Lathe duplicator

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janos

janos

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I described the device in some details in the other thread,

https://www.shipsofscale.com/sosfor...78-bashed-to-death-kit-from-janos.1125/page-7

...but here are a few more details.
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The lathe is an EMCO Unimat 3 which is perfect for this purpose as well as for others... I made some attempts to make a duplicator on the Chinese wonder AL-30 and on the Unimat 1 (which is a bad joke in itself) but to no avail. All it needs is a chuck, the live centre and the tool holder.
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The pattern 'reader' is attached next to the tool holder. The tip of the reader supposed to be smaller to follow the shape of the cutter - some more refinements are needed here.
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The pattern holder is attached to the lathe bed (no holes are drilled in the bed!)

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The pattern holder in open position. Note the inserts, identical in thickness to the pattern plates, to provide proper grip on the plates.

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The pattern plate (1 mm brass plate) which is cut and filed to te required shape. Note the notches at both ends which represent the axis position.

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The bottom view of the pattern plate. Note the strip the edge of which is parallel to the axis and when inserted, is pushed against the froward edge of the pattern holder's front edge.

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The pattern plate goes into the holder. Note the arrangement of the plate's bottom strip to the holder's bottom plate forward edge.

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The position of the cutter in the tool holder is established using the pattern's reference notch at the rear...

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And at the front, using the live centre.

And so it goes. V-L emphasizes which is very true, that nothing automatic is in the device. It is a fully manual operation, needs patience and feeling, and experience. As indicated, I intend to make some betterments to it - watch this space.
Janos
 
Maarten said:
Hi Janos,

Is it an option to make the Tool holder spring loaded so it automatically follows the pattern?
Click to expand...
that would be difficult with a standard metal lathe because movements need to done manually when you travel from one end of the project to the other you need to manually reverse directions of the cross slide and tool post that holds the cutting tool. the other travel issue would be into and out of the work that also has to be manually moved to go deeper into the cut. the only real solution is CNC
 
Yes, the real solution is CNC. This duplicator is the poor (and lazy) man's CNC. :p
But having said that even if the spring-loaded tool movement would not work, an intermittent solution is - what VL does - making the tool's cross movement independent of the cross screw (name?) and allowing it being moved by hand, either pushing it against the pattern to follow it or pulling it out when the pattern comes to a bigger diameter, like the reinforcement rings. I could not work it out yet whether this can be done on the Unimat 3.
Janos
 
I made those modifications I indicated last time. Now the pattern reader 'reads' the master barrel instead of the 2D pattern. The same base plate is used, attached to the lathe bed, but in this case holding 2 brass squares instead of the original pattern.
With this change I also managed to move the pattern (or, rather, the master barrel) out of its unfortunate location where it was mostly hidden from sight by the live centre.
The master is confined at its ends, on the left hand side it sits in a hole and on the right hand side there is a screw with a cone end. On the left hand side there is a sliver of the raw material (in this case 8mm) for referencing the cutter.
With this solution the time, needed for the 'manual' refinements decreased dramatically. Now I have to sharpen the corners only (the main cutter leaves a small radius in the corners) and the tapered sections need to be somewhat refined as I find it still difficult to follow a tapered sections exactly - the feeding screws are still in place, so the cutter does not move freely by hand. A long learning curve is required of course.
The 'manual' refinements are done with manual gravers, supported by a brass flat in the tool holder.
In general, the copying work became much more convenient.
JanosDSC_0280.JPGDSC_0277.JPGDSC_0279.JPG
 
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