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Old 03-26-2019, 01:05 AM
Chris Lowry Chris Lowry is online now
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Flat lap polishing

For those that use your flat grinder and a felt pad to polish I have some questions.

Does slowing down the grinder help? I would imagine that it would help with the grabbing but does it help with polishing faster?

Anyone try the LP66 polishing pad?

Anyone do a prepolish on the Polpur pads?

I need to invest in some new equipment but first hand knowledge is great. Thanks
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Old 03-26-2019, 09:43 AM
Shawn Everette Shawn Everette is offline
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I've used the LP66 polish pads for some time. They're pretty good for a private studio, but I'd rather have napped felt or polpur style if your letting beginners near it; the LP66 can get gouged easily if not treated gently. That being said once it gets impregnated with cerium it stays there, can take a while to build up though.

The only time I slow it down is if I feel it's getting too hot. Once the cerium is on there it tends to shed the water right off the pad, so I have a tendency to run wet and slow.

Pre polish wise I just started using the diamond smoothing pads, those are a dream. Pricey, but do an excellent job. I'll post pics when I get a chance.
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Old 03-26-2019, 11:19 AM
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Pete VanderLaan Pete VanderLaan is offline
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I'm a polishing junkie and have a different machine for each grit (60, 120, 400 or 27mu) Then the pumice machine with a rodel GPX .125 pad and 0-3/4 pumice followed by a Universal photonics felt from Boston Felt at 1/2 inch thick.
All of those machines are a minimum 24 inch with the grinders being 30 inch. Wheelhead speed does matter. Diamonds want more water and more Surface feet per minute. Cerium will simply crack your work if you run too fast so, best to have more than one machine.

I think the first question you really want to ask is whether the glass you are using is receptive to a good polish. Sp87 is OK sort of. All the current cullets are marginal and unless you are melting a custom glass with high potassium, the concern over tooling may be a waste of your time. Surface feet per minute determine stock removal but getting greedy will rip the workpiece from your hand. By the time you are getting to 400 grit or finer, you have a real risk regarding suctioning down diamonds or grit. Cerium does not want those speeds and will overheat if pushed.

When we ran a lot of Schott optical as well as my high potash glasses, it simply was the case that silicon carbide was the way to get the best surface. Aluminum oxide optically graded at 27.5 mu followed the SIC and the rodel pad with the 0-3/4 pumice prepped a piece for a serious grade of Cerium Superox PMD or my chinese all time favorite Panda Brand cerium on the Universal photonics felt were best, unless one was polishing in a reciprolap and there we reverted to Rodel again. Rodel became unbelievably expensive some time back so I bought a fifty yard roll 54 inches wide and am still cutting pads from that. That was also true of the Universal photonics felt. In both I have a lifetime supply if I don't live too long.

So that was us in obsessive compulsion land.

These days, I don't do big slabs and mary beth just wants to shape jewelry so we use a 60 grit diamond from David Patchen and I can't say enough how superior those pads are. More diamonds, rigid, just perfect long lasting little buggers. I continue to use a 38 inch 120 grit machine for my work and then go to the optical grade 400.
The pads in Roberts video look exactly like Rodel pads but have gone up about ten times in price. I used to pay $20 bucks a pad and bought long rolls of it. Thickness is important and if you get thinner than a .125 They tear easily. I kept mine on a timer and when it reached 40 hours, it was replaced since the speed began to slow down quite noticeably. Similar things are true about the Photonics cerium pad and they do get lumpy bumpy if not dried well between sessions. Another annoyance with those pads is if you get 1/2 inch as opposed to 1.4 inch pads, the cerium tends to ride up on the edge of your workpiece, which if you are fuming is quite noticeable.

Eveline's Panda Brand Cerium is the worlds best and costs very little but it isn't exported. Price is controlled by the government unless you are smuggling it out which I did. I came close to real trouble doing that. Most Cerium's are going to run you around 2K per pail and all cerium is definitely not created equal. There are slurry Cerium's that sound better on price but are remarkably ineffective in polishing. Politishing is expensive and involves a serious financial commitment.
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Old 03-26-2019, 02:23 PM
Chris Lowry Chris Lowry is online now
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Thanks Pete there is a lot to read there. I do use Spruce Pine and to my eye it gives a nice polish. I do order wheels like David for the rough. On a small surface the diamond pads work fine but for anything nice or big I hate the lines they leave. I guess loose grit is the way to go.

