Acrylic Coasters: Edge Finishing, Round 1

Assembling acrylic pieces inside an epoxy-filled frame produces nice results:

Cut Acrylic Coaster - bottom
Cut Acrylic Coaster – bottom

The gotcha: epoxy oozes from between the layers to form a slobbery edge.

I tried introducing a similar coaster to Mr Disk Sander with reasonable results:

Coaster Epoxy Rim - disk sanded rim
Coaster Epoxy Rim – disk sanded rim

The coaster on the bottom has its original generous epoxy slobber around the acrylic disks.

Assembling the layers inside a mold seems fraught with messiness, particularly if I eventually want to get it out of the mold.

Using a finer abrasive disk would certainly help, but the whole process requires intense concentration and is utterly unforgiving of mistakes.

I figured I could attach the coaster to a lathe fixture and turn the rim, so I made a fixture from scrap acrylic:

Coaster Epoxy Rim - cutting fixture plate
Coaster Epoxy Rim – cutting fixture plate

The lathe chuck inside jaws fit inside the hole and I set up to turn the OD to a nice even diameter:

Coaster Epoxy Rim - turning fixture rim
Coaster Epoxy Rim – turning fixture rim

The fixture sat flush against the middle step of the jaws with plenty of clearance from the outer step, so I could turn the OD without whacking the carbide insert.

I planned to grab the OD and turn the ID to a (reasonably) concentric finish, but the outer jaws have an absolute diameter limit a few millimeters less than the 4 inch = 101.4 mm coaster OD.

After some increasingly desperate attempts, I concluded that, lacking a 4-jaw lathe chuck, there was no way to mount the coaster on the fixture and have it sit it even approximately centered on the spindle axis.

I do, however, have a 4-jaw chuck for the Sherline mill, normally used with the rotary table.

Next up: Round 2.

5 thoughts on “Acrylic Coasters: Edge Finishing, Round 1

  1. Re: Carbide insert on Sherline lathe

    I saw that you’re using an insert tool. Do you use that to cut metal too? It’s appealing to me to be able to swap inserts rather than grind a HSS tool as I usually do, but I think I’ve seen it said that HSS is better for cutting aluminum (which is what I’m usually cutting).

    That led me to wonder whether HSS inserts could be a thing. Probably not or they would exist?

    1. For my simple / low stress / noncritical needs, carbide works fine for everything from plastic to steel. I have some Warner HSS inserts, but never had enough motivation to swap ’em in:

      https://littlemachineshop.com/products/search.php?tabName=Products&term=hss+inserts

      A shop-made quick-change toolpost came with the South Bend lathe, so IMO a QCTP / toolholder is the only way to fly! Haven’t ground a bit in a long while and don’t miss the experience hardly at all.

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