square dovetails

[Simon]

Hi guys; 
Can one of you who has described how to hand cut dovetails tell me how to lay out a square dovetail on a tapered barrel?  I tried to use a machinist square but it is cocked to one side.  I finally eyeballed it but it is still not perfectly square.  I was able to get the sights in almost square and they will be OK.  However  the next time I would like to know how to get the layout square.   

Thanks for your time;

Mel

[bob in the woods]

For the lugs, I eyeball them. For sights, I mark a centre line. Square up from that.

[smylee grouch]

You can skribe a line with a square from both sides of the barrel and then skribe another line across the open end of the triangle that you just made, this should give you a line that is square to the bore. Hope that made sense.  Gary

[flehto]

I take a small 4" lg pin or drill that  is held up against the undercut and eyeball it for being at a right angle to the bbl centerline. To ensure that both undercuts are parallel, 2 pins are used. and only eyeballed..the 4"  length greatly exagerates any deviation.....Fred

[Red Owl]

Just thinking out loud here...Seems to me the best way would be to make a filing guide type jig out of a single piece of material that could be clamped at a perfect 90 degree angle to the barrel.

[Lucky R A]

The simple way is to find the center line of the barrel over about a distance in the area of the sight.  I then use a 18' steel rule that is 1 1/2 " wide and has a center mark on each end (3/4").   Center the center mark on the end of the rule on the center mark of the barrel on both ends of the center line on the barrel.  Draw your line across the square end of the steel rule and you have a perfectly square lay out line.  Do this at both edges of your dovetail and off you go.   It takes longer to describe than to do.   
Ron

[dannybb55]

If the bbl is straight then you need a deeper fence on your square like a speed square. If swamped, make a jig out of some thin oak that you can lay the barrel next to, with the square built in.

[dannybb55]

Find the center near the sight and scribe an arc with a compass. The intersection of the arc with the barrel flats are the ends of your square line.

[dannybb55]

Pull a tape from the muzzle to the sight duftail and mark the two ends of your crosscut.

[dannybb55]

Set a bevel gauge to an approximation of the straight line and lay it off from both sides, then split the difference.

[Keb]

You could use the protractor head if you have a machinist combination square. Figuring the angle is elementary. You can scribe a square line for the front sight off the muzzle which should be square to the world and go from there if you don't have the protractor head.  Do the same for the breech end.

[Benedict]

I use a 6 in. steel ruler that is about 1/2 in wide.  I lay it on the barrel lengthwise and scribe along the end of the ruler.  I can center the ruler up pretty accurately regardless of the width of the barrel.  quick and easy!

Bruce

[Daryl]

I like Gary's method - would be very easy to do and give perfectly 'square' lines.

[D. Taylor Sapergia]

I use a small machinist's square, and scribe a line from one side only, of the barrel, for each end of the minor dimension of the dovetail.   Then I eye-ball the hacksaw cut just inside the line. A sight dovetail takes less than fifteen minutes if I drag my arse, and filing it out square becomes second nature.

[Daryl]

40 years of filing dovetails gives a bit of experience, but thinking back, Taylor was always very good at it - me? - nnnnnnot so hot - 

[Dr. Tim-Boone]

What Lucky and Bruce say!!..........

[D. Taylor Sapergia]

I think that the trickiest part of filing that dovetail slot is keeping the floor of the slot level with the top of the barrel flat - not tipped down on one end, and at the correct depth for the sight, especially the front one.  Filing it at 90 deg. to the bore is quite easy.  If it isn't perfect, you'll be in good company.  Almost none of the sight dovetails in the big fat juicy Yaeger book are square.

[northmn]

I think that the trickiest part of filing that dovetail slot is keeping the floor of the slot level with the top of the barrel flat - not tipped down on one end, and at the correct depth for the sight, especially the front one.  Filing it at 90 deg. to the bore is quite easy.  If it isn't perfect, you'll be in good company.  Almost none of the sight dovetails in the big fat juicy Yaeger book are square.

Can't argue with the comments about fitting sights.  There really is nothing about a sight that requires absolute square when fitting.  Eyeballing would be adequate.

DP

[Simon]

Thanks guys,  there are several methods there that I should be able to use.  I got the bottom of the dove tails fairly flat by checking often and the depth by checking with the sight base.  It was the square part that I missed. 

Thanks to all;   Mel

[smylee grouch]

Another aid in good dovetails is a parallel sided three corner file with at least one safe side. Brownells sels them. You can do the job without them but they do help alot.           Gary

[Acer Saccharum]

Not square is only one point off. Don't worry, because the rest of the gun will be perfect. Right?

I just eyeball them. The eye square sometime fails, but it's pretty good. This is handmade art, rather than a Thompson Center. That's not a reason to do sloppy work, it's just to add some perspective.

Tom

[Nate McKenzie]

To  get the bottom of the dovetail parallel with the top of the barrel from side to side, try placing an octagonal pencil in the dovetail and another on top of the barrel behind it and sight down the barrel to make sure the tops of the pencils are parallel. 

[Simon]

In regard to files, I use both a 3 cornered and a 3 cornered with a safe side.  I don,t have a pillar file and very carefully use the fast cut 3 cornered file to clean out the hacksaw cuts after using the chisel. I guess I would have to say that my brain  locked up on the lay out because some of the methods described are pretty simple.  I should have thought about them.

[Acer Saccharum]

I have a triangular file with the teeth ground off one side. This allows me to get the bottom flat without filing the dovetail wider...or, widen the dovetail without filing the bottom deeper.

I hacksaw closely spaced cuts just shy of depth. Then with a 1/8 wide die sinker chisel I cut the fins out. Then file level. Then take a big cold chisel and drive it into either side to form the dovetails, and clean up everything with the file.