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Author Topic: Pewter Lap build  (Read 1609 times)

Faceting Frank

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Re: Pewter Lap build
« Reply #15 on: August 03, 2021, 12:19:34 PM »
When I get this sorted will start a new thread on making mandrels.
Haven’t done any concave cutting since thinking of making a mod to the pushrod that drives the back-and-forth motion of the mandrel. Not going to do very well with my concave entry in this year’s OZ guild comp because of the ruts in the polish. The only way they can be created is at the end of the stroke, so will have the pushrod doing a random stroke.
Still working on ideas about the mold for coating the copper mandrel, one idea is coating the inside of it with alfoil.

MakkyBrown

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Re: Pewter Lap build
« Reply #16 on: August 03, 2021, 05:33:58 PM »
Just tried to make an 8inch, made an aluminum backer. Tin to aluminum adhesion = 0  :P ::) The copper was good. Might be the grade of aluminum or something. So now to find a 200mm saucepan with sharp corners and give that a go. Knowing my luck it will get stuck in the saucepan :) It is going to be a bit weighty about 3kg being all pewter.

MB

Bucket

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Re: Pewter Lap build
« Reply #17 on: August 03, 2021, 05:35:03 PM »
MB, novel use of a hose clamp, I've seen them used for a  lot of things, but this is a first. RC, I've used the white cerium oxide on pewter laps most of my time and can say that quartz comes up a treat. Not as good for harder stuff though. I have a darkside as well which does work well, but unfortunately it's got something in it which is causing fine scratches so haven't cleaned it properly yet, it may need refacing.
Common sense isn't exactly common

RoughCreations

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Re: Pewter Lap build
« Reply #18 on: August 03, 2021, 08:27:54 PM »
I have a darkside as well which does work well, but unfortunately it's got something in it which is causing fine scratches so haven't cleaned it properly yet, it may need refacing.

I occasionally place a clean sheet of 1000 or 1200 wet and dry paper back-side down on a piece of glass if this happens. Lay the Darkside polishing surface on the dampened sandpaper and do some small circular orbits. Any quartz shards or similar are quickly removed, and you can wipe the disk with a clean rag, rinse and continue polishing.
That said, I am enticed to try pewter/tin with cerium just the same.
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MakkyBrown

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Re: Pewter Lap build
« Reply #19 on: August 03, 2021, 09:31:30 PM »
Hey RC, what sort of cerium are you using and where did you buy it. I only have the pink stuff and it has some how got coarse crystals in it.
MB

FlashGP

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Re: Pewter Lap build
« Reply #20 on: August 04, 2021, 07:35:27 AM »
Frank,  Clarry Trevena uses a lump of aluminium with 1/2 inch holes drilled into it and smaller holes drilled in the bottom to hold the shaft around which he is pouring the pewter. 

He stands the shafts in the holes and the pours the pewter into the mould and extracts them by twisting the shanks with a peace of multi grips.

His pewter is a specific aluminium alloy bearing metal from a machinists handbook.  From memory there are 3 reveries that give different hardness bearings.  He uses soft or medium.  He made Bob. Boddington a hard one, I am not sure how successful it was.  He has the local
Metal supplier make 5kg mixes at a time for him.

PS, he then machines down 3 at a time so they are within 0.01mm diameter of each other as a matched set. 
« Last Edit: August 04, 2021, 08:16:18 AM by FlashGP »
Yours Sincerely
Flash (Gordon)

Bucket

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Re: Pewter Lap build
« Reply #21 on: August 04, 2021, 09:23:08 AM »
Makky you could try Aussie Sapphire, the last lot of white cerium I bought was from Shell-Lap in Adelaide and they not longer exist. I think they got rid of a lot of their stuff to Gemcuts in Ballina NSW. If you get really stuck let me know, I may have some to spare as I use very small amounts. I mix it into a milky like liquid and now that the pewter is charged, I only use 3-4 drops usually per stone, depending on the size. Charging was just by use of the lap, started using a reasonable amount of cerium and polishing a bit on the dry side. Now if the lap starts to dry out, I just give it a very light spray of water, just enough to dampen the lap, not wet it, as if you use to much water, it'll wash the cerium off.
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RoughCreations

