Saturday, August 31, 2013

Circle Sander

So I have been making several wheels from a hole saw on a drill press.  This leaves a ragged edge that has to be sanded. The technique that I usually use is a bolt chucked into the drill press with the wheel on it.  This makes the drill press like a lathe in some aspects.  There is still some play between the bolt and the axle hole which does not allow for an consistent sanding.  I have been wanting to make a circle cutter for my band saw.  So this became the prototype.  It works well and is not that hard to make.  It took me about 4 hours.
Back end view of the sanding jig
Side view

Peg acts as stop so the there are no flat spots on the wheel
The adjustment on the glide allows for the wheel to just touch the paper so I only sand about a 1/16" and the base to be close to the belt for support.

The Body
I took a 3/4" piece of scrap plywood and grooved it in the center about 3/8" deep.  The depth of the groove is the thickness of the glide minus the thickness of the top piece.  The width of the groove depends on the width of the glide.  I then took the glide and put a rabit on either side so the bottom of the rabit sat just below the surface.  I then took a 1/4" piece of plywood and nailed it to the top of the piece of 3/4" plywood.  I then cut a groove through the 1/4" piece of plywood for the glide to fit in.  I made sure it was a tight fit.  I then sanded the glide so it was a smooth tight fit.

The Glide
To finish off the glide I drilled a 1/4" hole at one end.  Most hole saws have a 1/4" starter bit.  After that I marked on the bottom of the glide two lines.  I then marked a 1/2" scale starting at the hole all the way to the end.  I marked on the other line a 1/2" scale starting 1/4" from the hole.  At each of these marks I drilled a 7/32 hole.  This fits an axle peg.  This is used as a positive stop.  I now have a positive stop every 1/4".

Things to Note
The table for a belt sander is not always centered on the belt.  This is usually the case when there is a disk sander that is all with the machine.  This is not a huge problem because any part of the belt will work.  It is probably better to be on one side anyway.  Sanding circles does wear a groove in the belt about 3/8" wide.  I would not change the the fact the groove was centered.  Right now the jig is clamped to the table.  I will put a stop on the jig that will square it up with the table and make sure that it is not touching the belt during setup.  It will also allow me to attach it from the bottom so the table is completely free.

Wheels with a Hole Saw
If you are wondering how to cut wheels on a hole saw here are a few tips.  Buy a hole saw 1/4" larger than the wheel is needed.  Hole saws are measured by the outer diameter and the wheel will be the inside of the diameter of the hole saw.  When cutting the wheel out there are two things to consider. First, the hole saw makes a lot of dust.  You can get a much cleaner cut if there is a hole or edge that is open to expel the dust.  Just make sure the hole or edge does not create a flat spot on the wheel.  Second is that this is a two step process.  Cut about 90% through the board then flip it and cut the rest of the way.  This also makes it easier to pull the wheel out of the hole saw.

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