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Thread: Box Joint on a router table

  1. #16
    Join Date
    Dec 2010
    Location
    WNY
    Posts
    7,894
    Thanks for that post Charley. I may just have to check out the IBox some more. I use the original Incra jig which indexes in precise 1/32" increments, no other option, so I have to use bits really close to 1/4", 1/2", etc. for the joints to fit together correctly. Being able to adjust for bits that are over/under sized would give some added flexibility.

    John

  2. #17
    Join Date
    Apr 2018
    Location
    Cambridge Vermont
    Posts
    1,754
    I've never tried it but I have watched a video of the Leigh jig for doing dovetails and box joints on a router table. It seems like a homemade jig could be made that was a copy of it. Not sure how it compares to the jig you made. Personally I like larger diameter shank router bits to help reduce flexing. Leigh likes to use 8mm shank bits.

  3. #18
    Quote Originally Posted by John TenEyck View Post
    Thanks for that post Charley. I may just have to check out the IBox some more. I use the original Incra jig which indexes in precise 1/32" increments, no other option, so I have to use bits really close to 1/4", 1/2", etc. for the joints to fit together correctly. Being able to adjust for bits that are over/under sized would give some added flexibility.

    John
    John, only one of the reasons I prefer tablesaw box joints is that lots of carbide, cast iron, and horsepower is a better way to remove all that waste. The other reason is the fact that the dado set allows adjustiment of the slot width while keeping the spacing fixed . I have recently built a jig which uses the threaded rod indexing scheme if the Incra ls positioner. I had a lot of time on my hands during covid sheltering during which I designed what I call the "inchworm advance". It is a technique which allows very fast advance to an approximate position, then locked in to the threaded rod grooves. Don't have any pics at present, but may write it up in the near future.
    Dan

  4. #19
    I too use an Incra jig for box joints (on small boxes). It is absolutely critical to use a backer board but I also use a front board so I end up with a sandwich. Everything is clamped tightly to the jig before cutting. The jig has teflon bolts for taking up slack and I keep this tight enough so that I can just slide the jig easily on the track. For small boxes where the joint has to be perfect, it has worked beautifully.

  5. #20
    Join Date
    Dec 2013
    Location
    Central New Jersey
    Posts
    578
    Quote Originally Posted by Jim Barstow View Post
    I too use an Incra jig for box joints (on small boxes). It is absolutely critical to use a backer board but I also use a front board so I end up with a sandwich. Everything is clamped tightly to the jig before cutting. The jig has teflon bolts for taking up slack and I keep this tight enough so that I can just slide the jig easily on the track. For small boxes where the joint has to be perfect, it has worked beautifully.
    I was walking around Woodcraft today and splurged on the incra I-Box jig. I might not have time for a few days to get it going with some other projects in-front of it.

  6. #21
    Join Date
    Nov 2003
    Location
    Central North Carolina
    Posts
    1,773
    Justin,

    Now that you have an I-Box jig, here are several tips -

    1 - The miter bar must be adjusted so that it slides easily in the miter slot, but with no side play.

    2- Get a piece of 1/4" MDF. I buy the Handy Panels from Home Depot in 2' X 4' size, because I never need much of it at a time and storage is difficult in my small
    shop. Cut it up to match the dimensions of the sacrificial strip that comes with your I-Box jig. Then make a drill press set-up to drill one hole. Then flip the piece
    and drill the adjacent hole. Now flip the piece end for end and repeat the process to drill the two holes in the other end. Then remove your positioning jig and
    countersink all 4 holes from the shiny side. A 2' X 4' piece of 1/4" MDF will cost you about $6, but will let you make several years worth of sacrificial strips for
    your I-Box jig. Incra sells them at about 3/$10, so in an hour fun and easy shop time you will have saved about $50. You don't need a new sacrificial piece for
    every cut. Just slide it left and right to use an un cut area for the next cut. You can invert the sacrificial piece and use the top edge too, so probably 30 box joint
    setups for each sacrificial strip.

    3 - When adjusting your I-Box jig, always remember to unlock the adjustments with the top knob and lock the adjustment when complete. The red and silver knobs
    at the end of the I-Box jig are for calibration and setup. If you make an adjustment without unlocking with the top knob, you may damage internal parts.

    4 - The initial calibration requires that you adjust the jig so that the finger just touches (kisses) the cutter or blade. This is critical. It should touch, but not deflect.

    5 - After you have set up your I-Box, make a test cut before committing your work pieces to be certain that they are what you want.

    6 - Once you are happy with the test cut, move the sacrificial strip to a fresh position and load your work piece(s). Since the front and back of a box are the same size,

    My Cutting Method -

    I label both of the box front and back work pieces with an "A" on the side that will be facing out when the box is complete. I also always begin with them against the pin for the first cut, and do the same with the other end of the "A" pieces, so both ends start with a pin. For me, they get positioned against, but touching and not deflecting the fingers in the jig. After each cut, the work is moved and the previous cut is now placed over the fingers in the jig. IT should fit with no play, but should not be tight. Also both ends must receive the box joint cuts beginning at the top edge with a pin. Don't cut one end beginning with a pin and the other top end beginning with a notch. Keep them the same on both ends. Do the same with the "B" labeled pieces, but both ends beginning with a notch at the top.

    Use a clamp to hold the work in position and down against the jig. If you are cutting two or more at the same time, use additional clamps or double sided tape to keep them moving together without any movement in relation to each other.

    When beginning the cuts of the "box sides", I label them "B" on their outside face and always begin the cut by using the first pin and notch of an "A" piece as the spacer to get the "B" pieces started correctly. Just insert an "A" piece first notch on the guides with the first pin to the left. Then insert your first "B" piece against the edge of the "A" piece. Then make the first "B" piece cut. You don't need to use the "A" piece again after this first cut.
    So the first cut of the "B" pieces will be a notch and not a pin.

    I have found that my I-Box jig holds it's calibration so well that I can place it in it's storage box, and if cutting the same box joint again, just take it out of the box, change to the same saw blade, set the correct blade depth of cut, then move the sacrificial piece in the jig to a fresh position, and begin cutting perfect box joints again.

    If your miter gauge does not fit the miter slot of your saw or router table and there is side play, your box joints will not be accurate, varying by the amount of side play of your miter gauge bar and slot.

    Charley

  7. #22
    Join Date
    Dec 2013
    Location
    Central New Jersey
    Posts
    578
    Quote Originally Posted by Charles Lent View Post
    Justin,

    Now that you have an I-Box jig, here are several tips -

    1 - The miter bar must be adjusted so that it slides easily in the miter slot, but with no side play.

    2- Get a piece of 1/4" MDF. I buy the Handy Panels from Home Depot in 2' X 4' size, because I never need much of it at a time and storage is difficult in my small
    shop. Cut it up to match the dimensions of the sacrificial strip that comes with your I-Box jig. Then make a drill press set-up to drill one hole. Then flip the piece
    and drill the adjacent hole. Now flip the piece end for end and repeat the process to drill the two holes in the other end. Then remove your positioning jig and
    countersink all 4 holes from the shiny side. A 2' X 4' piece of 1/4" MDF will cost you about $6, but will let you make several years worth of sacrificial strips for
    your I-Box jig. Incra sells them at about 3/$10, so in an hour fun and easy shop time you will have saved about $50. You don't need a new sacrificial piece for
    every cut. Just slide it left and right to use an un cut area for the next cut. You can invert the sacrificial piece and use the top edge too, so probably 30 box joint
    setups for each sacrificial strip.

    3 - When adjusting your I-Box jig, always remember to unlock the adjustments with the top knob and lock the adjustment when complete. The red and silver knobs
    at the end of the I-Box jig are for calibration and setup. If you make an adjustment without unlocking with the top knob, you may damage internal parts.

    4 - The initial calibration requires that you adjust the jig so that the finger just touches (kisses) the cutter or blade. This is critical. It should touch, but not deflect.

    5 - After you have set up your I-Box, make a test cut before committing your work pieces to be certain that they are what you want.

    6 - Once you are happy with the test cut, move the sacrificial strip to a fresh position and load your work piece(s). Since the front and back of a box are the same size,

    My Cutting Method -

    I label both of the box front and back work pieces with an "A" on the side that will be facing out when the box is complete. I also always begin with them against the pin for the first cut, and do the same with the other end of the "A" pieces, so both ends start with a pin. For me, they get positioned against, but touching and not deflecting the fingers in the jig. After each cut, the work is moved and the previous cut is now placed over the fingers in the jig. IT should fit with no play, but should not be tight. Also both ends must receive the box joint cuts beginning at the top edge with a pin. Don't cut one end beginning with a pin and the other top end beginning with a notch. Keep them the same on both ends. Do the same with the "B" labeled pieces, but both ends beginning with a notch at the top.

