Hello there!
I'm new to this blog, but thought I could throw something out to get some help.
I've built a couple of tonearms as a hobby, don't think there necessarily the greatest, they used a pinched ball bearing system using cup point set screws, but I want to use multiple ball bearings.
This is the first one I built 3 years ago:
PGE Homebuilt Tonearm - YouTube
Does anybody know a good supplier of very small bearings? The smallest I can get where I live are 1/4"outside 1/8" inside, there small but still mean the gymbal must be quite large to house them.
Or has anybody experimented with making their own bearings from scratch?
Patrick
I'm new to this blog, but thought I could throw something out to get some help.
I've built a couple of tonearms as a hobby, don't think there necessarily the greatest, they used a pinched ball bearing system using cup point set screws, but I want to use multiple ball bearings.
This is the first one I built 3 years ago:
PGE Homebuilt Tonearm - YouTube
Does anybody know a good supplier of very small bearings? The smallest I can get where I live are 1/4"outside 1/8" inside, there small but still mean the gymbal must be quite large to house them.
Or has anybody experimented with making their own bearings from scratch?
Patrick
Jewel Bearings
Jewel Bearings | Swiss Jewel Company
Most high end gimbal type tonearms use these. You may be able to scavenge some from old analog kilowatt-hour meters.
John
Jewel Bearings | Swiss Jewel Company
Most high end gimbal type tonearms use these. You may be able to scavenge some from old analog kilowatt-hour meters.
John
I've been working on the table slowly. Got a large piece of 11 ply board to use as the base. But I still need to do quite a bit. I'm not sure at what radius the arm must mount yet, but I haven't decided on a total arm length yet. Also actually have to write the program that runs the speed control.
I've noticed that a lot of tables (well at least the ones I've taken apart) use bushings to support the platters. Is this because there is a problem with angular contact or thrust bearings? I've always seen then as superior.
I've noticed that a lot of tables (well at least the ones I've taken apart) use bushings to support the platters. Is this because there is a problem with angular contact or thrust bearings? I've always seen then as superior.
Assuming you are talking about the platter main bearing - the issue revolves around very low frequency noise - caged ball bearings are much noisier than good vertical sleeve bearings with a single small ball running on a thrust plate. Better still of course is the air bearing - might be worth checking out.
I've never actually seen a gimbal (aka Cardanic) arm that uses jewel bearings and I wouldn't have thought they'd take the required loads : if you look at the load ratings on those jewel bearings they're very very small.
Everything I've pulled apart has used pivot ball bearings such as these from NSK Micro. To see the sizes you need to click on " Catalogue PDF mm Download" on the right side.
I've tried to purchase these in Australia with no luck - eveidently the local NSK distributor doesn't stock them. I've also asked Boca Bearing in the States, no answer yet. I used to know someone who worked in the car biz in Tokyo, I might ask him if he can find them.
I'm after BCF9 and BCF6 with the intention of substituting Si3N4 balls before use. Maybe if we get a group buy together we can get some traction with one of the distributors.
Everything I've pulled apart has used pivot ball bearings such as these from NSK Micro. To see the sizes you need to click on " Catalogue PDF mm Download" on the right side.
I've tried to purchase these in Australia with no luck - eveidently the local NSK distributor doesn't stock them. I've also asked Boca Bearing in the States, no answer yet. I used to know someone who worked in the car biz in Tokyo, I might ask him if he can find them.
I'm after BCF9 and BCF6 with the intention of substituting Si3N4 balls before use. Maybe if we get a group buy together we can get some traction with one of the distributors.
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@ Mark
yeah, that style of needle into concave race is the most common I've seen to. I'm guessing the jeweled bearings in arms are generally much larger than what is considered a 'common' jewel bearing. I've only seen jewel bearings from watch mechanisms, but I'm sure there are large variations around. The ones shown in the link posted by jlsem above, seem quite large indeed.
The BCF9 is very similar in principle to the bearings I'm using on the latest creation, except the bearing is complete, making the cone a non-bearing surface, and is actually just a 4mm cone-point set screw.
