Shaping large boards - Page 2 - Woodworking Talk - Woodworkers Forum
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post #21 of 25 Old 02-22-2019, 08:11 AM
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Quote:
Originally Posted by GeorgeC View Post
Please translate that post into English. I have no idea what it is that you wrote.


George
He is referring to using two fences at a parallel angle across the table saw, where you run the lumber trapped between them to make the molding.

Gary
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post #22 of 25 Old 02-22-2019, 08:16 AM
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Quote:
Originally Posted by GeorgeC View Post
Please translate that post into English. I have no idea what it is that you wrote.


George
He is referring to using two fences (guides) parallel across the table saw to trap the board as you make the molding. Could also be helpful using a radial arm saw.

Gary
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post #23 of 25 Old 02-22-2019, 12:15 PM
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Quote:
Originally Posted by pro70z28 View Post
I would generate a 2 rail sweep, 3d file and run it on the CNC with a 1/2" bull nose cutter.
Quote:
Originally Posted by GeorgeC View Post
Please translate that post into English. I have no idea what it is that you wrote.
2 rail sweep:
A design concept with two parallel rails and a contour shape. You can make it as long as you want. The two rails represent the long edges of @steve4king's bed rail design. The contour would match the simple profile that steve4king showed in his drawing. You use a special graphics program on your computer to draw your desired contour and look at a 3D image of the bed rail that would be made by the CNC machine.

3d file:
When you are done drawing the 2 rail sweep with its contour on your computer, you will save it to a "3d file". This file contains the instructions that tell the CNC machine how to carve the three dimensional shape. In a typical use, you would save the file to a USB flash drive.

CNC:
This is a computer controlled carving machine with a flat bed and a router (or spindle motor) with a rotating bit. CNC stands for "computer numerical control." The CNC moves the spinning bit around the wood to cut out the desired shape. In a typical use, you insert the USB flash drive into the CNC, load the 3d file, calibrate the CNC for your board's thickness, and tell it to start carving the wood according to the instructions in the 3d file.

Some CNC machines are limited by the size of their bed. Commercial CNC machines are available that can cut a full 4x8 sheet. For steve4king, a "feed through" CNC machine might be more suitable. Because they pull the wood through as they go, feed through CNC machines can operate on long boards.

1/2 inch bull nose cutter:
CNC machines use carbide bits, like router bits. @pro70z28 suggests that steve4king use a 1/2 inch bull nose cutter bit in the CNC machine to do the actual carving.


Additional Notes:
* The term "CNC" applies to much more than just wood carving machines, but obviously that is the type of CNC machine that is implied here.

* The reason for this post is to help define terms for George and others. I do not have an opinion on whether CNC is the best solution for steve4king's question.
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post #24 of 25 Old 02-22-2019, 12:59 PM
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Quote:
Originally Posted by gmercer_48083 View Post
He is referring to using two fences at a parallel angle across the table saw, where you run the lumber trapped between them to make the molding.
Quote:
Originally Posted by gmercer_48083 View Post
He is referring to using two fences (guides) parallel across the table saw to trap the board as you make the molding. Could also be helpful using a radial arm saw.
Respectfully, your definition is incorrect. It is true that cove cutting jigs have two fences that might be called "rails", but that is not what @pro70z28 is referring to. See my definition above.

Here is an example of a cove cutting jig with two fences:

https://www.rockler.com/cove-cutting-table-saw-jig

A similar jig with two fences could be used with a radial arm saw as well. Neither is what pro70z28 was suggesting with the CNC. Just because it can be done doesn't mean that it is a good idea. If I were to do a cove cut on a radial arm saw, I would want to plan and prepare it very carefully, with a strong emphasis on safety.

Last edited by Tool Agnostic; 02-22-2019 at 01:09 PM.
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post #25 of 25 Old 02-22-2019, 04:21 PM
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Simple is good. Use the table saw coving method, 1/8" deep passes. Several set overs to get an approximation of the cove desired. Use hand planes to finish shape the convex areas after sawing away most. Make a cabinet scraper to the desired cove out of an old hand saw blade. This will greatly reduce or eliminate the massive sanding effort.
Me, I'd run it on my CNC if I was feeling really lazy or on my Weinig molder if I needed multiples. But neither would result in the pleasure of nice hand work.
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