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Post by outbackrockkai on Jul 11, 2020 1:48:15 GMT -5
Hi Everyone, my name is Kai and I'm an opal collector from Germany. So please be kind with mistakes in language and grammar. As I cannot fly to Australia this year to look for some stones, I've decided to build my own lapidary machine instead and work on the rough pieces I've got sitting here waiting to be cut. It's gonna be a 6 wheeler with an option to maybe carry more wheels in the future. Due to that I've chosen a 20mm by 1m long shaft to have plenty of space to fit 6-8 wheels on it without having to worry about my knuckles too much. I'll start off with 80 and 220 grid SiC wheels, an 360 Diamond hard wheel and then a 600, 1200 and 3000 grid diamond soft wheel. That's gonna be the set up for the beginning. The motor will be a 1/4 hp electric motor with about 1400-1500 rpm and the turns will be transmitted by a beld. So pretty basic and common. I've been looking around for some homemade builds to get ideas how other guys did it and for now there's one thing I'm not sure about and that's the position of the bearings. The hard wheels, especially the SiC wheels are much heavier than the soft wheels. Do you think it's gonna be a problem if the bearings are centered or will the shaft start swinging due to the different weights on the left and the right side of the shaft? If the bearings are sitting centered with about 15-20cm distance in between and the wheels on the side, shaft's gonna stand out for about 40cm each. Do you guys think that could create a problem? Would like to avoid to put bearings on the side for comfort and easier maintenance like changing wheels plus I imagine it's easier that way to get enough tension on the wheels to get them carried. What do you guys think? I reckon and hope some of you can help me out with your experience and knowledge. Cheers Kai
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Post by stardiamond on Jul 11, 2020 11:10:38 GMT -5
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stonemon
Cave Dweller
Member since January 2017
Posts: 1,024
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Post by stonemon on Jul 11, 2020 12:41:16 GMT -5
Welcome to the forum!
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Post by outbackrockkai on Jul 11, 2020 16:19:55 GMT -5
cheers Thanks for the hint with the wheels. I've purchased those wheels with a dealer in Germany. I just chose SiC for the two coarse wheels as it is much cheaper and I reckon it's gonna do the job to get the rough shape. Let's see. I might switch to all diamonds in the future then. I'm sure, the boulder opal will wear the 80 grit out pretty quick anyways. I'll do some cutting first tho. I've planned to put on a polishing wheel as well but for the start I'm gonna do the polish with the multitool I've used for cutting in the past. Works quite well and provides a great finish as well. But it's definitely on the list. The cooling system is already in progress but I'll use one way water with a 20l bucket.
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nik
spending too much on rocks
Member since May 2019
Posts: 315
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Post by nik on Jul 11, 2020 22:54:15 GMT -5
Hello, and welcome to the group. It sounds like you are off to a good start with your basic design. You might run into issues finding adapter bushings to fit a 20mm shaft. Nearly every lapidary grinding wheel that I have seen is bored for 1 inch shaft, so my line of thinking would be to run a shaft that size to avoid the need need for adapters. If you can find it, 1144 steel, turned, ground, and polished shafting is a great material to work with. It machines beautifully and is not terribly expensive. In regards to your inboard bearing placement, I am not a fan of long sections of unsupported rotating shaft, but there are plenty of home built grinders that make it work. If possible, get some pinch style shaft collars to clamp your wheels against, they will isolate the bearings from the axial clamping load. In my experience, they hold better than the set screw type, and do not damage the shaft. Additionally, getting the right end of the shaft drilled and tapped with 1/4 20 threads will open up the option for thread on polishing discs.
I look forward to seeing how your project comes together.
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EricD
Cave Dweller
High in the Mountains
Member since November 2019
Posts: 1,142
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Post by EricD on Jul 11, 2020 23:20:10 GMT -5
nik brings a very valuable piece of information to the endeavor. 20mm is close to 3/4" but you would not be able to purchase bushings to increase it to 1" that most wheels have that you can readily buy. You are going to need a fractional shaft/bearings in order to use commonly available wheels. I would rather use metric measurements myself! I would also not recommend using less than a 1" shaft for your project because of "swinging" as you put it. Wobble I will go look for a recent member's self build machine that looks pretty darn good and link it here
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EricD
Cave Dweller
High in the Mountains
Member since November 2019
Posts: 1,142
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Post by EricD on Jul 11, 2020 23:22:39 GMT -5
Here you go. This guy did an awesome job with very little resources:
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Post by outbackrockkai on Jul 12, 2020 2:00:00 GMT -5
Thats NIK and ERICD ! Yap, good point with the shaft size. At first I planned on getting a 1" shaft but over here in Germany everything is calculated in the metric system so it's a pain in the ass to get the shaft, bearings, belt wheel etc. and the company I've ordered the wheels with told me straight away, that they give a set of spacers for free to every wheel. Received the wheels a couple of days ago and the spacers look good acoording to the measurements but didn't receive the precious metal shaft yet so I can let you know more when everything is here.
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Post by outbackrockkai on Jul 12, 2020 2:04:22 GMT -5
I've ordered some screw on shaft collars in precious steel but will try to get the ones you've mentioned as well and give it a try I think.
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Post by outbackrockkai on Jul 12, 2020 2:09:10 GMT -5
I've ordered the shaft already and it'll have an 10mm inner thread on both sides. Will try to get a polishing wheel that fits.
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Post by outbackrockkai on Jul 12, 2020 2:12:47 GMT -5
Here you go. This guy did an awesome job with very little resources:
That looks nice! Thanks for linking this. I'll try to get some pictures together as soon as I have the shaft and better ideas how it's gonna look at the end. I was also a bit worried about the wobbling but a friend of mine who's an engineer told me I shouldn't worry about that to much hope he's right at the end. fingers crossed.
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