belt/disk sander question

[elizabeth]

OK, guys. Spent from 8:30 to 4:00 today working as a grease monkey and I'm no further ahead of the game.

I have an old Riobi 4X6 combo deal. I've not been successful in flattening a face with the belt in the horizontal, so wanted to try my luck in the vertical position, using the work table and auxiliary fence as a support. My suspicion has been that as I lowered my wood on the belt and moved it back and forth across it I was tilting the wood.

Won't bore you with the daylong ordeal except to say I took the machine apart and reassembled it in trying to align the belt to the work table. Have not been able to get it dead-on square. I can do it with the belt off, but when I make test runs, the belt isn't cutting the wood evenly. It's a new belt, and yes, I've tried it with different grits. The machine does vibrate a lot, and the belt table has a cup in it's center of about two business cards thick. The worktable is flimsy. It bobbles if I put any downward pressure on it. And, of course, the plastic miter is a joke but I can't use any other because of the size of the miter slot.

Know you've been there too with the same complaint.

My question is: Is this endemic in bench top combo sanders or are there better ones to be had. I'm trying to use this machine to miter my little boxes and flatten the top and bottom rims. If I'm tilted more than a 1/32" it's visible.

Thanks!

[dicklaxt]

You need to find an alternative,,,,,,,,,,that machine is not nor was it designed for precision work ..even if you had dead on holding jigs it would still not perform the way you need it to.

Sorry but thats the way it is.

dick

[dcarter636]

Two things spring to mind:

1. The work support platform is likely flexing when you hold the work piece down. So, you need to fix that somehow and then look at #2 below.

2. The sanding belt will tend to bunch up, and ripple of of the platen, ahead of the workpiece on light duty machines. More tension on the belt reduces that tendency but the machine elements may start to flex and change shape before you get enough tension to tame the ripple.

When better precision is needed or the workpiece is small I prefer the disk.

[TDHofstetter]

I have definitely been there - with three different combo sanders. The WORST of 'em all was the Delta, the best was the Craftsman. Trust me - the problem is nature of the beast. Those machines are all built with a lot of sloppiness in them, and the looseness of the belt makes all the inherent deficiencies worse. I had one belt that - honest - flapped out into the air a good 1/4" along both edges as it ran.

Can we get ya to go neanderthal for this? With a piece of MDF (for flatness) carefully cleaned, then a sheet of sandpaper glued carefully to its surface? Then you can rub the workpiece against it as a manual "table sander". You get tons & tons of control that way, and no chance of accidentally beveling an edge at touchdown. Or losing a whole workpiece into the machine...

[Beamer]

Tim's advice is where i was headed as i read your post, Elizabeth.

A flat platform with a sheet of good sandpaper is gonna give you a flat surface more reliably for sure. Plus things ain't hapenin' so fast that you have to lose too much before you know you've lost too much.

[elizabeth]

Thanks, guys. I suspected as much after I tried it. I thought it would have been cool if it worked since efficiency and precision would increase.

Dave: I've just started using the disk to miter, as you suggested in other posts. I've set up a little system with a stop and it works pretty good. Better than the TBS because I get really nice fits and no tear-out. I was so happy with my little success, I tried the belt with a comparable set-up but it didn't work. It's OK. At least I know what not to do on my next boxes!

You are all right. This machine is not meant for this. I will, and have used the traditional way of taping a sheet of sandpaper to the TBS surface and hand sanding (your suggestions at work). It's laborious but it works. My technique isn't so great because if I start with edges that aren't equal in height I tend to end up with a flat slant, so my boxes are tilted. Using a sanding block hasn't improved my technique. I just have to work harder at it. What I'm going to to is draw a line and only sand to it, which is what I should have done to begin with if I'd followed your advice earlier, Dave!

And, BTW, Dick: Your instructions on adding the mitered stops to the chevron sleds work like a charm. I made a bunch of small miter stop blocks and after drawing the center line I glue them in place. Takes all of two seconds and the cuts are consistent!

Beems: After we all had fun with you for not taking the plunge on your dovetail cuts I thought I better try what I was doing or have to bite my words! ;D Should have followed your example instead of ruining three little boxes representing six week's work!

What can I say, guys. I'm still an idiot but a slightly wiser one! ;D

Thanks again!

[art3427]

The flat hand powered sand block is what I use in such cases. Next would be a good disk sander. I have the same Ryobi sander and it has the same problems. Have you tried using 2 faced tape to fasten small parts to a flat substrate then running them through a planer making a light cut?

art

[elizabeth]

Art: I was trying to use the belt sander to even the edges on my already glued boxes. I can't use a planner that way. Block sanding, or sanding on a flat surface is the way to go. Thanks!