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Thread: Boring out a fixed choke with lathe?

  1. #1

    Boring out a fixed choke with lathe?

    Well, can't find much about this in searching, so here goes...

    Ok, so my niece gave me this shotgun. It is an H & R Pardner 12 gauge break action in fairly nice, serviceable condition. It is not worth much, but it is important to me since it was a gift and I want to make a "project gun" out of it. I am going to order and fit a custom stock to it, etc., etc., just for fun.

    It is a modified choke gun, and I want to convert it to screw in chokes, and I want to do the work myself. I will rent the thread-in choke reamer and tap set.

    The question is about reaming it out to cylinder bore so that the screw in choke reamer will fit. Can't I just chuck it up well centered in my lathe and bore out the fixed choke with a boring bar?? The screw in choke reamer would then pilot on its bushing and take out the remaining material in a bore centered/indicated fashion, right??

    Please don't just refer me to someone. I am aware of the fine services available out there, but want to do this myself. I would LOVE to buy/own all the special tools, but an old disabled guys budget just can't swing it. I do however love working in my shop when I can.

    Note: I also have access to a manual Bridgeport Mill, but I don't see as how that would be useful in this case.

    Thanks!
    Vettepilot
    Last edited by Vettepilot; 11-04-2018 at 01:38 AM.

  2. #2
    Boolit Buddy adcoch1's Avatar
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    It should work fine if you have a smallboring bar and get the barrel rotating smoothly and secure. The only possible issue is if there is enough meat for the threads, and most h&r shotguns have pretty thick barrels so it should work. Just measure, then measure again before you start. Good luck and take some picures as you go.
    "Give me liberty, or give me death!" Patrick Henry ,March 23, 1775

  3. #3
    Thanks for the answer.

    Yes, there is plenty of meat for the threads.

    Vettepilot

  4. #4
    Boolit Master Cap'n Morgan's Avatar
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    It could be done on a manual Bridgeport but it would take some careful alignment of the barrel which must "hang" outside the table and the head must be swung to center over the barrel - I once sleeved the chambers on a side-by-side this way.

    A single barrel would be easier to do in a lathe. If you're up to the challenge you could skip the reaming and cut the choke to finished size - threads and all...
    Cap'n Morgan

  5. #5
    Boolit Master

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    The reamer removes the exiting choke, you don't bore anything and your certainly don't need a lathe. What you do need is the pamphlet from Brownell's on "How to install screw-in chokes" It explains everything in complete detail. I've installed choke tubes in hundreds of barrels with nothing more than a carpenter brace, a micrometer and a calculator. It isn't difficult, take your time and measure many times to confirm, there are plenty of barrels that can't be fitted with chokes. I might suggest that if your measurements indicate that you proceed, find a scrap barrel and practice on the junk one before you risk the good one. It can save a great deal of heartache if you know what to expect when you begin in earnest. It is a fun project, good luck.
    Last edited by Jeff Michel; 11-04-2018 at 05:37 AM.
    Before you embark on a journey of revenge, dig two graves.

    ― Confucius

  6. #6
    I don't understand...

    The reamer pilot must be very close to bore size. You select the pilot bushing that most closely fits your bore. Then the pilot fits on the reamer, and is held there with a "C" clip.

    This whole assembly then slides in through the muzzle, and you start reaming out for the threads for the screw in choke. Once reamed, then you tap.

    What am I missing here?

