, that's a different discussion...

 

[tonyben]

My target demographic are shooters that shoot the vintage sniper matches. These shooters use Remington 700 receivers of all vintages and some want the action trued and a new barrel made from a Kreiger or Bartlein barrel blank.

 

[WSnyder]

I have the GRE TAN receiver fixture

I know you’re already invested in that one but look into making and using the Mike Bryant style fixture. Much easier to adjust and use IMO than the Gre-Tan/Viper style you have. I never use the Gre-Tan type anymore. There are pictures and discussions about the Bryant on this forum.

 

[ELR LVR]

To each, their own.
IMO, it's one of the highest risk, lowest reward ops in bolt gun smithing and rarely needed.
But, that's a different discussion...

I tend to agree with this opinion
I think it is more important that all mating surfaces are flat with respect to each other
recoil lug ground flat
and the threads lapped to each other

 

[LVLAaron]

I'm not qualified to be giving advice, but I don't like the gretan/viper style jigs. They move pretty easily.

I built this fixture for actions and dies. With this you're just holding onto the front of the action and aren't going to bend it like you can with the larger jigs.






More unsolicited commentary I'm not qualified to give: I'm glad I know how to clean up threads, but I've never recommended it to anyone. I check them with an indicator and assess the situation. I've yet to see one that warrants cutting to a non-standard size. I would much rather you spend your money on sleeving the bolt, or fitting a bolt shroud.

I always clean up the action face, and pin the recoil lug.

If the threads aren't perfect... just turn your tenon thread another couple of thou. As long as your barrel shoulder meets the action face properly, the threads don't matter.

My two cents.