Replies

1. 
   RalphBarker | Dec 10, 2012 08:32pm | #1

   Scribe away

   To paraphrase Shakespeare, "Scribe on, Macduff, And damned be him that first cries, “Hold, enough!”  ;-)

   If you're getting tear-out with a backer board, it may be too soft, or the stock isn't being held tightly enough to it, or perhaps both. Try clamping the work piece each time you shift it in the jig, and see if that improves things. (Your fingie wingies shouldn't be getting that close to the blade, anyway.)

2. 
   retired08 | Dec 11, 2012 03:03pm | #2

   Okay

   I'll have to try that, I do clamp but maybe I should try to get the clamp as close to the blade as possible.  My backer is a piece of MDF.  Any thought though on scribing if all else fails?  I don't know if I'd like seeing the line.

1. 
   RalphBarker | Dec 12, 2012 08:39am | #3

   backer board condition

   You might examine the backer board to see if it is doing its job. If the edges of the cut are not sharp, it is letting the work piece splinter along that edge. Replace it as needed.

   Another option is to mark the work pieces, so you know which side is the outside surface, and scribe only the inside surface. If you are getting splintering along the vertical line, however, you'll still get little spaces in the corners of the joint.

   You might also recheck the sharpness of the blades, and make sure they are free of pitch, etc.

3. 
   Rob_Sp | Dec 25, 2012 11:17am | #4

   Box Joint

   First I would ditch the clamp, It should not be necessary on a jig such as this. Not only cumbersome and time wasting, it could be contributing to the problem as it could be springing the piece away slightly from the backup material. Simple hand pressure is more than ample to keep it fenced, not to mention the tactile feedback you will have to let you know you are properly fenced or in position. Dust accumulation between the workpiece and fence can also cause problems, a relief cut at the bottom of the jig may help keep this area clear as well as an air nozzle nearby. Over time the backup material will become eroded with repeat use, the material at the rear of the cut must be present right up to the margins of the blade, the slightest opening will allow for tearout. You might want to plough out the area behind the cut so a sacrificial piece can be attached and easily replaced when worn- without having to rebuild the jig. Feed rate is also an issue, fast enough to avoid overheating of the tool, wich will cause dulling contributing to poor quality of cut, but not too fast blowing through the material and not giving the blade enough time to do it's job. Obiviously a sharp tool is absolutly necessary, Freud is ok for the money but would not be my first choice, a Forrest or similar quality dado set would be a better choice- a lot more money but you get what you pay for. As a last ditch, you could run the boards twice, pre cutting, then taking a light final cut. You don't say where the blowout is, if just at the top a single scribe with a sharp knife might work, if the sides are blowing out as well then-Not.

   With good quality sharp tooling, jig and technique I don't think you should have to scribe.

   Happy Christmas

   Rob

4. 
   retired08 | Dec 25, 2012 12:16pm | #5

   Thanks Rob

   First off, Merry Christmas to you as well.  Your points are very well taken, I've probably been lax in trying to get too much milage out of the MDF backer board for the jig and, like you say, clamping is a pain in the rear!  My initial Freud set was returned because of terrible cuts, I even sent them sample pieces that were basically burned through so I too am not real crazy about the quality of the set.  I have an Amana dado set which works great but leaves little points in the corners but I think I'd rather have that then the tear out along the top of the cut.  Santa hasn't given me enough gift cards for the Forrest set but you're right on with the quality issues -- why, other than greed, do manufactureres make crap!

5. 
   roc | Dec 25, 2012 05:08pm | #6

   Here is a good backer solution

   I don't cut many finger joints.  I made this jig as one of my first projects after I got my table saw and it shows.  Don't judge it too harshly I was young, I was crazy, I didn't know what I was doing I MADE MISTAKES AND LEARNED FROM THEM.

   I ' MMMMMMM SORRY !  

   Oh Bob . . .  shall I show this or not?

   . . . yes . . . no . . . yes . . . no . . . ALRIGHT !   I will swing by for a minute, (allow them to envy me), grab a hand full of popcorn shrimp and blow out of there.

   (from Jim Carry's The Grinch)

   The backer strip is half dovetailed into the fence so it is held in place and still be able to remove it and cut off the end last used to expose a fresh section.

   http://forums.finewoodworking.com/fine-woodworking-knots/jigs-fixtures-tips-tricks/finger-joints-do-not-line

   
1. 
   retired08 | Dec 25, 2012 10:07pm | #7

   Finger Joints

   Here's a link to my blog where I showed the fingerjoint jig I use on the tablesaw.  It does work well and I think the blow out is caused by me trying to get too much milage out of the backer strip ( I am Dutch!) and also the mediocre quality of the Freud box cutting set.

   http://woodworksbyjohn.blogspot.com/2012/05/finger-joint-jig-final-version.html