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Author Topic: Pewter Lap build  (Read 1602 times)

MakkyBrown

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Pewter Lap build
« on: July 30, 2021, 08:55:52 PM »
I went shopping today and purchased some pewter. Got a bit over 1.75kg for the grand total of $12.30 which is not bad considering the tin spot price is getting close to $50aus/kg and would be a good bit more to buy locally.
I have two trpes. Four piece are from reputable Asian manufacturers and would be 97% tin, 1.5% antimony, 1.5% copper. They are newer and slightly less tarnished than the other two pieces. The other two pieces are made in Melbourne and say super fine lead free pewter, they would be older than the Asain pewter. I am not sure of their tin content but they are not that tarnish compare to some other pewter I looked at today so I suspect the tin content is still quite high.
The plan is to melt it all and put a 3-5mm layer onto some old copper laps I have and don't use. :) Hopefully I have enough for 3 laps.

CheersMB





Bucket

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Re: Pewter Lap build
« Reply #1 on: July 31, 2021, 03:01:31 PM »
They are great for polishing Makky! One of our members melted down pewter some years ago and produced some pure, all pewter 6 inch laps. They are thick enough for re facing if they spoon and work really well as polishing laps, I use one with white cerium oxide and it works really well on quartz. I have another with 50,000 diamond for harder stones. I do have a spare, which I haven't used yet.
Common sense isn't exactly common

MakkyBrown

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Re: Pewter Lap build
« Reply #2 on: July 31, 2021, 04:52:08 PM »
That's the plan Bucket, I need an oxide lap so I'll be making one hopefully later today using the 97% tin pewter. I wanted to try a darkside but they are out of stock at aussiesapphire so I'll go tin. Just ran a cut over my copper laps to clean them up, gee 600grit on copper is a bugger to machine  ::)

FlashGP

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Re: Pewter Lap build
« Reply #3 on: July 31, 2021, 09:22:59 PM »
Hope you have a good cutter and grinder to resharpen your tooling
Yours Sincerely
Flash (Gordon)

MakkyBrown

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Re: Pewter Lap build
« Reply #4 on: July 31, 2021, 10:12:46 PM »
I kept pulling the carbine tip and sharpening on my cabbing machine. I made two laps, first one looks better, might melt the second one again. Will machine tomorrow and have a look.
MB

« Last Edit: July 31, 2021, 10:17:14 PM by MakkyBrown »

Faceting Frank

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Re: Pewter Lap build
« Reply #5 on: August 01, 2021, 12:14:03 PM »
Since you know a bit about molds MB, what would you recommend for coating a copper concave cutter mandrel with some metal I'm going to cut off an old BATT lap.

MakkyBrown

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Re: Pewter Lap build
« Reply #6 on: August 01, 2021, 02:30:17 PM »
Here is one done. Probably the flatest lap I own.  Made up a large backer plate to bolt the laps to. Gee my 3 jaw chuck is good, face run out on the 6inch lap face and backer plate only about 0.0024mm. It hardly moves the needle on the gauge. Lap is about 11mm thick , should be lots of tin thickness for machining in the future.Bit of a pain machining the backs as I can only hold 125mm on my lathe.
MB



MakkyBrown

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Re: Pewter Lap build
« Reply #7 on: August 01, 2021, 02:40:14 PM »
I am not really a mold expert. I was going to use steel to make mine, but that is down the to do list quite a bit.If your mandrels are of copper and close to size you might just get away with tinning them. Perhaps tin them on a  rotisserie to build an even thickness then machine flat in the lathe or grind flat/round on your faceting machine
MB

Bucket

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Re: Pewter Lap build
« Reply #8 on: August 01, 2021, 03:38:46 PM »
Had a bit of a laugh when I read you're not a mold expert, the guy from the club that mad them found an old saucepan that was just over 6 inches in diameter and poured the molten pweter into that, then milled it to the correct size, he used to do them while he was at the club!
Common sense isn't exactly common

MakkyBrown

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Re: Pewter Lap build
« Reply #9 on: August 01, 2021, 06:37:01 PM »
I think I've taken the process to the next level bucket  ;) .  Mold = hose clamp(conveniently 12.7mm wide) around the copper lap and pour in the pewter. Probably easier in one piece. Now to find some more pewter to make an 8inch or maybe 9inch split lap.

RoughCreations

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Re: Pewter Lap build
« Reply #10 on: August 02, 2021, 10:23:15 AM »
That worked really well! Looks to be well-bonded to the copper base. I haven't tried cerium on tin for polishing quartz, will be interested to hear about the results.
Now Makky, if you can just come up with a way of also doing sintered bronze diamond disks in your workshop...
RC
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Rusted

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Re: Pewter Lap build
« Reply #11 on: August 02, 2021, 02:28:02 PM »
Rough Creations, for the Cerium and Tin for Quartz, head to your office/art supply place and pick up a sheet of tracing film. It's not paper but a sort of plastic film, very tough stuff, impossible to tear.
Cut disks.
To get it to stick to your master lap a small drop of sewing machine oil on the lap will stick it down. To use the oxide polish mix a very thin mixture in a dropper bottle and just drop the occasional drop on as you go.
These are good and cheap and if you get any contamination throw it out and fit a new disk. One sheet will make dozens of disposable polishing disks.

RoughCreations

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Re: Pewter Lap build
« Reply #12 on: August 02, 2021, 03:28:39 PM »
Rough Creations, for the Cerium and Tin for Quartz, head to your office/art supply place and pick up a sheet of tracing film. It's not paper but a sort of plastic film, very tough stuff, impossible to tear.
Cut disks.
To get it to stick to your master lap a small drop of sewing machine oil on the lap will stick it down. To use the oxide polish mix a very thin mixture in a dropper bottle and just drop the occasional drop on as you go.
These are good and cheap and if you get any contamination throw it out and fit a new disk. One sheet will make dozens of disposable polishing disks.

Thanks, that's a great idea for disposable laps. I do regularly polish quartz successfully with a Darkside lap and cerium, it's just that I have never tried cerium on tin, guess I have never needed to as the plastic composite Darkside lap does the trick. I do have a Battlap that I could try one day with cerium oxide, just out of interest, but I have reserved it for use with diamond.
RC
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Faceting Frank

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Re: Pewter Lap build
« Reply #13 on: August 02, 2021, 04:04:13 PM »
Not having a lot of luck trying to plate the copper mandrels. Tried putting the mandrel shaft in a pistol drill, setting the speed to a good balance between gravity and centrifugal force.
Worked well, didn’t take much heat to get the mandrel hot enough to be able to melt a stick of batt metal on it and let it cool as it rotated. Looked good, but on the lathe patches of copper were showing through.
Electroplating won’t be any good, as the plating is measured in microns. So, thinking of making an aluminium mold, with the mandrel in the middle. Heat it all up and drop chips of batt metal into it, then turn on the lathe.

MakkyBrown

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Re: Pewter Lap build
« Reply #14 on: August 02, 2021, 09:41:22 PM »
You could mold a cylinder, drill a hole in it and stick brass 1/4 rod in the center of it. Or make mold that has a hole for the center to be held in position. Maybe steel mold and paint with heat resistant paint. I'll be interested in how you go as I'll be doing the same one day.
MB

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