I have read most of the duplicator discussion and I don't believe you have to have a 500 lb mass of metal to make your own machine. I have worked on the Don Allen and the North Star duplicators. Show me one that can be control with one hand. It can be done with the carriage control which I put on my machine. It may be a piece of junk in the eyes of a machinist, but this duplicator can be made in a small shop with only a lathe. Don't cuss it until you try this design.
I have a PDF file that tell how and why this works. I will forward this file if you send me PM with an email address. Several pictures to view and hash over.

Les Brooks, retired gunsmith

Les,
Not a thing wrong with your design. I do like this version with the slightly heavier legs.

I have grown to running mine from the side vs the end. I have no brake and I "feel" working from the side allows my old eyes to see better and give better control.

Little pantographs can work just as well as monsters as long as they are well made. You make a big jump in accuracy when you go from tracks to split line bearings. The only drawback to the light units is the cutter size, geometry and the amount of material you can remove at a crack. As long as the cuts are light, everything is peachy. But just like a small mill, once you start using big cutters and heavier cuts they start to spring, twist and grab.

I have fluted a lot of bolts on 900 pound 9 X 32 column mills. I have also fluted and octagon tapered A LOT of barrels on the same equipment and they came out perfectly. I defy anyone to prove to me that those jobs were done on a can opener. The only difference between doing it on the can opener verses a knee or horizontal mill is .010 inch cuts and .100 inch cuts.

Heavy is better but it's definitely not required. But I still think that the original ebay unit that was posted would have been an exercise in futility.

You did a nice job on your machine.
It's a thing of beauty. Kenny

Dpcd,

Looks good the way you designed your own machine. I will post a few pictures and explain why I came up with my design. The purpose was to make a machine without having a large machine shop. I didn't have more than $400 dollars in parts with the first machine back in 1982.



I thought that if you had a carriage moving only in one direction it would put pressure on the tailstock end. There would be less of a problem of bending the pattern and the blank. I used a 1/2 in. high speed cutter in trying out the theory. Later I switched to carbide cutters. With a 1 1/2 hp commercial router it cut chips in a hurry and was smooth to handle with the carriage lock. I would cut to about 1/4 in. in the first pass to get rid of the extra wood in the blank. I thought that a smaller cutter of 1/4 in. would have less push on the wood. I didn't have to block the pattern or the blank to route the blank. By cutting forward the chips fly away from the operator


This original machine could be stored on its end and only took about 4 sq. ft. of floor space and then could be rolled out into the shop to set up. It weighed in at 135 lbs total. The wood frame of hard maple keep inline without walking away. It looks cheap, but it served well in the shop. Working with wood is a lot different than making metal parts on a lathe that will hold .001 tolerance's. I would cut about .025 over on the outside and .025 under size on the inletting. This will allow for the final inletting by hand tools.

Now all I want to see is the final custom stock and it should not look like a couple of beavers making it look lot a stock.

quote:

Trick is to rough out the stock to within 1/4 inch first,, that way your cutters won't grab

I really hate when that happens

I run a 3/4" flat about 2 popsicle sticks+ then finish with a 3/4" round cutting only on the leading edge. My router is on the right so I stand on the left and chips go over the head end. Sometimes on heavy removal I cross cut and the chips go over the right side. Either way chips to my side a minimal. Like Les shows cutting only on the top flat rotating as I go.

Bottom line there are any number of ways to kick the cat. Take everything I've cut and it wouldn't be a drop in the bucket compared to Les and many others here on AR.

Thanks for the file.

Okay, having never used one of these duplicators or even seen one outside of photographs, does the fixture holding the cutting head and tracing probe have 3 axis movement or only 2?

quote:

does the fixture holding the cutting head and tracing probe have 3 axis movement or only 2?Dave

Actually the head moves in the x,y & z direction. Add the rotation and you get a 4 axis.

On most of the homemade and even more expensive units the cutter will swing in a arc. Add more $$ and the cutter and styles will move up and down perpendicular. Add even more $$ and head will rotate so you can actually cut perpendicular (or other angle) to the centerline of the stock.(5 axis)

Does that help any?

Answered the mail. I guess if the cutter head rotated it might be an A axis or possible C. Always have to look that up for each new application. Guess it doesn't really matter in this case as I am not programming any CNC operations.

Thanks,

In a 4 axis the rotation of the stock is the 4th. I'm not sure what letter you call that.

The real expensive allows the cutter to swing along the center line of the pattern as well as move up and down. Big advantage is you can easily keep the cutter parallel to the front and back of the inletting as well as perpendicular to the bottom. Allows for closer inletting.

In a lathe it would be "C" IIRC. In a mill ??? I used to teach this stuff and can't recall the differences though I can still recall the 12 axis of movement: ABC, XYZ, UVW, IJK. I hope that was correct. LOL.

quote:

ABC, XYZ, UVW, IJK.

Had to put away the and grab the (wine actually).

So what I "think" I should have said is standing at the head the cutter moves across is the X along the stock is the Y and up and down is the Z. Rotation of the stock is the B and on a high grade machine the cutter also moves in the A. Or do the cutters that swing in an arc actual doing the A and the straight up and down a Z.

Crap my brain hurts. As to the other 6 letters I HAVE NO CLUE!!!! Petroleum Engineers didn't worry about them.


A is around the X
B around the Y
C around the Z. So you machinist figure it out.

I think I need more