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Unread 04-10-2010, 22:04
sneakyimp sneakyimp is offline
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Re: lazy susan type bearing? thrust bearing?

J@GMFlint, I tried one of those 6" square lazy susan bearings that I bought at True Value hardware and i really liked the lateral stability and simplicity of it, but It doesn't spin as easily as I'd like and it's far too noisy. Those large-diamter ring-style turntables look pretty interesting.

Dick, I tried finding the sleeve bearings / bushings at my local hardware store and they didn't have any. Home Depot didn't have any bearings at all as far as I could tell so I went to Grainger Industrial supply. Thanks for the link on those bushings/bronze bearings. Those prices look good and I'll probably be buying some here shortly.

I broke down and bought two 2-bolt flange mount ball bearings and a 5" aluminum pulley with 1/2" bore.

jspatz1, thanks so much for the advice about the thrust bearings. I kind of thought they might work that way. The problem I'm having is that only a few of the flange bearings and pillow-block bearings I've seen have an extended inner race -- I worry about the lower thrust washer rubbing on the outer race of my flange/pillow block bearing and causing friction. Of course, it is a thrust bearing? Not really sure how it works. I suppose I'll have to just watch the dimensions carefully.

Thanks for the tip about the andymark hubs. I had seen some on a couple of the robotics sites I stumbled across but the lack of a set screw looks like trouble. I'm not really sure how I would couple these to the shaft. I'm not using keyed shafting or hex shafting.

Thanks for the tip about shielded/sealed bearings and yes I'm looking for very low friction. The bearings I bought at Grainger (which appear to be sealed) seem pretty stiff and the inner diameter is too small to fit the 1/2" steel tube I bought. They were also fairly pricey (@$16) so I think I might take them back and get some flanged bearings (and a thrust bearing!) instead.

The 5" pulley I bought looks like it'll make a nice hub. It's nice and wide and I've drilled 4 holes in it. I'm a bit concerned about the shape of it though as the part containing the set screw is precisely the shape that would scrap against the outer race of a bearing [see attached image].

Truly excellent suggestion about coupling to the speed reducer. I was considering trying to have the shaft machined to 6mm at the end. I'll figure that out once I've costed out the options. Thanks also for bushing suggestion, I'll probably get one of those recommended by Dick.

Tom, thanks for the drawing! And thanks for the suggestions about pulleys and belts. I had originally looked into that and decided that it was going to be difficult to get spin ratios high enough. I probably need 20 or 50 to 1 unless I want my entire song playing several times per second. That's pretty tough with pulleys.

Thanks for being sensitive to my inability to key the hubs and bearings. I'm going to look for some flanged bearings tonite and see what I can find.

I'll also be looking for shafting that will actually fit into the tolerances I get from grainger. Is it safe to assume their 1/2" shafts will fit into their 1/2" bearings or do manufacturers expect customers to machine these parts after purchase?

EDIT: Forgot to attach picture of my hub. Note the set screw bulge and the holes I drilled.
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Last edited by sneakyimp : 05-10-2010 at 18:47. Reason: forgot to attach pulley hub image
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Unread 04-10-2010, 22:05
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Re: lazy susan type bearing? thrust bearing?

BTW, the Dayton flange mount bearings from Grainger are SO QUIET. I'm kind of excited about using a good bearing. Really hoping for some really quiet, sturdy, low friction results. I'll be using 1/2 inch shafting so I expect it will be pretty sturdy.
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Unread 04-10-2010, 22:11
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Re: lazy susan type bearing? thrust bearing?

You could use epoxy to attatch the shaft to the hub.
Just don't get any anywhere you don't want it. (like on/in bearings/bushings or any part of the shaft that thet passes through these.)
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Unread 04-10-2010, 22:33
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Re: lazy susan type bearing? thrust bearing?

Don't worry if the bottom thrust washer contacts the other bearing. It is a bearing, eliminating this friction is its job. (If you are still trying to picture how the thrust bearing works, it is a 3-piece sandwich...washer - rollercage - washer. They are not connected, just aligned together by the shaft.) You should however make sure the bottom thrust washer is relatively well supported, not just by its very inner or very outer edge. If in doubt, add a another plain washer between the bearings.

A tapped setscrew hole is very easily added to any hub or coupling you encounter that needs one. A tap at the hardware store is < $5, and you'll have it for next time. If you need a lesson on tapped holes, we could do that.
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Unread 04-10-2010, 22:52
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Re: lazy susan type bearing? thrust bearing?

