DIY turntable spindle bearing tutorial - diyAudio
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Old 18th February 2015, 07:35 PM   #1
giuz0 is offline giuz0  Italy
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Join Date: Dec 2011
Default DIY turntable spindle bearing tutorial

Hy everyone,

I would like to open a new tutorial for people like me who want to make his own diy turntable spindle bearing avoiding waste too much time on bed working experiments.

As a standard bearing I suggest the bearing of the following image

Click the image to open in full size.

A lot of thigs, can be customized from the diy'er, for example:
- design
- recirculating oil pump like the spindle of the image
- external geometry of the spindle housing
- choice of the material for the ball
- thrust pad (delrin PTFE for example)
- Plate weight between 3 and 15 kg

On the other hand, some point of the project is extremely important and fixed, like:

- materials to use (steel, bronze?)
- clearance-tolerance between the bore and the spindle for a perfect precise work
- grade of polishing the internal part of the bore and the spindle
- typeof oil
- other?

I think that a lot of diy'ers who have a medium lathe, are attracted to machining their own bearing, but is not easy to find all detailed information about this particular project.
Personally I find some intresting table like the following:

Click the image to open in full size.

And this

Click the image to open in full size.
But I'm unable to define which tolerance is optimal for my project

I also believe, that with chineese lathes (I have a small sieg and a bigger newton 25), is possible to turning a spindle precise in a 2-4/1000 of millimeter (between 2 or 4 um), so there is no reason to not try building a really good spindle.

Of course is extremely important to have precision reading instruments like external and internal micrometer, good and sharped tools, and a lot of patience.

As a starting example idea:

1- machining a 15.000 millimeters housing, (15.000 millimeters allow you to work and polishing the hole)

2- machining the spindle to the right diameter, but which is the right diameter?
14.960mm? 14.985mm? 14.990mm?


I hope some member of this forum will contribute to define the basics for this tricky work, I'm sure that a lot of undecided diy'er will start to machining his own super bearing system!

Thaks to all

Luis
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Old 18th February 2015, 10:03 PM   #2
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Wow, holding tolerances of that nature on a small chinese lathe (2 to 4 um) is unheard of. It would be challanging on a Hardinge or even my Monarch 10EE.
Anyway, as far as your spindle design is concerned I don't see any bearing material in your housing. I would press in bronze sleeves and hone or lap the bore to size. The spindle should be hardened and ground to size. Use the center on the end of your spindle where the ball goes so that after grinding it is concentric to the OD of the spindle.
It looks like your planning on running a steel shaft in a steel housing. Don't, it will gall up. Plain bearings work best if the materials are very different from one another. Hardened steel shaft running in a bronze bushing or even in a fine grade of cast iron works well. I would think that a running clearance of some where between 0.007 um to about 0.012 um should work well. I base this from building machinery and using a rule of thumb for plain bearings of 0.001/per inch of shaft diameter. I'm not used to working in the metric system so double check my calculations.

BillWojo
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Old 18th February 2015, 10:17 PM   #3
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GiuzO, take a look at a thread about a dozen post down from this one titled "Modern bearing engineering, a sad story" on how not to design a spindle bearing. Also if you can get your hands on a Pioneer PL-41 TT or one of it's variants, take a long hard look at the design of that. It's very well engineered. Study the materials and the surface finishes.

BillWojo
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Old 18th February 2015, 10:41 PM   #4
AVWERK is offline AVWERK  United States
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Centerless grinding and proper heat treating are the proper way to exact tolerances for the shaft.
Oilite bushings cannot be bored and honed, but bronze and brass can. But do you want to bore and hone? The oilite style bushing is much better and more difficult to get a proper tolerance, but doable

The spiral grooves are not necessary and reduce surface area. If you use proper machining an oil film is enough. Looks like the fill hole will keep it topped off anyway
You would be better off looking for a VPI bearing assembly that come up quite often on Ebay or Audiogon, if you can,t get proper linear dimensions on your own.

