184 – Coves on the Tablesaw & the Parallelogram Cove Jig


Marc:The Wood Whisperer is sponsored by Powermatic. The gold standard since 1921. Rockler Woodworking and Hardware. Create with confidence. And Clear Vue Cyclones. Clear the air and breathe easy. After the recent changes to the Wood Whisperer Guild structure, some older videos just didn’t fit anymore. I’m bringing those videos here for your viewing pleasure. Please enjoy. Now on today’s show, I’m gonna give you some great tips for creating beautiful cove
moldings on your table saw. (lively music) Now to make a cove
molding at the table saw all you really need to do is run the board across
the blade at an angle. The first time you hear that that sounds a little bit crazy because it kind of flies in the face of everything we’ve learned
about table saw safety, but trust me. There is a very safe way to do it and I’m gonna show you exactly how. Now you may be wondering why we are using the table saw to do this instead of some of the other tools that you might think
would be more appropriate. Let’s say like a shaper or a router or even a planer molder that has a nice big wide
profile knife to it. The reason is primarily most of us don’t have those things. Even my router table I’ve got a good selection of bits but I don’t really have
anything that can do this. Smaller maybe but certainly not this size. Even if I did, I would be limited by the bits that I have in my collection. At the table saw you can
do an incredible array of different shapes, different sizes and really your imagination is the limit. I’m gonna show you a
couple different methods. Some a little bit easier than others but I think you’ll find one
that’s gonna work for you and be prepared because
it’s gonna make a mess. Now let’s break our coves up into two specific groups. The first is symmetrical. Symmetrical basically just means that the center point of that cove is the highest point. It’s known as the apex. Now in an asymmetrical cove that highest point is
gonna be off to one side or the other and it kind of gives it a
little bit of a bottom heavy or possibly a top heavy look. Very cool but it requires
a slightly different setup. To make the symmetrical all we need to do is keep
our blade up and straight. We just vary the angle at which we run the piece across the table saw. But when you’re doing
an asymmetrical curve, you need to actually bevel the blade to whatever particular degree you need and that becomes a little
bit more complicated. Let’s start off by making
a few symmetrical coves and I’ll show you that process. Now what I consider to be the absolute simplest way to make a cove, not necessarily the fastest way but the simplest way is
really trial and error and lining things up by eye. For instance if you look straight on and you hold your work
piece in front of the blade and you vary the angle left to right. First of all, the blade
height that’s a constant because we usually know how deep you want that cove to be but let’s consider that one
of the variables as well. Maybe we’re not sure what we want. You can change the angle and you can change the
blade height up and down, and sight from the side that you’re gonna be pushing towards. Sight from the other side and see what that blade looks like if you were to sort of
with your imagination imagine it just cleaning
out all of that material in one fill swoop. Now in order to do a cut like this safely you obviously need some kind of an auxiliary fence installed so that you could ride
the work piece across it and not have any chance of
anything moving out of place and kicking back. At the very least, you want to have some sort of rigid fence. Piece of plywood works well. It’s actually even better
if you’ve got something a little bit wider because there’s less of a chance of it deflecting as you push across. Now I take it one step further. I don’t like having just one piece. I want a fence on both
sides of my work piece which gives me a lot more security. You don’t absolutely have to do that unless you’re doing a
really, really deep cove, but I do recommend it. I feel much more comfortable
when I’m doing that and it makes it easier just
to guide this work piece through a channel than to have to constantly
force it into this fence which could also lead to eventually deflecting it a little bit. At the very least though, you want to take a board and clamp it down to both the front of the bench and the back of the bench. Now incidentally, we have
a directional issue here. Should we be feeding from right to left as you see it here or should I be going from left to right? Really on a symmetrical cut it doesn’t matter so much either way but it’s good to get into the habit of doing it the way you should just in case you ever wind
up doing an asymmetrical cut where we bevel that blade. I’ll go into more detail about that later but suffice it to say we should probably just learn the rule now so that if you have a left tilt saw you’re gonna wanna go from
left to right like this. If you have a right tilt saw you want to go the other way. You want to go from right to left. Just lock that away in your brain and we’ll get back to it in a little bit. I was reading an article from
Fine Woodworking recently about this exact technique and the author was using
a parallelogram jig something like what I have here. They were just using it for setup but then once they had
the angle established he would go back and he would have some sort of a single-sided fence
system that he would use. I like a double-sided fence
like I mentioned before and I figured you know what? A parallelogram jig like this why can’t that be the fence system if we’re using it to set
everything up anyway? That’s exactly what I did. I just beefed it up a little bit. I made the two sides a little bit wider, a little bit more heavy duty and I think it’s gonna
