Underlugs - staples vs. dovetails?

[GregC]

Several have suggested that I cut dovetails for my underlugs on my Pedersoli pistol v. staples. I am just wondering what the difference is. Pros and cons of both?

 

[bioprof]

I've done both, and installing staples is much, much more nerve racking. Dovetails only need to be about 1/16" deep or less, whereas the holes for staples have to be a lot deeper. As far as I'm concerned, the more metal that you have between the bore and the underlug the better.

Once you've done a few, dovetails are one of the easiest tasks of gunbuilding.

 

[rich pierce]

I agree. Everybody knows somebody who slipped up and drilled into the bore when drilling for staples. I've never heard of anybody making a dovetail so deep it went into the bore.

 

[Vaino]

A stop collar on the drill prevents a too deep hole, although I only use dovetailed lugs .040-.045 deep.....Fred

 

[Mike Brooks]

I agree. Everybody knows somebody who slipped up and drilled into the bore when drilling for staples. I've never heard of anybody making a dovetail so deep it went into the bore.

Don't ever talk to me then..... :shake:

 

[kanati]

It would be very easy to do on some barrels. This swamped barrel I have, I did the dovetails in a CNC mill. I started measuring at the waist, there isn't much material between the bore and the flat at that point. Especially considering the channel of the rifling.

.710 at the waist, 45 cal and really .470 with rifling. That leaves .120", now take out .06" for a dovetail, it only leaves .06". Less than a sixteenth of an inch between the bottom of the dovetail and the bore. As someone else said, I wouldn't go over .04" deep.

I did mine .06" deep on this one, but never again. In the future they will be just deep enough to hold the lug and that is it. I'll use a good sharp cornered drift and swadge more material to hold it. What makes me a feel a bit better about it is, I though about a revolver cylinder and how thin the wall is on that.

-Ron

 

[Birddog6]

I have a .36 cal barrel that was bored in a arc & had to replace it. When I did I cut the barrel in half & had it been turned over the dovetails would have been into the rifling.

You put them too deep in the waist of a A40 or a B50, you could get into the rifling. :shake:

 

[MSW]

i agree with Bioprof... at first a bit daunting, now underlugs are pretty straightforeward.

before you take a file to the barrel, however, be sure to 'do the arithmatec,' and make sure you have enough material to work safely.

good luck with your build!

 

[kanati]

I'm pretty confident, I know how they are doing these swamp barrels. In a rotary 4th axis and simply side milling the profile. They should leave a thick spot on one flat at the center lug area. There simply is not enough material there to be removing anymore to install a lug on some calibers.

-Ron

 

[Stophel]

I've seen a couple of old (mid-late 19th century) barrels with staples. They were VERY professionally done...SO neatly done, that I really don't know how they did it. They had to have very specialized jigs/machinery to do it. They were NOT done the same way that the modern ones are done.

The very thought of drilling holes into the barrel and trying to peen the metal over to hold the tenon scares the manure out of me.

Cutting dovetails isn't (generally) hard, just tedious. And they don't need to be very deep. For example, take the commercially produced milled barrel tenons that you buy from TOTW and others, and file at least half the thickness off the bottom before fitting. :wink:

 

[Birddog6]

I'm pretty confident, I know how they are doing these swamp barrels. In a rotary 4th axis and simply side milling the profile. They should leave a thick spot on one flat at the center lug area. There simply is not enough material there to be removing anymore to install a lug on some calibers.

-Ron

They would have to leave the whole bottom thick as everyone puts them in dif. places. Some use 2, some 3, some 4, just depends on the builder & barrel length. I saw a lil 24" barreled Jaeger at Friendship with 2 underlugs & a tang bolt. If ya did a 48" barrel ya may want 5 if it is a thin forestock.

I have yet to have an issue with doing a dovetail.

 

[B.Habermehl]

When I have a lug that really needs to be near the waist of a light swamped barrel I solder it on... No metal removal! I remove the flange that would be where the pin slot will be and solder the lug on. Drill and slot the lug as if you dovetailed it in place. The slot will fall along the bottom surface of the barrel with no metal removed from the barrel itself. BJH

 

[Birddog6]

I have soldered them on as well & never have had any come off, just thinned the base of the underlug & lay the lug on the barrel & solder it. But I prefer to dovetail them in. I wonder how much stress a soldered one could take ? I tested a .030 deep dovetail in a piece of stock one time. Ripped the wood off & bent the pin & dovetail stayed in place.

 

[ron ward]

providing you use good, solid, machined lugs, dovetails are certainly stronger than the solder joint. one reason solder joints fail in an application like this is because the barrel's mass acts as a heat sink, cooling the joint to quickly. you might get the spot on the barrel hot enough to flow the solder decently, but a good joint doesn't end there. with the two pieces joined being so different in size the little lug stays hot longer than the barrel and clod fractures the joint. what looks like a good joint when soldered will actually have a faultline through it where the difference in cooling capacities has fractured the solder. one of the important factors for a good solder joint is that both pieces cool at roughly the same rate. i would imagine that, besides the fact that there's no room for a dovetail on a fowler barrel, the thinner wall of the barrel more closely matches the cooling rate of the lug and allows much better strength of the joint.

 

[Vaino]

Am presenly building a very trim Bucks County LR and the bbl is a Rice "B" weight, 46" lg and seeing the "waist" is quite small, used a soldered on lug at that location. Because of only a 3/32" web at the breech, a .050 deep dovetail was cut and a 1/8" thick piece of brass standing on end was fitted and soldered. Tight spots such as these is where .062 dia. music wire really comes in handy. These types of solder joints were tested and didn't fail using Swif 95 solder paste....Fred

 

[ron ward]

fred, that is exact what i though a good under lug would be. when you say "stood on end" i assume it was stood on end the length of the lug aligned with the centerline length of the barrel and the dovetails cut into the ends of the brass lug across the 1/8 inch thickness, right?
that's a good idea, the solder in that case is only there to lock the lug in place in it's dove tail. lugs like that would be easy to do and could be done with mild steel and maybe with 3/16 or 1/4 inch thick material if if a guy might think 1/8 isn't strong enough in the dovetail.
i actually planned on doing my lugs that way.

 

[Birddog6]

I think you are putting way to much thinking into this...... These are underlugs to hold the wood to the barrel........ that is all. We are not anchoring a roof down for hurricane winds..... :grin:

You dovetail a .030 underlug into a barrel & inlet it on the barrel channel & pin it with a dang finish nail, the wood will break or the pin will bend before the underlug comes out.

 

[ron ward]

hey birddog,
i do have a tendency to overthink things!..... :hmm:
it really doesn't have much to do with the strength of actually holding the wood on the barrel. i realize how strong,(or not strong) they have to be. my thoughts on making them out of thicker material has more to with subsequent pinning and un-pinnng of the barrel for cleaning over a long time. with the lug being brass only 1/8 thick plus standing on end in the dove tail, there's not allot of lateral strength there. it will get some slop from the lug being tipped sideways as the pin is driven through. this slop will result in the barrel being able to move around abit in the chanel and vibrate some.....unwanted vibrations led to a reduction of accuracy and basicly a less "solid" feel to the gun. a little thicker lug give the dovetail area just a bit more resistance to to being worked loose. i just hate loose stuff that should be tight, so i tend to figure out a way that won't let that happen. i know a dovetail can be peened tight if it loosens, but why do that if you can avoid the reason you have to do it. that's just the way i operate :grin:

 

[Birddog6]

:grin: OK...... whatever you say........ but it seems you are still way overthinking it...... :wink: These rifles stayed together for 300 years with a pin in a dovetailed lug... Seems to me they held up pretty good.. :idunno:

 

[Vaino]

That's exactly how I did it....but the 1/8" thick brass was used not for strength but for stability when soldering. The total height of the lug is only .140 and the .062 dia. pinhole is w/in .010-.015 of the bbl. so there's minimal leverage trying to knock it over when the pin is inserted. I make all my other underlugs from .045 brass and dovetail .040-.045 deep and they're plenty strong for attaching a flimsy LR forend....Fred