just another newbie builder question...

[bjmac]

about dovetails. I have the barrel sight dovetail cut and finished. What is the best way (using only hand tools) to match the angle of the barrel dovetail to the new sight base? Do you 'eyeball" it or am I missing something?
Thanks,
BJ

[ottawa]

most use a triangle file with a safe edge or face ground on one side this will give you the angel needed take the safe side put it flat in you dove tail and carefully file your angle.

[Bob Roller]

A three cornered file with SHARP points at all three sides.
Grind one flat smooth and the two remaining ones should
be the same angle as the sight base.

Bob Roller

[WadePatton]

Also, in combination with or alternatively (to the dovetail) metal can be pushed up with a cold chisel, then tapped back down onto the sight base.

They sell chisels ground for this, or as a builder you can/should grind your own.   

[Acer Saccharum]

WHat I do, which is neither right or wrong*:

I use a hacksaw to cut the notch, side by side cuts, then cold chisel out the fins in between cuts. Don't try to saw to full depth, just shy of your layout line.

Then file the floor flat, use the Bob Roller triangular file to start. I like to tap the dovetails with the Wade Patton chisel. It gets into the corners better than a file, in my experience. It also makes a smooth surface. The chisel should be polished, which helps it move metal easier. A little film of cutting oil helps the metal flow, too.

Anyway, raising the dovetails gives you a lot of flexibility for fitting the dovetail to sights and lugs. The raised metal can be tapped down around the lugs to really capture them, can be tapped down if the sight slot is a little sloppy. I never did that, but some folks do, so I heard. 



*useless commentary on my part. I've had too much coffee, and grew up too Catholic.

[Bob Roller]

What I do,which is neither right or wrong. That is like one of my favorites
from Heinrich Schnibble* that says,"The hurryder I go,the behinder I get."
The smoothness of the dovetail is determined by the cut of the file.
I sometimes use a #8 cut,Swiss made and supposedly has 233 teeth
per inch.(NO I will NOT count them).

Bob Roller
* Heinrich Schnibble was a cartoon in the Saturday Evening Post before it was
reduced to a pamphlet.

[whetrock]

You will sometimes see antiques that have bumped up metal (cold chisel technique) in the dovetails at the rear sight, but don't show bumped up, raised metal at the front sight. But that doesn't necessarily mean that the smith used a different technique for the front sight. Rather, if the tool marks show that he used a cold chisel to cut the angle for the rear sight, then he probably used the same tool to cut the angle for the front sight. He then filed down the raised portion (the raised metal left after bumping up the angle with the chisel) at the front, so as to get the raised metal out of the way so that the blade of the front sight could slide in and mate up properly with the surface of the barrel.  (I'm talking about a blade that "hangs over" the base to the front and rear. It is somewhat advantageous for it to fit down against the surface of the barrel, so that it doesn't snag cleaning rags, etc. and get deformed.)

(Just my humble opinion here, of course.)

The sights in the images below are from the same antique rifle. (The rough dimples around the rear sight are because the guy used a smaller punch to set the sight in a little tighter. )




Here's another set that shows the front sight better. In this one, you can see where he used a punch to set in the front sight, as well. But since there was no raised metal, he just punched down the edge of the notch. (That's only one technique. I've seen other antiques where the smith didn't mess with the edges of the notch, but instead used a punch to fuller out the width of the base, so as to lock it into the notch. And then there are some examples that show the work of a very careful old smith who just patiently fitted everything, and didn't seem to need to punch anything.)  I guess my point here is to say that the old smiths didn't necessarily "match the angle " for a perfect fit. In some cases, they seemed to have thought that close enough was good enough.

[bjmac]

thank you all for your responses and now I have one more piece of the gunbuilding puzzle in place! Thanks again to all for sharing your knowledge!
BJ 

[whetrock]

BJ,
The images above are from a revolutionary era flintlock.

There is a Hawken discussion in the antiques page that also shows this contrast between upset metal at the rear sight and no obvious upset on the front sight. (I'm referring to photos of the first of the two rifles shown there.)

http://americanlongrifles.org/forum/index.php?topic=28091.0

The Hawken experts on here might be able to share some opinions about what notches were upset with a chisel and what may have been cut with a file. Tool marks can be hard to see with the naked eye, but easy to see when the image is blown up to 400%!

[Acer Saccharum]

I agree with Whetrock's assessment of the process.

[smylee grouch]

If you plan on doing more than one rifle I would sugest a sight dove tail file from Brownells. They have equal /paralell sides not the tappered sides of the common triangler side file. Its not as hard to keep your dovetail square to the barrel. By all means make sure you have a safe side or two on what ever kind of file you use.

[Acer Saccharum]

As the sharp corners of the triangular file get chipped or dull, you can grind the safe side down to expose fresh corners.

[EC121]

I had a rifle that someone dimpled the bottom of the rear sight dovetail to tighten it up when they over-filed the base area.  Don't do it.  This can cause a bulge into the bore on a thin walled barrel.  I kept wondering why I felt a tight spot when I cleaned the bore.  Usually the tighter dry patches.  Finally removed the sight and found the problem.