work rather well for this. I’ll give you guys the plans for this very, very simple jig and you could make your own if you think it’s something
that’s gonna be useful to you. Let me show you how I use it to set up for a specific-sized
symmetrical cove. Now here is a drawing. It’s a good idea to draw
your coves on the end grain so you know exactly what you’re going for. This is gonna be about a half inch deep and three inches wide. I know my cove is three inches wide so I set the parallelogram
jig to three inches and lock it down. Then I set the blade to the
maximum height of the cove, a half inch. Now with the saw unplugged I manually rotate the blade while varying the angle of the jig. You have the perfect
angle when both the front and back teeth just kiss the surface of the front and back inside rails. Now I use a pencil to mark the position of the inside rails on the table saw top. As an alternative, you can use a few strips of blue tape which I find works even better. Now I loosen the jig and
use my work piece itself to give the jig its final setting. Remember we previously set the jig for the width of the cove not the width of the work piece itself. Now it’s a simple matter of centering the jig on the lines. This is why I like to use the blue tape. I usually do this part by eye and the bright blue color
makes it very easy to see. Finally I clamp the jig into place and here’s a look at the final setup. Now before making my first pass I put the blade down to
about a 16th of an inch. With the dust collection on I begin making my passes. Now I always use push
pads for this operation and I never raise the blade more than eighth of an inch per pass. Doing so will put a
significant amount of strain under a saw so don’t rush it. Notice that I’m bringing the wood back across the blade after each pass. I’m comfortable doing this simply because I have a two sided fence. If you have a one sided fence I definitely would not
recommend doing that. Now with the final passes you could see the cove come to life, and don’t worry about that
cut halfway up the board. This is just a piece of scrap wood. All right, now it’s time to try our hand on an asymmetrical cove. You could see in my example here the cove’s apex is slightly off centered. The first line is my center line and the second line is the peak, the apex of the cove. The first thing I’m gonna do is tilt my blade to approximately,
roughly 45 degrees and I’ll show you the low tech way first. The first thing I do is change
the bevel angle to roughly somewhere between 40 and
45 degrees approximately. Then I bring the blade’s height up to the maximum height of my cove. Once that’s set, that’s unknown. We don’t have to really
worry about that too much. I have the two variables to play with and that is the exact bevel angle as well as the angle of attack that this work piece is gonna take. The only way I could really
see what’s truly going on is to sight at this level from all the way over there. As soon as I have that angle I can kind of go back and forth with a little bit of trial and error and eventually get something
that’s pretty darn close. Once I’m there I lock this down. Maybe use a pencil again
to mark the location and I bring my parallelogram jig back, and clamp it down to the table and then you’re done. All right, that is the
quick and dirty method. Sometimes the quick and
dirty method is gonna work but other times it’s just
not gonna be good enough. If you have a very specific
cove profile that you need you can’t really use that method. Fortunately there are calculators online that will do all these math for us because I certainly have no idea how to begin approaching
the calculations required to get these numbers. One in particular that I found online was on Fine Woodworking’s website and it goes with a great article about cove cutting as well, but the calculator itself is really simple and it works really great for this. All you really need to do is plug in two or three numbers that we’re gonna know in just by drawing this out and it spits back out an exact angle that you need to approach the blade as well as the bevel angle of the blade. You can’t really ask
anything more than that. As soon as you have those numbers you have everything you need to know to get the exact profile that you’ve drawn on your work piece. That’s where it starts. Let’s draw this out. I’ll show you exactly
what numbers you need for the program and then we’ll punch those numbers in and see what we get. Okay, drawing the arc
shouldn’t be too bad here. We just need to create a center line. The total span of that cove is going to be three inches so I want to go an inch
and a half this way. Put a mark. Okay and an inch and a half this way. I normally don’t use a sharpie for this. Just want to make sure you can see it. Now a half inch from the center line is the apex offset. That’s the top of the cove. That’s gonna be about a half inch away. Let’s put a little line
and we’ll extend it. The distance from the bottom or the total depth of the cove is 3/4 of an inch. There. For fun you can grab a French curve. Connect this point to these two points. That represents the cove. Okay. The numbers that they need here are the apex offset. That’s this distance here. For me that’s a half inch. They need the total height or what would be the depth of the cove. Okay, that’s 3/4 of an inch. Let me write that half inch in. Okay, so that’s 3/4 and then want the total length from this point to this point. The total span of that cove. Now we know that to be three inches. Let’s plug those in. Using the program at finewoodworking.com I simply plug in 3/4 of an
inch for the cove depth, three inch for the cove length and a half inch for the apex offset. Then I hit calculate. The program reports back a