Regards
David

Last edited by AVWERK; 18th February 2015 at 10:43 PM. Reason: Spelling
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Old 18th February 2015, 11:06 PM   #5
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Quote:
Originally Posted by AVWERK View Post
Oilite bushings cannot be bored and honed, but bronze and brass can. But do you want to bore and hone? The oilite style bushing is much better and more difficult to get a proper tolerance, but doable
I've bored hundreds of oilite bushings, to .0002/.0004" clearance, manually. Easy peazy.

jeff
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Old 18th February 2015, 11:07 PM   #6
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AVWERK, the reason I would use a regular cylindrical grinder on the shaft is so the center drilled end would be supported by the center of the tailstock. This would place the center of the ball bearing in the center of the shaft. Centerless grinding is a mass production type of grinder and not suitable for this application.
As far as oilite bearings go, I would not use them in this application. Reaming them to size spears the surface and boring them to size leaves a lot of loose particles enbedded in the surface. I think something like Ammco 630 bronze would be the ticket. It's nice to machine to.
A small Sunnen hone is a joy to use and it's so easy to "split tenths". The OP would have to check around to find a shop that has the required mandrel size. Or since he has a lathe, go on ebay and get a mandrel, set of stones and a driver he can rig up in the lathe. Leave about 0.005" in the hole and check often. Use lots of oil for flushing. Doesn't take much skill to hold really tight tolerences. Sounds like a fun project.

BillWojo
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Old 19th February 2015, 06:09 AM   #7
lexx21 is offline lexx21  United States
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A friend of mine made his own turntable and for the bearing he used the head of a vhs vcr. It worked VERY well. Very cheap, no need to "machine" anything as that has already been done for you. You can pick up a vcr from a thrift shop for about 5 - 10 bucks.

Give it a try, it works great.
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Old 19th February 2015, 09:37 AM   #8
giuz0 is offline giuz0  Italy
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Thanks for your replies guys!

About chineese lathe (im)precision, I need to specify exactly what I meen, in fact is possible to reach tight tolerances, but only without moving the piece from the chuck, and once all the carriage screws are properly tighten.
I'm not a professional lathemaster, but from my little experience if you start and finish turning the piece without move it from the chuck is possible to reach a good precision.

Bill, I take a look to the thread you mentioned me, and sadly I have to confirm you that now I'm not sure to machining my own spindle.
Probably, even if the spindle and the housing are made with an unbelievable precision, there are lot of variants that can compromise the (supposed to be long) life of the bearing system.

At the moment I'm stuck with my turntable project, the arm is finished, both bases also, I only need to solve this "little" problem then I will be ready for painting.
I will not consider to buy expensive finished bearings, the goal of a diy'er when possible is to create a lot with less in a reasonable way, so I will check all the solutions.


I think this afternoon I will considering to disassemble my VCR and take a look on the vcr head :-)

Anyway, about this thread purpose, at this point will be interesting to hear someone that already built a good working spindle that is running from a certain amount of time

Thanks GG
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Old 19th February 2015, 11:03 AM   #9
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giuzO I never meant to discourage you. I think you have the required skills to make a very good if not great spindle bearing setup with some additional work. I can see that your skills on the lathe are very good and your 100% correct about doing everything you can in one chucking to keep concentricity in check. Just look at the other thread I pointed you to, That was an expensive TT and allready I see you have more skill than the maker of that TT.
Forget about VCR heads, I'm pretty sure it uses a rolling bearing element of some sort. A plain bearing is what you want to use. Since you have limited equipment to work with, lets look at what's avalable commercially. Precision ground drill rod is not expensive and is avalable in air, oil and water hardening. I'm not sure what you would call it over there but a common alloy would be 01 tool steel. This would give you a precision ground but machinable blank length of steel to work with. Over here it's commonly avalable in 18" and 36" lengths at a reasonable cost. Plenty of info on the net about how to harden it.
Bronze bearings can be pressed in and bored almost to size. Look on the net for how to make a split lap to finish it to size,
A great resource for machining help is the website Practicalmachinist.com
Keep us posted on your progress. I like where your going with this.

BillWojo
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Old 19th February 2015, 11:22 AM   #10
Hiten is offline Hiten  India
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How about some new materials ? For example 'Delrin' bushes. I don't know how Delrin and steel interact but idea is to deliberately have one material wear out sooner (with reference to steel) and design a turntable bearing in such a way that it can be easily replaced, say after one or two years or so.
Regards.
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