mgroothuis
starting to spend too much on rocks
Member since November 2022
Posts: 167 
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Post by mgroothuis on Sept 23, 2024 20:06:36 GMT -5
Will the All-You-Need backer discs fit a true 1/2" arbor on an old Gemlap 5A? Rock Shed claims a 1/2" arbor, but KN reads "non-standard .4985 in" hole. That's only .0015" off for a composite molded disc.
I built this flat lap table a few months back, but am looking for some diamond smoothing discs rather than just my SiC discs for soft rocks.
Any experience with these? Maybe a better option? Pretty new to this.
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lapidary1234
spending too much on rocks
"If you like rocks you can't be all bad!!" ~ old timer quote
Member since October 2021
Posts: 293
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Post by lapidary1234 on Sept 26, 2024 20:58:03 GMT -5
Alot of times things are measured in the metrics system and then approximated to sae. However.4985" equates to 12.66mm so not sure about this instance. If the arbor is less than a true 1/2" though any disc with a 1/2 bore will fit on it. I doubt you'll notice the .015 gap.
If you are concerned about it try buying the cheapest lap you can find. I found great deals at treasures Hong Kong (thk.hk) for electroplated laps. They cost around $12.00 each and are great quality in my opinion. In fact I've come to a personal realization that most electroplated supplies all behave and cut the same way. It's the resin/matrix products that people seem to have problems with quality.
Either that or I believe MN lapidary supply sells silicon carbide laps. Maybe order one of them with 1/2 bore and see how it works!
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mgroothuis
starting to spend too much on rocks
Member since November 2022
Posts: 167
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Post by mgroothuis on Sept 28, 2024 14:24:06 GMT -5
I appreciate the reply. Thanks! I'll look into these.
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mgroothuis
starting to spend too much on rocks
Member since November 2022
Posts: 167
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Post by mgroothuis on Oct 4, 2024 12:07:41 GMT -5
I answered my own question about the size. The Hi-tech laps fit the old Gemlap 1/2" arbor perfectly.
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Post by Rockoonz on Oct 4, 2024 13:11:19 GMT -5
If the "flange" surface is at a good 90 degrees to the shaft, the lap shouldn't have runout. I think the acrylic backing plates they want you to use with those are not super flat anyway, but a metal one is too heavy for the machine. They all vibrate at certain speeds in my experience, but still usable.
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Post by pauls on Oct 5, 2024 1:07:21 GMT -5
I think most of the plated disks come from China and are a metric equivalent of 1/2 inch, I bought a cheap reamer and use it to ream just a smidgen off the inside of the hole, even on the faceting machine the amount taken off is no consequence to run out.
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