I’m brand new to making templates and I’m finding out making a good one is not as simple as it looks. Luckily I’ve got the Ridgid oscillating edge belt/spindle sander to make it easier for me. My problem is making smooth inside arcs. After about an hour of practice my outside arcs or curves are nice and smooth, but my inside curves feel lumpy when you run your finger down the edge.
What I figured out that got my outside curves smooth out was that almost all sanding passes must be made as long as possible. I zeroed in on flattening down the proud parts by doing long passes and keeping a steady speed, but then doing a gradual application of pressure at those sections. I applied this technique to my inside curves but because I have to work on the curved part of the sanding belt I’m not able to get the same effect. I’m sure it’s because the flat part of the sander is more forgiving than the curved part which has a much smaller sanding ‘foot,’ or contact patch I’ll say. I’ve tried to lessen this effect by keeping my approach angle as shallow as possible but this still isn’t producing the smooth edge I’m after.
So what am I missing? Do I just need to keep refining my sanding technique to be even lighter and sneak up on the template edge even slower doing more long and shallow passes? Or is there some kind of technique out there I haven’t run up on yet?
I’m using 3/4 melamine for making this piece. Paper template is on the bottom side for the pic.
Replies
Outside curves are always easier than inside curves, no matter what tool you're using.
I haven't used that sander. I have an oscillating spindle sander, which has different diameter sanding spindles. Generally speaking, the largest diameter spindle that will fin inside the curve I'm sanding works the best. The smallest diameter spindle will leave the most ridges. I'm not sure if your sander allows this.
But, I do as little sanding as I can. I use a router for template or pattern routing to get as close as I can. There is very little to clean up after. To make that pattern, I usually finish with rasps. The result isn't pretty, but it smoths the pattern enough that when the router's bearing rides over it, the result is perfectly smooth.
I believe I have the same ridgid sander as you. It sounds as though you're using the belt sander attachment to sand inside curves? That's what the spindles are for swap out to one of those. As john_c2 says, use the largest size spindle as will for the radius of your curve and try to keep pressure smooth.
Side note, I hope if you've been sanding with the edge, round part of the belt it's been on the left side when facing the sander, not right. The right side is not meant to take any pressure and you run a high risk of damaging something.
I abandoned my spindle sander for this task a number of years ago and bought a spokeshave. I get to my final shape much faster and with a better result.
One solution is to use the oscillating sander to fabricate a smoothing block for the final passes on the inside curves. Get as close as you can to a smooth curve on your workpiece and then make an outside-curve block that’s a pretty close match and cover it with sticky-back sandpaper. It won’t take too much elbow grease to knock down those bumps.
Also, +1 to spokeshave, but maybe not for particle board.
This was a very timely question from my perspective. I making an Ikebana flower base with inside and outside curves and am experiencing the very same situation. I am using the same Rigid sander as the OP I think. The sanding sleeve on the oscillating cylinder is the same one that came with it. Maybe 80 grit.
A coarse grit oscillating sander removes a lot of material quickly but it is unforgiving in my hands. I wonder how finer grits might refine the curve after most material removal is accomplished with the coarse grit. This relates to both sanding the curve templates and sanding of the curves in the finished piece.
Suggestions about spokeshaves and rasps are very helpful. The idea of using the cut out portion of an interior curve as a sanding block is very clever. I didn’t preserve this piece intact when I cut the interior curve on the bandsaw. In the next attempt I will be more aware of its value for subsequent sanding.
Two final questions that may have have obvious answers:
Is finish sand of the inside and outside curves always done by hand?
Can a spokeshave produce a finished surface in the way that a smoothing hand plane can?
Russ
I would certainly recommend final sanding by hand. That oscillating sander will leave a lot of scratches that are diagonal to the grain. On end grain they will probably be especially noticeable once finish is applied.
A sharp and we’ll-tuned spokeshave should be able to leave a surface like a hand plane—after all, it’s nothing but a hand plane with a very short (and possibly curved) sole.
I have no idea as to what your inside pattern looks like. But might it be possible to cut your pattern into two or more pieces using say a bandsaw. All the pattern curves may well be outside curves at this point. Sand all the surfaces and then epoxy the pieces back together.
A spokeshave can produce a great finished surface on an inside curve. As can a scraper.
All inside curves are not the same. Some are easily done with a spokeshave. Some radii that are much too tight. With a small, closed opening -- picture a cutout to be used for carrying -- you'll never get a spokeshave or scraper in there. If youre making many, starting with a template and router bit is a great step one. For one or two such holes, the most efficient tool for that job is an oscillating spindle sander. As with all sanding, working your way up through grits is the best practice. Fine grit and a light touch, with a diameter spindle closest to the radius you want, will get you a finished surface.
Thanks, John. Very helpful advice as always.
I have made templates of the inside and outside curves to use as marking guides rather than router guides. Because both inside and outside are arcs are large radius, I can bandsaw to the line reasonable well. But sanding is required to refine the curve and smooth the surface.
I am a hobbyist woodworker and have used scrapers but not spokeshaves. This will be an opportunity to get acquainted with a new tool.
Thanks again.
Russ
If the curve is big enough, spokeshaves are great. And fun, too. But remember grain direction. It works great going downhill with the grain, not so great uphill. And end grain is harder than long grain.
I would think a belt sander is pretty aggressive for what you are doing. I bought a Triton Portable/Handheld Oscillating Spindle Sander specifically for doing inside curves and should have bought it years ago. It's a real time saver and variable speed and at a slower speed and light touch with finer sleeves gives a perfectly smooth finish. Can be used mounted to your bench or freehand. Don't know how I got along without it!
There used to be a template sanding gizmo for the drill press called "robosander" ...a bearing guided drum sleeve.
I have an old oscillating spindle sander. I smooth the lumps (slight) that come off the sander or from a spokeshave using a flexible steel rule (or flexible piece of thin metal) with a strip of sandpaper around it. It will bridge over the low spots and remove the high spots. You can feel the irregularity with your fingers and tell when it is gone. I almost always start with 220 grit, as my bumps are pretty small, and I don't like putting more scratches into the surface. I often use a spokeshave to remove the scratches from the spindle sander and get closer to a smooth curve. But sometimes the curve is too tight for my curved bottom shaves. I use different flexibilities of metal for different curvatures.
Ditch the melamine, 3/4" is too thick. The particle board core I'm assuming it has is coarse and difficult to sand.
You just need enough thickness for the bearing to ride. 1/4" is plenty and can be faired or sanded easily by hand or shaped block. Baltic birch works well with it's solid cores.