Talk to me about templates, routers and double-stick tape

[Morgans]

"Swingman" wrote

Yep. Bearing gets hot and melts into the pattern. Not good. Plexi is nasty to cut and clogs sandpaper.

[dadiOH]

And me.

[Greg Guarino]

Is that a jig designed by a committee? :)

I don't believe I have heard that name before, but I have seen the device. One potential problem: the radius I intend to use would put the center "pin" inside the piece to be cut. I wouldn't want to put a hole in the piece, so I'd have to affix some sacrificial piece to the work.

The jig idea I had was something like this:

But I saw at least two problems upon looking at the drawing. All of the layers (the router table, the two-layer jig and the work itself) mean that the router bit would not be long enough. I've been planning to build a router table (although not right away) and could then do away with one layer; drilling a pivot hole into the table itself. But there's also the issue of stopping the cut at the right point. I suppose I could figure that out as well, but it is starting to seem more complex than I would like.

I'm now thinking it might be simpler to use a trammel to cut a template and the template (screwed into a still-oversize workpiece) to rout the arcs.

[Swingman]

There you go, Bubba ... "thinking" is the operative word, and you are now thinking like a problem solving woodworker. ;)

Two main reasons for coming up with a jig design to use in the situation you outlined in your original post:

Accurate Repeatability and Safety (both yours, and the work piece's).

[dadiOH]

I seem to recall that you wanted an arc from a circle. If so, why not just make a circle cutting base for your router? Make one, cut virtually any arc you want. The 1/4" acrylic would work fine for that.

[Greg Guarino]

As I mentioned, the center of the arc would be (slightly) inside the workpiece itself, which complicates things a little as I wouldn't want a hole in the finished piece. I have thought of a few ways around that, but I'm still sifting them in my brain.

[Greg Guarino]

With my limited experience and the gaps in my tool arsenal, problem-solving is a nearly continuous activity.

[Pat Barber]

It works quite well as long as you have the following.

1. double sided tape
2. a smoothly sanded template
3. the correct router bit.

(1) Cheap carpet tape from Lowes or Home Depot. Use just a small amount, using too much will make taking the template almost impossible.

1. Make the template as smooth as possible because any lumps,bumps or imperfections will be shown in the finished piece.

1. You will end up needing a bottom or top bearing bit. In some cases, both types of bits are needed.

You can also buy a bit that has both a top and bottom bearing which can be fairly handy.

Browse through this list of bits to see some options.

[dadiOH]

I'm assuming that both sides will show so you can't put a hole where it won't show? In that case, do as the turners do...glue a piece of wood to the piece with paper inbetween; make your hole in it, rout, knock off the wooden tab, scrape off paper.

[Swingman]

And, add shims, of the same thickness as the "wooden tab", to the bottom of the router end of the trammel to keep the trammel parallel to the workpiece, otherwise the edge of the routed arc will not be perpendicular to the face.

Now, that's where that double sided tape will come in handy. ;)

[Greg Guarino]

Yes.

In that case, do as the turners do...glue a piece of wood to

Paper? What kind of glue? I haven't heard of this method.

I was thinking of clamping a piece of wood (with the pilot hole) to the workpiece.

[Greg Guarino]

Thanks. That bit I would have thought of myself. My mental, theoretical, "ideal" sense of geometry is good. I've always been adept at turning an object around in my head. It's the translation from the ideal to the material that I need some work on.

I'm still thinking it may be easier in the long run to make a template (that I CAN drill a hole in), then use the template to rout the workpieces.

[dadiOH]

Most any paper...wrapping paper, butcher paper, newspaper, notebook paper, etc.

Glue...white glue, hot melt, mucilage, airplane glue...anything that isn't super strong and can be removed with relative ease, preferably with water. Super glue wouldn't be good, wheat paste might, don't know, have never used it (for that purpose).