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Originally Posted by sneakyimp View Post
[b] The bearings I bought at Grainger (which appear to be sealed) seem pretty stiff and the inner diameter is too small to fit the 1/2" steel tube I bought.
I'll also be looking for shafting that will actually fit into the tolerances I get from grainger. Is it safe to assume their 1/2" shafts will fit into their 1/2" bearings or do manufacturers expect customers to machine these parts after purchase?
You will find that plain steel or aluminum rod or tubing will not fit in a bearing of the same nominal size, such as "1/2 inch." Bearing bores are made to very close tolerance, and plain rod or tubing is not, and is usually slightly oversize or out-of-round. If you are only inserting the rod into the bearing a short distance, you can sometimes grind or sand down the diameter until it fits. Not pretty. To get a shaft that fits the bearings you will need true "shafting". It is made to close tolerance and is slightly undersize. If you buy stock called "shafting", "machine shafting", "ground shaft" or "precision shaft", it should fit your bearing. Grainger should have some, it will cost more than rod or tubing.
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Unread 05-10-2010, 01:03
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Re: lazy susan type bearing? thrust bearing?

Using anything other than precision ground from mcmaster will result in getting bar that is over your required dimension and it will NOT fit (we had this experience the past year). The precision ground is a little more expensive, but will fit perfectively.

On another note, imagine my chagrin to discover that the pages I thought I was linking to linked to only the intro page and not the product I had looked up. Grumble. Do a search at Mcmaster for each one of these.

Ball Bearing:6383K241
Thrust Bearing:6655K17
Precision ground 3 foot 1/2 inch dia. bar: 9062K313

Last edited by Tom Line : 05-10-2010 at 01:13.
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Unread 05-10-2010, 10:30
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Re: lazy susan type bearing? thrust bearing?

You can get bronze thrust washers which can also be used as spacers ;

http://www1.mscdirect.com/CGI/NNPDFF?PMPAGE=3743

Drill rod is a cheap source of precision ground stock, though you still have to watch the tolerances. ENCO has drill rod on sale quite often.
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Unread 05-10-2010, 12:54
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Re: lazy susan type bearing? thrust bearing?

Despite all this discussion of ball bearings, thrust bearings, and pillow blocks, I would have to say that I agree with Dick's preference for plain bronze bushings for this job. Much cheaper, much simpler, and adequate for the light loads in this application. A simple flanged bronze bushing at the top, maybe an additional bronze washer under the hub, and a bronze sleeve bushing and the bottom. Would last a long time, and could be replaced several times for the cost of bearings and pillow blocks.

Also not mentioned yet....if this is an outdoor application, steel bearings and ground shafting will quickly rust out in the weather. Some stainless shafting through bronze bushings will work well and be fairly weather resistant.
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Unread 05-10-2010, 16:52
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Re: lazy susan type bearing? thrust bearing?

Amazing advice guys. Thanks.

I'm definitely going to try Dick's suggestion with oil-impregnated bronze sleeve and thrust bearings. They are just too cheap not to try and the argument about corrosion is a really compelling one. I also expect they'll be very quiet.

I can also get the flanged ball bearing and a thrust ball bearing for under $10 so it's definitely worth getting those too for comparison.

Dick's also right about enco's drill rods being cheap. They have product #409-0029 which is under $6 for a 3-foot length. Tolerances are +/-.001 so I'm not sure if they would fit with some of the bearings/bushings I linked above. Those tolerances are better than the +/-.002 that McMaster lists for #86705k411 Wear-resistant stainless steel (type 410, $6.50, 12" long) but it'd be nice to order everything from one place to maybe save on shipping. Plus I don't need the full 3' length. Any thoughts on whether I might get away with these tolerances for the bearings I plan to use?

If the shaft tolerances are important, I might forego the stainless steel shafting for the 12" Unhardened Precision Steel Drive Shaft #1346K17 (about $7). OR I might splurge for the 12" Easy-to-Machine Stainless Steel (Type 303) Precision Ground #88915K221 (about $13). The extra $6 is pretty cheap insurance to get something that is
* precision tolerance
* stainless steel
* easily machined

Since I'm using set screws I was wondering if I should maybe use a D-profile shaft (round shaft with one flat side). The have a 12" Type 303 Stainless Steel #8632T87 for $16.40 and a 12" AISI 1045 Steel #8632T7 for $9.27.

jspatz, Thanks for the additional info on the thrust bearing. I know how they work, I'm just a bit concerned about the diameter of the lower thrust washer and the shape and diameter of the races of the flanged ball bearing upon which it rests. I'm guessing it's bad if the lower thrust washer contacts the outer race of the flanged bearing. And what do you mean about a tapped set screw hole? Am I to understand that a local hardware store might drill a threaded hole in some arbitrary hub for $5 so I can put a set screw in it? That would be awesome as then I'd only need to find some hub stock.

It's beginning to look like I can get all my bearings, bushings, shafting, and shaft collars for under $30. I hope to place an order tonight or tomorrow on this. I hope you guys might weigh in on the shafting before I do. Is stainless important? Is drill rod enough or do I need precision shafting? Should I get D-profile or regular shafting?

THANKS so much. I'm getting pumped for this.
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Unread 05-10-2010, 17:20
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Re: lazy susan type bearing? thrust bearing?

Don't worry about a D-shaped shaft. You can easily file or grind a flat spot where it matters.

As far as tolerances on the shaft and bearing, I'd say it's a crap-shoot. Getting pieces-parts from various sources is hit or miss and you may have to do some fitting.

Stainless may be a good idea if you want to leave this thing out in the weather. Do consider some makeshift baffles/seals to keep stuff from blowing onto/into the bearing surfaces.
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Unread 05-10-2010, 21:05
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Re: lazy susan type bearing? thrust bearing?

One nice thing about bronze bushings, if your shafting doesn't quite fit, you can easily ream it out with a drill for an working fit.

As Dick said about D-shaft...you only need a setscrew flat in one spot so just grind that in, or drill a small crater with a drill point. Doesn't need to be precise. With bronze bushings, it would be best not to have the edges of a D-shaft turning in your bushings.

On tapping a setscrew hole...what I meant was that you can buy a tap (small cutting tool that turns a drilled hole into a tapped hole) and drill and tap a setscrew hole yourself. Easily done with a drill and vicegrips. Don't let lack of setscrew hole keep you from using a part that is otherwise perfect, you can add it.

Regarding the thrust bearing contacting the race of the flanged bearing...you do NOT want the thrust bearing resting on the inner race of the ball bearing. This would mean that the ball bearing is supporting the weight of the system, and the thrust bearing is doing nothing. The whole point of the thrust bearing is to bear the weight and keep side-load off of the inner race of the bearing. You want the thrust bearing supported by a stationary surface. Add a big washer under it if necessary to make it rest on the outer race or housing.

Yes, drill rod is perfectly good enough if it is cheaper for you. Note the tolerance to be sure it will go in the bearing.

As to whether stainless is necessary, that only depends on the environment it will be in. If it is outside, ground steel will rust pretty quickly. If you really want to avoid the expense of stainless, you can try to wax, oil, or clear-coat the steel shaft, but that will be somewhat temporary. Plated shaft with a rust resistant surface is sometimes available, but I don't recall McMaster having it.
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Unread 06-10-2010, 01:55
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Re: lazy susan type bearing? thrust bearing?

If you go with bronze bushings, once you get everything installed make sure you break it in. Chuck up a drill to one end of the shaft and spin it full speed for 15-20 minutes. This serves to wear-in the bushings if everything isn't aligned just right. It's served us very well on the robotics team when we've used oilite bushings.
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Unread 06-10-2010, 17:12
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Re: lazy susan type bearing? thrust bearing?

Ordered the following yesterday:
2 x Sae 841 Bronze Flanged-sleeve Bearing For 1/2" Shaft Diameter, 3/4" Od, 3/4" Length (#6338K423)
1 x Steel Ball Bearing Flanged Open For 1/2" Shaft Dia, 1-1/8" Od, 7/16"w (#6383K234)
1 x Steel Thrust Ball Bearing Steel, For 1/2" Shaft Diameter, 15/16" Od (# 6655K17)
1 x Graphite Sae 841 Bronze Thrust Bearing For 1/2" Shaft Diameter, 1" Od, 1/8" Thick (#7447K7)
1 x Unhardened Precision Steel Drive Shaft 1/2" Od, 12" Length (#1346K17)
2 x Sintered Steel Set Screw Shaft Collar 1/2" Bore, 1" Outside Diameter, 7/16" Width (#6166K25)

Total, about $22. Everything but bushings should arrive today. Bushings tomorrow. VERY excited.
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Unread 06-10-2010, 19:56
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Re: lazy susan type bearing? thrust bearing?

Good deal! Can't beat the price. Which company did you order these from?
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Unread 06-10-2010, 20:41
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Re: lazy susan type bearing? thrust bearing?

Curious, what was the open bearing for?

Quote:
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Good deal! Can't beat the price. Which company did you order these from?
Part numbers look like McMaster to me.
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