I need to fabricate a cap for the top of a guard wall on the inside of a circular staircase. The design spec calls for clear coated VG fir in a simple rectangle 4 1/2″ wide x 3/4″ thick. The radius is fairly tight, 24″ at the inside face of the wall. I had a stair shop machine up a series of fir strips 3/16″ thick by 1″ high and I’ve formed up a series of blocks screwed to the wall framing that will create a form to bend the strips to. I can see how to do the glue-up, but how do I machine the whole thing down to a uniformly smooth 3/4″ high cap? When I decided a while ago this was something I could have a go at, I was thinking belt sander, but now I wonder if that will give me the true, dimple-free surface I’m after.
The dilemma is that any sander or planer with a bed long enough to give smooth linear surfaces won’t be suitable for this spiral application. I see there’s a Makita planer with a curved base, but this is the first time I’ve come across this need and I’m unlikely to take it on again, so I’m reluctant to drop $400 on a one-time tool. I decided to do these stairs in-house as they are closed and have a simple finish (linoleum, by others) and figured I should do one glued-up handrail in my career.
I do have an old 3 1/4″ planer I keep mostly for rough work like framing. Anyone got any tips on ways to modify it to deal with this curve? Maybe I could do the final finishing with a random orbital sander from there.
Replies
Skykarma- I just did this 3 inch thick curb stringer that had interior strips to fill in between the outside and inside face laminates. I took the stringer out of the forms and used my DeWalt 4 inch electric planer just to hack it out....then used a jackplane to further shape it to its desired helical surface. I next used a belt sander skew sanding at an angle as I went up and down the stringer....constantly changing the angle of bank on the sander. I follow up with a finish sander....followed by light finger tip strokes running lightly up and down the surface. You can feel very subtle discrepencies this way.......
Then take a bright light and shine down at a low angle...and a stringer that you think is perfect...all of a sudden looks like a Jr. High shop project. The bright light is your best friend and maybe your enemy if its not appied to after the stringer is done and stained.
Stan
You can add handles to a power planer to make an electric draw knife to handle curves etc. This one was customized by a fellow in CA to make tapered ends on this log porch. Works similar to the curved Makita, but more of a handful and kinda dangerous.
Thanks to both of you for the replies. That modified old planer looks dangerous all right. Think I'll follow Stan's suggestions. This cap is not really any different from the top of a stringer.Lignum est bonum.
I've got a Stanley Compass Plane, with a flexible steel base. It will do both concave and convex curves.
My sequence to modernize the operation is:
1) Build it oversize,
2) Rabbet it top and bottom with a router to leave a narrow strip in the middle of the piece,
3) Use the Compass Plane to fair that center ridge,
4) Run the rabbetting bit over it again to smooth out the rough rabbet,
5) Run a flush-trim bit over it to smooth everything out, and, finally,
6) Sand.
This works great, takes a lot of the effort out of handplaning hardwoods, and greatly reduces tearout in difficult woods.
The multi-bearing rabbet kits work best, because a 1/16"- 1/8" rabbet is usually plenty, and you can always repeat the process if it's not.
So there's a lot less wood wasted than with a standard 3/8" rabbetting bit.
The Compass Plane is the biggest expense. I got mine for about $90, but that was almost 30 years ago.
AitchKay