[dadiOH]

Makes a nice bevel though :)

Actually, I have on occasion afixed a block on one side of a router base for that purpose; works fine as long as you keep the router oriented the same way throughout the cut (a straight edge on the base helps).

[-MIKE-]

I've done this to turn drum shells and it works great... almost too great. I used paper grocery bags, which I always keep handy for sanding between finish coats.

[Larry Blanchard]

Brown paper grocery bags are used the most. They are strong enough to hold but can be separated into layers without having to soften the glue. Just hit with a mallet or pry with a chisel.

[Brewster]

On 2/25/14 8:36 AM, Greg Guarino wrote:

I do a bunch of template routing and have always used masonite and the thin carpet tape (from HD). For the curved edges of a cutting board sized object (10"x16"), I find 4x 2" square pieces to be plenty. Cut as close a practical to minimize router work (I use a bandsaw) and use a spiral fluted template bit. The straight flute bits tend to grab and throw a bit too much for my liking. I also make a *lot* of circular frames for my wife's glass art. For these I use a template cut from masonite with a 1/2" hole in the center. I mount the template to the workpiece (with carpet tape) and use a bandsaw jig to get a rough circle that is about 1/8" larger in diameter than the finished size. For routing, I have a circle jig with a 1/2" post clamped to the router table. This is set up to provide the final diameter by measuring from the post to the edge of the bit. I then lower the bit (a spiral up-cut), place the workpiece over the post, then raise the bit for the first of a series of cuts. As the bit cuts, I rotate the workpiece, raise the bit, rotate, etc. until the outer diameter is finished. For the inside I just move the jig in towards the bit for my desired opening size and repeat the operation as before. The only difference is I keep track of the bit height so I don't cut through the template (you can't see the bit while doing this). The tape holds everything in place while doing this. The result is a doughnut shaped frame with all the necessary rabbets, perfectly round, and only requiring minimal sanding.

Back to the templates and template router bit: I often find that after tracing my pattern onto the masonite and cutting it out, the process of hand shaping and sanding will leave the surface with a slightly beveled and/or rounded edge. I usually take this template and attach it to another piece of masonite (with carpet tape) and cut out a matching 'production' template, this time with perfectly square edges and a smoother surface.

For me, the key points are to use spiral fluted bits. If grain direction becomes an issue, swapping between top and bottom bearing template bits solves the problem.

-Bruce

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[Greg Guarino]

Firstly, thanks for taking the time to write such a detailed response. And thanks to everyone else as well.

I've been thinking about the "beveling" problem, especially now that I have decided to really get myself in trouble and go for a more complex curve. I may indeed need to follow your advice.

The spiral fluted bit makes perfect sense, but I don't have one today, one of the rare days when I have a stretch of free time. So I intend experiment a bit and see what I can accomplish.

I've printed a paper template from Sketchup which I intend to affix to some mdf with spray adhesive. Than I'll try to cut, file, sand and possibly dremel the mdf to the proper shape.

Assuming I still have some time (and hair) left, I will try to make my pieces out of plywood. If they don't look too bad after edge-banding, I may even use them. If not, at least I won't have made my first attempts at pattern routing on expensive stock.

Here's the latest (revision number 1,000,000):

[Greg Guarino]

I don't know why my previous post took several hours to succeed, but here's the "after" report.

I printed a paper template of the curved shelf support I intended to make. I couldn't figure why Sketchup insisted on printing it on 3 sheets of paper when it could easily have fit on 2. I did a little cutting, aligned the sheets and taped them together.

Taking advantage of 2 factory edges, I used spray adhesive to mount the paper template on a piece of 3/16 MDF. (I would have used rubber cement, but there was none to be had)

I jigsawed the piece to rough shape - rougher than necessary as it turned out. I hardly ever use a saber saw and was pleasantly surprised at how smooth and square the cut was. I could have saved myself some filing.

I filed the MDF down to the line as best I could. Inspecting the piece afterward, I noted that I had indeed made the edge less than perfectly square. It wasn't too bad though, and my plan was to work through the process to the end, even if just for practice.