fence angle of 61 degrees and a blade tilt angle of 38 degrees. Now the bevel’s the easy part. The program told us that
we need to go to 38 degrees so that’s a simple
adjustment on the table saw. Now setting the angle of approach is a little bit trickier. 61 degrees is what the
program told us that we need and I’ve got one of
these little angle finder [dilly wackers] here. I’m gonna set that for 61 and this could be all you need if you happen to have one of these. I just use the front line of
the table saw for reference and it tells me that this is
now the angle that I need. I just butt my work piece up against there and that is my 61 degrees. At this point again, using the pencil, I could just draw on the table. I could use blue tape
to mark those positions and then drop my parallel
jig right on top. Now another way that you can do this and this is the method that I’m gonna use involves using your miter gauge and a very simple square. The program told us 61 degrees. We subtract that from
90 and that gives us 29. Make sure your blade is
at the maximum height of the apex here. You want to make sure
it’s 3/4 of an inch high. Now I take my square, put it up against the miter gauge and bring it forward. What I’m looking for now is to point that the blade
just contacts that square and then I just back it off just a hair. Once, you’re at that point of contact then again, drawing on the insert. Right now I’m drawing a line that basically intersects with
the front tip of that tooth. The very front of the blade. Now that line that we just drew represents the very front tip of the blade which means just the very
front tip of our cove. What is the offset that we need because if we put our jig there that’s not really gonna work. We need to make sure that
the blade sits inside of this work piece. My offset is a half inch on both sides. I’m gonna go back to the line there and draw a parallel line a half inch back toward me. Now you may be wondering
why we’re not measuring the same way at the back of the blade and then measuring off 3/4 of an inch and drawing another parallel line. Well, because of the parallelogram jig we don’t really need to. If we get the jig set
to the perfect width, we just basically use our
work piece to do that. Lock it down. All we really need to do is set the jig up, line it up. The inside face gets lined up with our outer most line that we drew, and because we know the jig is parallel, we know that the back piece is exactly where it needs to be. We don’t have to measure. We just line it up by eye and clamp it down. Now we just lower the blade and let the fun begin. (lively music) As you could see what we’re left with is just the gorgeous cove. Those offset coves very nice. Making the cove that’s the fun part. Cleaning it up, that’s
the not so fun part. Just gonna put my cove
out of this cherry board into the bench and show you a couple of the ways that I like to clean it up. You can use sandpaper or you could use some sort of a scraper. I have two scrapers that
I like to use for this. One is basically a straight scraper with one concave and one convex side that works really well, and then of course a gooseneck scraper. Either one of these. It’s really the same principle. The fact that it’s got
a nice curve edge on it. Allows us to get all of those extra ridge marks out of there. (scraping) Let’s try this guy. (scraping) Now after the scraping I probably would go and do a light sanding just to make sure everything
is nice and smooth. Here is a few possible ways that you could go about the sanding. First of all I’ve got one of these rubber oscillating spindle sander spindle dillies and if you can keep the sleeve on there you can actually just use that by itself. You can go all the way
from the rough sanding to the super fine sanding using this. If you run out of sleeves just use regular sandpaper
and wrap it around. Now here’s another option and this one’s kind of neat. It’s a little sanding apparatus that has these little
plastic inserts in here that are spring loaded so you can actually push
them into the surface and they’ll mold to that surface. You have this little
velcro sandpaper sheets that go on to it like so. You sand away. (scraping) Now you’ll probably have
to change the profile of this thing every once in a while depending on the type
of curve that you have because it’s only going to take on what this inch and a half
portion of your cove. Now the final option which is actually the cheapest is just using a dowel rod with some sandpaper wrapped around it. This is just something
from one of our closets in the house that I had cut down and would be perfect
for a project like this. Just wrap some sandpaper. Maybe tape it on the back end or something so it doesn’t slip off and back and forth. Obviously you’d want to cut it down from this big long one, but that will do the trick too. Once you get the technique down, the possibilities are endless. There’s just so many different shapes and different sizes that
you can make with this and you’re just limited
by your own creativity. Hopefully you’ll give
this technique a shot. Let me know how it works out for you. Thanks for watching. (lively jazz music) Now the design for this jig was inspired by very similar jig that I saw in a Fine Woodworking article. In that article they used
the jig for set up purposes and then went to some
other type of fence system and I figured, well, why not just make it a little bit sturdier and have that be my fence. Then I get the added benefit of having a fence on both sides. That’s basically the idea behind this. Now in using it for the video I’ve realized a couple areas where I might be able to improve things and stuff I want to
bring your attention to before you build yours. First of all, the length of the rails. Depending on the angle here, it may be kind of tricky
to clamp this down to the table saw. You may want to make
