Turning by light...

Brian Altop

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Tacoma, WA
I just watched a video where someone was turning by light. They used the light shining through the wood to gauge the thickness of the wood. Looked kinda neat.

Has anyone here done that and is it a reliable way to gauge the thickness when trying to turn thin walls?

Thanks!

Brian
 
I've only done it a little, but it's used quite a bit by the guys who turn very thin pieces, especially the lamp shade and cowboy hat turners. It's only effective on light-colored woods, and some are better than others. Norfolk Island pine is one of the best for this.

I also turn in the dark sometimes. When I'm turning something with a lot of voids or odd-shaped pieces where I need to see the "ghost" image as it spins, I turn off all of my overhead shop lights and only use the task lamp mounted on my lathe. Having the rest of the room dark makes for a strange atmosphere in the shop, but it makes it easier for me to see the "ghost" as the piece turns.
 
I have Brian McEvoy's video on large vessel turning and he turns by light. http://www.onegoodturn.ca/

Since then I have modified my large hollowing rig so there is a light on the front of the cutter. I do it the same way Brian does his in the video.
My large rig is also setup for either hollowing by light or I have the arm attached on it that holds the red laser so I could cut that way also. Hollowing by light works great on light colored woods - on dark woods I revert to the laser light. Hollowing by light has a little learning curve to it though as there are a few things you will want to do differently.

I use GE bulbs as Brian does with a converter that you can switch from 18 to 24 volts....18 when hogging and 24 when bringing to final wall thickness. Your shop should be darker than usual so you can see the light comming thru the wood easier but I have also used this method out doors.

Also, if you hollow by light you should stop frequently and blow the chips out as they can give you the illusion that you still need to cut more in a certain area and you will end up going thru the side.....guess how I would know that?.
 
I have done this several times. Like Dan said, it works better on some woods than others. It is a useful technique when turning thin, it is not a complete solution. If you try this, remember that moisture and grain orientation greatly affect the amount of light transmitted. As you cut around a curve and expose more end grain; more light will be transmitted with the same thickness. If the wood begins to dry as you are turning, less light transmission may cause you to cut through the side.
 
Yep - learned a few things the hard way with that kind of hollowing.
You will learn that there are differences in how you do the hollowing and Dennis is right about what happens to the wood as it drys or flexes from the hollowing (true with both types i guess). I keep it sprayed lightly with water and hollow in stages from top to bottom. I have only used this method on large turnings.

Most of what I turn are smaller in diameter and my Monster rig with the laser works perfectly on these. For the larger diameter, and/or longer pc's of wood the light method is a very good method. I have a package of light bulbs and use 2-3 per turning on larger deep hollowing.

Day off tomm and im going to actually hollow using it.........ill try to remember to take pictures and ill create a post to show you tomm.....
 
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Thank you all for the advice, I appreciate it. When you are using the laser, is the laser used to shine through the wood like the light or is it used to shine on the outside circumference of the wood to let you know when you have reached the outside diameter that you are looking for?


Brian
 
Thank you all for the advice, I appreciate it. When you are using the laser, is the laser used to shine through the wood like the light or is it used to shine on the outside circumference of the wood to let you know when you have reached the outside diameter that you are looking for?


Brian

It's the second way you mentioneed...the laser is shining on the outside surface of the piece. By setting the laser dot a known distance from the cutter tip, you can tell when you've reached the desired wall thickness.
 
I was unable to turn the larger blank today so I did not set up the large rig with the light at the tip to show you. I will in the near future and post something so you can see how I do it with the light.

Instead I made some small hollow forms and used my Monster hollowing rig with the laser. I feel more comfortable with this method but both work - I just dont have alot of experience with the light method. With both methods you do have to stop and adjust the cutter as you hollow - I probably adjust 3-4 times when hollowing - I know others that adjust more and I suppose some will adjust less - either way they both have a learning curve but its still fun.

One final thought - emphasis is placed turning a thin wall which only may impress another turner. So when you start hollowing turn one that is thin walled so you can prove to yourself you can do it. Then turn to whatever thickness you want and have fun - they still sell just as well.
 
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