Clamping Cauls for Box Joints - Router Forums
 19Likes
  • 11 Post By PhilBa
  • 2 Post By Arcola60
  • 1 Post By Stick486
  • 1 Post By Cherryville Chuck
  • 1 Post By furboo
  • 1 Post By chessnut2
  • 1 Post By old55
  • 1 Post By TwoSkies57
 
LinkBack Thread Tools Display Modes
post #1 of 9 (permalink) Old 02-21-2016, 03:49 PM Thread Starter
Registered User
 
PhilBa's Avatar
 
Join Date: Sep 2014
Country: United States
First Name: phil
Posts: 1,046
 
Default Clamping Cauls for Box Joints

One of the challenges of making good box joints is clamping during glue-up. You can't clamp directly on the joints (because the fingers stand a bit proud) so we are forced to put clamping pressure next to the joint which introduces torque and pulls the sides in a bit. For 1/2" or thinner wood, this can cause small gaps in the box joint plus it distorts the sides of the box a bit and makes it hard to use an inside square to check the squareness of the box. See the attached picture for an example.

The solution to this problem is to use clamping cauls that allow you to place pressure directly on the fingers. There are commercial products that do this. In particular Rockler has them for 1/4", 3/8" and 1/2" finger sizes. The cauls are reasonably priced though you need a band clamp as well. While they do work, the fingers are open and, even with moderate clamping pressure, they press marks into the box fingers. See the attached picture. The wood is cherry and the mark was made just by squeezing with my arthritic fingers. Needless to say, this is not desirable.

So, the answer is to make clamping cauls yourself. It's not hard and if you have an Incra LS Positioner, it's really easy. I've put together a tutorial on how to do this with the Incra LS Positioner using Rob Lowrie's pyRouterJig software.

If you don't have an LS Positioner or similar, you can still make cauls. Basically, it's very similar to making box joints with fingers that are 1/8" deep. The caul fingers should be around 1/16" narrower than the box joint fingers. You cut them out of a 3 1/2" x 1" thick piece of hard wood. The length should be about 1 1/2" longer than the joint you are clamping. See the pictures to understand the process. It should be easy to modify your box joint jig to do this. But, it should be possible to make just using a dado blade and miter gauge - precision is not needed. You might want to look over the above tutorial to get a better idea of the process.

Note that the measurements in the attached pictures are for custom finger spacing - don't use those measurements for a standard spacing box joint.

The final picture has been posted before but it shows the results of getting direct, square and even clamping pressure via cauls on box joints.
Attached Thumbnails
Click image for larger version

Name:	20160115_103625.jpg
Views:	515
Size:	474.9 KB
ID:	191265  

Click image for larger version

Name:	20160115_115459.jpg
Views:	218
Size:	356.5 KB
ID:	191273  

Click image for larger version

Name:	image007.png
Views:	240
Size:	24.7 KB
ID:	191281  

Click image for larger version

Name:	image005.png
Views:	218
Size:	32.7 KB
ID:	191289  

Click image for larger version

Name:	image015.png
Views:	201
Size:	64.6 KB
ID:	191297  

Click image for larger version

Name:	image013.png
Views:	209
Size:	61.1 KB
ID:	191305  

Click image for larger version

Name:	image019.jpg
Views:	394
Size:	67.0 KB
ID:	191313  

Click image for larger version

Name:	image021.jpg
Views:	188
Size:	20.1 KB
ID:	191321  

Click image for larger version

Name:	image023.jpg
Views:	495
Size:	85.2 KB
ID:	191329  

Click image for larger version

Name:	image025.jpg
Views:	726
Size:	96.3 KB
ID:	191337  


Measure twice, cut once and CROSS OUT THE WRONG MARKS.
PhilBa is offline  
Sponsored Links
Advertisement
 
post #2 of 9 (permalink) Old 02-21-2016, 04:10 PM
Registered User
 
Join Date: Jul 2009
Country: United States
First Name: Ellery
Posts: 286
 
Default

Excellent work and great attention to detail Phil. The box joints look great also. Thank you very much for sharing it with us. I have been doing a few box joints for some shop boxes for tool storage. This will help with all of my box joints.


