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Author Topic: Scratch marks from soft wheel 14000 and 50000  (Read 337 times)

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Pusscat

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Scratch marks from soft wheel 14000 and 50000
« on: August 12, 2017, 09:03:46 AM »

Hi,
Normally producing cabochons from opal. I go up to about 3000 on a soft wheel and then final polish with an oxide on felt. I bought a 14000 and 50000 soft wheel as I was finding if I wanted to work on koroit /boulder, then the oxide was an absolute 'B' and I couldn't get it out of the matrix.

I've tried breaking  the wheels in by taking the sort of 'icing sugar' type peaks off the resin using a sharp edge, tried using agate for what seams ages, but it still appears to add scratches.
The soft wheels I have are 'premium' and need to be broken in but I just can't appear to get them to perform...any advice out there at all!?
Cheers,
Peter
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Redrummd

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Re: Scratch marks from soft wheel 14000 and 50000
« Reply #1 on: August 12, 2017, 09:34:15 AM »

You may have picked up some contamination from trying to break them in - which is not unusual.  Take the wheel(s) off and turn them around to run in the opposite direction. 

1) Get an old towel and get about 1/3 of it wet.
2) Turn on the machine and press part of the damp area onto the wheel with enough pressure to slightly bog the motor down.
3) Quickly switch to a dry part of the towel and do the same.
4) Repeat a few times.

Test to see if there are any more issues.

If this fails try using a aluminium oxide dressing stick while running the wheel with water on.  Test again and if there is still an issue I suspect a factory contamination issue and you will probably have to return the wheel.

I have found that it is best to only use CLEAN washed aluminum oxide dressing sticks to "break" in new wheels as they do not contaminate but quickly smooth out the sharp high spots on new 1200, 3000, 8000, 14000 and 50000 wheels.

Pusscat

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Re: Scratch marks from soft wheel 14000 and 50000
« Reply #2 on: August 12, 2017, 10:27:37 AM »

Hi Michael...
Thanks for the tips...will definitely try!
I've already scrubbed the wheels with soapy water and power sprayed each one I turn. I wash in between each wheel( tooth brush in clean spay water and rinse) and the scratches are there. It's got much better than it was when I first got them...

With the Aluminium oxide sticks, in uk I can get 220...will that be ok? Will reverse where's tomorrow and give them a towelling!
Cheers, Peter
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vitzitziltecpatl

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Re: Scratch marks from soft wheel 14000 and 50000
« Reply #3 on: August 12, 2017, 10:36:12 AM »

Check out this tutorial on cutting boulder.

http://www.koroit.com/koroit.com/Cutting_Boulder_Opal.html

It's written by a miner/dealer of koroit opal, and he recommends against using a 14K wheel. Go down to the section on cutting - pretty far down in the body of the text - and you should find the following:

Quote: "If your machine has a 14,000-grit wheel I strongly suggest not using it to cut boulder opal. I have found that this wheel often introduces scratches. Many of the Australian miners and cutters I know also skip the use of this wheel."

Good luck with it. Boulder is a lot of fun - even if quite messy. The ironstone will stain your hands, clothes, etc, for sure.

Pusscat

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Re: Scratch marks from soft wheel 14000 and 50000
« Reply #5 on: August 13, 2017, 12:55:07 AM »

Thanks both, playtime!
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Pusscat

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Re: Scratch marks from soft wheel 14000 and 50000
« Reply #6 on: August 31, 2017, 07:05:52 AM »

Well, I've had a play.

First I did the turn around the wheels bit and pressed a damp towel then dry towel.

The towel got pretty shredded and parts appeared to melt into the resin. Maybe I pushed a little too hard...
Tried this a few times and tried a stone. Scratches were way worse than before.

I'd ordered some while aluminium oxide dressing bars and when they arrived, I washed  / scrubbed each individually, labelled each one and give it its own zip lock bag. Tried this and didn't really get too much joy.

Revolved wheels again, probably slightly less scratches but on one, it was definitely to one side of the wheel...also the 14000 was now gouging huge scratches in agate.  Hmmmmm.

Had a look at the wheel very carefully, I think it was a red resin and found some lumps of grey material in the resin in the area where the scratches were...also found some other areas where there were these lumps embedded. It looked like they were part of the original resin.

I cut these out as gently as I could with a scalpel and tried again. That wheel was better but still scratched.  The 14000 that was gouging out sections that you could 'click' with your fingernail.  The resin was a grey colour...I tried to look for lumps like I found in the red wheel but couldn't really see, probably due to the colours being the same.

Really frustrated, have had the wheels for about over a year and the red one looks like it's worn down to the grey bits ( but it has a fair bit of resin left, only really getting worn in) so I decided to buy some more wheels from another supplier.

This supplier is in Asia, got the order in, tracked it to the uk, got a delivery....and yep...they'd got a bit confused and sent belts instead of wheels!!

Arrrgh!! Anyway, an email later and they've apologised as the original order was for wheels and are now sending the correct order.  I just hope these are better!

Frustrating...


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vitzitziltecpatl

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Re: Scratch marks from soft wheel 14000 and 50000
« Reply #7 on: August 31, 2017, 08:26:32 AM »

Saw your comment about your supplier being in Asia. I had mistakenly assumed you were probably using Nova, or maybe Eastwind wheels. Here in the US they are the top brands according to most comments on the forums here.

Know your shipping costs are really high if you order from the US, but sometimes it might be worth it if you can put together a large enough order to reduce the shipping cost per item.

Redrummd

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Re: Scratch marks from soft wheel 14000 and 50000
« Reply #8 on: September 01, 2017, 04:46:54 PM »

I will admit I too thought we were talking about NOVA wheels.  They are the only wheels I will use from 3000 to 14,000 as they never seem to have any contamination issues.....

Pusscat

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Re: Scratch marks from soft wheel 14000 and 50000
« Reply #9 on: September 02, 2017, 01:31:59 AM »

I haven't tried the Asian wheels yet as they haven't arrived...I'll let you know ow I get on!
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finegemdesigns

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Re: Scratch marks from soft wheel 14000 and 50000
« Reply #10 on: September 13, 2017, 04:52:08 PM »

For opals I go:

180-220 metal to preform
270 fabric on expanding drum
600 fabric on expanding drum
600 grit on worn out CrystalPad on flat lap. (works like a 1200 grit)
I also have one of these everything the same except the pad is backed with a 1/4 inch sponge pad. This works well for curved surfaces.

This is the key point. You need to be sure you have ALL scratches out at this point and have a perfect clean satin 1200 frost finish.

Then I polish on a flat lap with soft leather with 100% pure cerium oxide.
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