I just need to perfect my polish set up. Iíll try some of your suggestions. Iíve been debating buying a variable speed grinder but maybe just having a detracted slow one for cerium would work.

When on a rociprolap do you go straight from 400 to cerium?
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Old 03-26-2019, 03:50 PM
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Pete VanderLaan Pete VanderLaan is offline
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First, I do have six laps. That being said I now use just one. I go directly from a 120 grit rough to the lap. I use a 15T also called fifteen hundred microgrit in that lap and leave the piece(s) in for two hours. If it's a vessel, I put a few inches of water in to it for deadweight. Everything needs to be wrapped carefully to avoid destruction. You cannot use 1500 grit on a standard wheelhead. The work will instantly be ripped from your hands. It's actually frequently hard to get the piece off a reciprolap. Suction.

After two hours,it comes out and goes directly to the pumice with 0/3/4. Prep usually takes about 1.5 minutes. Then it goes to Cerium. Salt to taste.
There are interesting layers in the pumice/ cerium processes. In Pumice, if I really wanted a superb polish where I saw mirror reflections on facets, I'd drop to an "0" pumice. Canneto Lipari was the italian pumice of choice. The Navajo brand has some iron in it and needs magnets in the slurry tray. Then, going to cerium, polish occurs at two levels. You get one very quickly but if you look at it carefully, it resembles orange peel. That can indeed be polished through but it takes a while. At that level is when I was referring to how good your actual glass is. For Schott optical, it's important and it's important for my formulation as well. I would suspect you would not see major benefit in SP and any of the current cullet won't show well either.
With Mary Beth's work in Schott, we came out of the 1500 lap and went directly to a rodel pad with cerium in another rociprolap. Typically that took four hours.
Back when Jack Rose sold the business off, I formed a buying club with David Lindsay so we could get additional trays at a reasonable price- about $275.00. I ordered a lot. The new price was $700 dollars, a huge increase. His had a distributorship. I bought more than they did. Then HIS glassworks complained to the manufacturers about that deal and I was cut off. I never order another tray from anyone. That really pissed me off.

What I do is tried and true. There's no better machine that the Rose lap. It's just not cheap to do. I do tend to think that individual machines are the way to go. It indeed takes up space but you get great surfaces if your work demands it. If you get serious about it, you need a machine shop that can true the dishes. They don't have a very long lifespan before being worn too thin. I think I have something like 18 trays.
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Old 03-26-2019, 03:54 PM
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Quote:
Originally Posted by Chris Lowry View Post
Thanks Pete there is a lot to read there. I do use Spruce Pine and to my eye it gives a nice polish. I do order wheels like David for the rough. On a small surface the diamond pads work fine but for anything nice or big I hate the lines they leave. I guess loose grit is the way to go.

I just need to perfect my polish set up. Iíll try some of your suggestions. Iíve been debating buying a variable speed grinder but maybe just having a detracted slow one for cerium would work.

When on a rociprolap do you go straight from 400 to cerium?
******
Indeed. Diamonds give a great surface with one long scratch- every damned time. Then you have to polish through the scratch.

You can go direct from the 1500T to Cerium but it takes its sweet time.
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Old 03-26-2019, 10:02 PM
Marty Kremer Marty Kremer is offline
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I'm usually liking diamonds to about 140 and then hand grinding on a glass plate with 220 SiCa slurry. Gets right past those big bling scratches.
But then I'm not looking for polish....

But- Bullseye set up that way and then fire polished at around 1350F is plenty good for my stuff. Pavel Novak polished some BE for me but complained the whole time. This stuff just isn't made for optical finishes.
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Old 06-20-2019, 10:44 PM
Chris Lowry Chris Lowry is online now
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Pete... another question, what are you using pumice on? Can you use it straight on the metal rociprolap?

