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Old 02-04-2019, 12:18 AM   #1 (permalink)
 
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Default Duplicating A Turned Blank

So what's the best way to precisely duplicate a blank that has already been turned? Is it just a matter of measuring and frequent use of calipers? Or is there a secret way to easily duplicate a profile?

I am wanting to be exact; close enough is not close enough.

Any help or suggestions would be much appreciated.
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Old 02-04-2019, 01:33 AM   #2 (permalink)
 
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There are duplicating lathes (or duplicating attachments for lathes). . Here is a video that may be of interest: https://www.youtube.com/watch?v=2tzKazf-vUY

If you have enough volume to justify the expense of a CNC lathe, that could be a more attractive (and more expensive) way to go.
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Old 02-04-2019, 02:27 AM   #3 (permalink)
 
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Do you need machine precision, like CNC or could you use one of these to copy the profile and then cut a template?
https://www.sealantsandtoolsdirect.c...xoCsToQAvD_BwE
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Old 02-04-2019, 08:23 AM   #4 (permalink)
 
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Can you tell us what it is you are wanting to duplicate? That might help with some answers to your questions. Note that most duplicating rigs use a fixed cutter which basically scrapes your turning to shape. This most likely will require more sanding to get the turning where you want it.
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Old 02-04-2019, 08:48 AM   #5 (permalink)
 
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"Exact" is a very high goal, especially on an item only a few inches long and relatively little variation in diameter.

You could by trial and error develop a thin cardboard negative pattern that closely matches the existing profile, then use that to evaluate work in progress. But the cardboard will be subject to bending and wear over time. A longer lasting negative pattern would be to trace the cardboard onto a thin piece of metal, perhaps an old saw blade or a woodworking scraper blade, and file till it matches the existing pattern. But I would NOT suggest using this thin metal pattern to shape a blank turning on the lathe - that could be quite dangerous.
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Old 02-04-2019, 09:16 AM   #6 (permalink)
 
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Is this a one of or multiple?? If one of just use calipers. Who is actually going to know for sure. What kind of profile are you talking about??
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Old 02-04-2019, 09:51 AM   #7 (permalink)
 
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"There are duplicating lathes (or duplicating attachments for lathes). . Here is a video that may be of interest: https://www.youtube.com/watch?v=2tzKazf-vUY

If you have enough volume to justify the expense of a CNC lathe, that could be a more attractive (and more expensive) way to go."


Interesting but too complicated and expensive for my project.

"Do you need machine precision, like CNC or could you use one of these to copy the profile and then cut a template?
https://www.sealantsandtoolsdirect.c...xoCsToQAvD_BwE"


This is a good idea. I already have something similar to this. I may give that a try.

"Can you tell us what it is you are wanting to duplicate? That might help with some answers to your questions. Note that most duplicating rigs use a fixed cutter which basically scrapes your turning to shape. This most likely will require more sanding to get the turning where you want it."

Handles for measuring spoons. Each set requires one original and four duplicates.

"'Exact' is a very high goal, especially on an item only a few inches long and relatively little variation in diameter.

You could by trial and error develop a thin cardboard negative pattern that closely matches the existing profile, then use that to evaluate work in progress. But the cardboard will be subject to bending and wear over time. A longer lasting negative pattern would be to trace the cardboard onto a thin piece of metal, perhaps an old saw blade or a woodworking scraper blade, and file till it matches the existing pattern. But I would NOT suggest using this thin metal pattern to shape a blank turning on the lathe - that could be quite dangerous."


I have in the past used x-ray film for this. It is easy to cut, maintains its edge and is sturdy enough that it does not wear after being used many times. It works well but is tedious and very difficult to get a precise profile.

"Is this a one of or multiple?? If one of just use calipers. Who is actually going to know for sure. What kind of profile are you talking about?? "

One original and four duplicates. Being the unrepentant perfectionist that I am, I will know for sure. I have not yet turned the first one so I don't have a profile yet. Wanted to read these answers before I cut the furst one. Whatever method I use for duplication will have a bearing on how simple or complicated the profile turns out to be.

Thanks everyone for your help and suggestions. I'll let you know how it turns out (pun intended).
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Old 02-04-2019, 12:05 PM   #8 (permalink)
 
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Remember you are making hand made items and not mass producing using robots or CNC machines. You need to sell your product on those basic ideas. There are usually flaws in hand made because we are human.
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Old 02-04-2019, 12:15 PM   #9 (permalink)
 
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Quote:
Originally Posted by jttheclockman View Post
Remember you are making hand made items and not mass producing using robots or CNC machines. You need to sell your product on those basic ideas. There are usually flaws in hand made because we are human.
I guess I am very human.
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Old 02-04-2019, 08:03 PM   #10 (permalink)
 
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As you noted, tedious and time consuming to make a profile to match a turned item. So draw out the profile first, glue to xray film or whatever and cut out, the turn all 5 to the profile.
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