this a little bit longer. Have maybe a four to six inch extension on each one of these just with the bottom piece so that you can clamp
it down more securely. You may even want to go further out with the hole thing, just make it really long but I did find that this particular one was certainly adequate but required a little creative clamping at times. The second thing. If you have a thin piece
of material no problem. You could fit that right
under this little bridge here and you have no issues there. Let’s say you have a big fat piece of a quarter material
that’s not gonna fit there. Now if you could fit
it in between the blade and the bridge here, you’re fine. You could run it back and
forth with no problem. A lot of cases, you’re gonna have a longer piece than this. You need to be able to
feed it from behind. In order to accommodate that in the second build of this, I think what I’m gonna do
is create some extra inserts that you could just pop down on here and as long as your bolt is long enough to go through there, it will keep raising the
bridge up higher and higher depending on the thickness of the molding that you want to make. Let’s go ahead with the redesign and I’ll show you as we go some of the improvements and the entire process
from start to finish. I’m disassembling the old jig just to give you a general idea of how it was constructed. Removing the knobs allows me to remove the connecting rails. Notice it’s a pretty tight fit. The bolts are easily removed and notice that on the bottom of the jig it created a recess so that the head of the bolts sits below the bottom surface of the jig. If you don’t do this, the bolt will scratch your table saw top. Now let’s build a new version of the jig. I start by making two four-inch wide rails from some Baltic birch. Consider ripping a third piece for other parts of the jig. With the two pieces gang together I trim one in flush and then carefully flip the pieces around and trim them to final length, 54 inches. Keep in mind that your
cut outs from this step could also be used
later on in the process. My cut outs weren’t long enough so I needed to rip a third piece of Baltic birch for this step. I’m cutting the small
four-inch by two-inch pieces that go under the connecting rails. To make quick work of it I use a pencil line on the
saw surface as a guide. If you’re careful to put the work piece up to the line the same
way every single time, this is remarkably accurate. I cut eight pieces this way. Now we need to drill the bolt holes in the dead center of the small blocks. I simply draw a couple
lines corner to corner to find the exact center. At the drill press I set
up my fence and stop block so that I can make a repeatable hole. I drill all eight pieces this way. Now we need to make the
two connecting rails. Mine are 13 inches long and 1 1/2 inches wide. Using the adjustable square I mark a line one inch in from each edge. Then I mark the center point of that line which is approximately 3/4 of an inch. Using the drill press
and a stop block again I set up for repeatable drilling. Each end of both connecting
rails is drilled this way. Now I need to mark the locations of the support blocks. I mark a line in two inches from the edge of one of the long rails. Using my line for reference I use glue and a couple of brad nails to secure the support block. Now instead of measuring on the other side and drawing a line, I want a more accurate way of ensuring exact spacing
on both of my rails. I use a scrap piece of ply cut to 46 inches as a guide. I rest the other support
block right against the guide and secure it with glue and brads Repeat the process for the second rail. Now I need to use the holes and the support block as guides for drilling all the
way through the rails. Then I use a Forstner bit to create the recesses for the bolt heads. Now with the bolts inserted we can assemble the jig. After just an hour’s worth of work you got a pretty functional
parallelogram jig. Now you could pretty it up a little bit. Sand it, maybe put a coat of
wax or coat of poly on it, round over some of these sharp edges just to make it a little
more user-friendly, but for the most part this
is all you need to do. You got plenty of room here for nice wide pieces. Just lock it in place, tighten these down and you’re good to go. Now the other thing that we
discussed in the beginning was possibly modifying
some of the original plans and making it easier to clamp and also allowing us to put
taller pieces under here. I did do those improvements. On the outside I’ve got
an extra two inch leap on each side that should help facilitate better clamping on the table saw. On the ends here I had
to cut four extra pieces that are gonna work like shims basically. You just drop those on top and then now that
effectively raises the height of our little bridge here and you could very easily now fit a quarter stock right underneath there. I guess if you really wanted to you could just glue these
secondary blocks down and put the bridge on top of that because really there’s no
harm in it being taller. It’s just an issue of
it’s not tall enough. For most of the work I do, it’s a little bit more lower profile stuff so the jig doesn’t quite jot out as much. Maybe that’s one reason not to do it. It’s your jig, do whatever you like. Either way, for an hour’s worth of work it’s a pretty good time investment, and not a whole lot of
material goes into it. If you haven’t already
seen the cove molding video go back and watch that because I show exactly how
you can incorporate this into your workflow. I hope you have fun building yours and please e-mail me and let me know any modifications and changes
that you’ve done to yours. I would love to see it and we can even post the
pictures on the website. Thanks for watching and have fun building your jigs. (lively guitar music)

