Lapidaryforum.net
Gadgets, Gizmos, and Dohickeys => Fixing, Modifying and Refurbishing your Lapidary Equipment => Topic started by: cabomoon on January 19, 2019, 05:35:29 PM
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Hello
With my new and growing interest in lapidary, I bought a used combination unit made by Powr Kraft. I can't find the exact machine online anywhere, much less a manual. Closest thing I found was a couple pictures of a Gem Making Combination unit model TSH-2684A that sold in the past.
What I am trying to do is replace a grinding wheel on it, but I can't seem to figure out how to do this. I will eventually need to change the blade too. Was looking for information on my unit, maybe an old user manual, or any guidance for a Newbie, that anyone can offer.
Thanks in advance for your help. See picture of the unit attached.
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The main thing you need to know is that you probably have left hand (reverse from normal) on the left side of the machine. Thus you turn the nut clockwise to loosen it and counterclockwise to tighten. It may be tight due to age, butk when you reinstall it don't overtighten, its inclined to tighten as the machine runs. Getting off the outside wheels should be easy, saving all bushings that might be needed to make the new wheel (s) have the correct spacing and centered on the shaft. Any wheel on the inside of the bearing may require removal of the bearing and I'd advise help on that if you don't immediately understand the problems. Of course the nut on the blade should be normal threading if its on the right side of the blade (machine). I hope this helps. Manuals are not really necessary but reading a good book on lapidary may make you more comfortable with machine care and feeding.
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BTW I have the strange feeling that I'm looking at the back of the machine based on the shape of the hood opening over the wheels. But . . . your saw seems to be facing the correct way (i.e. toward the photographer). Is it possible that someone reversed the shield or the saw for unknown reasons? For some reason, I'm used to seeing saws on the left side of combos and wheels on the right. Think it over and if in doubt ask a friend. The wheels and saw should turn down when running and you are facing the machine.
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In this case, both wheels are between the bearings. It is assembled correctly. If you are not familiar with bearing removal then as Peruano suggested you should enlist the help of someone who has done it and has the proper tools. The machine will require complete disassembly for the task. I would definitely consider diamond wheels for this so you don't have to do it often.
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Thank you both for the fast response!
I looked again and it is threaded as you suggest, that makes part of this task easier. Based on the suggestions you have for the bearings, I will be more patient and try to find someone to help me with that.
I have a feeling that this machine is from the 40s or maybe 50s. It is definitely oriented properly in the pictures, the top back is completely closed off and screws into the base.
Removing the plate on the end is not clear either. I assume it will have to come off to get the wheels off. It looked like a hex nut held it on, but a closer look shows it is more of a pin. Should the arbor disconnect at the threads to allow for the wheels to slide off. Or will the plate at the end need to be removed to allow this?
Thanks again!!!
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The polishing plate should be the first thing removed. I have never seen one that was not threaded onto the shaft, but anything can happen. On the left end, the thread would be left hand. Try holding the pulley and see if it won't just unscrew.
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I have a beacon star that has the polishing plate that slides on the end of the shaft and secured only be a set screw. You can spin it all day long, but until that set screw is loosened, its futile.
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Thanks Peruano,
I think this is a similar design. I need to move the polishing plate, and then deal with the bearing before I can remove and replace the wheel. I think there is a roll pin holding it on. I am not familiar with this type of stuff at all. I will see if I can post a close up picture.
Any thoughts are appreciated!
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I hope this helps explain, thanks!
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Yes, just slip the appropriate allen wrench in that set screw and loosen it. You still may need to use some gentle force to get it to slide off but a bit of penetrating oil and an overnight pause may help. If you can get it to spin on the shaft that should loosen it a bit as well.
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Thanks! I will work on it more today, I am limited to working on this over weekends right now. I will get some oil on it, but the fastener I highlighted is not a hex nut. This is what is hanging me up. Do you think it could be a pin that I need to hammer out of there and then replace? I am hoping some oil solves the problem. I will keep at it, thanks agin!!!!
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It is very unlikely that is a roll pin since it sees torque. Roll pins have very little shear strength. Check the diameter on each end of the hole (assuming it is a through hole). If one end is bigger than the other then you can assume a taper pin. Punch it out from the smaller end. Far more likely though is that it really is a set screw. Clean it out as best you can and see what you can find. Some older set screws were slotted.
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I downloaded your pic and lightened and zoomed in and it definitely looks like a set screw. I can see the angles on the inside forming the hex. Are they just worn badly or maybe have you tried both US and Metric Allens? Cabomoon I also noticed your text saying it is not a hexnut. It is an internal hex and not a nut and this requires an allen wrench to unscrew.
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Here is the little bugger. Just tapped it out after showing it to a friend. Hope I can put it back after figuring out how to get these bearings off. While I wish this was already done, I recognize the value of the process. Thanks to everyone for your input!!!
On to the bearings....
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Wow guess I was way off, sure looked like hex walls on blowing up the pic, still does when I look back at it. Grats on getting it out.
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It makes sense in retrospective. Look at the wear around the hole in the hub of the polishing plate. Its worn laterally and far from round in all dimensions. I might be tempted to drill a new hole on another side of the hub and tap it with a set screw. Then again I might leave it alone if it seems tight on the shaft.
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Who'd a thunk. I would have expected a dressing down if I ever designed anything with a roll pin in that kind of application. But in small specialist machines, anything can happen. Glad you were able to solve the problem.
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I am joining this thread late but love to see the old school machinery produced back in the day. You look to have acquired a nice little unit. Good luck on the updating process, it is very much a learning process but most of the solutions, once you determine them, turn out to be really quite simple. Have fun with it as well.
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UPDATE: I got the bearings off and after a couple attempts, pieced everything back together. Thanks to everyone who helped guide me along the way. This weekend I was able to figure out a gravity fed drip system to get water on the wheels, which seems to be easier to control than the pump that came with the machine, and give it a try. I will post a picture of two when I have something finished up.
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congratulations. Its always good to get something back together and find that it works. Gravity feed works fine; it makes you stop once in awhile to refill the source container and in my shop for the winter, it allows me to add hot water. If you find you are leaving a stone dust streak on your wheels, its a sign your are not using enough water; otherwise you are fine.