Making duplicate pieces

[loberg]

I need some help on keeping several pieces the same size and shape without using a duplicator. I am making a chess set and although I can make good looking pawns, I can't make them the same. I have used the pencil method and use calipers to make sure the pieces start out the same size. When I finish there are major differences in the pieces. Any suggestions?

 

[GeorgeH]

One approach is to obtain some casting material at your local hobby outlet and cast a profile of the base model. I assume you always use the same base model and aren't making the mistake of replacing the base model with a newly turned model as you duplicate the series of pawns.
This cast profile is then used as a method for contact comparison of each sequential piece as you advance through the set.
Another idea is to prepare a cardboard profile outline cutout that you can fit against the side of each piece as turning progresses to check your accuracy.
Another method, although quite involved, is a shadow comparison test using photographic lighting equipment. But that's fairly involved and time consuming.
Last, but not least, a duplicator. Expensive but accurate.

 

[loberg]

George
I am using the same piece to try to turn the others. I might try a profile cutout to see if I can get consistent profiles. I have an old Sears duplicator for my old lathe and could set it up. Thanks

 

[Dick Sowa]

Another idea is to prepare a cardboard profile outline cutout that you can fit against the side of each piece as turning progresses to check your accuracy.

That's exactly the approach I use. When I draw up my segmented bowl plans, I also make a profile template from cardboard or thin hardboard. For hand duplicating, that's the easiest way I've found to get consistent results.

 

[Joe Greiner]

This one has been on my bucket list for a few years, so no guarantees: http://www.delorie.com/wood/tips/parallax-jig.html It seems related to the shadow test mentioned by George, but less involved.

The cardboard profile templates can get beat up just by pressing against the stationary workpieces. OK for minimal repetitions (2 Kings, 2 Queens, etc.), but sheet metal or plastic (e.g. dead credit cards) will work better for the 16 pawns. The profile templates test only the profile; for best results, add semi-circular templates for the diameters at two locations along the piece - these should be robust, and brightly labelled about their function.

True following duplicators usually work by scraping cuts, with substantial sanding needed afterwards. On small-scale turnings, variations in sanding will introduce deviations from the turned profile, especially for different woods; no sweat at larger scale.

Last, but not least, tell 'em that the minor inaccuracies were deliberately introduced design features to test their character.

Joe

 

[hockenbery]

When making duplicates
Use a story stick and always copy the same piece. If you copy the last piece the tendency is to drift in style.

I used to do short runs of sash pulls out of poplar for a client who would cover them with fabric. These were usually 6-12 of some design sent by the client. Some looked like pawns, I used a story of 1/4 plywood. used a square to mark the element high and low points. I then made 1/4 cut with bandsaw in each line. turn the cylinder. hold the story stick on the tool rest slide the pencil point down the cut line to mark the blank. Part in the proper amount. turn one practice piece to copy. then turn them all using the practice piece as a model for the curves.


For pawns I would make a story stick. a short piece of wood. mark the key elements, High points, low points. for pawns you might drill holes and glue in cut off nails.
turn the cylinder. push the story stick into the turning wood to scribe lines.
Part in to the depth for each element. Her having a caliper for each element would be helpful.

This method keeps all the elements at the same height and within the same diameter + or - a tiny bit.

On Pawns if you are havin trouble matching a long curve.
put a length of scrap wood on the lathe and cut that curve 10 times on the scarp piece. If the last 5 look alike go for it on the real object.

The don't need to be "engineering" alike they just have to look alike.

Happy turning
Al

 

[loberg]

Al

The story stick with pins to mark the blanks sounds very promising. I will give it a go this week. Made a horizontal router table yesterday to make tenons. Worked great. Today wifey things in the front yard.

 

[john lucas]

Rude Osolnik simply ground a large piece of steel to the shape of the pawn and used it as a scraper to get the final shape. He had an article about that waaaaay back in one of my magazines. I can probably dig up a copy of it if you have a day or so.

 

[davepeck]

Hi Bruce,

You have been given a lot of good advice here. The story stick gives you accurate points along the height of the piece. An outside caliper will give you accurate diameters at each of these heights. Then it's just a matter of making a bead or a cove in the appropriate places. The pros may be able to make just the required number of pieces but beginners and amateurs usually make extra pieces and then pick the best ones. It's good to have a little variation between pieces. It shows that the set is hand made rather than spit out by a machine.

Dave Peck

 

[Gretch Flo]

random idea

Just a thought-Has anyone used the hand held metal pins used to make contour for cutting out floor tiles?? I only have experience buying one (must have been cheap) 25 years ago to help my brother retile the linoleum in my folks kitchen. Got there too late, and said it would have made lifer easier. Gretch

 

[Joe Greiner]

Yes. I used them for making an almost duplicate set of small vases, converted to tea light holders. The pins are somewhat flimsy, though. Harbor Freight has a more robust "Contour Gauge" with plastic bars, made in Taiwan, not China. Item No. is 00907. Precision is about 7 bars in 10mm. You can do the arithmetic conversion.

Joe