    Vettepilot

  7. #7
    Boolit Master

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    The information that I originally suggested through Brownell's, It's free for the asking. This project will require you do a bit of homework, it's going to be a lot more effective that way instead of me typing four pages of instructions in which I don't place enough emphasis on a particular step and you overlook something and I end up being a jerk. FWIW, I remove the exiting choke with an expanding reamer or shorten the barrel behind the existing choke. Working with a shotgun is not like a rifle barrel, the bore is seldom if ever concentric with the OD and the wall thickness will vary considerably within the same gauge even the same manufacture. You can do it all start to finish on a lathe if you have the skill,
    you don't need the reamer or the tap for that matter. If your going to do it by hand, the minimum you will need besides the appropriate tap /reamer/bushings. A brace, an electric drill might work but will likely be too fast (chatter). A micrometer, a caliper is not accurate enough. Vise jaws that fit the barrel, an expanding reamer or a hack saw, high sulfur cutting oil, a floating reamer holder (this is imperative) a real good light source and an effective means of removing metal chips from the bore as you ream and tap. a cylinder or tru-hone to blend the joint between the barrel and the bottom of the choke tube,and never seize to lube your choke tube. And an assortment of rags, brushes, cleaning solvents. Often time, the wall of the barrel is too thin after the installation to retain a bead sight and you will have to solder on a sight ramp, I used the same type as found on Browning A-5's and then the barrel will have to be reblued since the flux removes bluing. My intent was not to give any sort of lecture, I apologize if it is received as such, but you should be aware, though it is possible to do this at home it will take some practice in a number of disciplines in order to have a successful outcome. If you can find a copy, Shotgun Gunsmithing by Ralph Walker is a good read if you want to work on shotguns, he covers screw in choke installation pretty thoroughly. He designed the Winchoke system for Winchester if I remember correctly. Good luck.
    Before you embark on a journey of revenge, dig two graves.

    ― Confucius

  8. #8
    Hi,

    Thanks for the info. I am a few steps above the average DIY-er, being a machinist, fabricator, welder, etc. But, this would be my first foray into gunsmithing, hence my research, to include posing the question here.

    Thanks again,
    Vettepilot

  9. #9
    Boolit Grand Master

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    One of the reasons for the removeable pilot is it can be replaced with one that correctly fits any bore size simply by ordering or turning one up. Another is it dosnt mar when being used like a snug fitted solid pilot can. Last on a rifle or pistol reamer they allow oil flow thru the barrel to the cutters and chip flushing

  10. #10
    The pilot bushings for the screw in choke reamers are only sized in graduations of a thousandth of an inch or so, to accomodate variations in cylinder bore size between barrels, not to accomodate choke sizes. The fixed choke is supposed to be removed BEFORE using the screw in choke reamer. This info is from Brownells and other trusted sources.

    I am just needing to know if it would be acceptable to machine out the fixed choke on the lathe so I don't have to rent the special screw in choke reamer, the tap, AND choke reamers as well in order to use the screw in choke reamer tool.

    Vettepilot

  11. #11
    Boolit Master
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    Quote Originally Posted by Vettepilot View Post
    The pilot bushings for the screw in choke reamers are only sized in graduations of a thousandth of an inch or so, to accomodate variations in cylinder bore size between barrels, not to accomodate choke sizes. The fixed choke is supposed to be removed BEFORE using the screw in choke reamer. This info is from Brownells and other trusted sources.

    I am just needing to know if it would be acceptable to machine out the fixed choke on the lathe so I don't have to rent the special screw in choke reamer, the tap, AND choke reamers as well in order to use the screw in choke reamer tool.

    Vettepilot
    I think I am a bit better than average hobby machinist and I have not done what you propose but to me it looks like a difficult way to do it. Your setup (and the whole process) is going to need to be top notch to get this right with a boring bar. Need a challenge? Go for it. We never improve by working within our comfort zone.
    Practice first -- get a piece of 3/4 steam tube - polish the inside mirror smooth - turn the outside a couple thou off center to the bore - put a slight taper on that outside as well.
    now set it up - chucking the wonky outside you turned off centre and slightly tapered and bore the inner - again with a slight taper away to zero cut - can you do that excercise good enough that where the taper cut meets the straight polished bore there is zero runout - thats a pass - if there is the slightest hint of cutting more on one side than the other at the join - go back to school.

  12. #12
    Thanks for the input everyone, but as it turns out, it is all a moot point. My lathe is too small, but I thought my brother-in-laws was plenty big enough. Nope.

    I ordered choke reamers...

    Thanks,
    Vettepilot
    "Those who sacrifice freedom for security, have neither."
    Benjamin Franklin. (A very wise man!)

  13. #13
    Boolit Master

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    Quote Originally Posted by Vettepilot View Post
    Thanks for the input everyone, but as it turns out, it is all a moot point. My lathe is too small, but I thought my brother-in-laws was plenty big enough. Nope.

    I ordered choke reamers...

    Thanks,
    Vettepilot
    Just something to think about, normally in a lathe the part is rotated and the tool is stationary but you do not HAVE to do it that way. The part can be mounted on the carriage and the cutting tool rotated in the spindle. I am pretty sure that if you removed the tailstock that you could machine the barrel that way.

    Bill
    Both ends WHAT a player

  14. #14
    Yeah, thats what I figure on doing with the reamer for the screw in choke itself.

    For first removing the fixed choke, I will back bore using piloted expandable reamers and turning them by hand.

    Vettepilot
    "Those who sacrifice freedom for security, have neither."
    Benjamin Franklin. (A very wise man!)

  15. #15
    Boolit Master

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    Quote Originally Posted by Vettepilot View Post
    Yeah, thats what I figure on doing with the reamer for the screw in choke itself.

    For first removing the fixed choke, I will back bore using piloted expandable reamers and turning them by hand.

    Vettepilot
    Ideally the existing choke should be concentric to the bore. On cheaper guns the choke may be swaged in rather than machined ?? They just squeeze the outside of the barrel down for lack of a better term. The H&R topper that was my first new gun purchase looked like they did it that way. There was a co that sold a device to do that yourself at home, the screw in choked obsoleted all that jazz really .
    Both ends WHAT a player

  16. #16
    Boolit Master Clark's Avatar
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    Click image for larger version. 

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    I bought the Remchoke setup from Brownells. That is a reamer and some pilots.
    That reamer took too long to cut that much material.
    So I made a drawing of the reamer, and cut to a little smaller than the reamer size with the boring bar.
    The reamer then cleaned up quickly.

    Click image for larger version. 

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    There is an accessory for the R8 mill that converts to a right angle.


    There are lots of variations in shotguns and lots of ways to deal with them:

    1) I am set up for 12 ga Rem Choke in a few pilot sizes.
    32 threads per inch system.
    I need a barrel to be .845" diameter.

    2) Winchoke is also 32 TPI and needs .845"

    3) The Tru Choke system with 44 TPI needs at least a .825" barrel muzzle.

    4) The Tru Choke Thin Wall also with 44TPI needs at least .805"

    When the late Randy Ketchum of Lynnwood guns and ammo did it [he was a real gunsmith], he cut off the last 2" choke and all, only to find that the bore is off center sometimes. He described that as a terrible disappointment. I use the whole length of the barrel and spend too much time reaming out the old choke steel mass, so I have gone to a boring bar to prep for the reamer. Reaming through the choke gives more wall thickness to work with, but it also means more slow reaming.

    I also have a shotgun that has a bulge where the threads are. Stan Baker [famous late shotgun gunsmith] swaged the barrel out and then cut the threads. That pushes the front sight up higher.

    Jack Belk, famous gunsmith, sometimes re sizes the outside of the barrel with rollers.

    I sold a minty 870 for dirt cheap, with the caveat that Remington had reamed and tapped the choke off center and crooked, and so it shoots way to the left.
    Last edited by Clark; 11-16-2018 at 09:08 PM.

  17. #17
    I still just don't understand how one would use the screw in choke reamer with a fixed choke. The bore must be open, no choke, cylinder bore to use the tool.

    You select the pilot bushing for the reamer that best fits your particular bore. Then you secure that pilot bushing to the reamer with an "E" clip. Then you slide that reamer/pilot bushing assembly into the muzzle, and start reaming the bore to the size necessary to tap the threads, that then receive the screw in chokes.

    The way I see it, and the way it is explained at Brownell's and other sources, you MUST remove the fixed choke with expandable reamers, (or cut the barrel short enough to remove the choke), BEFORE starting to ream with the special screw in choke reamer.

    Anyway, I now own the expandable reamers required, and will rent the screw in choke reamer and tap.

    Vettepilot
    "Those who sacrifice freedom for security, have neither."
    Benjamin Franklin. (A very wise man!)

  18. #18
    Boolit Master Clark's Avatar
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    I used old shot gun barrels. I put female remchoke threads on the muzzle and male remchoke threads on the breech, and screwed them end to end.
    It shoots ok, but is awkward in the house.

  19. #19
    That would benefit from a sloooww burning powder!


    Vettepilot
    "Those who sacrifice freedom for security, have neither."
    Benjamin Franklin. (A very wise man!)

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