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Re: Pewter Lap build
« Reply #22 on: August 04, 2021, 10:43:11 AM »
Hey RC, what sort of cerium are you using and where did you buy it. I only have the pink stuff and it has some how got coarse crystals in it.
MB

Yeah, Bucket is on the money with his technique. Seems like cerium is something to be very careful buying and not try to save money by using Ali Express etc. Aussie Sapphire sells the 2 micron white stuff which I use religiously on my smoky. I have used other cerium and I have certainly experienced the occasional 'foreigner' in the powder giving me scratches and heartache. I reckon the Cerium Battstiks would be another option. I have a Zirconium oxide Battstik from AS which is also good on quartz, but seems to be a *lot* slower than cerium oxide.
« Last Edit: August 04, 2021, 10:47:52 AM by RoughCreations »
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MakkyBrown

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Re: Pewter Lap build
« Reply #23 on: August 04, 2021, 08:26:38 PM »
Hey Bucket the pot($5 tip shop alloy saucepan) worked great. Thought it was stuck but gave it a few FIRM, last resort, bangs on the bench and out it popped. Much to my amazement  ;D . I have split this one for 3k/100k, 195mm diameter, 11.8mm thick and roughly 40mm wide bands.RC order some cerium from AussiesSapphire, also noticed today Ruby Vale is selling the Chinese resin laps we purchased for $200 each.
MB


« Last Edit: August 04, 2021, 08:28:44 PM by MakkyBrown »

Faceting Frank

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Re: Pewter Lap build
« Reply #24 on: August 04, 2021, 09:02:56 PM »
Thanks for the info Gordon. Can remember seeing cast aluminium moulds years ago for those who want to make their own fishing sinkers, they were made in two halves.
So, looking at making an aluminium mould out of 25x25 bar which I have plenty of. Cutting it in half length ways, milling the surfaces, join together, then bore it 12.5mm. Bore a 10mm diameter copper bar right through for the shaft to protrude, so I can support it at both ends.
Heat it all up and pour the batt metal in the gap and then turn it to 12mm diameter, should work ok.

Lap looks good MB.

MakkyBrown

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Re: Pewter Lap build
« Reply #25 on: August 04, 2021, 10:02:53 PM »
The new 8inch lap weighs 2.7kg = at least a dozen tankards and goblets. I've pretty much cleaned out all the op shops of cheap pewter in local Hobart area. Going to be awhile before I can make a couple more.

MB

MakkyBrown

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Re: Pewter Lap build
« Reply #26 on: August 19, 2021, 10:46:05 PM »
These laps are becoming addicting. I have made two 8inch ones so far and I am not really wanting to use 6inch polishing laps again. Need to make more. :) Oh and they are polishing perfectly.
The only problem making the 8 inch ones is uneven cooling causing pitting indenting in the center, requiring a few mm to be machine off. But the end result is great. Tested on quartz, sapphire and spinel so far. Faultless polish.They are a lot harder than tin laps.

MB

RoughCreations

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Re: Pewter Lap build
« Reply #27 on: August 20, 2021, 12:23:43 PM »
I much prefer the 8" laps too. Have you tried cerium oxide with them on quartz?
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MakkyBrown

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Re: Pewter Lap build
« Reply #28 on: August 20, 2021, 03:33:12 PM »
Tried it on one of the 6inch ones, works well. But preferring my 8inch 100k and split 3k/100k atm. Need to make a few more 8inch laps :)
« Last Edit: August 20, 2021, 10:03:16 PM by MakkyBrown »

Bucket

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Re: Pewter Lap build
« Reply #29 on: August 21, 2021, 09:04:49 AM »
Glad to hear they're working for you Makky, the 8" split sounds like a good thing except for the weight! A bit more lower tech than what you're normally doing though! The three I have are all 6" and quite frankly, for polishing, I wouldn't use anything else.
Common sense isn't exactly common

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