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#1

Greybeard
Member
From: Toowoomba, QLD
Joined: 21 September 2016
Posts: 24
Member
26 October 2016 10:30 pm

Hey guys.

I charged a copper prepolish lap with 3000 using olive oil and used in to do my first stone. It worked fine. When doing the second stone it didn't seem to be working as well and I seemed to get some fine scratches.

How often should I recharge a prepolish lap? How do I tell?
Should I clean it to remove the olive pil and recharge with light machine oil like Singer oil?
A bit unsure here and any advice appreciated.

1 user likes this post: AtomRat

#2

AtomRat
Member
From: Katazone, VIC
Joined: 22 May 2014
Posts: 5,080
Member
29 October 2016 08:41 am

Bump


Wisdom is knowing how little you know

#3

Lefty
Member
Joined: 01 May 2014
Posts: 1,041
Member
29 October 2016 09:06 am

Didn't see it somehow neutral

It's had to say exactly - if it's only the second stone on that lap then it probably isn't a buildup of swarf.

I've scratched softer stones on a copper lap that has been heavily used for sapphire. Maybe particles of a harder stone left on the lap?

Sometimes you can overload the lap with diamond and under pressure particles can clump together to form a larger ball of grit that makes bigger scratches.

Or maybe the lap is contaminated with a few particles of a heavier grit - when you use loose grits you need to be pretty pedantic about cleaning everything in between stages, I always wipe the stone down thoroughly with metho on a tissue or paper serviette. Plus everything else and give hands a good wash.

Try giving the lap a very good clean down and re-charging it.

1 user likes this post: AtomRat

#4

Mr Magoo
Member
Joined: 04 May 2014
Posts: 210
Member
29 October 2016 10:09 am

How often should I recharge a prepolish lap? How do I tell?

When it's 'blunt'. And you will know it's blunt because it just won't cut. If it's a new copper lap it's going to take a bit to coat (actually embed into) the soft copper. To charge a copper lap it's good quality diamond powder and a carrier. I use vasoline - which is a bit too thick, others use Almond oil.
As a lube I use WD40 or such like, but very little. When the lap dulls I'll spray, lightly with WD40 and wipe down. Usually it will sharpen right back up again - beware of over cutting here.
If it doesn't 'sharpen' up, only then do I add more diamond.

Should I clean it to remove the olive pil and recharge with light machine oil like Singer oil?

Just remember the higher the viscosity the more likely the stone will 'hydroplane' over the lap (so reduce cutting and round edges) but at the same time you need some substance so it can act as a carrier. (That is why I use WD40 as a lube). But a lap does need wiped down regularly.

If you need some decent diamond powder send RoughtoCut a PM. He has De Beers diamond powder and a good lube (I think it's Almond oil - unsure) available. Also he manufactures (he makes them for a well known Aussie web supplier) a wicked sintered lap. A bit of an investment but his are the cheapest available (I paid $400 for my 6 inch) and boy do they cut. Awesome laps.

1 user likes this post: Kingsolomon

#5

Kingsolomon
Member
Joined: 16 May 2013
Posts: 489
Member
30 October 2016 01:25 am

Aniseed oil . And yes the laps are good made by him . Think he's having a break for a bit from making them . But will start again early next year .


Got stuff to dig stuff up .. Got stuff to detect metal stuff .. Got stuff to facet stuff ...

#6

Lefty
Member
Joined: 01 May 2014
Posts: 1,041
Member
30 October 2016 06:48 am

Aniseed oil

And the best thing is that it smells so much nicer than WD-40 - kind of like faceting in a black jelly bean factory smile

#7

Greybeard
Member
From: Toowoomba, QLD
Joined: 21 September 2016
Posts: 24
Member
08 November 2016 10:44 pm

Thanks everyone for the comments. I went ahead and cleaned the lap down well and used Singer machine oil. Seems to be fine now. Maybe the olive oil was the problem.

However, I do find I have to clean it off regularly as it builds up a dark gung. So I add a single drop of oil and use toilet paper to loosen and clean off the gunk.

I am cutting a smokey quartz at the moment and it seems to build up gunk after just a few facets so I am cleaning the lap often

#8

Lefty
Member
Joined: 01 May 2014
Posts: 1,041
Member
09 November 2016 01:21 pm

Black gunk is an unfortunate fact of using loose abrasives - at least, every carrier either oil or water based that I've tried seems to ultimately break down into black gunk under the friction.

I wouldn't clean the lap after every few facets, you'll just burn up heaps of diamond. I tend to put up with the black gunk unless it suddenly starts to scratch.


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