First, some professional woodworkers use, and advocate using, chalk for marking your parts (numbering, indicating mortises, reference faces, etc.) so I have been trying that – DON’T DO IT! I have found (and it cost me) that the chalk “rubs off” quite quickly and your marks become barely readable. And today because of that I now have to remake the parts of two of my drawer parts (well that and a poor choice on my part – but more on that).
I have tried to keep the parts of each drawer together so as not to get them mixed up, but today they spilled and in trying to put them back together got some of them mixed up (since I could barely read the markings) with the result being some of those parts are so messed up I have to start over from scratch (cutting them to rough size, re-sawing them to rough thickness, etc.).
Basically even though I tried to plane these parts to the same width they came up slightly different. Initially I tried to gang the four pieces for each drawer together and plane them at the same time, but because oak has so much grain reversal I found that would not work (at least not without tear-out on some of the edges plus it made the planing more difficult). So I set up the finger joints for each based on their width.
As I mentioned earlier I had cut these parts 1/16″ longer and had set my dado blade 1/32″ higher than the thickness of my pieces (or so I thought). And since the fingers originally turned out to be the same length as my stock is thick, I decided I wanted to cut them that 1/32″ deeper; this was my first and “fatal” mistake although leaving them as they were would have resulting in these drawers being slightly bigger than planned and possibly not fitting the openings (another set of problems with more difficult solutions).
I reset my jig based on one of the drawer pieces but having gotten some parts now mixed up, the fingers on at least two of the pieces for each drawer came out quite a bit thinner than the slots (or the slots too wide depending on your perspective), so back to square one!!
One other thing I should have done in the beginning was to have double-checked the length of my fingers (height of my dado blade) and locked it down when it was correct. Though as I mentioned before, some of the slots cut by my dado blade fit differently on the indexing pin – some were tight and some were not; still not sure how that happened.
I guess by the time I finally get through will all these finger joints I should be almost an expert – though I doubt it.
One comment is if you plan on doing fingers joints be sure to prep at least a couple of extra pieces so if anything does go wrong you can pick up a spare and keep going (but then that really applies to any project). And believe me it is VERY easy for things to go wrong.
For one you really have to pay attention to how you are cutting each piece. I started by putting my front piece (finished face out) against the indexing pin to establish the first finger, then moving that slot onto the indexing pin and continue cutting until all the slots are cut. To get the spacing correct on the piece/end that butts up to it, you have to turn that piece (the front piece in my case) 180 degrees with the first slot on the indexing pin (finished face now against the jig) and butt the mating piece against it (with its’ finished face out); that puts the top edges together and the slot in the same place as the first finger. Then remove your first piece and move that new slot against the indexing pin and continue cutting the remainder of those slots. The same process goes for the back piece and its’ mating edges. I hope none of that is confusing.
To add another bit of complexity to all of this, the articles I read about cutting finger joints say that you need to score each piece on the exit side of your dado blade so as to prevent tear-out at the end, and from my test pieces I found that to be completely true. SO you have to now decide which side will be against you jig and score that side with the length of your fingers, and then figure out which side of the mating piece will be against your jig and score that side, and so on. I found this to be quite a challenge, resulting in several pieces being scored on both sides since I had them turned around. One helpful tip here is to put a “V” mark on what will be your top edge with the ‘V’ pointing like an arrow head toward which face is the outside (I got that tip from an e-book I have been reading – but do not do it with chalk).
I realize this is all a bit long (and hopefully not toomuch of a jumble), but I needed to out it all down “for posterity” and maybe help you not make the same mistakes.