I laid out the shape of the finished piece on a piece of oak ply and cut that roughly to shape. I put a template bit in the router table with the roller on the bottom. Thus the template was beneath the work piece. I decided to just fasten the template to the work with spring clamps to see how that would work out.

I can't overemphasize how pleased (and surprised) I was at the ease of the process. In a very sort time I had a piece exactly the same shape as the template, which is of course what is supposed to happen, but I have come to expect complications.

The spring clamps worked out pretty well, too, although I will probably try to use a different method in the future.

The process, including making the template, was so easy in fact, that I found myself thinking I could do it a little better. The curve on my test piece was made from three arcs. It looked goo on the computer screen, but something about it didn't quite "flow" when I saw it in the flesh.

Back to Sketchup. As an aside, I find that one effect of Sketchup is that a perfectly innocent project can acquire complications. :) I wanted the curve to "flow" into a straight edge at the bottom.

(the original curve)

But a single arc could not be tangent to that edge AND intersect the front of the upper shelf. Some other shape was needed. I figured (correctly) that someone must have created a plug-in for Bezier curves and I downloaded one.

Here are the two templates, to compare the curves:

It turns out that Sketchup defaults to printing the shape of the viewing window (geez - is there a setting to fix this?). I narrowed the window on the computer and was then able to print the template on 2 sheets of paper.

This time I jigsawed the MDF a little closer to the line. I got to thinking about how I could keep the template edge square. I laid the mdf on a piece of scrap and turned the file edge-down on the (sacrificial) work surface, hoping that would keep the file face plumb.

After a few seconds of that I took out a block plane instead(feel free to tell me this was crazy). I raised the template MDF a little above the work surface with a scrap of the same MDF. Then I laid the plane on its side on the work surface and started removing the waste down to the line. Although using a straight plane to shave down a curved surface (convex, of course) seemed a little odd (and MDF at that), it worked pretty well.

To further smooth the edge, I wrapped a piece of sandpaper around a small block and laid THAT face down on the work surface, using its edge to sand the curve. Again, the edge removing the material was kept plumb.

As ass-backward as this may sound, the edge of the template was a marked improvement over my first attempt. It had no obvious waviness to it.

I proceeded to make the four pieces. It was remarkably quick and I like the results. Fun too. I can already see ways that I might have improved the process. I will definitely be doing more of this sort of thing in the future.

Thanks to all for the advice.

[Swingman]

Just a few, of dozens, curve making concepts:

Download SU 2014, there are a couple of new ways to make arcs.

Use the SU "Bezier Curve" plug-in to make your curves.

Cut a 1/8" thick strip off the edge of a board long enough to make your curve; drill a small hole in each end and use a piece of string, like a bow string, to bend the strip to the proper curve, thusly:

Using that same thin strip, hammer in some small finish nails in the appropriate spots to bend the strip around for the curve you want.

Use purchased or homemade pencil compasses of various sizes to make your curves.

Cheap plastic "French Curves", available at any office supply store, of various sizes are hard to beat for laying out curves, particularly when using it in conjunction with that compass, or the appropriate sizes edge of a can, a lid or a bucket.

A "pattern maker's rasp" is a nice thing to have when fairing curves in your template.

When fairing a curve, cut a thin, flexible strip off the edge of a scrap board and glue your sandpaper to that. Putting little wooden "knobs/blocks" on each end makes it easier to hold and to keep the faired edges perpendicular to the face.

Often attaching sandpaper on the edge of the off cut when rough cutting your curve will make a good fairing tool.

An "oscillating spindle sander" is a good investment if you are going to be doing furniture with a lot of curved parts. Great for both making your templates, and for smoothing/making perpindicular the curve edges in the work piece.

Most important: Make the effort, and take all the time you need, to make your curved templates PERFECT, for you will eventually save more time in its use than you will in the making of it.