Dovetail cutter???

[SIGP2101]

Originally Posted by sheepherder

You bought a Luger dovetail cutter??? Do you remember where you bought it???

Since you guys resurrected this thread I will chip in as well. I am getting my cutters directly from Triebel one of the major gunsmith tools manufacturer for Germany. They are nice and they ship all over.

[sheepherder]

I have not yet found a way to accurately measure an existing dovetail. If anyone has a tool or instrument that will do this, please share.

A few days back, I needed to cut a dovetail for a Luger artillery rear sight base. I had an original base to work with (butchered LP-08 barrel, I think), but none of my dovetail cutters (including the Harvey front sight blade dovetail cutter mentioned previously) looked right...I even cut up small pieces of plastic to the angle of the dovetail and then extended the lines and measured them with a protractor...As far as I could see, it looked like 58º...

I ended up cutting the dovetail with a 60º cutter, the most common...

2º doesn't sound like much, but I can assure you that when you're milling steel it can be a lot...

[John Sabato]

On those occasions when I needed to reform or create a sight dovetail, back in my formative gunsmith days, my tools were as many hacksaw blades that when stacked together and mounted on the same hacksaw frame carefully made the vertical slot to near dimensions, followed by a "safe" triangular file, or a standard file ground to produce the dovetail angle... used VERY carefully by my calibrated hand. If I made a mistake, and there were a few , we got the welder out and filled the dovetail and started over...

I did have a dovetail cutter for a 1911A1 rearsight dovetail at one time, but only used it once...

[cirelaw]

Simply Amazing!! I'm very impressed. Theres so much more thats never seen.. Luger art perfection!~~Eric..

[Hugh]

Not exactly what you guys are talking about, but....be very careful of cutting a dovetail in a Mauser rear toggle, I ruined 3 expensive cutters before I realized that you have to grind off the surface hardening before attempting to cut a dovetail in it! No problems with the DWM & Erfurt ones!

[GySgt1811]

Originally Posted by sheepherder

I have not yet found a way to accurately measure an existing dovetail. If anyone has a tool or instrument that will do this, please share.

A few days back, I needed to cut a dovetail for a Luger artillery rear sight base. I had an original base to work with (butchered LP-08 barrel, I think), but none of my dovetail cutters (including the Harvey front sight blade dovetail cutter mentioned previously) looked right...I even cut up small pieces of plastic to the angle of the dovetail and then extended the lines and measured them with a protractor...As far as I could see, it looked like 58º...

I ended up cutting the dovetail with a 60º cutter, the most common...

2º doesn't sound like much, but I can assure you that when you're milling steel it can be a lot...

Sheepherder,

Is it possible that the difference in the angles could be on purpose so as to result in a slight interference fit to help hold the sight blade in place?

Gunny John

[sheepherder]

Originally Posted by GySgt1811

Is it possible that the difference in the angles could be on purpose so as to result in a slight interference fit to help hold the sight blade in place?

Yes it could. You would want the top of the dovetail to be slightly less than the bottom, if that was the intent. IOW, to 'lean in' a bit. I'm not very well versed in dovetail design to say whether it is a common design element or not.

If it was, I would expect that both angled cutters would be generally available for quantity production. One for the dovetail itself, and one for the part to be dovetailed in place. Is that what is common in a production workplace???

[G.T.]

Hi Rich, they may have been roughed out and broached to the final dimension?? If I was running production, that would be a real consideration for speed and efficiency?? And, I might add.. accuracy... It might explain some of the taper found in the original dovetail slots... I don't know for sure, but I would guess it could be so... best to all, til...lat'r...GT...

[sheepherder]

Originally Posted by G.T.

Hi Rich, they may have been roughed out and broached to the final dimension?

I dunno...My broaching experience has been limited to cutting keyway slots in gears, pulleys, etc. While in a production job, I've never cut a dovetail.

We did our broaching with a 24" geared arbor press, with a hand lever, .010" at a time. I never saw a dovetail cutter until I got into gunhacking. I now have some big ones, but they're for cleaning up milling machine/lathe ways. And cutting the adjustment shims for the ways.

A tapered dovetail...I don't know if that's even possible...Is it??? You would have to stop the broach at a specific point of the broach stroke, to get the same size taper each time...And have some way to push the broach back out in the opposite direction...

Beyond my experience...

[SIGP2101]

Here:
http://homemetalshopclub.org/news/dec02/dec02.html

Scroll down near the bottom.

Then this:
http://www.neme-s.org/Model_Engineer...l%20Slides.pdf

and this video:

http://www.youtube.com/watch?v=0VGOa69sePo

[sheepherder]

Originally Posted by SIGP2101

Here:
http://homemetalshopclub.org/news/dec02/dec02.html

Scroll down near the bottom.

They taught me that in shop class. I'd like to know how to determine the dovetail angle.

[SIGP2101]

Originally Posted by sheepherder

They taught me that in shop class. I'd like to know how to determine the dovetail angle.

Once I measure dimensions I use mm paper to make large drawing and then just measure angle.
European angles are 60, 65, 70 and 75 for most of the gun industry. So if you measure 63.5 for some reason that should be actually 65.

Or you can use known dimensions to calculate angle with given formula which brings us to 67.5 angle for the front post male dovetail.

[sheepherder]

Originally Posted by SIGP2101

Or you can use known dimensions...

That sounds the simplest way. Could you please post the dimensions of the Luger artillery barrel, especially the rear sight base dovetail?

Originally Posted by SIGP2101

Once I measure dimensions I use mm paper to make large drawing and then just measure angle.

That's pretty much how I do it. I don't use paper, I use plastic sheet. I label the triangles so I can hold them against an unknown angle and see how close they are, then lay out what I think the angle is and cut it out and compare it. These are some I use to set my compound rest and/or set my fixture to mill a feed ramp [first pic]. It works good enough for my work. I don't demand perfection.

I use the plastic template to get my angle, then use the machinist's level to transfer that angle to my fixture [second pic]. This is a Luger feed ramp being cut.

The dovetail dimensions are less than a tenth of an inch in any direction; hard for me to see light under the template. 60º seems to be the closest I can come, so 60º it is.

[Olle]

Originally Posted by sheepherder

That's pretty much how I do it. I don't use paper, I use plastic sheet. I label the triangles so I can hold them against an unknown angle and see how close they are, then lay out what I think the angle is and cut it out and compare it.

Have you had any luck with the CAD yet? It's great when you want to determine an angle, and only have the side dimensions to go by. Just draw it and snap the angle, and you'll get an accurate number without having to do the trigonometry. I have made some templates by printing them and transfering to cardboard or acetate, it works well if you're lazy like me.

[sheepherder]

Originally Posted by SIGP2101

Or you can use known dimensions to calculate angle with given formula which brings us to 67.5 angle for the front post male dovetail.

IIRC, I got 41º for that...(first page)...

The Harvey 40º dovetail cutter works pretty good...I think I found my problem, G.T. - I have to knock off the sharp edge before trying to fit the sight blade...

Too late now on three dovetails here...That edge seems to hold the blade up...

[John Sabato]

Originally Posted by sheepherder

I'd like to know how to determine the dovetail angle.

Trial and error is probably best. 60 degress/58 degrees will probably work the best for an interference fit if you don't have a setscrew to hold the sight in place. If you do, the 2 degrees difference won't make much of a difference with a setscrew.

alternative 2. You can also use a CAD program to draw a variety of dovetails, then print them out, and cut them and see how they fit in the dovetail you are using as your example.

BTW, did you check the Luger blueprints to see what angle is actually specified on the P.08 for the sight dovetail?


The same measurement is probably used for the LP.08, and since you are talking about a sight for NAMBU, which never had an artillery version before, I don't think the dovetail police will visit you if you freelance the dovetail size.

BTW, Dimensions shown on the front sight blade above are IDENTICAL on the blueprints to the dimensions for the dovetail that sight fits into

Also, Someone recently posted the blueprint of an artillery barrel from a published reference book. I don't remember who did it, or what the subject of the thread was, but if you can find that posting, the angle of the dovetail on an artillery barrel is probably in that drawing...

[Ron Wood]

Here is a dumb question, but can you click on the point/line in your drawing to highlight it and then just hit the "delete" button on your keyboard? Just asking because I do not have that program and have never used it.

[sheepherder]

Originally Posted by Ron Wood

Here is a dumb question, but can you click on the point/line in your drawing to highlight it and then just hit the "delete" button on your keyboard?

Short answer is that the delete key does nothing inside the program (so far). There must be another way to delete points, lines, whatever; I just haven't found it and the tutorial hasn't mentioned it. Yet.

The delete key would be intuitive, wouldn't it???

I think I found how to delete text [it's the Er key]; now I just need to get rid of that pesky point I mistakenly added...

I'm drawing the calculator, slowly...It's not very easy...Hey, my IQ is only 103...

OK, I got through the tutorial. I now have a printed-out stick drawing of a calculator outline.

Envelopes are much more intuitive.

[Olle]

Originally Posted by sheepherder

Short answer is that the delete key does nothing inside the program (so far). There must be another way to delete points, lines, whatever; I just haven't found it and the tutorial hasn't mentioned it. Yet.

The delete key would be intuitive, wouldn't it???

I think I found how to delete text [it's the Er key]; now I just need to get rid of that pesky point I mistakenly added...

I'm drawing the calculator, slowly...It's not very easy...Hey, my IQ is only 103...

OK, I got through the tutorial. I now have a printed-out stick drawing of a calculator outline.

Envelopes are much more intuitive.

The delete key does work, but you also have to confirm by hitting "enter". Look at the bottom of the screen when you hit "delete", and you will se text saying "press ENTER to erase selected objects". There are some commands that have to be confirmed with the enter key, so if nothing happens: Just look at the bottom of the screen and see what it says.

[SIGP2101]

Still, easiest way is to use mm graphing paper. Draw what you want and read values directly of the paper. Substitute mm with cm and you accuracy reading could be within 0.01 mm/0.0004 in.