Smoothing Out Curves

[Teresa Jones]

I am working on a headboard and it is curved across the top. I am using 3/4 Cherry plywood and the jigsaw did not leave the smoothest of cuts.

Short of hours of hand sanding, is there anything I can use on plywood to cut the edges smooth, flowing and even?

As always, thanks for your feedback!

TJ

[David Wilson]

Teresa
One option would be to make a pattern/template out of masonite or ply and use it to guide a router with a patern bit.

[Chris Padilla]

Teresa,

I built this: http://www.sawmillcreek.org/showthread.php?t=6911

I used a straight bit in a router. I simply put the router at the end of a long, narrow board, pinned the board at the opposite end of the router, and cut out a very nice and clean arc. The radius in the above floating shelf was about 5 feet.

To figure out the radius of any arc (assuming the arc or curve is a part of a circle...it may not be), you need to use this formula:

R = (4h² + L²)/8h

h is the maximum height of the arc and L is the length of the arc...both of which you should be able to measure. R will be the radius of circle and the distance from the pivot point to the router bit.

You can use this to make a template as David suggests and then use it and a pattern-cutting bit or flush-trim bit to rout a clean edge in your plywood.

[Marc Hills]

Hi Teresa:

Someone left the door open from the Neanderthal Haven and I wandered in. A very sharp spokeshave (not to be confused with a drawknife) will make short work out of that task.

[Teresa Jones]

Marc,

The spokeshave is OK for use on plywood?

TJ

[Teresa Jones]

Chris,

Thanks for the link and the information.

It never occurred to me to use a router to cut the curves. Ask and learn!

Thanks,

TJ

[Marc Hills]

Sure Teresa, the spokeshave on plywood is fine. I use my block plane on plywood all the time. The glue between the plies dulls the blade a bit faster, but really, it's not a problem.

Incidentally, what kind of jigsaw and jigsaw blade did you use?

[Carl Eyman]

The pattern out of thin plywood which you can smooth out with a sander pretty easily is the way I'd go, but if the router bit wants to tear out as it did with me on an "s" curve going against the grain, look in Klingspor's catalog. They have a sanding drum fitted with a guide bearing. It works just like a pattern cutter, but does it by sanding. You can start out with real coarse grit and go down as far as you want - or as far as Klingspor has drums.

[Teresa Jones]

Marc,

I used my Dewalt orbital with a 10tpi blade. I used the middle orbital setting.

I have the Veritas Low Angle spokeshave. I have a bit of a time getting it adjusted, but I think I will try again!

Thanks,

TJ

[Steve Jenkins]

A pettern and router are usually the best way. I make my patterns from 1/4 or 3/8 mdf. If you need to do any hand work to get the curve the way you want it it's easier on thin mdf. When you use the jigsaw for cutting ply don't use the orbital action. It makes a rougher cut.
If the piece you are working on is a flat piece of ply at this point you can come by and use my disc sander. It works great on outside curves.

[Teresa Jones]

Thanks a bunch, Steve. Unfortunately, it is the inside curves that are giving me trouble.

[Steve Jenkins]

Thanks a bunch, Steve. Unfortunately, it is the inside curves that are giving me trouble.

well I've got a spindle sander too.

[Teresa Jones]

Awesome, Steve!

I'm going to see what I can do with the spokeshave tonight. If I'm not satisfied, I'm coming to your place!!

I have a Ryobi spindle sander, but I did more damage than good with it.

I wish I had known not to use the orbital action on the plywood. Being a girl and all, I read the instructions and they never mentioned plywood.

Thanks,

TJ

[Roger Barga]

As someone who regularly likes to work curves into their projects (and enjoys using a hand plane) I use a compass plane. A compass plane will smooth both inside & outside curves, can be adjusted to match the degree of the curve,
and make quick work of smoothing long pieces. I will use a spokeshave for small projects (up to 18") but for longer pieces the compass plane is a better tool, imho.

You can find a list of sources for compass planes and a brief article on working with curves by Paul Schurch, in FWW 175.

cheers,
roger

[Keith Christopher]

I third using the router. every arc is part of a circle of some size. use chris's formula to determine the radius then trammel it. but next time before you start use some thin mdf make a template and use a double bearing spiral bit to get a super smooth and clean cut.

[Alan Turner]

Kieth,
I am not familiar with a double bearing spiral router bit. Could you give me some information on this? I love to learn.
Alan

[Marc Hills]

Marc,

I used my Dewalt orbital with a 10tpi blade. I used the middle orbital setting.

I have the Veritas Low Angle spokeshave. I have a bit of a time getting it adjusted, but I think I will try again!

Thanks,

TJ


Well Teresa, now you know: jigsaws aren't precision tools, especially on plywood and especially on an orbital setting. I only know that because I've made a similar mistake.

Well, can't blame the quality of the tool, Dewalt makes a very good jigsaw.

