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Duplicates for Sherline Lathe


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Normally, a 'duplicator' only works properly, when you can disconnect the cross-slide feed-screw and pull it against the work/template with a weight on a string. Cutting sharp corners/edges (e.g. bands on canon) with a duplicator is difficult to impossible, as the tracer on the template has to have a slightly rounded nose in order follow the template and you would need to work with a pointed tool, rather than a side tool. The whole arrangement also has to be very rigid and without any backlash on the x-feedscrew.

 

Personally, I would not bother with duplicators, but rather make myself a sketch of the object with a precise 'turning schedule'. This means that you decide on a zero point from which to take measurement in both, x- and y-direction. You write down the various carriage movements required to turn up to particular points of your object. You will also have to think about a strategy in order to minimise carriage movements and to support thin parts - for instance, very thin parts with various diameters are not reduced to the major diameter in the first machining step, but you work on the diameters from the tailstock end towards the spindle in order to preserve as much 'meat' as long as possible in order to keep your part rigid.

You may need several set-ups to finish parts. For canon, for instance, you may need to off-set the top-slide for taper turning at some stage. Therefore, you decide on the reference surface (the zero point from above), against which you can zero your handwheels after changing the set-up.

I am usually working with a small tool that is cut like a grooving tool, i.e. it has a cutting edge left and right, so that I do not need to change tools, when turning up to sharp corners, say the left- and the righ-hand side for a band on a canon. I know the exact width of the tool and consider this in the measurements for my 'turning-schedule'.

 

This sounds complicated, but in fact is only structured working. It is much more precise than any duplicator on the amateur market. It is probably also faster, as you do not need to roughen out the part first in a different set-up, before you work with the duplicator.

 

 

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Years ago I made my own duplicator with a sharp wedge-shaped tracer and similarly ground tool bit. Even with solidly built geometry the results were never more than mediocre for small parts like cannon. There was still lateral deflection.

 

I had much better success with turning a master pattern, then casting the parts. I concur with wefalk and Greg.

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I also made my own using Druxey's published idea and pictures.  I experience the same finish results and restrictions pointed out by Wefalck and Druxey,  The greatest problem is getting the blade for the tracer to be fine enough to allow a precise copy.  I am in the process of modifying my tracer rod to accept interchangeable blades which will be ground with a left flat, right flat etc.  This will not eliminate the 'rounding' issue needed on the tracer blade but will make it a little more precise.  Not great for smaller jobs but work fine for larger copies such as columns/pedestals etc.

 

Note this design removes the need to free the cross slide as the cutting tool is ground to match the blade and is part of the duplicator.  The template is held within the duplicator also as shown.  I have also redesigned the way it is fitted to the bench since I took these photos. It now sits on a much longer aluminium base plate drilled with equally spaced holes  (matched to the current mounting slot space) allowing me to better place it relative to the work.  I have invested in some travellers and jackstand to support longer work also.  The longer baseplate has also allowed me to utilise it to support an off lathe 'stop'.  I am still adapting that to hold a micrometer head to allow repeated cuts to the stop.  PLEASE ignore my learning 'whoopsie evident on the Y table - hence my need for a stop :) - major embarrassment)

897697748_DuplicatorFront.jpg.9f68994a473781ccb3e14943f59fb919.jpg

1967014498_DuplicatorLeftside.thumb.jpg.86e9dd819f42bf9eb922202af5d3d05b.jpg

119328396_DuplicatorRightside.jpg.baabbb7c41fb7a6dcdc4d8d8832c1226.jpg

 

cheers

 

Pat

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A nice piece of engineering, Pat ! It works on a similar principle as the cone-turning devices that used to be available for many quality engineering lathes.

I would agree that for columns and such things with curved surfaces it would be a good implement. If one creates a reference face to set the tool against, there is also the possibility to finish off sharp corners etc. using the cross-slide, or doing it the other way around, depending on the part.

Edited by wefalck
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I beiieve artisanal pen-makers use such duplicators to produce small series of identical pens.

 

I don't know the article referred to, but there used to be a thread-'chasing' system using followers for the Unimat lathes that probably could be converted into a duplicator.

 

img10.gif

From http://www.lathes.co.uk/unimat/page2.html

 

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9 hours ago, Jaager said:

Based on an article in (I think) Model Shipwright,  about using a duplicator with a Unimat SL , I found a generic unit at Penn State Industries.  https://www.pennstateind.com/store/universal-duplicator.html

I have not had occasion to use it yet, so no idea how effective it is, but you can take a look.

I have this duplicator and I also have a Sherline lathe. Have done some work (wooden cannon barrels for my Victory 1:98) with this setup - works reasonably well. Still, you have to finish your turnings with miniature files and fine steel wool for details. (Nothing beats CAD/CAM turning in brass, though!)

The article mentioned was in nr. 105 of Model Shipwright ( I believe that in the Ships in Scale as well) and the Unimat lathe was used there. For a Sherline lathe you'd have to slightly adopt this duplicator, fashion legs for the base to bring the entire unit to an appropriate level. But it can be done fairly easily. 

If you want this article (4 pages), I have it digitalised and can send it to you via the email for your reference.

 

PS: Similar setup can be seen in the Channel Islands Maritime Museum in Oxnard, S. California. This is a duplicator used by Ed Marple for his models (See pics attached).

09duplicator setup.jpg

10duplicator setup.jpg

11duplicator setup.jpg

Edited by Dziadeczek
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7 hours ago, Jaager said:

Dziadeczek,

For successfully turning canon barrels @ 1:96 scale, please accept a deep bow in admiration, that scale pushes the physical limitations of any wood species.  Did you need new glasses when an armory's worth of ordinance was finally turned?

:-)     I forgot to mention that my Vic model I was building ~ >10 yrs ago and never to this day finished it (some masting and rigging remains...). That was an old Corel kit which I substantially bashed, added my own wood, rigging line, ornamentation and cloth for sails, and so forth... Among the items missing in the kit were four top deck cannons. Rather than ordering them directly from Corel, I decided to make them myself. And - apologies - now that I checked the (very dusty  - sorry!) model again, I see I turned them not from wood, but from brass! I remember I used one of the kit cannons for its overall shape and filed a brass template of its profile. I mounted this template in the duplicator and CAREFULLY and DELICATELY following its shape, I turned them.

Each one came out  tiny bit different than the others (especially the reinforcing rings on the barrel) , but after cleaning them with files and polishing them, they turned out acceptable. Also, it is advisable to grind both ends of  duplicator's bits to form a steeper cone, more pointy, the tip should be narrower and almost as sharp as the exacto knife? That way you can turn more intricate details.

 

Long time after, and now, I am scratchbuilding 1:48 scale French 74 gun ship (after Boudriot) and for this one, I used all brass turned cannons, using a CAD/CAM method. This is a far better way than using a duplicator - all cannons turned out beautifully, all are identical!!! But, if you are unable to turn them on a computer, I think that using a duplicator is a worthwhile try - see if it works for you.

 

Here are 5 pics of what I was talking about - first two show those 4 missing in the kit guns mounted on the quarterdeck, I made. Actually, I made 6 of them - two spare ones you can see placed loosely on the poopdeck.

The rest of the pics show other guns placed on the top deck and especially on the forecastle - those came in the kit.

Vicmodelguns1.jpg

Vicmodelguns2.jpg

Vicmodelguns3.jpg

Vicmodelguns4.jpg

Vicmodelguns5.jpg

Edited by Dziadeczek
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