    Use a clamp to hold the work in position and down against the jig. If you are cutting two or more at the same time, use additional clamps or double sided tape to keep them moving together without any movement in relation to each other.

    When beginning the cuts of the "box sides", I label them "B" on their outside face and always begin the cut by using the first pin and notch of an "A" piece as the spacer to get the "B" pieces started correctly. Just insert an "A" piece first notch on the guides with the first pin to the left. Then insert your first "B" piece against the edge of the "A" piece. Then make the first "B" piece cut. You don't need to use the "A" piece again after this first cut.
    So the first cut of the "B" pieces will be a notch and not a pin.

    I have found that my I-Box jig holds it's calibration so well that I can place it in it's storage box, and if cutting the same box joint again, just take it out of the box, change to the same saw blade, set the correct blade depth of cut, then move the sacrificial piece in the jig to a fresh position, and begin cutting perfect box joints again.

    If your miter gauge does not fit the miter slot of your saw or router table and there is side play, your box joints will not be accurate, varying by the amount of side play of your miter gauge bar and slot.

    Charley
    Charley,

    Thank you for the tips and tricks. I printed this out and will keep it with my jig so I have it. The parts about the cut I am going to need to review again just as am going to use the jig. I do have a fair amount of 1/4" MDF cut-offs that should be big enough to cut a bunch of sacrificial boards. My daughter uses MDF for her art sometimes so there I end up with the cut-offs. If not, home depot is not so far.

    The time I had today i've been finishing up my down-draft dust collection box for my new router table.

  8. #23
    Join Date
    Dec 2013
    Location
    Central New Jersey
    Posts
    578
    Quote Originally Posted by Charles Lent View Post
    Justin,

    Now that you have an I-Box jig, here are several tips -

    1 - The miter bar must be adjusted so that it slides easily in the miter slot, but with no side play.

    2- Get a piece of 1/4" MDF. I buy the Handy Panels from Home Depot in 2' X 4' size, because I never need much of it at a time and storage is difficult in my small
    shop. Cut it up to match the dimensions of the sacrificial strip that comes with your I-Box jig. Then make a drill press set-up to drill one hole. Then flip the piece
    and drill the adjacent hole. Now flip the piece end for end and repeat the process to drill the two holes in the other end. Then remove your positioning jig and
    countersink all 4 holes from the shiny side. A 2' X 4' piece of 1/4" MDF will cost you about $6, but will let you make several years worth of sacrificial strips for
    your I-Box jig. Incra sells them at about 3/$10, so in an hour fun and easy shop time you will have saved about $50. You don't need a new sacrificial piece for
    every cut. Just slide it left and right to use an un cut area for the next cut. You can invert the sacrificial piece and use the top edge too, so probably 30 box joint
    setups for each sacrificial strip.

    3 - When adjusting your I-Box jig, always remember to unlock the adjustments with the top knob and lock the adjustment when complete. The red and silver knobs
    at the end of the I-Box jig are for calibration and setup. If you make an adjustment without unlocking with the top knob, you may damage internal parts.

    4 - The initial calibration requires that you adjust the jig so that the finger just touches (kisses) the cutter or blade. This is critical. It should touch, but not deflect.

    5 - After you have set up your I-Box, make a test cut before committing your work pieces to be certain that they are what you want.

    6 - Once you are happy with the test cut, move the sacrificial strip to a fresh position and load your work piece(s). Since the front and back of a box are the same size,

    My Cutting Method -

    I label both of the box front and back work pieces with an "A" on the side that will be facing out when the box is complete. I also always begin with them against the pin for the first cut, and do the same with the other end of the "A" pieces, so both ends start with a pin. For me, they get positioned against, but touching and not deflecting the fingers in the jig. After each cut, the work is moved and the previous cut is now placed over the fingers in the jig. IT should fit with no play, but should not be tight. Also both ends must receive the box joint cuts beginning at the top edge with a pin. Don't cut one end beginning with a pin and the other top end beginning with a notch. Keep them the same on both ends. Do the same with the "B" labeled pieces, but both ends beginning with a notch at the top.

    Use a clamp to hold the work in position and down against the jig. If you are cutting two or more at the same time, use additional clamps or double sided tape to keep them moving together without any movement in relation to each other.

    When beginning the cuts of the "box sides", I label them "B" on their outside face and always begin the cut by using the first pin and notch of an "A" piece as the spacer to get the "B" pieces started correctly. Just insert an "A" piece first notch on the guides with the first pin to the left. Then insert your first "B" piece against the edge of the "A" piece. Then make the first "B" piece cut. You don't need to use the "A" piece again after this first cut.
    So the first cut of the "B" pieces will be a notch and not a pin.

    I have found that my I-Box jig holds it's calibration so well that I can place it in it's storage box, and if cutting the same box joint again, just take it out of the box, change to the same saw blade, set the correct blade depth of cut, then move the sacrificial piece in the jig to a fresh position, and begin cutting perfect box joints again.

    If your miter gauge does not fit the miter slot of your saw or router table and there is side play, your box joints will not be accurate, varying by the amount of side play of your miter gauge bar and slot.

    Charley
    Charley,

    I made my first box joints tests. It took a few tries to really dial-in the pins and notches, moving it the red dial just a hair to get the pins and groves to match up. My last test join is still really tight but I was able to get the joint together light hammering with a dead blow hammer. Putting a dial indicator on the pin and the notch, I am about just about a hair off. When I have time, i'll do 1 more test to try and get the joint tight but easier to fit together. When I actually use glue, it might help make it slip together easier as well.

  9. #24
    Join Date
    Dec 2013
    Location
    Central New Jersey
    Posts
    578
    I finally had some time to get back to the I-Box to make some more boxes, actually using it to make some drawers for router table organization. The first 7 boxes were small boxes to hold spice jars in the kitchen. I used an 1/8 inch joint and while they were a bit tight, I worked the joints with some sandpaper and got them to fit, plus a bit of light tapping with the dead blow hammer.

    This time I used a set of calipers to dial in the adjustment and the pins and notches fit together like a glove.
    Distraction could lead to dismemberment!

  10. #25
    Join Date
    Nov 2003
    Location
    Central North Carolina
    Posts
    1,773
    You don't want them that tight. They swell when glue is added and it will not go together. My guess is that you did not get the calibration right. Do you have a precision way to measure the pin and space widths? Dial or digital caliper? You need one of these. A ruler won't do at this precision. A few thousandths difference with the space being a few (0.002-0.003") thousandths wider than the pin is perfect in most cases. The joint will go together with only moderate pressure after glue is applied.

    I went with Titebond Extend glue after having trouble with Titebond II setting up too quickly. Elmer's white glue is slower than Titebond II as well. You should never need a hammer to put your joints together. Just a bump of the heel of your hands should be enough. Almost any glue will make a strong box joint. The problem arises when the glue sets up before the joint can be assembled, and this can frequently happen with so many surfaces that need glue applied to them before the joint can be assembled and clamped. I also remove the clamps about 2 hours after assembly. The glue has set up well by then, but isn't hard yet, so by removing the clamps you remove chances of the box being warped by any excess clamp pressure. If you did bow the box sides, there is still enough flexibility in the glue to allow the warping to straighten out. Check the box diagonally for square often, and add a diagonal clamp if needed to keep the box as square as possible.

    I apply blue tape to the inside surfaces close to the base of the slots of the joints. This keeps glue seepage from getting on the inside of the box corners, but remove the tape after the joint has set up and before the glue has become too hard. Wait too long and you will need a chisel. Sanding after the joint has fully dried takes care of outside excess glue, but this is very difficult to do inside. The tape helps eliminate this problem.

    After the four corners of the box have dried (about 24-48 hours), I then attach the box tops and bottoms. If made from plywood, I just glue them on since plywood is stable enough not to shrink and swell with moisture changes, enough to cause problems. If solid wood they must Be installed in rabbets cut into the box sides or their cross grain shrinkage and swelling will break them over time. For small boxes, I use a Lee Valley Box slotting bit in my router table with the height set for the distance in from the box edge that I want to place the box top or bottom. The Lee Valley Box Slotting Bits are a small diameter that allows cutting fully into the corners of a dry assembled and clamped box sides. Other slot cutting bits are too large a diameter to cut fully into the corners. I just slide the box sides around the bit to cut the desired slot in all box sides. It's then only necessary to slightly round the corners of the panel for it to fit well into these slots without leaving a gap at the box corner. Larger diameter bits will not cut fully into the box corners, leaving an area that must be chiseled out. These Lee Valley Box Slotting Bits come in several slot widths with 1/4" shanks. If you cut these slots on a table saw, they will cut out through the box joint, leaving a hole in the exterior. If you cut the slot on a router table using a small diameter router bit, you will have a risky job when cutting and stopping the cut at each end before the box end. The Lee Valley bits make this box slotting job easy and much safer.

