MIMF

I'd like to build a simple sanding edge jointer that can handle edges up to at least 1" thick. I'd like one with a vertical surface covered with easily replaced abrasive - sandpaper, sanding belt, or rolled sanding strip would be OK, but I don't want to have to deal with spray adhesive every time I need to change it. The workpiece should be held flat (horizontally) and slid manually along the abrasive.

It would be nice to have about 30 inches of sanding length.

My immediate need is to joint the ends of two halves of wood rings glued up from sectors, to glue together for making block-built banjo rims.

Has anyone made something like this that you can post pictures or plans?

Thanks,
Jon

Hi John,
A simpler solution might be to use a router. I built a segmented picnic table out of corian scraps and the way I fitted the two halves together was to align them so the maximum gap was less than the width of the router bit and use a straight edge as a router guide. The result was a uniform width, parallel sided gap that allowed the two halves to butt together. You could do something similar by attaching the half rings to a substrate you don't mind routing partially into.
If you want to go the sanding route a four foot level with 36 grit sandpaper glued to one edge should give you a straight line sander for the half circles. I would slide the level along the stationary halves ( I think it would put less pressure on the end grain glue joints).

I haven't seen a level that is thick enough to give me the width I'll need.

I've been flattening the faces of the half rings on 80-grit sandpaper glued on glass. It's been a lot of exercise but I need the workout. I think it would be best to put the half rings back to back and joint the ends together, to compensate for any angle error. That will make the width of the jointing abrasive path need to be greater than two inches.

I'm still contemplating the router option. I might be able to set up my Shopsmith in overhead router mode and use that pretty easily. It will probably depend on whether I have a straight bit that is long enough (or how much I have to spend to get one).

Now that I think of it, I could even do the same thing with a sanding drum rather than a routing bit. I'm worried about chatter at the low (for a router) Shopsmith speed of about 5700 RPM.

Jon, before I got a Performax drum sander I thickness sanded my guitar plates with my Shopsmith using the 12" disk sander with the set up in the drill press mode. Bring the disk sander down to the table, lock it, and move the wood between the two. Advance the disk sander a hair at a time. You might be able to do the same thing with your ring, especially if you had the ring held to a base plate of MDF or plywood. Assuming that the 12" diameter disk is big enough.

Jon, here's what you can put together real quick, and have a tool that you'll use for years....

Take a length of plywood, roughly 12 to 18 inches wide by about 4 feet long. Cut a 1/8" wide(or whatever your saw blade's kerf width is) by 1/4" deep slot the full length, about 4 inches from one edge, and another 3/8" deep, by 3/4" wide slot in it(dado cutter on the table saw) the full length again, roughly 4 inches from the narrow slot. This is now your base.

Joint two edges of a 30 inch long 4x4 to exactly 90°. Now, fix this 4x4 to the base with a few screws(or better yet, some anchor bolts), with its edge just barely over the narrower slot, and ever-so-slightly closer to the 3/4" slot at the left end than at the right end. just barely off-parallel. Now, figure out a way to clamp an abrasive strip(buy common 3x36" sanding belts and cut them open!) at the right end of the 4x4; perhaps a pair of 1/4" anchor bolts and wing nuts acting on a little block of wood or flat steel bar), and loosely clamp the other end of the strip. You want this strip to extend down into the narrower slot so that your work will be sanded completely across its width.

Now, set a miter gauge to the angle you need, place a block against it and the abrasive strip, and working from right to left(reverse if you're a lefty...), sand away! the abrasive strip will remain tight simply with friction; if we tried to cinch it tight at both ends, it would seek to buckle as you neared the end.

the reason for having the 4x4 slightly off-parallel is that your work will now naturally remain in good solid contact with the abrasive as you push it along with the miter gauge.

If you go into semi-production of some things, make individual miter gauges that have a fixed angle, for each piece, and you'll forever have 100% repeatable results.

We'll want to see photos of what you come up with... <bg>

Barry Daniels wrote:Jon, before I got a Performax drum sander I thickness sanded my guitar plates with my Shopsmith using the 12" disk sander with the set up in the drill press mode. Bring the disk sander down to the table, lock it, and move the wood between the two. Advance the disk sander a hair at a time. You might be able to do the same thing with your ring, especially if you had the ring held to a base plate of MDF or plywood. Assuming that the 12" diameter disk is big enough.

I've got a Safe-T-Planer and I plan on using it for surfacing the other side of the rings after I glue them them up on the lathe faceplate. I'm just sanding them flat on one side to give them a flat reference. I suppose I could double stick tape each one to a board and run them under the safe-t-planer and get them a lot closer to flat before spending time sanding. But really I can flatten each half ring out in about 5 minutes by hand so I'm not sure it's worth it.