Ellery Becnel
Murtu01 and PhilBa like this.
Arcola60 is offline  
post #3 of 9 (permalink) Old 02-21-2016, 04:30 PM Thread Starter
Registered User
 
PhilBa's Avatar
 
Join Date: Sep 2014
Country: United States
First Name: phil
Posts: 1,046
 
Default

Thanks man. Before using the cauls, I was really bothered by some of the gaps I was seeing. Bought the Rockler product and was really happy to see an improvement but then I had to sand to crap out of the sides to remove the clamp marks.

Measure twice, cut once and CROSS OUT THE WRONG MARKS.
PhilBa is offline  
Sponsored Links
Advertisement
 
post #4 of 9 (permalink) Old 02-21-2016, 05:34 PM
Forum Contributor
 
Stick486's Avatar
 
Join Date: Jan 2013
Country: United States
First Name: Stick
Posts: 25,138
 
Default

this is a well thought out and executed answer...

great joinery too...
PhilBa likes this.

This would have been the week that I'd have finished chewing thru the restraints...
If only new layers hadn't been added....

Stick....
Forget the primal scream, just ROAR!!!
"SNORK Mountain Congressional Library and Taxidermy”
Stick486 is online now  
post #5 of 9 (permalink) Old 02-21-2016, 06:20 PM
Moderation Team
 
Cherryville Chuck's Avatar
 
Join Date: Sep 2010
Country: Canada
First Name: Charles
Posts: 14,992
 
Default

Nice solution.
PhilBa likes this.

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
Cherryville Chuck is offline  
post #6 of 9 (permalink) Old 02-21-2016, 09:12 PM
Registered User
 
furboo's Avatar
 
Join Date: Oct 2015
Country: United States
First Name: Rob
Posts: 544
 
Default

Excellent Phil! Adding the caul templates to pyrouterjig was a great idea of yours, and it's nice to see it in action.
PhilBa likes this.
furboo is offline  
post #7 of 9 (permalink) Old 02-22-2016, 11:35 AM
Registered User
 
chessnut2's Avatar
 
Join Date: Sep 2011
Country: United States
First Name: Jim
Posts: 1,506
 
Default

Fantastic idea, Phil. Getting those joints clamped well is one of those things that we worry about in making those joints. Well designed, well drawn out and presented.
PhilBa likes this.

It seems I never finish what I
chessnut2 is offline  
post #8 of 9 (permalink) Old 02-22-2016, 06:33 PM
Official Greeter
 
old55's Avatar
 
Join Date: Aug 2013
Country: Australia
First Name: Ross
Posts: 6,563
 
Default

Nice work Phil.
PhilBa likes this.

Ross,
Rockhampton, Queensland, Australia


Enjoy the knowledge of others that can be found within.

‘Members are requested to add a first name in their profile as we are a very friendly bunch here'.
old55 is offline  
post #9 of 9 (permalink) Old 02-22-2016, 07:19 PM
Retired Moderator
 
TwoSkies57's Avatar
 
Join Date: Feb 2009
Country: United States
First Name: Bill
Posts: 5,989
   
Default

Phil's blogs are worth the read.....agree or disagree, points are well made and elevate the debate..

philsbunker
PhilBa likes this.

"..... limited only by imagination"

"Just smile and wave boys, smile and wave"
Skipper the Penguin
TwoSkies57 is offline  
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Router Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Similar Threads
Thread Thread Starter Forum Replies Last Post
A suggestion from Maurice harrysin Woodturning and Lathes 48 12-08-2013 10:16 AM
box joints? mah New Member Introductions 6 12-30-2012 11:48 PM
Incra Ultra How-To (Box Joints + Other Stuff) Nickbee Show N' Tell 17 06-22-2009 01:42 PM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome