Filing a dovetail for a site and underlug

Discussion in 'The Gun Builder's Bench' started by Loonsfoot, Dec 15, 2004.

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  1. Dec 15, 2004 #1

    Loonsfoot

    Loonsfoot

    Loonsfoot

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    I am replacing an octagon barrel and want to try cutting dovetails on the new one to fit a TC and use a TC front site. What is the best way to go about this? (By hand.)I've read of grinding a side off of a triangular file to make a safe-edge file. What tips or advice should I hear? What would be the sequence of steps, and how do I ensure proper positioning of the underlug? It seems pretty simple, but I'd like to hear from those with experience doing it. thanks
     
  2. Dec 15, 2004 #2

    LSU TIGER

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    It's really pretty easy. Locate the spot for the dovetail and color it black or dark blue with a marker. Place the dovetail on the barrel and scribe he ends of the bevels on the barrel. Measure the thickness of the dovetail and mark it on the barrel with a tri-square. Measure in 1/16" from each end of the dovetail and scribe another line. Using a hack saw, cut down almost to the mark that is the bottom of the dovetail, making several cuts from inner most line to inner most line on the other side of the dovetail. I use a cold chisel to remove the standing bits of barrel. Use a small mill file to make the area flat and square. Take a three-suqare file and gring the teeth off of one flat, dipping it in water often to keep the temper. Place the smooth side in the bottom of the dovetail and file almost to the outer most scribed lines. The lug should fit TIGHT! in other words, you will need a hammer and punch to install it. File off any excess metal from around the dovetail. You're finished!!!
     
  3. Dec 16, 2004 #3

    djnye

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    loonsfoot and inland sea--perhaps kewenaw bay
     
  4. Dec 16, 2004 #4

    RussB

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    Loonsfoot, Welcome to the forum.

    Doing a dovetail by hand is best left to the experts. Period! :imo:

    A machine shop, or your local gunsmith can do it for you at a minimal cost on a mill....there are special DT cutters that can cut this for you in just a matter of minutes after set-up.

    The chances you will ruin your barrel are very great if you have no experience doing this same thing...trust me.

    Russ
     
  5. Dec 16, 2004 #5

    Darkhorse

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    Loonfoot,
    Follow LSU Tigers procedure and you should be alright. But first, you do need experience. Try turning the barrel over and practicing a small dovetail slot where it won't be seen. After that you'll know whether or not your ready to try one where it can be seen.
     
  6. Dec 16, 2004 #6

    Guest

    Loonsfoot
    :imo:better yet, rather than have a mess on your barrel and you want to do it yourself, get some metal 1/2 inch thick and a foot long and 2 or 4 inches wide..... you will have plenty of material to practice on . The width won't matter at this point as long as you can make a dovetail. :m2c:
     
  7. Dec 16, 2004 #7

    WV-Rocklock

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    I kinda cheat on dovetails. I bought a dovetail jig from Cains Outdoors and it sure makes life easier for me. I think it was 30$ or so. I use the jig, hacksaw and files and in a few minutes I have a perfect dovetail.
     
  8. Dec 17, 2004 #8

    TANSTAAFL

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    :imo: If first time out of the chute for this task, do the dovetaing for the underlugs first. Will allow for practice, and if a slight goof up there, just you and the shadow will know. :redthumb:
     
  9. Dec 17, 2004 #9

    Deadeye

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    They're very easy to do, just follow LSU's instruction and it wouldn't hurt to try it on an old piece of barrel first.
    I have a milling machine and sometime use it to cut dovetails but I can have one done by hand as quick as I can
    do the setup and cut it in the mill.
     
  10. Dec 18, 2004 #10

    Zonie

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    While your doing your first ones (and every one after that) keep in mind, the biggest error is a failure to keep the file moving in a straight line, perpendicular to the barrel.

    It is a good idea to sit a square or a block of wood or anything that is at a right angle to the barrel somewhere close to where your working. Keep an eye on it and try to keep the file moving in the same direction.

