Clamping a piece of burl wood

This forum is for general discussion about Aspire

Clamping a piece of burl wood

Postby Stephen50 » Tue Sep 18, 2018 4:06 pm

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.
Attachments
burl.png
Stephen50
Vectric Apprentice
 
Posts: 58
Joined: Sun Jul 28, 2013 9:09 pm
Model of CNC Machine: Shopbot Desktop

Re: Clamping a piece of burl wood

Postby dealguy11 » Tue Sep 18, 2018 4:18 pm

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.
Steve Godding
D&S Artistic Woodworking http://www.dsartisticwood.com
User avatar
dealguy11
Vectric Wizard
 
Posts: 1271
Joined: Tue Sep 22, 2009 9:52 pm
Location: Henryville, PA
Model of CNC Machine: Anderson Selexx 510

Re: Clamping a piece of burl wood

Postby eph210 » Tue Sep 18, 2018 8:11 pm

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
eph210
Vectric Craftsman
 
Posts: 172
Joined: Mon Mar 11, 2013 1:23 am
Location: southern Alberta, Canada
Model of CNC Machine: Stinger 1 and Mabel, both with 4 axis

Re: Clamping a piece of burl wood

Postby scottp55 » Sat Sep 29, 2018 12:14 pm

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
User avatar
scottp55
Vectric Wizard
 
Posts: 2292
Joined: Thu May 09, 2013 11:30 am
Location: Kennebunkport, Maine, US
Model of CNC Machine: Shopbot Desktop 5.5"Z/spindle/VCP9

Re: Clamping a piece of burl wood

Postby martin54 » Sat Sep 29, 2018 5:18 pm

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:
User avatar
martin54
Vectric Wizard
 
Posts: 3907
Joined: Fri Nov 09, 2012 2:12 pm
Location: Crossgates, Scotland
Model of CNC Machine: Gerber System 48 (modified)

Re: Clamping a piece of burl wood

Postby scottp55 » Sat Sep 29, 2018 8:36 pm

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
User avatar
scottp55
Vectric Wizard
 
Posts: 2292
Joined: Thu May 09, 2013 11:30 am
Location: Kennebunkport, Maine, US
Model of CNC Machine: Shopbot Desktop 5.5"Z/spindle/VCP9

Re: Clamping a piece of burl wood

Postby Tailmaker » Sat Sep 29, 2018 8:54 pm

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.
Tailmaker
Vectric Apprentice
 
Posts: 141
Joined: Sun Jun 16, 2013 4:40 am
Location: Pasadena, CA
Model of CNC Machine: Home Built 4-axis Router

Re: Clamping a piece of burl wood

Postby Dale1944 » Sun Sep 30, 2018 3:05 am

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.
Dale1944
 
Posts: 37
Joined: Tue Aug 26, 2014 3:03 am
Model of CNC Machine: CNC Router Homemade

Re: Clamping a piece of burl wood

Postby highpockets » Sun Sep 30, 2018 3:37 am

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?
John
Maker of Chips
User avatar
highpockets
Vectric Wizard
 
Posts: 1772
Joined: Tue Jan 06, 2015 4:04 pm
Model of CNC Machine: PDJ Pilot Pro

Re: Clamping a piece of burl wood

Postby LittleGreyMan » Sun Sep 30, 2018 9:44 am

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

LGM

W7 - Aspire 8.517
LittleGreyMan
Vectric Wizard
 
Posts: 770
Joined: Fri May 15, 2015 1:10 pm
Location: France
Model of CNC Machine: 3 axis small size machine

Re: Clamping a piece of burl wood

Postby scottp55 » Sun Sep 30, 2018 1:46 pm

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
User avatar
scottp55
Vectric Wizard
 
Posts: 2292
Joined: Thu May 09, 2013 11:30 am
Location: Kennebunkport, Maine, US
Model of CNC Machine: Shopbot Desktop 5.5"Z/spindle/VCP9

Re: Clamping a piece of burl wood

Postby Stephen50 » Tue Oct 09, 2018 6:27 pm

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?
Stephen50
Vectric Apprentice
 
Posts: 58
Joined: Sun Jul 28, 2013 9:09 pm
Model of CNC Machine: Shopbot Desktop

Re: Clamping a piece of burl wood

Postby IslaWW » Tue Oct 09, 2018 8:16 pm

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

A most emphatic NO!
Gary Campbell
CNC Technology & Training
The Ultimate Woodworking Machine
GCnC411 (at) gmail.com
User avatar
IslaWW
Vectric Wizard
 
Posts: 1109
Joined: Wed Nov 21, 2007 11:42 pm
Location: Marquette, MI, USA
Model of CNC Machine: The Ultimate Woodworking Machine


Return to Aspire - General

Who is online

Users browsing this forum: No registered users and 33 guests