How To Fit A Dovetail Barrel Blank ?

[Walter Rego]

I have a Lyman Dovetail Slot Blank that I want to fit properly in a female dovetail slot in a rifle barrel. Please see photo, it is in from the right side as far as I can push it with my fingers which is barely started into the slot.

I want it to fit down lower into the bottom of the slot so that the underside of the top surface of the blank sits closer to the top of the barrel surface once it is fully tapped into the slot.

Do I start by carefully filing one edge of the male surface, maintaining the angle until I can push the blank most of the way across the slot before tapping into place with a plastic faced hammer ?

Will I then need to remove some of the bottom surface of the blank so that it sits deeper, and is there a correct order in which to do the filing (edge first or bottom first) ?

What type of files should I use ? I have a small triangle shaped diamond embedded file that should work on the male edge of the blank, do I use a mill file or bast*** file on the bottom surface ?

Thanks for any tips and techniques.

 

[StrawHat]

Removing ANY metal from the bottom of the blank will destroy the fit of the dovetail in the slot.

Kevin

 

[Protocall_Design]

It doesn't look like the 2 dovetails fit very well anyway. I'd file off the bottom corners of the blank a little, get it to go in with a light press if possible, and Loctite it in. If it goes in loose, the Loctite will still hold it.

 

[Drm50]

Look for another blank. Nothing can be solved by filing on this one. A dove tail file is triangular and only has one cutting surface. Someone use to sell oversized blanks, file to fit. Maybe Marble?

 

[Liftrat]

I agree, that blank will never fit well. And it looks like the angles are wrong. As Drm50 noted, Marbles makes at least one slot blank that might fit better.

 

[2152hq]

The dovetail edges of the bbl slot have been pushed upwards a bit from the old sight being driven into the slot previously. That's not unusual.
But it does change to original angle slightly and opens the dovetail up. Then when you go to place a new sight or in theis case a blank into the slot, right off you are dealing with dovetail angles in the bbl that are off.

Lightly peening the metal back into place can be done but over doing it can leave you with more headaches. Closing up the dovetail can be useful in fitting the new blank of course but you need a 'safe edge' tri-square file to do it right. Otherwise you will be cutting on more than one surface at a time and in the end nothing will fit right.

In truth, the blank looks right now like it's too undersize to fit the dovetail no matter what you do to reshape the bbl dovetail slot.
I would get the dovetail back into shape. Clear the edges with a few file swipes to get back to sharp angles and edges to start with.
Then the blank could be made to fit securely by using a shim on one edge of the sight to take up whatever extra space is needed.

That's a simple fix but not necessarily an easy one to do and come out with a nice looking job of it (meaning you don't want it doesn't show at all.)

That will pull the blank down tight to the bottom of the dovetail cut in the bbl which in turn will pull the flat top of the blank down onto the surface of the bbl which is where you want it.

If you start removing metal from anywhere on the blank right no it's just going to be a looser fit in that dovetail in the bbl and sit even higher than it its now.

If not up to shimming the blank for a good fit,
I would take the above given advise and search for another blank of greater size to start with.

One other thing,,I sometimes use a damaged rear sight that I can save the dovetail and a portion of the tang both in front and in back of the dovetail.
Cutting and filing that to shape you can make a sight blank like you have and often one that better fits the dovetail slot in the bbl.
But that's stuff you do if you have old sights around and do this type of work.

 

[Walter Rego]

2152hq, you were right about the Lyman Slot Blank being poorly manufactured. I wanted to use it as the top surface was slightly rounded and I thought it would look nice with the barrel contour. I dug through my box o'parts and found an old Marbles Slot Blank. I very, very lightly and carefully peened the top edges of the barrel dovetail and it only took a few minutes with a diamond cut needle file to remove a bit of material from the edges of the Marbles blank and it tapped in nice and snug.

It's interesting to see what a good macro photo will reveal sometimes. I have a visor with 2X and 3X lenses and even they don't always show the details that I need.

The Lyman part will be returned to the seller for a refund. Thanks to everyone who responded.