46 thoughts on “184 – Coves on the Tablesaw & the Parallelogram Cove Jig

  • One thing you might consider doing is dovetailing the joints first. You can even do this technique on the fully assembled box. That way you won't have to worry about joinery after the coves are cut. It'll take some practice runs and planning but it can certainly be done.

  • A flat ground blade is best. Most ripping blades will suffice. And you can certainly use purpleheart wherever you want in the piece. Depends on the design and the look you're going for.

  • if you die before me can i have your tools please? So so jealous!!!! going to cry myself too sleep now! look after that baby.

  • Thanks for another great video, Marc. I have some 6" cove crown molding to make, and I'm wondering if it would be easier to remove the bulk of the cove with a dado blade in a conventional fashion, first. You know – deepest at the apex of the cove, drop down a little and make a pass flanking the middle channel on the left and right, and repeat, working my way out. Then use the parallelogram jig to cut the coves like you show above. Make sense, or am I thinking too much about it? Thanks again.

  • I think turning the saw off is the "proper" way to do it, in terms of absolute safety. But to be honest, I frequently make small adjustments while the blade is moving. Probably shouldn't do it as much as I do.

  • I was just wondering. I inherited a workshop with a lot of tools and i am trying to learn how to use them. You and Steve Ramsey have been a ton of help! Thanks and keep up these great videos!

  • Rather than a bridge that interferes with the workpiece why not flip the parallelogram jig over, you could then have the connecting short pieces flush with the height of your table saw. A slot in the connecting short sides of the jig could be cut so the locking bolts can be adjusted along the length of the short sides to account for varying width in each workpiece each short side could ride on the front & back edge of the table & the jig locked parallel again using the workpiece?

  • Heres a possible sanding solution: 

    Place a piece of scrap at the end of the work piece so you can draw the exact curvature of the work piece.  Cut multiple pieces out on the band saw at the same time so they all have the same curvature.  Sand these down to get them as close as possible to the exact curve of the work piece but it doesnt have to be perfect, just close.

