For the Sellers-inspired step stools I've been building, I need to mark a 7/8" circle on the end of a cylindrical leg blank. I'm using an old wooden curtain rod for the legs, so I didn't have the option of marking the center while the blank was square.
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| Cylindrical leg blank |
There are devices that make this easy. For instance a centering head used on a combination square will work nicely, but I don't happen to have one. I'm sure there are other devices that could be used (please write in the comments if you know of one), but I don't have them either.
So what do you do? You improvise. For this project I made some very useful helpers in holding round stock. I made these cradles fairly accurately so that the angled walls are very close to 45° relative to the top (and bottom) surfaces.
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| One of four "cradles" I made for holding round stock |
I can use one of these cradles with a square to draw a line through the center of the end of the leg blank. Set the leg blank in the cradle so that the end is even with one side of the cradle. Then clamp them in a vise so that they are about 1/2" to 1" above the benchtop - this just has to be enough to use the combination square.
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| Use a square lined up with the vertex of the cradle and draw a line on the stock |
Reference the square on the bottom surface of the cradle and have the square's blade line up with the vertex of the cradle's angled cutout. Draw a line on the leg blank. Then rotate the blank in the cradle and repeat.
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| Rotate the stock and draw another line |
Where the two lines meet is the center of the blank's end. Sometimes I'll draw a third line, as my stock is not perfectly cylindrical and this helps get a "weighted" center.
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| That's pretty good |
As a side benefit, the cradle is great to use for clamping round tapered legs. I put a piece of leather in the cradle's cutout section, put the leg in there and clamp in the vise. The leather protects the leg and keeps it from moving so I can work on the other end.
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| Clamping the tapered leg with the help of the cradle and some leather |
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| A closer-up view |
You use a pair of dividers. Step it off to find the radius, then step if off around the diameter. Connect those dots and you have the center.
ReplyDeleteSeems like you'd need a way to accurately find a centerline to know where to step off the radius. But I think I get the idea. Thanks.
DeleteHey Matt,
ReplyDeleteI can't wait to see your stool. I watched Paul's build recently and I'd love to make a few. My shop stool is a garbage find and it's ok, but I'd love to make a new one. I think my first chair project will be the four legged stool with a seat that Paul made a few years ago. Thanks for sharing,
Take Care,
Chris
Thanks, Chris. While I made the shop stool too, the ones I'm making now are the step stools - plank of wood with four legs, total height about 10-11". I'll be posting them when completed.
DeleteIndeed there are a variety of ways to find and mark the center. I used this marking devices from LV which does the trick nicely by my lathe. http://www.leevalley.com/en/Wood/page.aspx?p=43205&cat=1,330,49237&ap=1
ReplyDeleteIt essentially works as you described your method except that it marks the wood instead of just drawing a line for further punching out the center.
Bob, drinking coffee and reovering along with Rudy from the grand kids :-)
Nice! The only issue I can think of with that device is if you have longer stock, it could be challenging to keep the end to be marked registered on the two sides of the device while hammering the other end.
DeleteIndeed Matt, you should see me marking an eight footer with that thing, No hammer required, just ram it! :-)
DeleteBut seriously, for my every day work on the my lathe, works great! Although, I have splitted the odd 3/4 in blank for penmaking. Hard, brittle exotic wood and a tad too enthousiastic on the mallet, Oups!
Bob and Rudy
eyeball center with a straight rule, draw a line. rotate your rule randomly, do it again, and again, and again. You'll see the center appear.
ReplyDeleteThanks Gryphin. Doesn't get much simpler than that.
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