Threading barrel tenon with a die?

My lathe isn't equipped to cut metric threads. Best I can tell, I'd need 3 new gears to cut the metric pitch I want. OR, I could buy a M26 x 1.5 die on Amazon, make a piloted die holder from scrap in stock, and cut my threads with the die. I'm not trying to build a match rifle, just a basic hunter. A couple thou off center isn't going to hurt anything. Is there any good reason not to cut barrel tenon threads with a die?

No reason at all.........provided you get a clean ,nicley fitted thread.......or even if not,then loctite will come to your rescue.

I'd try threading it 16TPI a bit oversize and use the die to shave it down to size

I would definitely try a test piece or 2 first though.

And I believe there's a thread here, recently, about this same subject, more or less.

A die from Amazon ... hmm. Seems most of the large name brand dies I've seen wouldn't do a decent thread. Smaller stuff are fine. Just a matter of how much material each tooth has to plow off.

Another issue is the lead-in on them, you won't get a full thread to a shoulder. I've had fair luck flipping them over to clean up the taper, but I've never used anything this big.

First problem is going to be the die is fixed size........and for sure will cut an undersize thread.............and without knowing the quality ,or lack of,in the amazon product,it may be problematic to get the setscrews in the holder secure enough to cut such a large thread in one go,.............The only time I recall running a threading die over a barrel tenon thread was a fail ,as the barrel steel was so soft the die immediately dug in and cut undersize.............this was a special situation ,as normally ,you wont have a die to match any barrel thread,but in this case the thread was 1x14 tpi Enfield,and an old NF (not UNF) 1" is close enough.

wesg said:

I'd try threading it 16TPI a bit oversize and use the die to shave it down to size

I would definitely try a test piece or 2 first though.

And I believe there's a thread here, recently, about this same subject, more or less.

A die from Amazon ... hmm. Seems most of the large name brand dies I've seen wouldn't do a decent thread. Smaller stuff are fine. Just a matter of how much material each tooth has to plow off.

Another issue is the lead-in on them, you won't get a full thread to a shoulder. I've had fair luck flipping them over to clean up the taper, but I've never used anything this big.

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Yes, I was thinking about making a short 16 tpi thread to get the die started off well.
For the price of change gears, I'd definitely be open to shopping for the highest quality die I could find.
I'd definitely flip the die to clean up as much of the lead in as possible, then clean off the unfinished threads to the shoulder with a parting blade.
I was thinking I should definitely start with the tenon at minimum (or slightly under) diameter for the required thread.
Luckily, I have extra barrel length to practice with. I'm repurposing a used 375 H&H Winchester barrel to become a 375 Raptor (308 based) barrel for a Howa. The first 1-3/4" of the existing barrel is available for practice. I have a second barrel available, but if I can't get the thread right on the first, I'll probably just pay someone else to thread it.

I feel so blessed that my Graziano has a lever to flip from inch to metric.

Of course, there are other things I can't do because I didn't get the change gears with it. But that's what a CNC is for.

Invest the money in change gears and you'll have a tennon done rite and an asset on the shelf for future projects.

NewGunPlumber said:

Invest the money in change gears and you'll have a tennon done rite and an asset on the shelf for future projects.

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I generally spend freely on tooling, but 3 new gears only gets me one metric pitch likely to be useful in gun work. Each subsequent pitch I may want to cut costs me another gear. As a 63 year old amateur, I'm not anticipating a lot of future metric projects. If I didn't have a couple of perfectly good 375 barrels sitting here, I'd just pay someone else to fit & chamber a barrel. Until someone proposes a specific reason why a die is a bad idea, I have little to lose by trying it.

i find this a bit hard to believe but but an old gunsmith told me this one back in the early 60's he was rebarreling a Mauser clone of some sort that had metric treads and being his lathe would only do English threads and may have been a lose change gears he set it to do an approximate to the metric but only cut a thread and a half then set it back up in phase with what the metric thread would be and cut another thread and a half then one more time so it would have a fuller thread depth and contact . do i believe it ? i would like to see it ! has or can it be done ? never say never ! but it would be a lot of work . most lathes had metric change gears that could be had but like you say at 63 so beg borrow or steel a lathe you can cut them threads on and be done with it

Until someone proposes a specific reason why a die is a bad idea, I have little to lose by trying it.

It's really a good idea to have the threads concentric with the bore and it will be really difficult to do this using a die. What you will lose is the barrel, or you will not be able to sight-in because the barrel is pointing a different direction than the receiver.

You don't say what kind of rifle you are building so I can't tell if cutting off a bum tenon would shorten the barrel beyond usefulness.

There are tables of "near enuff" conversions worked out by various hobbyists for just the situation where no conventional imp/met conversion is available..........some of these are within .01% ,and completely satisfactory..........unfortunately ,they often need change gears you dont have .....Back in the 80s,there was a massive table published in Model Engineer,to allow a Myford ML7 to cut British Association (BA) threads......BA is a mathematical arrangement of metric based threads.,and no satisfactory replacement has ever been developed.

GGaskill said:

Until someone proposes a specific reason why a die is a bad idea, I have little to lose by trying it.

It's really a good idea to have the threads concentric with the bore and it will be really difficult to do this using a die. What you will lose is the barrel, or you will not be able to sight-in because the barrel is pointing a different direction than the receiver.