I just tried polishing a 16Ē x 11Ē piece and it was a bitch going from 600 grit to cerium on felt. The felt wasnít perfectly flat so it wouldnít polish the whole surface. Also seemed like it would be nice to have a stage in between those.

Thanks
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Old 06-20-2019, 10:57 PM
Chris Lowry Chris Lowry is online now
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oops I just read it again and noticed you said Rodel GPX pad.
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Old 06-21-2019, 08:54 AM
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At one point, in a reciprolap, I was very sucessfully able to use the rubber floormats one finds in a bar behind the counter. I could go from a 27.5 micron grit to a cerium on that pad. It took some time but I didn't have to stand there doing it.
To get away with that stuff, you need a lot of trays, a whole lot. I used to buy them when they were fairly priced around $200 dollars. Now, over $700. I haven't gotten a new one in years.

I don't even know if Rodel is still around. They jacked the price on the GP IV-x so high it was hard to justify ever buying them again. The last time, I got a 53 inch wide by 30 yards piece of the material. I still have enough left to make four or five pads, a lifetime supply. That was back when it cost about $18.00 a pad. \\
Universal Photonics used to sell some good quality pad materials. They also had felt material in a 53 inch width by yard. It was eithe 1/4 or 1/2 inch thick. Nice stuff. Very aggressive.
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Old 06-21-2019, 12:39 PM
Eben Horton Eben Horton is online now
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My quick contribution to this thread is yes, I polish on a flat lap with diamonds. I don’t get a long scratch that Pete describes. I do have issues with hydroplaning if I don’t turn the water down with higher grit pads and with the polishing pad, I do not use any water and keep my cerium in a squirt bottle.
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Old 06-21-2019, 02:00 PM
Chris Lowry Chris Lowry is online now
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Eben, Iíd like to try the squirt bottle thing. What is your mixture like? Do you wet your felt first?

Pete, when you buy pad material by the foot... do you put a magnetic back on it?

Thanks for all the good ideas
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Old 06-21-2019, 02:22 PM
Eben Horton Eben Horton is online now
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Chris, I really donít have a ratio.. I add cerium to the bottle and then enough water to make it the consistency of very runny crepe batter. Yes I wet the pad first.
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Old 06-21-2019, 03:40 PM
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Pete VanderLaan Pete VanderLaan is offline
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Quote:
Originally Posted by Chris Lowry View Post
Eben, Iíd like to try the squirt bottle thing. What is your mixture like? Do you wet your felt first?

Pete, when you buy pad material by the foot... do you put a magnetic back on it?

Thanks for all the good ideas
**** I have five machines, a 60, a 120, 1 27.5 micron, a pumice and a cerium. We scaled it down... Used to have two different pumice set ups. My 60 Grit has a magnetic backing. The others are all grit. I use squirt bottles on pumice and cerium as needed.

My cerium and pumice pads are contact cemented to an aluminum wheelhead cementing only one face. Do two and you'll never get them apart. I use a water feed on both machines, one into an 0-3/4 pumice and the other a cerium mix applied in all sorts of differeing ways, always with a drip water feed at the center. Both the pumice and cerium pads are 24 inch. The grinders are a lot larger.
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Old 06-21-2019, 04:17 PM
Chris Lowry Chris Lowry is online now
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Thanks guys Iíll try it out.

So Pete you donít use homemade polish pads in a rociprolap? Iím guessing in that situation a magnetic back would be good but Iím worried about getting them perfectly flat.

I do have multiple machines but donít want to glue felt right to the machine.
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Old 06-21-2019, 06:17 PM
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My best results were with the rodel GPX non perforated. Keep in mind it was almost always a 40% lead glass I was polishing from a 27.5 micron surface.

I have seen indoor outdoor carpet used as a polish pad with varied results. I recall Hugh Jenkins doing that and if you're on decent terms with him, you could ask. I think he is near the end of his career which I hear from so man of my peers these days. Ask questions now, time is getting important.

I simply put the bartenders rubber mat in the lap itself. Just make it really tight so it doesn't sashay around the machine which stops all progress.
You try lots of stuff , some works, some doesn't. Weird huh?
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