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Thread: Wire wheel safety
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6th Jul 2020, 01:08 AM #16
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6th Jul 2020, 01:41 AM #17
Hi Mal, Guys,
Yes I agree with your comments about the centrifugal switch in the starting circuit. You would have to test your particular motor to ensure that you couldn't run it or load it enough for the switch to drop out at low speeds. You would also need to make sure that you couldn't try to start it at a low speed either.
They seem to open the CF switch at about 80% of nominal speed and close at around 50% of nominal running speed. That would be about 2300 rpm before it opens. I've had a 1Hp single phase induction motor running at 75Hz about 4000 rpm, but it got hot a lot more quickly. Split Phase, capacitor start and run motors like they use on shower pumps do a lot better.Best Regards:
Baron J.
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6th Jul 2020, 09:01 AM #18Member: Blue and white apron brigade
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I realise there are thousands of existing SP motors around that could use speed control but in an interesting discussion I had recently with my cousin, who makes electric motors, many with built in VFDs, he reckons in terms of new motors its just not worth messing about with SP motors and sees 3P motors with VFDs eventually replacing SP motors in many applications. One of the drivers for this is stiffer EU requirements for energy efficiency and he is required to make all his motors more and more energy efficient. I guess millions of small SP motor operating at say 75% versus say 80% adds up to a lot of Watts. He says SP motors will eventually become the incandescent light globe of motors.
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6th Jul 2020, 10:58 AM #19Diamond Member
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As a matter of interest, one of the Australian electronics mags some years ago published a design for a single phase VFD to suit swimming pool pump motors. The idea was to save power charges as the pump didn't need to run full bore all the time, and the payback period was short enough to make it worthwhile. The designers were quite specific that this VFD was only for motors with no start winding switches, and if I was home at the moment I would be able to include more details as I would have the Magazine and could include a photo of the specs and design synopsis from it. I would not be surprised if current Jaycar catalogues still had kit details, if not some of the older ones certainly do. When I get home in a few days I can dig up more details if anyone is interested.
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6th Jul 2020, 05:23 PM #20
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6th Jul 2020, 05:31 PM #21
Hi Bob,
I tend to agree with your cousin, a lot of the motors that I'm seeing today tend to be three phase VFD driven and BLDC ones that don't have field coils, so much less copper in them. Though a couple that I've taken apart recently had aluminium windings in them, no copper at all.Best Regards:
Baron J.
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6th Jul 2020, 10:02 PM #22Diamond Member
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1) Another way is to use different machines. I use 1.25" wire brushes in a Dremel to clean up rusty old drill flutes.
I have also been slowly collecting a few different old grinders for just this purpose. A weak little 5" Black & Decker for light polishing, a 6" with a nylon+grit wheel for de-rusting, and an 8" with an inch wide wire wheel for cleaning large threads, taps, et c.
2) In terms of safety, I always try to stand beside the grinder, so the ejected bits of wire do not end up in my hands/arms/chest/face.
(I also usually wear gloves, but that is more to limit grit insertion than to stop high-speed hypodermics)
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7th Jul 2020, 09:17 AM #23Member: Blue and white apron brigade
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7th Jul 2020, 04:51 PM #24
Hi Bob, Guys,
These Scotchbrite wire wheels in my opinion are much safer and nicer to use than a steel wire wheel.
scotch-britetm-radial-bristle-brush-ta.jpgBest Regards:
Baron J.
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7th Jul 2020, 11:58 PM #25
wheel side
Using the side of the wheel is considered to be dangerous by many . I tried a technique that seems to be effective. I turn the grinder on and as the wheel is gaining RPM's , turn it off again I use the side of the wheel for a light touch up on a HSS lathe tool. The timing takes a little getting used to but after a while the method is good .
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8th Jul 2020, 02:56 AM #26
Hi Morrisman, Guys,
For thin wheels I would agree ! However most DE grinders have wheels 3/4" to 1" inch thick, unless you have replaced them with thinner ones, for the amount of touch up grinding that an HSS lathe tool takes, I'm of the opinion that it matters little. There is more wear and tear on the motor and its components switching it on and off like you suggest.
Anyway if you are shaping a piece of HSS for some purpose, you would use the face edge of the coarse wheel !Best Regards:
Baron J.
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8th Jul 2020, 09:58 AM #27Member: Blue and white apron brigade
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I'm a big fan of 6 or 8 fold Scotchbrite wheels which can tackle a wide area in one pass.
Plus the folds can get down inside grooves and gaps.
This is an 8 fold wheel I made by combing from 2, 4 fold wheels.
Yes, on assembly it is uneven but it wears flat fairly quickly
IMG_3389p.jpg
They cost a fair bit and only last me for about 2 years then it gets too small for me but SWMOB will use it for a couple of years after that.
For thread like gaps a wire wheel is hard to beat.
Depends on the wheel, if the abrasive is fixed to the outside if a steel wheel (as in diamond or CBN wheels) then this is not a problem.
Screen Shot 2020-07-08 at 6.36.27 am.png
I have two of these wheels plus a diamond wheel and no longer have any standard abrasive wheels in my shed. If I want to do some heavy grinding I use 40 grit on a belt sander.
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8th Jul 2020, 12:56 PM #28Most Valued Member
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So those scotchbrite wheels come with 4 layers Bob?
Are they genuine 3M ones, or just generics?
Steve
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8th Jul 2020, 02:59 PM #29Member: Blue and white apron brigade
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These are generic but I have bought 3Ms when I can find them but there's not many available that I have been able to find lately.
I like to use 8" as they are the best value for available surface are.
Every time I go to buy them the availability, size and numbers of layers seems to change.
Sometimes I get a pair of 3 or layers and combine them.
Sometimes if I can find them I get a 6 layer.
Usually I order from this site
https://abtoolsonline.com/search-res...chbrite&page=1
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10th Jul 2020, 09:24 AM #30Diamond Member
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Well here you are John, BobL and anyone else interested, I finally found it. Silicon Chip still has a presence, and a website where reprints of past articles from their magazine and also several other now defunct Ausie electronics mags as well. (Electronics Today, Electronics Australia and their previous masthead, Radio, Television and Hobbies.) I will put a link up for anyone wanting to get more info, but here are a few pics from the magazine to provide a synopsis of the article.
Silicon Chip Project Index - Silicon Chip Online Go down to section 10, Mains Power control to see the reference to this project. It appears that Altronics still supply kits for this project, but they are a bit spendy considering the low cost of commercial VFDs these days. https://www.altronics.com.au/p/k6032...ontroller-kit/
I have tried unsuccessfully to add some photos of the introductory pages to the Silicon Chip project, and will have another try tonight, but I am otherwise occupied today and don't have time to fiddle with computers and finicky forum software.
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