Alabaster Turning Addenda
The Articulaser, a laser guided turning tool
Three versions of the pin chuck; on the left is the old six-in-one version, on the right one made by a machine shop, and in front a chuck from Best Wood Tools. I'm delighted that Best Wood Tools has made a good pin chuck readily available again.
Grace Ice & Water
I'm still searching for the perfect gasket material for the vacuum chuck. It needs to be soft enough to make a seal, yet hard enough to prevent tool chatter and the surface needs to be a bit grippy, to keep the piece from sliding. Roofers use a product called Grace Ice & Water Shield®. It's a rubber membrane with a sticky back, slightly soft, a bit stretchy, sticky enough on the front and very sticky on the back. While the proper name of this material is Bituthene®, it seems to be universally known to the trade as "bitchathane". Up on a roof on a hot afternoon I can understand the term. Find someone in the construction trade to get you a few square feet -WITH THE BACKING STILL ON IT. True up a disk of whatever you like best, I use MDF, and stick the membrane to it.
Are you nervous about losing your piece off the vacuum chuck? I am, or was anyway. Now I use stretch wrap to hold it on. Get it centered and attached with the vacuum. Then wrap the piece and the faceplate with stretch-wrap, leaving the base exposed so you can finish it off. I no longer use the tailstock in this operation, this works so well. (Thanks to Wayne Fitzgerald for this one).
I tried a different brand of Gel Varnish called Jel'D Poly Kote. Thumbs down, it may work well on wood but it is a sticky mess on stone. I'm still using Bartley's. There's another I haven't tried called Petri Wipe-On Polyurethane available from Klingspor's (800-228-0000). Has anybody tried this one? Let me know.
I have added an ultraviolet sensitive dye to the glue bath. You can get something called Blacklite glue additive (from Woodworker's Supply 800-645-9292, for $12.99). It is listed for aliphatic glues only but my guess is that it would work in Weldbond®. Or, for $1.49, in the laundry department of most large grocery stores, there is a product from Rit Dye called fabric whitener (or is it fabric brightener? possibly either would work). The whitener/brightener is an ultraviolet dye and salt. I used the Rit, I doubt the salt will adversely affect the glue.
Having the UV dye in the glue makes it easy to tell if you have all the glue off the surface, and whether it has flowed into the cracks. I'm now doing a final vacuum glue bath just after the initial 60 grit sanding. Then after sanding with 120 grit, a quick check with a UV lamp shows up any sanding scratches from the 60 grit. The UV also shows that the glue doesn't penetrate areas of uncracked surface at all. Small quartz crystals on the surface fluoresce differently and are easily seen. Unfortunately submerged quartz doesn't show up with the UV.
Turning in Egypt
Penny Bauer sent these images