Dictionary stand with turned column

[BillWoodturner]

I have been trying to figure out a problem in geometry. I an trying to make a dictionary stand.

I am going to turn the post and then attach the lectern at the top, no problem. But, the base is different. I have decided to make legs by "bent laminations". This means I build a framework and then cut all the wood into thin pieces and then put them with glue into the framework.

After the three legs are dry I am going to dovetail the ends that attach to the post. Now the problem, I can either attach the legs with a sliding dovetail into a triangle or to the round pole. The wood pole at this time is square from top to bottom.

Plan number 1.
One plan is to cut the bottom 6 inches into a three sided column and turn the rest into a round pole. The three sided end would then have the matching dovetail cut into the center of each side vertically so the leg with the dovetail cut into it can be slid into place.

Plan number 2.
The other plan would be to turn the entire post round. Then the dovetails (3) would be cut equal distance apart on the round column up 6 inches so the leg can be slid into place. The problem here is the leg inside the dovetail needs to be cut out so the leg will "mould or fit" around the column without any air showing.

Problem:
I do not know how to make a triangular column with equal length sides using the maximum side length from the square or to find the points equal distant around the round column to make the sliding dovetail. Also how do I make the leg "mould or fit" around the column? Do you have any ideas?

 

[helang]

An easy way to attach tripod legs to a cylinder is to rout three flats 120 degrees apart on the cylinder. The depth of the flat is such that the width of the flat is the same as the width of the leg. A fixture to support and guide the router is required. The same fixture is used to rout the dovetails in the cylinder.

Howard

 

[BillWoodturner]

Thanks Howard,
So, If I understand, I need to turned the bottom of the column to a round then create a system to hold the whole column in place and also to hold the router to create the flat. Then I need to turn the column 120 degrees and do the same twice. Then I need to go back to the center of each flat do the vertical dovetail. Correct?

 

[C Edward Moore]

Fitting a leg to a round base.

Suppose you have a Forstner bit which is 2" in diameter. Then turn the "pole" to a 2" diameter where the legs will attach. Now for the tricky part.

Cut the leg "flat" so that it would be tangent to the pole if placed in its proper orientation, leaving some waste. Attach some waste wood with glue. When dry, use the Forstner bit and drill down the joint you just made so that the drill removes the wood where the pole will fit. Obviously, the arc of the circle you just cut can't be more than 120 degrees if there are to be three legs. Also, the drill bit must cut exactly down the center of the leg.

Then, attach the leg to the pole.
Option A: Use three dowels per leg to attach the leg to the pole.
Option B: Make a piece of wood that serves as a tenon into the leg AND as a tenon into the pole.
Option C: Make a piece of wood that serves as a tenon into the leg and as a sliding dovetail into the pole.

I have made stands to display scarves that are basically round crosses on a round base. I use the drill method described above to get a good fit where the arms attach to the vertical. (SWMBO is a weaver and at craft shows other fiber folks try to buy the stands, known affectionately as "St Christophers".) I use a dowel to attach the arms.

When making the arms for the crosses I start with square stock that is more than twice the length needed to make two arms. On both ends I clamp the stock to the table of the drill press on a piece of flat waste wood. Then I drill through the center of the stock using the Forstner bit and effectively cut the stock in half while making the arc that fits around a portion of the round vertical. Mark the centers of each end and turn a tenon on the square end. Put the square end tenon in the chuck and align with the tailcenter before tightening. Now drill the hole for the dowel. Then you may turn the arm between centers or leave the stock in the chuck and bring up a tailcenter that fits into the hole that was drilled. Turn the arms.

 

[MichaelMouse]

Thanks Howard,
So, If I understand, I need to turned the bottom of the column to a round then create a system to hold the whole column in place and also to hold the router to create the flat. Then I need to turn the column 120 degrees and do the same twice. Then I need to go back to the center of each flat do the vertical dovetail. Correct?

You could. Standard woodworking books usually cover this technique. You make a plywood box with a slot on top to guide your router which will mount to the ways of your lathe. Using the indexing feature of the lathe, you make the flats, change bits to an up spiral bit slightly smaller than the narrowest part of the dovetail, and use to make a clean cut to ease passage for the dovetail bit. Final bit change to the dovetail. After you've done a few to gain confidence you'll lay out and use only the straight bit and dovetail, raising the dovetail to cut the flat.

If you can't find a suitable book outlining the technique, you might try http://www.newyankee.com/getproduct3.cgi?110 plans or pictures.

 

[john lucas]

Bill
I built a box and put screws through to hold the center of the column. The router sits on rabbits in the top of the box. I lock the column in place with another screw. I simply drew lines on the top of the column to aling the screws. Then I mill a flat spot that matches the width of the legs and then mill the dovetail.
I've also done it where you make the dovetail on the round column and then undercut by hand the dovetails on the legs so they match the column. This wasn't as hard as it seems but did take a while. If you recess the part of the column where the legs sit the step on the top will cover the joint and make it easier. You still need to make it fit perfectly at the bottom however.

 

[Bill Grumbine]

Hi Bill

I have done this in the past, although I ended up taking the easy way out. From my unerstanding, the traditional way was to chisel flats on a round post as has already been described. Today most of us would use a router. When I made mine, I built a box to go on the ways of the lathe like John describes, but then circumstances changed, and I ended up buying a Legacy mill to do some other work. The box went by the wayside (so to speak) and I ended up using the Legacy in the same manner. It would not be an economical way to do it for a one off piece, although if you know someone who has one you might consider getting some time on it. That is what a friend of mine did. He even had the box I has started to build, and ended up using my Legacy. Maybe we should send you the box! 😀

Bill