You don't say what kind of rifle you are building so I can't tell if cutting off a bum tenon would shorten the barrel beyond usefulness.

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I want a 17" 375 Raptor (308 necked up to 375) barrel on a Howa Super Lite (M26 x 1.5).
Until proven otherwise a custom piloted die holder pushed by the face of the tailstock ram should achieve acceptable concentrically and alignment.
MSC offers a better looking die than Amazon, but now the cost is up to $67 plus shipping. I'll probably get a quote for the gears from Boston Gear before committing one way or the other.
I have 2 Model 70 Win 375 H&H takeoff barrels to work with, so opportunity for do overs.
Since the first 1 3/4" at the chamber end has to go anyway, that area will be bored for the pilot and used to start the thread.

NRDock said:

I want a 17" 375 Raptor (308 necked up to 375) barrel on a Howa Super Lite (M26 x 1.5).
Until proven otherwise a custom piloted die holder pushed by the face of the tailstock ram should achieve acceptable concentrically and alignment.
MSC offers a better looking die than Amazon, but now the cost is up to $67 plus shipping. I'll probably get a quote for the gears from Boston Gear before committing one way or the other.
I have 2 Model 70 Win 375 H&H takeoff barrels to work with, so opportunity for do overs.
Since the first 1 3/4" at the chamber end has to go anyway, that area will be bored for the pilot and used to start the thread.

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what is the make of your lathe ? and i hope the barrels are post 64

4D reamer rentals often had common “gun smithing” taps/dies

You could also fabricate a bore guide of some sort like the muzzle threading guides

I'll post this as I'm fairly sure the author is a poster here. And it came from a simple search anyway.


Note the 'error', or lack thereof, with some reasonable size gears.

Also consider what sort of tolerance the receiver might have after machining, heat treating, and whatever abuse it's encountered in it's life.

I don't think my Graziano cuts 'perfect' metric threads. And I don't really care. As noted in the article, I'm not making gauges, just short threads that will distort to bear 'good enough' when torqued up.

I don't remember, and don't have the manual here, but I think it reverses the drive path thru the gearbox with another set of gears. Slow to fast, coarse to fine, is backwards, and I think the direction, RH/LH, is reversed as well.

No way there's a 127 in there anywhere, maybe the 47/37 combo.

Have to stop and reverse. Big deal, I do that anyway. It's got a threading brake, turn off the spindle it stops, now. Right up to a shoulder, no problem. A typical barrel thread length is faster to reverse than picking it up on the dial anyway.

No extra change gears, so I'm limited to a range that includes just about anything that might be considered 'normal'. Bummer ;-) It would do module threads as well with the extra gears, but considering I don't have a clue what a module thread is ...

I can't do .5mm ... so my first sight tunnels were done on a clapped out EE, using the data on a heavily yellowed piece of paper taped to it. Same basic process, stop and reverse. Later batch went in the Fadal, much easier. So will the next.

1yesca said:

what is the make of your lathe ? and i hope the barrels are post 64

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16 x 54 Pacemaker
I'd need 81, 54, 60, &127 T gears to cut the 1.5mm pitch. I already have the 60 T gear.
I don't know if they are Pre or Post 64 barrels. They both have a coned breech end with a wide extractor cut. Both have Winchester markings, but one is marked HCR Harvester and the other is marked Safari Express. I bought them years ago on EBAY for a 38-55 double project that evolved into a 357 Max instead.

NRDock said:

16 x 54 Pacemaker
I'd need 81, 54, 60, &127 T gears to cut the 1.5mm pitch. I already have the 60 T gear.
I don't know if they are Pre or Post 64 barrels. They both have a coned breech end with a wide extractor cut. Both have Winchester markings, but one is marked HCR Harvester and the other is marked Safari Express. I bought them years ago on EBAY for a 38-55 double project that evolved into a 357 Max instead.

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interesting about the barrel also nice lathe yes a set of metric gears for that machine would be pricey to bad there's not someone out there with a set you could use

There are several different combinations that dont need a 127 t gear

NRDock said:

I want a 17" 375 Raptor (308 necked up to 375) barrel on a Howa Super Lite (M26 x 1.5).
Until proven otherwise a custom piloted die holder pushed by the face of the tailstock ram should achieve acceptable concentrically and alignment.
MSC offers a better looking die than Amazon, but now the cost is up to $67 plus shipping. I'll probably get a quote for the gears from Boston Gear before committing one way or the other.
I have 2 Model 70 Win 375 H&H takeoff barrels to work with, so opportunity for do overs.
Since the first 1 3/4" at the chamber end has to go anyway, that area will be bored for the pilot and used to start the thread.

Click to expand...

Try this one - https://www.ebay.com/itm/3918427821...MK883tjGWV2IqN6G60y8U3ecmlJ8|tkp:BFBMuv37maFh


I buy a lot of single use tooling on ebay and have had pretty good luck with it/

[ piloted die holder pushed by the face of the tailstock ram should achieve acceptable concentrically and alignment ]

i have fixed more then one muzzle brake treading job someone tried that on . for the most part concentrically and alignment are not something your going to get from a die . it would even be a tall order for one of these a

PRECISION SELF-OPENING GEOMETRIC STYLE DIE HEAD​