Sneaky Gems.

SneakyCuttlefish said:

I have been using plated laps with a backing plate but my laps are rubbish. They don't sit flat on the backing plate so the dial indicator waves like a royals fanatic at a Buckingham parade. So annoying!!

This causes the facets to have a slight curve in them so they always need a bit of extra attention with a 3000# pre-polish BATT. I have tried everything. Even had the backing plate machined flat as a BATT. Still no difference.

As soon as I have a bit of spare coin I'll be swapping them all out with scintered laps and hard back laps.

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That doesn't sound right. Why don't you just stick another one on. They're cheap as.

and I have read the ultratec uses gears roll to transfer the angle to a potentiometer??. Other than the omni I suspect they all might use high precision potentiometers

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That's what I had heard. Contrary to the owner of a well known lapidary supplier, potentiometer are not reliable. And the example he gave, that is why the automotive industry uses them, is a bad example. They were notorious for failing - causing all sorts of problems. In fact they went to using two so one could check the other but now the likely hood of a problem occurring has doubled . Which is why the auto industry gave up and started using hall effects. Either way, I wouldn't like to swear on the capabilities of a pot for reliable accuracy.

:Y: Looks like a good gift looking forward to seeing the reults.

SneakyCuttlefish said:

I have been using plated laps with a backing plate but my laps are rubbish. They don't sit flat on the backing plate so the dial indicator waves like a royals fanatic at a Buckingham parade. So annoying!!

This causes the facets to have a slight curve in them so they always need a bit of extra attention with a 3000# pre-polish BATT. I have tried everything. Even had the backing plate machined flat as a BATT. Still no difference.

As soon as I have a bit of spare coin I'll be swapping them all out with scintered laps and hard back laps.

Click to expand...

SC, I just put the cheap plated lap straight down on the master lap. It's what they did at the club and it's never caused my master lap any harm - unless you put it on abrasive side down and spin it round

I did get one or two of those backing laps but I've never used them.

That said, for blokes who facet as much as us, high-quality laps that last a long time such as sintered laps - make sense. Just have to save up the pennies to buy them coz they aren't cheap.

Lefty said:

SneakyCuttlefish said:

I have been using plated laps with a backing plate but my laps are rubbish. They don't sit flat on the backing plate so the dial indicator waves like a royals fanatic at a Buckingham parade. So annoying!!

This causes the facets to have a slight curve in them so they always need a bit of extra attention with a 3000# pre-polish BATT. I have tried everything. Even had the backing plate machined flat as a BATT. Still no difference.

As soon as I have a bit of spare coin I'll be swapping them all out with scintered laps and hard back laps.

Click to expand...

SC, I just put the cheap plated lap straight down on the master lap. It's what they did at the club and it's never caused my master lap any harm - unless you put it on abrasive side down and spin it round

I did get one or two of those backing laps but I've never used them.

That said, for blokes who facet as much as us, high-quality laps that last a long time such as sintered laps - make sense. Just have to save up the pennies to buy them coz they aren't cheap.

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Getting confused. :/

Isn't a master lap a backing plate? Or are you referring to the platen?

Isn't a master lap a backing plate? Or are you referring to the platen?

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Yes, the platen. But it can get confusing because people often use the terms interchangeably.

Lefty said:

Isn't a master lap a backing plate? Or are you referring to the platen?

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Yes, the platen. But it can get confusing because people often use the terms interchangeably.

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Yes it does. I did used to think the platen was called the master also. Then I thought the master went between the platen and the lap . Partly because of the term, backing plate which went with the topper. Then one day it clicked.

Any way never thought about using as is. But that's probably because if (which is very rare now) I use an 8 inch topper and my platen is probably only 7.
What ever works though.

My apologies I will clarify. I use a master lap/backing plate on top of the platen.

SneakyCuttlefish said:

My apologies I will clarify. I use a master lap/backing plate on top of the platen.

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Still not sure. Is the following what you are doing? I've done it step by step as I don't know if I'm missing some part or misunderstanding something. But I can't see why yours, from what you say, is getting so bad and not sitting flat. This is what I do, but others may do a variation. Or not stick it down at all.

The topper, which is thin and has the diamond encrusted into it, usually will have a peel off wax paper on the back to reveal a sticky surface. This is then placed on the (usually Aluminum) master/backing lap and remain there for the rest of it's usable life. There should not be much variation between the master and the master and topper. But there will be some
When you wish to replace the lap assembly, put it into the oven at some temp, that I can't remember, and the old topper will come off ready for the new one.
N.B. There are also magnetic variations of this.

They aren't perfectly flat but yours sounds bad.

I have been using the magnetic version of the master and topper laps, they seem to work ok for me, but i have never used any others.

SC, I think MM might be right there - it sounds as though you have a crook lap. Do all the laps you use cut a little out? If they do, the platen might be out of level somehow.

Just the cutting laps are like that. They don't sit flat on the master lap. The BATTS go straight on the platen and they run beautifully. The 8" Batts have a very slight wave towards the outer edge but that can be expected for an 8". Not sure if the master lap might be a bit rubbish or if the diamond laps are just not good quality. I have ordered a few new ones so will see how they go once they get here.

If the BATT sits flat on the platen then it sounds like your machine is ok.

I've often wondered about just how flat a thin topper lap would sit on a master lap which in turn sits on the platen. The topper is so thin that it can flex slightly compared to a thick, heavy lap like a BATT.

Try putting the thin topper straight down on the platen and see how you go. If the topper is an 8" then it might overhang the platen a bit and flex slightly anyway, I've only ever used the 6" ones.

Cheers

What a marathon! Cutting big stones is not easy. Especially when your laps don't cut flat facets. The polishing on this stone took forever. This is a Smokey quartz from the Swiss alps. Mitsubishi trillion cut. (My own design) Removed 60 carats of junk before I could even start to think about a cut design. I had originally planned to cut a hexagon design but this shape fit the rough better. I had to order a very coarse lap to speed things up a bit. Eye clean. Weighs in at 41.87 carats. These are seriously underrated stones. The colour is glorious. Direct sun is very rich chocolate. Diffused light is more flashes of cream. Makes me hungry looking at it.

Sneaky, I am drooling over that stone, truly beautiful and not to mention your excellent workmanship and artistry. Well Done.
Mackka

sweet stone

SC, that is bloody nice! Superb job!! :Y: :Y: :Y:

Smoky quartz can make a very attractive stone and is just the right sort of hardness for general jewellery work. Lowmead produces a fair bit of those deep shades like that one, varying between chocolate and copper-bronze (and also lighter).

Yeah, those biggies really are a marathon. Seems to take forever. ktmman gave me a smoky crystal from Proston that finished at less than half the size of yours (SRB with 16-fold symmetry) but it still took ages.

Well done sir! Going into a pendant for Mrs SC?

Thanks guys. Mrs. SC would love this one in a pendent but this would need loads of gold to set. Might have to send her out with the detector!

One in each hand mate
Mackka

Beautiful work Sneaky :Y: