Dovetail cutter???

[sheepherder]

Originally Posted by Olle

I got the same one as you have, from Harvey Tool. Seems to work just fine.

And a stock Luger front sight blade has the same angle???

Argh...I can't find $%^& around here!!!

Ah! I found it! What kind of RPM did you use for the dovetail cutter, after making the base cut???

[Olle]

Originally Posted by sheepherder

And a stock Luger front sight blade has the same angle???

Argh...I can't find $%^& around here!!!

Ah! I found it! What kind of RPM did you use for the dovetail cutter, after making the base cut???

I tried a sight blade in it, and even if I didn't tap it in all the way it seemed to fit very well. This is a carbide cutter, so I cranked it up all the way (2500 rpm) and ran it dry. The only precautions I took was to set the cutter as deep in the collet as I could to reduce vibrations, and I also brushed out the chips after each cut. It wasn't even remotely as scary as I thought it would be, no vibrations, no funny noises, no nothing. Just go for it!

[cirelaw]

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

[sheepherder]

Originally Posted by Olle

I tried a sight blade in it, and even if I didn't tap it in all the way it seemed to fit very well. This is a carbide cutter, so I cranked it up all the way (2500 rpm) and ran it dry. The only precautions I took was to set the cutter as deep in the collet as I could to reduce vibrations, and I also brushed out the chips after each cut. It wasn't even remotely as scary as I thought it would be, no vibrations, no funny noises, no nothing. Just go for it!

I did as you suggested; ran a 1/8" end mill down to sight base depth, then cut with Harvey dovetail cutter. Low cutting speed; extremely low [hand] feed.

I had no problems with the cut; my problem was with my depth measurement. I used two different calipers, one Starrett dial and one digital, and could not get the same measurement twice. The two also differed as much as 10 thousandths on a single depth measurement.

This applied to the sight blade itself as well as the cut.

I'll have to re-think how I want to do this in the future. I've tried a magnetic base dial indicator reading directly off the spindle and that is not precise enough either (too much play in the 'headstock').

This was matching a Luger sight blade with a 'new' dovetail; I've had no problems cutting dovetails and making my own sight blade for them & pressing the rough blade in and then finish machining it in place.

[Olle]

I didn't have any problems with the depth. I just indexed the end mill on top of the sight base, then I indexed the dovetail cutter on the bottom of the first cut. I hit it within 1/1000". Why are you using the spindle as a reference?

[sheepherder]

Originally Posted by Olle

Why are you using the spindle as a reference?

It's the part of the mill that moves up & down.

What do you use???

[Olle]

Originally Posted by sheepherder

It's the part of the mill that moves up & down.

What do you use???

Ah, I usually call that the "head", and the "spindle" is on the lathe. I thouht you were trying to make every cut with the centerline of the barrel as a direct reference. I assume that you have a dial and fine feed on the Z-axis, so why do the cuts end up wrong?

My procedure for this (as well as plunge cuts, grooves etc) is to move down until the end mill touches the work, zero the DRO and then start cutting. The fine feed on mine is like a Glock trigger, very gritty, uneven and can jump too far if you're not careful. The DRO helps a lot, as I can see the actual position without having to rely on the dial.

Working on these mini-machines can sure be aggravating, once you learn their shortcomings you have to come up with a lot of workarounds to get the accuracy you need. It would be nice to have those zero back lash ball screws, that should eliminate quite a bit of error.

[sheepherder]

Originally Posted by Olle

Ah, I usually call that the "head", and the "spindle" is on the lathe.

I should have said "quill".

Everything on this mill/lathe is crudely [Chinese] machined. One graduation of the 'quill' handwheel dial should be .040" according to the chart. But my dial indicator says .037".

But it's not the mill/quill I'm talking about. It's the dial calipers. The digital calipers is consistently .010" off in measurements under .100", compared to the mechanical calipers . Zeroing doesn't help. And I can't get consistent readings with the mechanical dial calipers. Starrett calipers.

Can't pin down the problem. The dial indicator method works pretty well for measuring the depth of cut, but trying to get a consistent measurement of say a front sight base is fairly unlikely.

[Olle]

Have you tried the Starrett with a standard, for example feeler gages? I have a Mitutoyo, and I try it with a known dimension now and then just to make sure that it's not out of whack. If it is, I'm sure that Starrett can recalibrate it for you.

I believe the small discrepancy in the dial setting could be due to the feed screw being metric. Seems like some older machines used metric feed screws, and for the US market they simply changed the dials to read the "closest standard equivalent". These are said to be a bit iffy sometimes, so if that's the case you may want to upgrade to true standard screws and dials.

[sheepherder]

Originally Posted by Olle

I believe the small discrepancy in the dial setting could be due to the feed screw being metric.

Or the threads being tight at one point and loose at another. Just another reason to buy American. Interestingly, the same 3in1 machine is sold by Harbor Freight, Grizzly, and Smithy with different nameplates and colors...

I have a short list of accessories I'd like to get for it from Grizzly; they import more accessories than the others...

Edit: Ha! Sears now sells the Grizzly 3in1 as well as Grizzly!!!

Here's the Harbor Freight [red] and Sears/Grizzly [green] 3in1 machines...

[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...

[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...

[G.T.]

Yes, beyond my experience as well... but, I think a big massive broach with the dove tail cut on the length face could be used on a very fast production scale... just too much leisure time is my excuse! .........til..lat'r...GT

[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.