Why Jointers Cut Tapers

and we all know that a joiner does very good job of making one edge or one face straight flat and true the problem is that there's a lot of people that still don't realize that a jointer has no way of making opposing faces parallel it'll do a good job of cutting one edge or one face making it nice and straight and true but if we turn the board over and cut the other edge it'll cut that edge straight and true but it has no way of knowing if that edge is parallel to this one there's some people around that will tell you if you raise or lower the outfeed table raise and lower the cutter head maybe both or maybe put a pickle in your pocket that the jointer will start cutting parallel faces how is this possible the reality is it's not possible the problem with the jointer is that it only has an indexing surface and a cutter and they're both on the same side there's nothing following the other edge to make sure that it stays parallel to the cutter and that's the only way we can cut another edge parallel to the one that's on the table another point of confusing is that while using the jointer spins we can cut this surface exactly square to that surface or whatever bevel we want the thing is that when it cuts those this surface doesn't necessarily come out parallel to that surface here's a good illustration of what can happen here I've joined a dis edge in this edge they're both straight flat and true but now look at how thick the board is on this edge flip it over on this edge and look how thin it is back here there's a huge taper following this edge but not on this edge the cuts are exactly Square to each other but they're not parallel now this is the other end of that same board see these are the two jointed surfaces and look how square the board is on this end not so much on this end we have to remember that the same problem occurs whether are you working with the thin edges or the wide phases we clean up one straighten it and flatten it on the jointer and then take it to either the table saw their planer because those have the registering surface that holds it parallel to the cutter [Music] now at the table saw I can take the edge we just straighten on a jointer put that against the RIP fence and make a rip cut that will cut this edge parallel to this one because we have the machine surface against a known guiding straight surface the jointer doesn't have this how the board has parallel edges I could go back to the jointer and take a single light pass on the sawn edge but for doing glue ups and just about everything else this is smooth enough now we've taken our board to the planer we put the jointed surface on the tables we know these are flat and we know that the knives are held perfectly rigid above them the knives are parallel to the table so if we send this through because the jointed edge is on the flat table the knives will make a pass and make this side clean straight true and parallel to this side the jointer has none of this to do that [Music] right now both sides of our board are nice and flat straight and true they're also parallel to each other the jointer can't do that the jointer really does do a very good job of straightening and flattening services on our wood it can also make two services square to each other but if you want them parallel you have to go to the table saw or the planer depending on which surface you're working on the jointer has limitations get over it

Channel: thintz12

Views: 70,091

Rating: 4.7939396 out of 5

Keywords: jointer, taper, square, woodworking, how-to

Id: 5af_yZQHo8k

Length: 4min 20sec (260 seconds)

Published: Fri Nov 28 2008