Hello all,
Hopefully this is posted in the correct place, it's been a while since i have logged in.

Anyway I decided I wanted to to do some simple box joint (finger joints) boxes.
I have a Freud double fluted 1/2 router bit (this is what i had in hand). I have this setup in a table with a variable speed control. I'm using 1/2 popular 5 inches wide. I have the bit set just a hair proud of the board so as to do a little finish sanding back to flush.
I have my Jig set correctly so as to get my first joint cut and then just move the board for each finger.
Here is where i'm getting in trouble and frustrated! the first cut goes find but then after that it is hit or miss. I get might get 1 or 2 joints competed but then I get a blow out on one of the fingers, I have tried full speed, half speed, and low speed! this is a new bit so is very sharp!
This is all on the end grain. So i tried using the long grain side of the wood and I get 100% joint cut out, my 2 pieces of wood match up and the joints are snug but not tight.
So my question is (I know you where going so get to the point already) what am i missing as to getting the fingers on the end grain sides like i see folks doing! I have watched video's at Rockler, and other sites and they seem to cut right through the end grain sides with no issue using 1/4, 1/2 and even 3/8 inch bits. So far I have only cut aromatic cedar on the end grain side and it cut wonderfully no blow outs. I'm currently using popular and or pine as that is all i have in the shop

thoughts suggestions This should be simple I would think!

thanks

Welcome to the forum Ed.

for the proud fingers.. DO NOT sand them flush.. Use a paring chisel or LS plane...
Poplar is too soft to sand away and you will be unhappy with the outcome...

Which is blowing out... the poplar or the pine... both???
what type/grade of pine...

the poplar ... it's sap wood heavy.....
the pine... the nature of the beast....
feed rate is too fast at the exit... the bit is generating too much lateral pressure on the wood and not really cutting it's way through...... ease up on the feed rate just before exit...

I figure the blowout is happening when the bit exits the wood, right? Have you tried a sacrificial backer board? If not, that will help. If so, try a new one. Maybe the old one has gotten wallowed out.

thanks...
forgot about that...

The first shot shows the first time that I used the new OakPark spacer jigs some years ago. The other shots show details of the pusher with 80 grit paper glued on the face. I've now made a sacrificial board, still awaiting 80 grit paper, so that I can use the other sizes of spacer fences without mutilating the pusher. I had no breakout with this set-up. The pusher was based on a design by the late member and my very good friend Bobj3, Bob Jergens.

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Hi Ed, I have tried both two-sided router bits and spiral. The spiral give a much better cut. If I am working with a wood that has the tendency to tear out, I will use a backer board. I run the router about about 1/2 speed and don't feed the wood too fast into the bit. I hope this helps. Malcolm / Kentucky USA

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Thanks all for the quick responses. Since this is a new Jig it has a fresh new backer board so I should be good there. I wondered about the feed rate and will try going slower to see if that helps.
as to the type of wood it is just Lowes purchased pine and poplar. I started out with a Harbor Freight spiral up cut bit and was getting the same results which was why i switched to the current bit, which is a straight 2 fluted bit.

I use a sacrificial backer and one in front (a fronter?) if the wood is particularly prone to "blowing out". This is especially true for plywood (and doubly so for the cheaper big box stuff). If you can make clean plywood fingers, you can work any wood. Also, I try to size my pieces so they are a multiple of the finger size so I can have full fingers at the ends. Those skinny little partial fingers have always given me trouble.

Slowing down the feed rate is good. I like spiral bits but don't have one for 3/8" work yet still produce pretty clean joints.

Above all else, practice. I built a whole bunch of boxes for shop related stuff before I felt like I could show my work.

I clean-up partial pins with the ski mounted router.

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