Clamping a piece of burl wood

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Stephen50
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Clamping a piece of burl wood

Post by Stephen50 »

Request your assistance in securing a piece of burl wood in such a manner as to allow me to carve the flat side. Any assistance is greatly appreciated.
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dealguy11
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Re: Clamping a piece of burl wood

Post by dealguy11 »

One idea -
- Make a frame a little bigger than the piece, nice and flat and square to the table. Put a bottom on the frame
- Put a malleable material, like green sand or perhaps that rubbery material they use for making molds that won't mar the burl in the frame, set the burl on top, dig it into the material until it's flush with the top of the frame. Needs to be a material that won't squish or vibrate away from the burl while carving.
- Put holddowns on each side of the frame to hold the burl down while carving
- Fasten the frame assembly to the table.
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eph210
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Re: Clamping a piece of burl wood

Post by eph210 »

I do this sort of work and the method that I employ uses wedges underneath the piece to level it. Once I am satisfied with the orientation I remove the wedges one at a time and put a liberal blob of hot melt glue on them before replacing them.
It helps if the piece is sealed before applying the glue. I usually use spray shellac to seal it.
Releasing the piece from the wedges can be accomplished using isopropanol.

Euan

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scottp55
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Re: Clamping a piece of burl wood

Post by scottp55 »

Stephen,
Would you please let me know what method you eventually used...how it worked, and if you'd do anything differently?
Just got gifted a Pin Cherry burl by Bobtail Farm yesterday. Had no problem while Brian was here doing both sides with a 5/4 section he had Woodmisered off by a friend, but the loose bark/outside section might give me problems.
Barely fits on the Desktop :)
Thanks,
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martin54
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Re: Clamping a piece of burl wood

Post by martin54 »

scottp55 wrote:Stephen,
Would you please let me know what method you eventually used...how it worked, and if you'd do anything differently?
Just got gifted a Pin Cherry burl by Bobtail Farm yesterday. Had no problem while Brian was here doing both sides with a 5/4 section he had Woodmisered off by a friend, but the loose bark/outside section might give me problems.
Barely fits on the Desktop :)
Thanks,
scott
If you have a bit with bark on & want to keep it that way then one method I use is to put 3 or 4 screws into the side through the bark, if you are careful about where you place them then when they are removed you don't even notice the holes. I normally varnish the bark as well before I start which seems to help prevent it all falling off not only while its being machined but afterwards as well. Got wood slices I made for my daughters wedding 4 years ago & they all still have all the bark on. Used a matt varnish because I wanted them to look as natural as possible,
When mounting on the CNC table I just use normal clamps onto the top of the screws to hold in place & a variety of different bits to shim the piece as flat as possible while I surface the first side. :lol: :lol:

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scottp55
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Re: Clamping a piece of burl wood

Post by scottp55 »

Thanks Martin,
Just got in from the shop. This outer bark piece when I looked and tested it in the drive, the bark was REALLY loose on half of it, and the wood was spalted a little.
Don't think half of it would stay on as it crumbled off with only a mild force by hand.
Decided to shim it and take enough off to get close to an interesting look, and a flat enough area to attach to a carrier board down the road.
Managed to jig it securely without the carrier board to surface the sawmilled side.
Got both sides down to 600G and a good first coat of pine rosin/linseed/D-Limonene mixture.
Wood is green, so now let it sit in house for about 2 years to acclimate(1.9" thickness), and see how it moves and what it wants to be:)
Both boards are just to max thickness(sawmilled board at 1").
Yep, bark is usually brushed by me, and then Linseed/beeswax butter brushed.
Pics will probably show in that burl thread I had sometime soon.
Thanks again Martin:)
scott
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Re: Clamping a piece of burl wood

Post by Tailmaker »

Just saw the thread and believe I can contribute. I did this not for a burl but a footlong piece of a half log. Goes as follows:
- Set the wood with the flat side onto a board with a hole for a shopvac nozzle.
- if the wood surface is very spiky, cover the spikes with fabric or duct tape
- drape thin PE film like painter's drop protection sheeting loosely over the wood and tape edges to the board
- pull vacuum so that the film conforms tightly with the wood
- set a cardboard or wood frame around the whole thing
- fill with spray foam.
- flatten foam surface with a hand saw after setting up
- now you have a nice block that you can clamp to the machine table. The foam will hold on to the bumps in the wood/film surface.
- the foam breaks off easily when carving is done.

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Re: Clamping a piece of burl wood

Post by Dale1944 »

I recall reading of a universal gripper some years ago. After some dead ends, I finally constructed the proper search terms and found this.

Called the universal gripper, instead of being designed to pick up a particular object the device conforms to the object it is grabbing. The gripper, which is attached to a robotic arm, consists of an everyday party balloon filled with ground coffee. The coffee-filled balloon presses down and deforms around the object to be picked up, and then a vacuum sucks the air out of the balloon to solidify the grip on the object. When the vacuum is released, the balloon becomes soft again and the gripper lets go of the object.

This idea might be worth a bit of experimentation.

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highpockets
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Re: Clamping a piece of burl wood

Post by highpockets »

The universal gripper looks cool. Never have seen that before.
My only concern, would it be a strong enough grip to allow machining a part held by the gripper?
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Re: Clamping a piece of burl wood

Post by LittleGreyMan »

Dale1944 wrote:I recall reading of a universal gripper some years ago. After some dead ends, I finally constructed the proper search terms and found this.
Here's a video:
https://www.youtube.com/watch?v=rVAHatP47lg
Best regards

Didier

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scottp55
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Re: Clamping a piece of burl wood

Post by scottp55 »

Hmmm:)
I LIKE Tailmaker's method, BUT can't always get to a store, and if there's one thing I do have it's an abundance of coffee grounds. :)
Time to start saving my espresso grind and letting it dry. Now to find a BIG rugged balloon and think about the set up for indexing a rig on my fences. :)

Stephen, do you have a pic of the other side of that burl? What species is it?
scott
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Stephen50
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Re: Clamping a piece of burl wood

Post by Stephen50 »

At this point in time, I haven't tried any suggestions thus far regarding clamping burl material. If I would take one it probable be the hot glue although, I'm wondering if spray foam the type used for insulation would work. My only concern is how to remove the spray foam from the burl. Would shellac work and alcohol works after the bulk of the foam is removed?

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Re: Clamping a piece of burl wood

Post by IslaWW »

Would shellac work and alcohol works after the bulk of the foam is removed?

A most emphatic NO!
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