    If you work without a visual reference, the dovetail will almost always be crooked or at an angle. It will often have a "belled" shape to it as well.
    This is where the ends of the dovetail slot are wider than the area in the middle.
    Not only does this look bad, but it reduces the strength of the joint.

    I've done dovetails by hand, but for the exposed dovetails, especially the front sight dovetail which is standing out there for all the world to see, I perfer to let someone with a milling machine do the work.
     
  11. Sep 8, 2019 #11

    BigShow

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    Look up Bill Rabay here or on YouTube. He has amazingly detailed videos on how he cuts dovetails.
     
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  12. Sep 9, 2019 #12

    Spikebuck

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    One thing to keep in mind is that dovetails do not need to be very deep at all. Some sights come with bases that are WAY too thick. So the first thing I do is file the base of the sight so it is fairly thin. When I use the hacksaw, I only go down about the depth of the teeth on the blade.

    It can be a unnerving doing your first dovetail, but if done slowly and cautiously, it's not too bad.

    Here's a few pics from installing a rear peep with a dovetail base.

    1st notice how thin the dovetail base is:

    [​IMG]

    After marking the dovetail location and proper width (does NOT include the dovetailed angles), I used the hacksaw to make a series of shallow cuts...as stated above, about the depth of the teeth on the blade.

    [​IMG]

    After very carefully removing this area with a fine flat file, I used my "safe" triangle file (one side with the teeth ground off that rests on the already filed surface and won't cut down anymore, just an angle into the sides.) and cut small dovetail edges. Go slowly here. A few strokes on each end, then try your sight. A few more strokes, try the base. You'll get to a point where it will start to go in.

    [​IMG]

    At this point, I'll use my brass drift and a small hammer and lightly tap to see if it will go in more. If not, I push it back out, take a couple more light strokes on each end with the safe file, then try again. I do put a very small drop of oil on the dovetail during this process. Eventually it will very snuggley fit with light tapping.

    [​IMG]
     
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  13. Sep 15, 2019 #13

    old ugly

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    length of the dovetale is your enemy.
    start short, get the depth correct, then work on the length slowly with a triangle safety file my opinion from my experiences.
     
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  14. Sep 27, 2019 #14

    Kansas Kid

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    A dovetail chisel or cold chisel ground correctly works real well.
     
  15. Sep 27, 2019 #15

    30coupe

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    Before you start to modify a hardware store file, note that most of them taper from tip to handle. This is one reason your dovetail can end up with belled ends rather than parallel. Instead, go to Brownell's website and order a dovetail file. It will already have a safe side and will have zero taper from end to end. It will be money well spent. Then take your time.
     
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  16. Sep 27, 2019 #16

    Baxter

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    This suggestion makes great sense to me; I read this string thinking that somebody really should make a file with no taper, for inexperienced people such as me.
    Thanks 30coupe.
     
  17. Sep 28, 2019 #17

    Kansas Kid

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    When grinding a file safe your gonna have to grind quite a bit off to get a sharp corner to match the sight or tennon, that’s why I like a chisel for that final detail. You’re mileage may vary.
     
  18. Sep 28, 2019 #18

    Grenadier1758

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  19. Oct 3, 2019 #19

    Vaino

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    After the square recesses for the rear sight and bbl lugs are done {.035 deep}, I use a dovetail chisel to raise a molding on all the bbl lug and rear sight dovetails...the front sight dovetail is filed in. and is .050 deep.

    When the bbl lug fits into the dovetail, the raised metal is peened down for a very tight fit and then filed smooth w/ the bbl.

    After the dovetail chisel has raised moldings on both sides of the rear sight dovetail which is still undersized, the sight is fitted w/ filing for a press fit. The reason for the raised moldings is to yield an effective dovetail depth of .07.

    I use a 1/32" cardboard shim under the rear end of the chisel to prevent marring the bbl when hammering. Bought the chisel from TOW.

    P1010009.JPG
     
    Last edited: Oct 3, 2019

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