Replies

1. 
   mrbird90 | Jul 29, 2009 06:13pm | #1

   I had this problem one time when making a battery box for an old 1900 era car. My solution was to put a strip of masking tape on the back side and it  and it about fixed the problem except for one or two small blow outs.

2. 
   daverichards | Jul 29, 2009 06:17pm | #2

   Have you tried backing up the wood with a piece of scrap? If the scrap is clamped tightly to the work where the blade exits, there should be no blow out on the work. It's sort of the same idea as a zero clearance throat plate.

3. 
   forestgirl | Jul 29, 2009 06:20pm | #3

   The tape trick should help, you can also trying scoring a line across the bottom of the soon-to-be fingers and slots on the back (exit) side.

   Whici model Freud dado are you using?? 

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 
   
1. 
   BrentD | Jul 29, 2009 07:26pm | #4

   I have tried tape without much success.  The backer board idea is a good one, but given that I have cut a new notch in the back of my jig with the current setting, it already is a zero-clearance set up all around the notch that is to be cut.

   Scoring is a good idea.  I'll have to remember that. 

   The blades I'm using are the Freud Dial-a-Dado blade set.  http://www.newwoodworker.com/reviews/Frdsd608rvu.html

   Brent

    

1. 
   forestgirl | Jul 30, 2009 12:34am | #5

   I will confess to having never made box joints in solid wood.  Only in Baltic Birch ply, which yielded little "flags" on the backside of the cut.  The scoring was recommended to solve that particular problem, so it could well work with your chip-out problem.

   I use the Freud box-joint cutter, which is an absolute dream.  It gives perfectly flat-bottom notches, as it doesn't need the bat-ears that are required in a dado for it to work properly for all its purposes.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

1. 
   BrentD | Jul 30, 2009 12:42am | #6

   I'll have to look for that blade, but the blade I use, does not give bat ears and does have a very flat bottom.  Nothing wrong with the cut when it is clean. 

   I like the scoring idea.  That's what I'll try next time. 

   Brent

    

    

1. 
   forestgirl | Jul 30, 2009 09:07am | #8

   Which Freud set do you have (model#)?  Good luck with the scoring approach, hope it works.forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 

2. 
   BrentD | Jul 30, 2009 04:12pm | #9

   fg - the blade model number is SD608

   Bob - the chips are always at the top of the cut (top being relative to the saw blade as the wood passes over the table.  Never on the left and right.  I'm sawing into end grain so that is where the chipping is most likely to happen of course.

   Everything is properly snug, so I don't think there is any lateral movement or vibrations in the blade or jig.  And vertical is the issue anyway. 

   Clamping the board to the back of the jig is difficult given the size of the boards.  I can't really clamp them as well as I would like.  Clamping to a separate backer board might be possible, but the clamps would be 4-5" above the blade, so I am not sure how effective it would be.  Certainly something to try however. 

3. 
   KiddervilleAcres | Jul 30, 2009 04:42pm | #10

   Brent,

   By any chance is there any buildup of pitch/sawdust residue on the ends of the cutters?  I have the same model Freud dado set and have not had any problems with mine.  I also have the box cutter set forestgirl mentioned and it also works flawlessly.

   It can be a pain in the patoot but keeping the cutters clean seems to help.

   Another question I had was how square is your stock?  If there is any cup in the ends it could cause a gap between it and your backer board, another possibility?

   Regards,Bob @ Kidderville Acres

   A Woodworkers mind should be the sharpest tool in the shop!

4. 
   KiddervilleAcres | Jul 30, 2009 04:47pm | #11

   Oh, almost forgot clamps.

   How about a Destaco push/pull model 601?  Another option might be a cam type clamp mounted to the bed of your sled, perhaps using a dowell as the pivot pin with an appropriately sized hole.

   Regards,Bob @ Kidderville Acres

   A Woodworkers mind should be the sharpest tool in the shop!

5. 
   BrentD | Jul 30, 2009 06:28pm | #12

   Bob,

   I am quite confident that the blades are not the problem.  They are clean, sharp, and well cared for. 

   The wood does not chip every time, but it will do it occasionally even when it seems to be flush to the jig.  In this case, the walnut is almost ideally quartersawn and quite flat. Yet, even though it appears to be tight to the jig, there is really no significant pressure holding it there. 

   That said, your last post sort of woke me up.  My jig lets the stock ride flush on the table top - just like it would in front of an ordinary miter gauge.  If I had a regular bed to it, well, then I could easily put clamps out in front as you suggest and that would almost certainly fix my problem!  I don't know why I didn't think of that myself.  Just didn't have my brain cells fully booted I guess.  But, that's what a forum is for I suppose. 

   It should not take too much to modify my jig to have a solid bed like a crosscutting sled. 

   Thanks a bunch!

   Brent

    

    

6. 
   KiddervilleAcres | Jul 31, 2009 04:21am | #14

   Brent,

   It should not take too much to modify my jig to have a solid bed like a crosscutting sled. 

   I must confess that I assumed you were using a sled.  Now, have you any idea(s) as to the best way to remove the red from my face?  :-)

   When I added an old Unisaw to the woodshop my 10" Delta contractors saw was redeployed as a, well I call it my dado machine.   The existing crosscut sled became the carriage for it.  The front fence (closest to the operator) is nearly 6" tall so it provides decent vertical support allowing for fairly long stock.

   Now the Unisaw does all the ripping/croscutting and the contractors saw does dados, rabbets and box joints.  I do need to come up with replaceable inserts for varying width cuts though.  Am thinking of using MDF.

   Regards,Bob @ Kidderville Acres

   A Woodworkers mind should be the sharpest tool in the shop!

7. 
   BrentD | Jul 31, 2009 05:28am | #15

   Though I have a luxuriously spacious shop relative to what I ever dreamed (24'x26'), when I upgraded from the Dewalt contractor's saw to the Steel City saw, I sold off the Dewalt.  In many ways, I wish I had kept it.  A dedicated dado saw was something that I thought of, but I just didn't want to give up the space.  I always seem short of space. Of course, having three projects going at any one time has something to do with that. 

   Anyway, between you and forestgirl, I think I may have my box joint problem solved. 

   Thanks,

   Brent

    

8. 
   spotcheck | Jul 30, 2009 09:00pm | #13

   Thanks - good idea - I can use that for a lot of things.  I will install some tee-tracks in my sled bottom.

2. 
   KiddervilleAcres | Jul 30, 2009 05:07am | #7

   Brent,

   Where is the blow out happening (bottom, left, right sides) and is it the same for all cuts?  Is it possible the jig is slipping in the miter slot?  Blade set up correctly and tightened on the arbor?  Not so tight it takes four men and a boy to loosen but ........

   If you can clamp the workpiece to the backer board do you still get blow out?  Also, if you insert a new backer board, clamp the workpiece to it and run it through do you get blow out then?

   Regards,Bob @ Kidderville Acres

   A Woodworkers mind should be the sharpest tool in the shop!

4. 
   cowtown | Aug 01, 2009 09:33am | #16

   go to youtube and search for box joint jig.

   There's a video there for an exquisite box joint jig.....by some canadian fella.

   I saw it, I made one,and it works really well.

   The link came from gluetube originally

   Eric inCalgary

1. 
   jimbell | Aug 03, 2009 08:16am | #17

   Although this thread seems finished, I'll add that I went through exactly the same problem last year. Putting in a new backer board almost always solved the problem. At one stage I was putting a new area of MDF behind the cut area with every cut. I'm not recommending this labour-intensive approach, but it indicated to me that part of the problem might be a microscopic gap in the well-used backer board.

   Also, I clamped the (fairly large) work piece to the sled fence with two clamps, one of them with a 12" reach so that I could clamp near the cutting area.

   In the end, I was not all that impressed with how "easy" a basic box joint was!

   Cheers!