    Charley

  11. #26
    Join Date
    Dec 2013
    Location
    Central New Jersey
    Posts
    578
    Quote Originally Posted by Charles Lent View Post
    You don't want them that tight. They swell when glue is added and it will not go together. My guess is that you did not get the calibration right. Do you have a precision way to measure the pin and space widths? Dial or digital caliper? You need one of these. A ruler won't do at this precision. A few thousandths difference with the space being a few (0.002-0.003") thousandths wider than the pin is perfect in most cases. The joint will go together with only moderate pressure after glue is applied.

    I went with Titebond Extend glue after having trouble with Titebond II setting up too quickly. Elmer's white glue is slower than Titebond II as well. You should never need a hammer to put your joints together. Just a bump of the heel of your hands should be enough. Almost any glue will make a strong box joint. The problem arises when the glue sets up before the joint can be assembled, and this can frequently happen with so many surfaces that need glue applied to them before the joint can be assembled and clamped. I also remove the clamps about 2 hours after assembly. The glue has set up well by then, but isn't hard yet, so by removing the clamps you remove chances of the box being warped by any excess clamp pressure. If you did bow the box sides, there is still enough flexibility in the glue to allow the warping to straighten out. Check the box diagonally for square often, and add a diagonal clamp if needed to keep the box as square as possible.

    I apply blue tape to the inside surfaces close to the base of the slots of the joints. This keeps glue seepage from getting on the inside of the box corners, but remove the tape after the joint has set up and before the glue has become too hard. Wait too long and you will need a chisel. Sanding after the joint has fully dried takes care of outside excess glue, but this is very difficult to do inside. The tape helps eliminate this problem.

    After the four corners of the box have dried (about 24-48 hours), I then attach the box tops and bottoms. If made from plywood, I just glue them on since plywood is stable enough not to shrink and swell with moisture changes, enough to cause problems. If solid wood they must Be installed in rabbets cut into the box sides or their cross grain shrinkage and swelling will break them over time. For small boxes, I use a Lee Valley Box slotting bit in my router table with the height set for the distance in from the box edge that I want to place the box top or bottom. The Lee Valley Box Slotting Bits are a small diameter that allows cutting fully into the corners of a dry assembled and clamped box sides. Other slot cutting bits are too large a diameter to cut fully into the corners. I just slide the box sides around the bit to cut the desired slot in all box sides. It's then only necessary to slightly round the corners of the panel for it to fit well into these slots without leaving a gap at the box corner. Larger diameter bits will not cut fully into the box corners, leaving an area that must be chiseled out. These Lee Valley Box Slotting Bits come in several slot widths with 1/4" shanks. If you cut these slots on a table saw, they will cut out through the box joint, leaving a hole in the exterior. If you cut the slot on a router table using a small diameter router bit, you will have a risky job when cutting and stopping the cut at each end before the box end. The Lee Valley bits make this box slotting job easy and much safer.

    Charley
    I use extend glue for these and it works well. Tape on inside joints is a known trick for any kind of joint but a good reminder.

    Now the box cutting joint. Well of course i find out about this after the 'gift card' cyber monday deal is over. That is a much better method than a 1/8 or 1/4 bit with stop blocks on the router table.
    Distraction could lead to dismemberment!

  12. #27
    Join Date
    Nov 2003
    Location
    Central North Carolina
    Posts
    1,773
    Justin,

    Another justification for buying an Incra I-Box jig - The inventor is a member of Sawmill Creek. So if you get really stuck on a problem, you can get personal help from him. I'll PM his name if you need it.

    Charley

  13. #28
    Join Date
    Dec 2013
    Location
    Central New Jersey
    Posts
    578
    Quote Originally Posted by Charles Lent View Post
    Justin,

    Another justification for buying an Incra I-Box jig - The inventor is a member of Sawmill Creek. So if you get really stuck on a problem, you can get personal help from him. I'll PM his name if you need it.

    Charley
    Charley,

    Thanks - his name would be great just in case, as well as to send a compliment on a great jig.


    Tx

    Justin
    Distraction could lead to dismemberment!

  14. #29
    Join Date
    Nov 2006
    Location
    N.E. Ohio
    Posts
    6,151
    I was once told "You can't cut Box Joints in Plywood", but I do it frequently.
    I have an original Lee reloading press from the 1970s that I bought back then.
    It came in a plywood storage case that converted into a stand for the press.
    They used box joints to make the case & I became an instant fan of the looks of that joint the first time I laid eyes on it.
    My granddad always said, :As one door closes, another opens".
    Wonderful man, terrible cabinet maker...

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