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Thread: Poly-V step pulleys
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3rd June 2014, 06:59 PM #1
Poly-V step pulleys
Looking for some help please.
I am re-powering a wood lathe with a 3-ph motor and VFD, the original motor pulley is 14mm shaft, new motor is 3/4" shaft size, the old pulley doesn't have enough meat on it to bore it out, and besides it is only a 3 groove poly-V belt ( a bit light duty).
So, I need to source new pulleys, or make my own.
I want 3 steps, 5 groove belt, maximum diameter step 70mm.
Does anyone know somewhere I might be able to buy something to suit my needs ?
The other option is to turn my own, I have a metal lathe, so can probably do the job if I have to.
The questions I have here, are ,
1- what material would be best. The originals are aluminium, would mild steel be better ? I assume cast iron would be best, but I don't like my chances of getting any to suit around here.
2- Would it be best to grind a tool with the profile of one of the grooves and cut each groove separately ?
I will probably have more questions later if I decide to make my own, but any help now is much appreciated.Brad.
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3rd June 2014 06:59 PM # ADSGoogle Adsense Advertisement
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3rd June 2014, 07:31 PM #2Philomath in training
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Al should be fine.
Yes, grind one groove and index it across.
Michael
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3rd June 2014, 07:43 PM #3Mechanical Butcher
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When I priced some mass-produced poly-V pulleys, I decided to make my own in Al. It was delightfully easy to make a serviceable pulley.
I used the data in the attached jpg.
I didn't worry about the radii, just made sure there was clearance at root and crest.
Jordan
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3rd June 2014, 07:44 PM #4Chief Swarf Maker
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I had this exact problem a couple of days ago trying to repower my drill press (same sizes and all)
Easy fix...
http://youtu.be/rc43tyy_ZOs
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3rd June 2014, 08:10 PM #5
Thanks Michael, will have a look for some aluminium through the week.
Thanks Jordan. Did you grind your own tool ? Did you plunge cut, or set the angle on the compound , and cut to depth by advancing the compound ?
Thanks Andrew, thats a good idea, except I want to put a wider belt on the drive, I think the narrow 3-V belt will be a bit flimsy, otherwise that would be a good option.Brad.
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3rd June 2014, 08:14 PM #6Senior Member
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Oh, something ive got experience in!
I made up some 5J sheaves for my hercus lathe to replace the motor to layshaft belt arrangement as it comes from the factory. I have a 2hp single phase motor in my machine, but it spins at twice the rpm as the original, so it affected the speeds that the lathe would turn at. I did some work on designing a pair of two step sheaves, I ended up going with some 1018 (i believe, scrap bin diving, but the owner of the workshop reckoned thats what it was) stock for both sheaves, which I cut on a hercus 260.
I think steel was a bit ambitious. To cut the vees, I would plunge .2mm at a time, then wiggle either side by .1mm, recentred and repeat. Measurement was with a ground pin i had, 1.5mm dia, to the other flat opposite. It took a bit of fiddling to get a good shape on the tool so that chatter wasnt a massive problem, but my lathe isnt very rigid and, because of the original pulley / motor combo, i couldnt slow it down as much as id have liked. If I was to do it again, id go with alu plate, largely because itd suit my speeds already available. Cast would be great as well, but finding some could be tricky. Because of the dumpster stock I had to pick from, I was actually using seamless pipe for the sheave and a seperate piece of steel as a hub. I did get the required dimensions in the end, but i had to cut so so gently.
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3rd June 2014, 08:37 PM #7
Thanks Scotty, sounds a bit fiddly but if I can find some aluminium to do the job with, I will probably give it a go.
I have been doing bit of googling, you can buy carbide inserts made for the job. http://www.toolflo.com/cats/AUTOMOTIVE.pdf
Probably a bit costly for a one-off job though.Brad.
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3rd June 2014, 08:40 PM #8Senior Member
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I did notice those inserts in my travels. I imagine plunging that into steel on my poor little hercus would probably rip the compound slide clear off the machine.
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3rd June 2014, 09:24 PM #9Mechanical Butcher
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3rd June 2014, 09:32 PM #10
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3rd June 2014, 09:51 PM #11.
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My shed thread has some details about how I did mine.
The stuff on the lathe starts at post 239
Stuff specifically on the pulley etc is here
https://www.woodworkforums.com/showth...134670&page=22 Post 349
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3rd June 2014, 11:20 PM #12Cba
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[QUOTE=Ironwood;................................
The other option is to turn my own, I have a metal lathe, so can probably do the job if I have to.
The questions I have here, are ,
1- what material would be best. The originals are aluminium, would mild steel be better ? I assume cast iron would be best, but I don't like my chances of getting any to suit around here.
2- Would it be best to grind a tool with the profile of one of the grooves and cut each groove separately ?
I will probably have more questions later if I decide to make my own, but any help now is much appreciated.[/QUOTE]
1- Aluminum is much easier to cut and lighter (less inertia).
2- If you have a heavy industrial lathe, you could grind a form tool. If you have a light benchtop lathe a form tool will probably chatter too much. You need to grind a pointed tool that lets you turn each side of the Vee on its own setting the topslide to the appropriate angle.
By the way, many people making Polybelt pulleys, overlook the fact that the V-groove angle you need to cut depends on the diameter of the pulley (60 degrees for larger diameters, 62 and 64 degrees for smaller diameters)! If you want to know more, it is necessary to consult the Gates Website www.gates.com and register with them (they will not bombard you with advertising), then you click on “power transmission” and click on “drive design engineering” and “drive design manual online” and download the “Light Power and Precision Drive Design Manual”. Page 97 is the most important with the dimensions for the Polybelt grooves, but the following pages help immensely to design your particular drive.
gates.jpg
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4th June 2014, 07:23 AM #13
Thanks Bob, I found your thread when I did a search last night.
Thanks for that CBA. It seems there is a bit more to it than I first thought, but still do-able.
I am going to look into buying some pulleys first, as that is the easiest option for me, as long as the price is not exorbitant.
I own a small business, and in the current climate it requires me to work 7 days a week to keep it in the black, so spare time isnt something I have much of. So I have decided making them will be the last resort. It takes a lot of the pleasure out of doing things like this I am afraid.Brad.
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4th June 2014, 10:51 AM #14Mechanical Butcher
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Here's a photo of the pulleys I made, to drive an alternator fitted to an old motorbike.
Jordan
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4th June 2014, 03:05 PM #15
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