I do agree with everyone else that in the future, a router, a template and a straight bit are the tools of choice.

For your future jigsawing needs, I don't know what kind of blades you have but I've been extremely impressed with the Bosch "Progressor" brand. It's made a huge difference in the quality of my cuts. If you want to try them out, I believe you want the "U" shank models for your Dewalt; the "T" shank ones are primarily for Bosch brand jigsaws.

Bully for you for already owning the Veritas low-angle spokeshave, that's exactly the model I would have recommended to you. By flipping around the base plate it can handle both inside and outside curves.

The real trick is getting that blade super sharp. Don't know what sort of sharpening set up you have, but a keen edge will be critical.

[Dave Richards]

I thought I'd add what came to mind from the title of your post, Theresa. In smoothing the curve I was thinking along the lines of sanding. When you get to the point make yourself a longboard from a piece of Masonite (maybe 2" wide) with a handle attached at each end. Run a strip of sandpaper along the length and use that to sand out the edge of the work. The longboard should conform to the curve like a compass plane. It will prevent you from sanding in flat spots.

[Teresa Jones]

Thanks again, everyone.

I just love this site. Everyone can have a different approach and still get great results.

I'll let everyone know how this turns out.

I was speaking with a fellow woodworker the other evening and the subject of sharpening came up. I use waterstones. We both agreed that the important thing was to pick one method and then use it and practice, practice. I think a lot of other techniques fall into this category as well.

Next time, I am going to use the template with router approach.

I appreciate you guys very much.

TJ

[Ellen Benkin]

I also use a pattern (I mamke it from 1/4" masonite) and a straight router bit with a bearing to follow the pattern. If there is a lot of wood to remove, get most of it with a jigsaw or bandsaw. Don't try to take too much wood off in one pass with the router. One good outcome is that you can reuse the pattern over and over. I use a spindle sander to make the curves on the template because you want the template to be as smooth as the final cut so that you reduce sanding the final product. I use double sticky tape to attach the template to the wood and that seems to hold just fine. But I do like the idea of using a spokeshave!

[John Pollman]

This would probably be perfect for the situation you described. Unfortunately NOT cheap. It's one of those tools that I saw Norm using one time and fell in love with. It's another one of those "One of these days" tools. :)



http://store.yahoo.com/tylertool/por121osspin.html

[Garry Smith]

I thought I'd add what came to mind from the title of your post, Theresa. In smoothing the curve I was thinking along the lines of sanding. When you get to the point make yourself a longboard from a piece of Masonite (maybe 2" wide) with a handle attached at each end. Run a strip of sandpaper along the length and use that to sand out the edge of the work. The longboard should conform to the curve like a compass plane. It will prevent you from sanding in flat spots.
This approach works very well. I use this approach alot.
I make this tool for outside archs with two handles and an 1/8" thick and 16 1/2 inch long piece of maple or cherry. This length is good because I by PSA sand paper strips used in the autobody industry that are precut to 2 3/4" wide x 16 1/2 iches long.
For inside archs just put one handle in the middle and it will conform useing some pressure of coarse. By using 80 grit paper to start, you will be surprise at how fast you edges come into shape.
Garry

[Keith Christopher]

Kieth,
I am not familiar with a double bearing spiral router bit. Could you give me some information on this? I love to learn.
Alan
Alan,

Here is a link, scroll down a little. I used to used flush trim bits only but man a spiral flush trim almost has NO tearout. Leaves a smooth as a baby's butt edges.

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/bt_solid.html#spiral_flushtrim_anchor


Keith

[Alan Turner]

Thanks. I had not seen that before, although I do shop with this company. I use spirals almost exclusively as straight bits. My preference is a top bearing guide, but it does not seem to come that way.
Alan

[Keith Christopher]

Thanks. I had not seen that before, although I do shop with this company. I use spirals almost exclusively as straight bits. My preference is a top bearing guide, but it does not seem to come that way.
Alan

I use the top bearing guide for routing dados, but lately I have been using flat bottom spirals with a collar for making dados and esp mortises when I can't use my mortiser.

Also whiteside has double bearing FT spirals, little pricy but of course it's a whiteside. :)

Keith

[Jerry Crawford]

I am working on a headboard and it is curved across the top. I am using 3/4 Cherry plywood and the jigsaw did not leave the smoothest of cuts.

Short of hours of hand sanding, is there anything I can use on plywood to cut the edges smooth, flowing and even?

As always, thanks for your feedback!

TJ

I'm not trying to muddy the water here and every one of the suggestions above is spot on, but there is another part of this you need to hear TJ. No matter how "smooth" you are able to get the plywood edge you are going to have splintering and get some very painful injuries inless you finish the raw edge of the plywood somehow with an artificial facing.

Plywood is a great building material as long as you can capture the raw edged in dado's or rabbits and face the exposed edges with solid wood or banding.