dovetail guide

[WVAED]

I saw on Ebay a dovetail guide. It was just a piece of square tubing with a dove tail slot in the top with small bolt tapped into a lower corner. It said good for octagon barrels. I was wondering if anyone on here ever used such a tool. Also has anyone made their own?

 

[ZUG]

Save your money -- any "guide" can lull you into a false sense of security during the filing process and when you are done you MIGHT end up with a very poor fitting mating piece. My suggestion is to practice hand cutting dovetails on sections of cut off barrels or scrap metal stock until you are confortable to do it on the real thing then do the underlug dovetails first and sights last. Don't cut the dovetails over 0.050" deep more around 0.040" deep and a "shade" less than 3/8" wide - say 0.360" to allow for fitting. OH -- and either make or buy a dovetail file or two - they are easy to make if you have a grinder, belt sander, or course stone & time.

 

[Col. Batguano]

There are many tasks in LR making that are very difficult to do properly. Cutting in dovetails by hand isn't one of them. Most of the time you can get them cut in in an hour or less. Just proceed slowly and cautiously, and make sure your hack saw cuts leave you room to file the bottom deeper. And make sure you have enough barrel left between the bottom of the rifling and the depth of the dovetail cut. Most people advocate at least .010". Some reinforcement to the barrel from the cut away area will be lent by the insertion of the lug though.

 

[ZUG]

There are many tasks in LR making that are very difficult to do properly. Cutting in dovetails by hand isn't one of them. Most of the time you can get them cut in in an hour or less. Just proceed slowly and cautiously, and make sure your hack saw cuts leave you room to file the bottom deeper. And make sure you have enough barrel left between the bottom of the rifling and the depth of the dovetail cut. Most people advocate at least .010". Some reinforcement to the barrel from the cut away area will be lent by the insertion of the lug though.

I think you meant to say 0.100" :v

 

[Spikebuck]

I agree with "save your money."

I remember the first time I cut a dovetail in a barrel...and it was for real, not on a scrap. I was scared to death, but I took my time, followed directions I had read, and it worked out just fine.

I also agree with the advice to start on a lug dovetail, if possible. If you do three lug dovetails successfully, you'll have the process down and be able to do the visible sight dovetails no problems.

Dovetails do NOT need to be very deep. I think the biggest mistake one can make is to think they have to be deep. On sights I buy, the first thing I do is take material off the bottom to thin it down so my cut in the barrel is more shallow.

Here the initial hacksaw cuts are no more than the depth of the fine teeth on the blade.

I then carefully filed those out, then used my safe triangle file to create the dovetail, slowly...just a few strokes at at time...as I tested the fit.

As you can see, the dovetail is not deep at all, but the sight is very firmly held in place.

Here's a front sight dovetail that's about as deep as I go. .0565 on this one.

I'd have to go measure, but I don't think my lug dovetails are any deeper than that.

 

[don hepler]

Now you've done it.....we need to see some more of that rifle.

You can't be teasing us with that little pic.

Sorry OP

Oh forgot...nice tutorial.

 

[Zonie]

The dovetail guides I've seen are a bit more than just a tube with a slot in it.

The slot is case hardened so it won't wear out.

That brings up another problem.

If the tools slot is hardened, it will dull any file teeth that come in contact with it.
This includes the two angular sides of the tri-cornered file that we need to undercut the sides and form the dovetail.

Needless to say, having a tool that frinkles up other, good tools leaves a bit to be desired.

I suggest forgetting about using one of these dovetail guides.

Speaking of dulling up file teeth, that is one of the things that needs to be done to make a dovetail file.

You'll want the teeth on two of the surfaces of a tri-cornered (3 cornered) file to be very sharp, right out to its edges.

On the other surface the teeth need to be either removed or dulled up to the point that they won't cut anything.

This "dull" side rests against the bottom of the slot after the bottom of the dovetail has been cleaned up with a narrow flat file.

As the flat file has already finished the depth of the dovetail, you'll use the 3 corner dovetail file to form the angular undercuts but not to increase the depth of the slot.

That's why the third flat needs to be dull.

In this condition, it can slide on the bottom of the dovetail while its two 60° sides form the undercut.

IMO, it's a good idea to blacken the surfaces on both sides of the place where the dovetail will be cut.
Scribe across the blackened area by using a small tri-square or a small square.
These scribed lines will serve as guides to help you keep the dovetail square with the barrel.

 

[WVAED]

Thanks for the good replies. I need to buy a safe dovetail file. I will take my time and your good advice.

 

[M. De Land]

If you ever get a chance to see one cut and fit properly on a mill or lathe first hand it will spoil you for ever looking at or doing one by hand again.

 

[Eric Krewson]

I bought one of the dovetail guides from Cain's for my first build, I believe is cost over $40.

I found it to be useless for the most part, too narrow, too deep, requiring lots of shimming. It works poorly on a swamped barrel, your dovetail will be out of alignment with your barrel unless you take the jig off and readjust it from the opposite side.

It is also hardened to the extent that you will wear out a couple files trying to cut one dovetail.

 

[Vaino]

Never used a "dovetail" guide and really don't need that complication for what amounts to a simple task.

For the bbl lug and rear sight dovetails and after the depth of .035 is attained, a one safe sided triangular file just starts the dovetail and then an upsetting chisel is used. The raised metal on both sides of the bbl lug dovetails is peened down onto the lug for a very tight fit. The surrounding areas are then filed smooth.

The rear sight dovetail w/ raised metal on both sides is fitted w/ the sight by filing and the raised metal is filed into a molding....a .035 actual dovetail depth is increased to an effective depth of approx. 1/16" because of the moldings.

The front sight dovetail is done w/ only the safe sided file.....Fred

 

[Spikebuck]

Fred, you don't happen to have any pictures of that process, do you? I've seen the chisels for sale, but in my mind's eye I see some big chasm opening up by the chisel that I know isn't the case, but I can't quite visualize what it should be.

 

[Vaino]

The above pic shows the dovetail chisel purchased from TOW and although there's no recess for a dovetail. this is how it's used. When the angled chisel end is in a recess of .035 or whatever depth is used, a shim is used at the other end to maintain a horizontal posture for the chisel. The depth of the angled part of the chisel minus the dovetail recess is the amount of the shim. The striking surface of the chisel is the step at the rear.

Some good smacks w/ a hefty hammer are req'd to upset the steel and trying to periodically fit the lug or rear sight ensures that the dovetail won't be oversize. When enough upsetted steel is achieved and the dovetail is slightly undersize, the triangular file is used for the final fit.

The chisel is aligned w/ the bbl by eyeball looking from above. It really isn't all that critical seeing the final fitting is done w/ the triangular file.

The rest of the procedure is described in the previous post.....Fred

 

[Col. Batguano]

The dove tail chisel is used for rear sights only, not for barrel lugs or front sights.

The other thing you need to be careful of is making sure your cut is undersize to the top width of the rear sight's trapezoid shape. the chisel will have the effect of opening it up wider once you whack it a few times, and if you're not careful, you can wind up with a loose fit on the sight.

 

[Vaino]

Please read my last post..... on all dovetails except the front sight dovetail, the upsetting chisel is used.

The angle of the dovetails' sides doesn't open up at all...it's the same as the upsetting chisel. The triangular file is used for final fitting.....Fred

 

[Fishdog64]

Great information. Thank you