Twelve inches is the final diameter of my pot, so the disk sander won't quite do it all at once, as the rings will be a little oversize to allow for turning them on the lathe.

Mario, that's the type of thing I'd envisioned until Clay mentioned his router approach. Now I'll have to decide which one to do. As you say, your tool can be very useful for many projects including joining tops and backs for wood instruments.

I don't quite get why you want to use a miter gauge to push the workpiece, though. Could you explain that a little more?

Jon, I was flattening guitar sized plates under the 12" sander by just moving them around by hand so you should not be limited by your size of work.

Using a miter gauge will ensure your pieces are jointed at the correct angle.

Also, if you free-hand it, you're likely to "roll" the work as you move it.

Mario, I see what you mean. It didn't occur to me because I need to joint both ends of each half-ring at once (or better yet, all four ends of both half rings stacked in a bookmatch together) so it's more like jointing a long straight edge than the end of a segment. The rings are already glued up except for two opposite joints, which need to be sanded perfectly colinear so they will fit together gap free. This compensates for the small errors in cutting the angled sectors.

I hadn't realized that they were all joined except for the (now) two halves. My idea was for a jointer that would do each piece individually.

For your current setup, all you need to do is to cut open a 36" or 48" belt and fix one end to a good, flat surface, and using both hands, run -both- halves(in a bookmatch, as you suggested) along it at the same time. Go with the finest grit you can find. That way, any angle induced will cancel itself when you flip and join the two pieces. Rather simple, methinks!

Another, even simpler, solution just jumped at me....

All you really need to do is to "floss" some fine sandpaper between the surfaces until they mate perfectly. You might need a helper to hold the two halves together while you pull the paper, or find a way to clamp it while at the same time allowing you to open-up one end enough to insert the sandpaper.

or put the 2 pieces together on a small sheet of plywood and run it through a table saw at the seem.

Mario, your first option is simpler than the flossing option, since I've already got sandpaper glued to glass to do it with. I was afraid of the angles not being perfectly 90, but it really doesn't matter. They will match, as you say, and will be close enough not to be detectable by the human eye. Especially if you're not looking for it.

Eric - that would work and I thought of that, but I don't trust my saw blade to give a smooth enough surface for a nearly invisible glue joint.

could test it on some scrap.

A 15 or 18" disk sander is probably your quickest option. They aren't cheap unless you bump into one on Craigslist. You could probably build a slow speed version if you could find a way to true a spinning plywood disk. A couple of layers of 3/4" russian birch plywood and then some 4" aluminum angle iron to help hold everything in alignment.

Jon
I used this jig on my table saw.

I had tried using a sanding disk on my Shopsmith, but I like the table saw method better.

Since then I have converted to a 16 block layer and I've got my block cutting jig dialed in pretty well so that I can glue up a ring and clamp it with a large hose clamp and have no gaps at the joints - most of the time.

Hi Dan, I saw that on your video. If I wanted/could afford to spend $60 or $80 on a good crosscut blade I probably would try that. As it is I cut the segments and then try to true up the ends with my Shopsmith disc sander and a jig. It works pretty good but not quite perfect. And I don't even know which way to go to make it better - some of them seem to be off one way, some the other. But they are all pretty close.

In the mean time I took a few minutes and jointed both halves of one ring at once yesterday by clamping them back-to-back and standing them up on my sandpaper-covered plate of glass, and sanding one or two hundred strokes. It worked really well and didn't take that long, so I'll just keep doing that for the next 5 rings (3 each for 2 rims).

I'm always conflicted on spending time on jigs and fixtures vs. spending time on building the actual instrument. Plus I tend to over think everything I do. I need to constantly remind myself of the KISS principle. I'm not to the point yet where time spent building the greatest jigs is paid back over the volume of instruments built, but it's good to see everyone's ideas if only for the brainstorming.

Jon Whitney wrote: If I wanted/could afford to spend $60 or $80 on a good crosscut blade I probably would try that.

Jon
That's exactly what I did. I went to Rockler and bought one of their best carbide tipped crosscut saw blades - on sale for about $40. I've got two of them now and I have Rockler resharpen them regularly. They've made a big difference in the accuracy of my blocks.

And I love jigs. If I plan to make more than one of a thing, I build a jig. I think that's the guitar builder in me coming out. Plus, I'm retired and this is my day job. What else do I have to do? Keeps me off the streets and out of the bars.

If you have a decent table saw then I'd just pickup a 7-1/4" diablo 40 tooth blade ($15) only to use it for that one operation (and keep it clean).

A router shooting board that works like a miniature jointer might also make quick work but not clear to me how to build it accurately or avoid chipping out at the far edges.