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Author Topic: Can you refreash laps?  (Read 475 times)

AlanMc

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Can you refreash laps?
« on: January 07, 2020, 01:22:37 PM »
I am new to faceting but very much enjoying it.

I have just acquired a Gemmasta GF3 machine, it came with about 20 laps.  I have purchases a beginner kit of laps, however I was wondering if anyone can offer some advice of the old laps.
The old laps have not been used in about 5 years and have just been sitting in a shed.  I was wondering how I could go about refreshing the laps, is this possible?  The laps look good but do show spots of rust in some places. Some people have suggested running the machine and using a cloth or old stone to clean.  Any suggestions or thoughts?  I just think it is a waste not to use the laps as some are still in the original packaging.

Rusted

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Re: Can you refreash laps?
« Reply #1 on: January 07, 2020, 02:38:18 PM »
Give them a go. Anything that still works keep in your armoury.

Finer laps can get clogged with dopping wax or glue and stop cutting, I have found that scrubbing with a solvent like acetone or turps sometimes makes all the difference. You might be able to remove the rust spots with a bit of acid or just give them a rub with some fine wet and dry.
Laps also wear out and only worn grit is exposed keep those ones for softer stones where you don't want quick removal of material.

Worn useless laps are also the bees knees for use as a sharpening stone, great for chisels, knives, scissors. They can be mounted on the shaft of cheapy bench grinders to make even better sharpening machines.

AlanMc

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Re: Can you refreash laps?
« Reply #2 on: January 07, 2020, 05:51:06 PM »
Thanks Rusted.  Good advice.  someone told me to use a brilo pad and then turpentine.  I will just try then and see if they cut and polish.  They are all solid metal, so thought a bit to good just to bin.

Rusted

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Re: Can you refreash laps?
« Reply #3 on: January 08, 2020, 02:43:42 PM »
Ooh if they are the solid metal ones do everything you can to salvage them, they are really good laps.

steveo

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Re: Can you refreash laps?
« Reply #4 on: January 09, 2020, 06:24:17 AM »
Let us know what you do and if it works on any of the laps.
Steve

Dihusky

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Re: Can you refreash laps?
« Reply #5 on: January 12, 2020, 05:07:22 PM »
AlanMc a lot is going to depend on what the laps are, rough cutters that need to be backed by a master lap are straight forward and have been covered by Rusted.

If you have solid laps the approach can be very different. I'm referring to Copper, tin, pewter, typemetal etc.

First clean the surface with eucalyptus oil, not the water soluble stuff, then inspect the surface and check for flatness with a straight edge. If they are hollowed or scratched badly get them re-machined by a good lathe operator. These laps need to be not only flat but parallel to their back within a few microns.

If they are not badly worn try lapping using wet-n-dry on a sheet of thick glass, 10mm is ideal if you can get an offcut from the local glazier. A bit bigger than a sheet of wet-n-dry, and get him to arris the edge, as you'll be using this glass regularly to look after your pre-polishing and polishing laps, also for prepping re-machined laps.

NOTE: Every facetor will have their own opinion and technique for re-dressing laps, so be warned. This is mine:

I use this for all my solid metal pre-polishing and polishing laps. I don't use synthetics and the laps I have are copper: One for 3000 & one for 8000 grit, Tin 50,000 and a very special Cast Iron duo which is 8000 outer and 50,000 on the inner, this lap is for very hard stones only.

My routine starts with either 120 or 180 WnD wet with a little soap. I have made a handle using a large timber drawer handle fitted with a 1/2" hardwood peg, this makes moving the lap over the WnD easy.

Now work the lap over the WnD until the entire face is fresh, can take a while and you'll be replacing paper. Once the surface is fresh, work over finer grits down to 600. Now your lap is ready, it will have micro scoring across the face which will hold the diamond, and they work with a miniscule amount of diamond.

With my laps I can move from a 3000 or an 8000 prepolish to the 50,000 and because they are all absolutely flat, I don't have to cheat, polish is 6 or 8 swipes...done!

And in case you're wondering, I don't use Cerium, all my polishing is done with diamond (beBeers) Cerium is for Opal.

Hope this helps.

AlanMc

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Re: Can you refreash laps?
« Reply #6 on: January 14, 2020, 01:04:33 PM »
This is one of the laps I am trying to save/refreash.

Rusted

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Re: Can you refreash laps?
« Reply #7 on: January 14, 2020, 01:37:21 PM »
There's not a lot wrong with that lap.
Best would be to get it to an engineering shop and get them to reface it.
Second best would be to give it a scrub with a scotchbrite pad with a bit of acid. soldering spirits or brickcleaning acid (Hydrochloric) would remove the corrosion in seconds. Careful it removes skin too, failing that vinegar or even Coke will do it but will take a bit longer.
If you use acid don't forget to neutralise it after by scrubbing with soap or bicarb.

Prooz

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Re: Can you refreash laps?
« Reply #8 on: January 14, 2020, 04:04:08 PM »
Good one, I have a copper lap the same, just looks like water marks on the face both sides. I would try the wet and dry first as per Dihusky instructions works for me.

Cheers Prooz

MakkyBrown

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Re: Can you refreash laps?
« Reply #9 on: January 14, 2020, 09:42:19 PM »
I know someone that puts a plated topper lap upside down on polishing laps and roughly surfaces them using lots of water and light hand pressure on the plated lap with machine running. I've never tried it.

Dihusky

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Re: Can you refreash laps?
« Reply #10 on: January 18, 2020, 11:19:58 AM »
Nothing major wrong with that Copper AllanMc, please don't use any acid as it will cause pitting, try the wet-n-dry method first then if it's way out get it re-machined.

FlashGP

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Re: Can you refreash laps?
« Reply #11 on: January 22, 2020, 08:08:33 AM »
Antibacterial Palmolive Dishwashing liquid with lemon is acidic enough to brighten your lap without pitting it if you use it straight with a scourer or a bit of cuttlefish and wash it off straight away.

Don't let it sit on the lap for long.  I pit a couple of shallow pits on the surface of a zinc lap (zinc is more reactive) when I put it down covered in detergent to run an errand.  Two drops of water hit the surface and in the 5 minutes I was gone, reacted with the zinc pitting it.

The pits were shallow and have since burnished out with euccessive cleaning and dressing of the lap.
Yours Sincerely
Flash (Gordon)

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