Can some one tell me if these are laps?

[rod]

I just got some nice gifts from a friend whose dad had passed away... two new diamond lapping discs, one is flat and 600 grit, and one is 150 grit and dished like a saucer. He also gave me these slightly larger seemingly Plexiglas discs, that are mirrored on one side and grey coated on the other with about 6.3 mm center hole.

Might these be some kind of polishing discs for lapidary work and to be loaded with diamond paste?

Rod

 

[K Frei]

I don't know what they are, but I know in jewelry sometimes when I need to clean up a rough casting fast (that is flat sided) I'll stick emery paper to something like that (usually, in my case it's an old CD) then I will run it on my polishing wheel. If you are any good, and care full you can rough out a ring in a minute or two, if your not carefull you can make alot of heart ache in a hurry K Frei

 

[monk]

not sure. it does bring to mind something i do now & then-- i use junk promotional cd blanks on my grs hone. i sometimes charge them with carbide grit, or even affix wet & dry paper to them for certain things i polish, such as very tiny gravers made from used dental drills. i like the wet & dry- as when it loads up, it can be used for progressively finer polishing.

 

[rod]

I do that too, Monkster,

However these are about seven inches dia and about 3/16 inch thick, and look like they were precision cut with a saw and have a protective paper on the mirrored side?

Rod

 

[Beathard]

Are there identification marks on either side?

 

[scott99]

Hi, they look like telescope mirrors and the tools to make them to me.

scott99

 

[lesholmes]

Rod,

Back in the 1970s a rough diamond disk was sold for roughing out stone cabochons.

Les Holmes

 

[medicbeedge]

I made something like this a while ago since I was starting out and couldnt afford a diamond lap. It consisted of a old cd, emory cloth and glue. Worked very well I might add.

 

[scott99]

HI, I don't want to seem repetitive but those are mirrors for a reflecting telescope. The hole in the center is for mounting the objective lens, they are covered in protective plastic because they are "front surface mirrors". This means the shiny bit is on the surface of the mirror not on the back side like a normal mirror. The other pieces are for blanking out the curve of such mirrors. Someone was probably making a home grown telescope, if you take the plastic off the surface of the mirror it will be ruined is not handled very carfully. Such stuff is hard to make and sort of pricy when purchased, it would be a shame to turn them into a sanding disk. Please check with a local sky watching club before you tear them up.

Thankyou Scott99

 

[Jahn Baker]

The dished lap is for rough grinding cabachon stones and the acrylic discs go on a faceting machine (precision flat lap) for polishing faceted stones. They get charged with extremely fine diamond compound. They might work for polishing gravers, but I fear they're probably a bit soft and will become scored or grooved. We have two faceting machines in my jewelry classroom, both equipped with a variety of different laps.

 

[rod]

Scott,

Thank you for your speculation about the mirrored discs, however these discs are light weigh plastic which has been mirrored conventionally on the back and then painted to protect just like a pocket mirror, and they are flat. My own guess is that some one got, surplus, some large plastic mirrored sheets and band sawed the discs from the bigger sheets, they do appear precision band sawed. I could hardly believe anyone would make a telescope from a flat plastic mirrored start. I am quite a keen astronomer and have several telescopes, one being an 18 inch Dobsonian that stands about 8 feet tall, and have made some major redesigns of it.

I rather favor Jawn's explanation, as he is equipped and experienced as a precious stone polisher. I can also agree that the plastic discs would not be scored with rounded cabachon stones, but would tend to be scored with the faceted geometry of a typical graver. A ready source of plastic discs for experimenting as graver laps is a blank CD or the plain discs that protect a batch of one hundred CD blanks, and I know from experience these do score quickly as diamond paste charged laps. For bright polished graver heels, I use diamond liquid charged cast iron laps or the hard ceramic disc, then back strop the heel with a disc of diamond charged leather.

Thank you all for having a go!

best

Rod

 

[rod]

My neighbor, Arlo, has built his own plane, a skilled pilot, well versed in emergency kits for surviving at sea or crash landing in the wilderness. His take on these plastic mirrored discs, is that they were not made as laps to be loaded with diamond paste, although they could be used that way, instead they were once made as signalling mirrors to attract search aircraft, if you were downed in the outback. Seemed like a plausible guess, I googled signaling mirrors, seems this may be the original intention. Arlo said they all had a small viewing hole to look through, and try to point the mirror towards the high flying search aircraft. Look at this diagram..... looks plausible? No, or no?

 

[scott99]

Thanks for the thanks, I seem to have been off the beam on that one.

scott99