|Forum topic by Ayoung||posted 02-25-2013 08:10 AM||3003 views||2 times favorited||4 replies|
02-25-2013 08:10 AM
I purchased a Porter Cable 4212 Dovetail jig for making drawers. the half blind template produced a flawless joint. The thru dovetail template however produced a joint where the front of the drawer was misaligned with the side by roughly 3/64”. This may be acceptable, but for a machinist turned wood worker, this was unacceptable, and the drawers would catch, sanding made them slide funny. searching the forums helped, some found the stamped steel side gauges to be out of spec. mine were slightly out, but only by ~0.005. Using a variety of Starrett precision measuring tools I checked all the parts of the jig, and found out what was accurate, and what was not. everything was off a small amount, but the most significant problems were:
with this in mind, there is procedure to correct for all these problems at once. You will need a cheep dial calipers, and a set of feeler gauges. it will take about an hour.
2-set up the jig so it makes a tight (hammer together) through dovetail joint. when flipping the template, make a habit of pushing it to the right when tightening the knobs
3-Reset the jig to cut tails, and center a piece of scrap wood, so there is an equal gap between the fingers and the edge of the wood on both sides
4-route the tails, and leave the board clamped in place vertically.
5-Flip the gauge to the pins side, release the vertical board with tails cut, and push up until the tops of the tails are = to the top of the template (the fingers should be in the tails gap.) and the edge is still against the side stop.
6-there will be a gap between the back of the tail, and the finger of the template. measure this gap with the feeler gauges. take the difference between the left and right sides, and divide by two, and select the corresponding feeler gauge (for example mine was off by 0.015. divide by 2 and get 0.0075 rounded to 0.008. I selected the 0.008” feeler gauge for my correction).
7-depending on which side the gap was the largest, you will have to place the feeler gauge between the side stop and the pin board or the tail board, when you cut either the pins or tails.
if you follow these steps, it will account for loose tolerances in machining all parts of the jig, and you will have a perfect joint.