    Now attach these pieces together so as to create a form for your sandpaper.  Attach a piece of foam to the sanding side of the block (any kind of soft flexible foam will do) you just made using spray adhesive ( or something like that ).  Wrap on the appropriate type of sandpaper for the job and go at it.  The foam will offset any flaws in your sanding block giving you that flexibility from not being perfect on the band saw.

    There are many ways to adapt this method or change it to your liking, but you get the idea. 

  • Hi I just that thought this was a great informative video I have made coves before bit my method was a bit more hit and miss. I'm not sure how stupid this suggestion sounds but if you are only working with smaller material would it be practical to use  a long sanding drum with soft outer fitted into a chuck on the headstock of  your lathe secure the other end with the tail stock and sand the cove out at low speed on the lathe.

  • thank you for the video, it was interesting.  I am surprised that you didn't cut slots down the center of each long rail and use those to attach them to the miter slots. 
    I do think though that even if you personally choose to use the sliding power miter box incorrectly <ie:  pushing the saw through the work instead of properly pulling it as they say in the instructions…so the blade pushes the work down into the table instead of trying to lift it…> I don't think you should be showing novices the wrong way.  I am amazed at how many 'teachers' on tv do this very same thing.  I think they are trying to mimic using a table saw but not realizing that the blade on a table saw is below the work and the leading edge is pushing down into the table where as the power miter box and radial arm saws are above the work causing the leading edge of the blade to try to lift the wood off of the table.  please check out the instructions that came with the saw, ty.

  • Thanks for sharing your insight and details on this process.  I screwed two planks into my table saw sled, clamped the sled down and began my passes.  Perfect semi-circles for my project!  (I used this "step" for my dividers and completed my version of  Steve Ramsey updated utensil tray)  Again, thank you!

  • My question is this: when you find the length and the apex and then you try to offset the cove by say 1/2 inch. Can you just measure from the center to the top of the cove offset to get the angle required to set the tilt of the blade?

  • Oh, also, what if you don;t have an INCRA mitre guage? just go 30 deg. then back off just an "unta" ? Plus, My CRAFTSMAN table saw has a piece of TIN for a bevel indicator; you can bend it back-an-forth. Maybe set blade to 90 deg., set tin arrow, then lay the blade over to desired bevel? Thanks, good idea, W.W. !!

  • I will make one off those jigs but one thing i think i will do is on the loong pieces ( front and back fence) i will make a 1/4" groove in the middle to take T nuts /bolt to be able just attach the jig to table t slots and not needing to use clamps , if that will work

  • Why don't you just make the fence longer and put the bridges on the bottom side to allow thicker work pieces to pass through it.

  • Fantastic demonstration. I love the jig you made for this process. Love your channel and will continue to watch. Thanks again,
    Al from Maryland

  • When I build mine I think I'll fit dowels in the extra height spacers and keep them on the fence rail until I need them.

  • I think I"m just gonna buy the Rockler cove jig. I might need a whole house worth of cove, but I don't have a whole shop at my disposal.

  • Instead of placing spacers in the jig for thicker stock, why not flip the jig upside down? Wouldn't that work just as well?

  • I know this is an old video and I come late to the party but as I watched I remember trying this and had a terrible time attempting to clamp the jig to the saw top. Then a light came on over my head (think cartoon). Why not imbed four of the new magnet clamps into the rails. The kind with the knob on them to turn the magnet on and off. http://www.google.com/shopping/product/14115516212033314260?lsf=seller:1135568,store:13956569731967360834&prds=oid:4621865376018551789&q=switchable+magnets&hl=en&ei=l4_RW7-QC4aJjwSruajQDw&lsft=gclid:Cj0KCQjw08XeBRC0ARIsAP_gaQBn9vLFHOKigk38IQiHRd1c0v2NJha2Blt6Roq1xSD8XwApIgf6wFoaAk2ZEALw_wcB

  • Great video. I know it’s been a while since you put this out. Not sure how thick your wood is but the piece I’m trying to do is three-quarter inch a little less. Can’t raise the blade enough to get the width I need what do you do with thinner stock to get the width ?

  • Here’s a thought , if the knobs were reversed so the jig could be turned over, the jig “could” potentially be more secure while cutting the cove.
    Great video!!!

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