Three corner needle files

[A.Merrill]

 I'm looking for a three corner needle files with a very low angle for making dovetails in thin barrels. Anyone know where I can find these. Thought about grinding off one side of a knife file. Any ideas or what do you use?   Al

[Bill Raby]

Undercut with a jewelers saw then file the angle in with a sharpened barrette file.

[P.W.Berkuta]

Use a flat chisel ground to the angle you want. File the dovetail slot then use the chisel to upset the edges of the slot.

[rich pierce]

Use a flat chisel ground to the angle you want. File the dovetail slot then use the chisel to upset the edges of the slot.

Yep, then peen down the raised edge over the dovetail.

[Gaeckle]

Look on Ebay

[D. Taylor Sapergia]

All triangular files come with the same angle, ie:  60 degrees.  Grinding the safe side at something other than flat is the only way to "get a low angle".

[Bob Roller]

All triangular files come with the same angle, ie:  60 degrees.  Grinding the safe side at something other than flat is the only way to "get a low angle".

That will work IF you have done a lot of tool altering.A lot of us on this forum have tool making experience.I THINK I have seen these files in gunsmithing supply catalogs but don't know where.Is Frank Mittermeier still around or long gone??
Bob Roller

[Bob Roller]

I just looked and Frank Mittermeier started in 1936 as did I.His shop still has a phone # and I assume his name is a well known identifier..
Bob Roller

[whetrock]

All triangular files come with the same angle, ie:  60 degrees.  Grinding the safe side at something other than flat is the only way to "get a low angle".

If you want to reduce the angle on a triangular file or make a safe side (toothless side), keep in mind that a triangular file actually has 6 facets, not just three. The "corners" are not full corners. They are just very narrow facets, and they also have cutting teeth. They are important if you want the corner to cut in efficiently. So take care not to completely grind off the corner facet when making one of the regular sides "safe".

A couple of other tips on reshaping files:
First, if you grind off all the teeth on one side of a fine/thin file, the file can warp, creating a very shallow bow with the concave side being the side that still has teeth. (I suppose you could heat to dull red, straighten it, and quinch in water, but my experience with retempering files is only limited to few instances, so I can't confidently offer details on that. Maybe others want to comment?)

Second, if you want the "safe" side you are creating to be complete safe, then you must polish it to a good luster. If you only grind it and do not polish it, the scratches in the surface left from the grinder may (almost certainly will) still cut and score the material surface that you had hoped to avoid damaging.

[D. Taylor Sapergia]

That is interesting information Wetrock, regarding the corners of triangular files.  When I grind a new safe-sided triangular file, I use my belt grinder and grind the flat to remove those corners of which you speak.  My last few strokes on the grinder are lengthwise with the file to remove the cross-grinds that would mark the bottom of the filed cut.  I want to cut the dovetail to an exact 60 degrees without a web in the inside of the corners.  So after I finish filing, I use a graver to finish the corners.
I often cut a rectangular notch when filing a sight dovetail. or one for an underlug.  Then I use a cold chisel with a sharp 60 degree angle ground on it to upset the barrel steel.  But I always finish the dovetail with a safe-sided triangular file.

[bluenoser]

All triangular files come with the same angle, ie:  60 degrees.  Grinding the safe side at something other than flat is the only way to "get a low angle".

Actually, not all triangular files have three 60 degree included angles .  A cant saw has one 105 degree included angle and two 37.5 degree included angles.  There may be others and not saying any of them are suitable for filing dovetails.  I too grind the flat corners away when making a safe edge file.  I am quite certain the commercially available dovetail files also have sharp corners.

[whetrock]

Thanks for the clarification, Taylor and Bluenoser.
The process I use is the same as Taylor described. I also have a triangular file that I ground down and removed the facets from the corners, and I use it for cleaning up the dovetail, as Taylor describes.
My point about leaving the corners was just to say that the file will cut in lateral movement a lot more efficiently if you leave at least a little of that corner facet.
Thanks for your explanation about how you use a belt grinder and finish up with tool marks in line with the axis, Taylor. That was helpful. I don't have a belt grinder, so I've ground them on a wheel and then polished on coarse and fine stones. More steps, but it only takes a few minutes.
I haven't seen dovetail files like you are describing, Bluenoser, so my experience is limited. Just to make it clear to anyone else reading this, what I am describing is "regular" triangular files, or saw files as they are sometimes called. I tried my hand at a handsaw sharpening business a few years ago. Went through a lot of files. The corners dull first, and if the corner is dull, it will not deepen the gullet. Anyway, I found that sharpening saws and making money sharpening saws were for me very different things, so it was a good experience but a short-lived venture.

[bluenoser]

Brownell's sells both 60 degree and 65 degree dovetail files.  Both files are parallel sided with one cutting face and two safe sides.
 The 60 degree would be a 3-square.  At $40.00 to $55.00 each, I will make my own thank you very much

[Scota4570]

I use regular triangular files with a safe side ground on the belt sander.  But, just for final adjustments.  I cut all dovetails in the mill.  I am not skilled enough to consistently do a clean enough job free hand. 

Back to the OP's question.  I assume we are doing a rear sight.  If the barrel is so thin as to require special procedures to make a minimal dovetail, I approach it differently.  I would make a base that soldered to the barrel and then cut my dovetail in that.  I could be done as to not be an eyesore. 

[kutter]

If the bbl wall is that thin, I'd just make the base of the part a good contact fit to the bbl contour and sweat (soft) solder the assembly together.
If done right, it won't come apart under any normal use.
I've mostly gone to just sweat soldering bbl pin lugs and the like into place on bbls now,no matter the size of the bbl or bore. Never a problem. They ain't coming off if done correctly.


Sight bases, sling swivel bases, scope mts, scope mt rings onto scope tubes, bbl ribs and countless other assemblys have held together for decades with nothing more than good quality fit sweat solder joining.

Small parts to be made are sometimes sweat soldered to a larger piece of steel to be able to easier hold on to them when machining them in a mill.
The solder joint foot print holds up just fine under the stress of milling cutters & drill bits machining it to shape.

[A.Merrill]

Thanks for giving me some ideas.   Al