This is someones picture of them,
http://www.vxb.com/ball-bearings-images/fr133zz-1.jpg
I'm gonna try and think of a way to make these bearings since 1mm balls are easy to get by the 1000's online. but I like the idea of creating a order group for those micro nsk's. they look like the proper thing.
@ kevinkr
hmmm, that's what I thought, I like the air bearing idea. Gonna have to get some practice if I'm gonna make some bushings. Thanks! something else to look into.
yeah, that style of needle into concave race is the most common I've seen to. I'm guessing the jeweled bearings in arms are generally much larger than what is considered a 'common' jewel bearing. I've only seen jewel bearings from watch mechanisms, but I'm sure there are large variations around. The ones shown in the link posted by jlsem above, seem quite large indeed.
The BCF9 is very similar in principle to the bearings I'm using on the latest creation, except the bearing is complete, making the cone a non-bearing surface, and is actually just a 4mm cone-point set screw.
This is someones picture of them,
http://www.vxb.com/ball-bearings-images/fr133zz-1.jpg
I'm gonna try and think of a way to make these bearings since 1mm balls are easy to get by the 1000's online. but I like the idea of creating a order group for those micro nsk's. they look like the proper thing.
@ kevinkr
hmmm, that's what I thought, I like the air bearing idea. Gonna have to get some practice if I'm gonna make some bushings. Thanks! something else to look into.
@ vinylkid58
Well angular contact, so not plain journal ball bearings, but without a cage, versus a bushing with a single thrust ball at the top of the inner bushing shaft I've seen some ceramic bearing examples that are in 10mm ID range that have amazing reviews for thier smoothness. I don't think there are any caged example when the bearings become as small as is required for a tonearm. But then I've only been using cartridge bearings. In my experience a bearing is only caged to make rebuilding easier.
I can see how a caged bearing would cause trouble in smoothness, as the cage is relativly free to float and click about.
Well angular contact, so not plain journal ball bearings, but without a cage, versus a bushing with a single thrust ball at the top of the inner bushing shaft I've seen some ceramic bearing examples that are in 10mm ID range that have amazing reviews for thier smoothness. I don't think there are any caged example when the bearings become as small as is required for a tonearm. But then I've only been using cartridge bearings. In my experience a bearing is only caged to make rebuilding easier.
I can see how a caged bearing would cause trouble in smoothness, as the cage is relativly free to float and click about.
I can see your arrangement working for the vertical* bearing at the cost of much higher starting torque due to the larger minimal contact circle.
For the horizontal* bearing you'll run into problems - normal radial bearings have a very low maximal axial thrust load and I haven't been able to find any angular contact bearings less than 10 mm ID.
One way to get around this would be a single point thrust bearing on the bottom to take the main load combined with preloaded radial bearings for stability.
BTW check the grade of any balls you buy online - you want at least grade 25, 10 is preferable. If your vendor can't tell you the grade walk away.
*Terminology as used here: vertical bearing allows vertical movement, horizontal allows horizontal.
Years ago I spec'd ABEC-9 Barden bearings for a fishing reel application, and thought at the time they would make fine vertical bearings for a conventional tonearm. They were basic number SR168 (.375"OD x .250" ID x .125" deep). I have an old Linn arm that looks like a candidate for these.
jeff
@ Mark
Yeah, I've been wondering about the horizontal bearings. The bearings I have are apparently have a contact angle of about 10 degrees or so. They do bind up if the set screw that holds them in place is too tight, but it isn't a nice progressive bind that one would expect from a 'over preloaded' bearing, they just grab stiff.
This makes me think that the 60 degree contact angle of those needle into cup bearings are a must.
I've come up with a small experiment that I performed on a Grace tonearm and the tonearm I've made with the 10 degree contact flanged ball bearings. The experiment is to see how long it would take the frictional forces of the bearings to eat away at the rotational inertia of the tonearm swinging in a vertical plane. The duration of time required for the arm to stop oscillating will be a measure of it's bearings performance. Of coarse weights are attached to the arms to make there respective COG and moments on inertia the same.
Lets just say the one I made stopped in about 1/2 the time the Grace did.
I must admit I wasn't paying enough attention When I purchased the bearings to get a grade of bearing, I know they were the best the shop could get at the time. I'm starting to feel like there not as good as I thought they were when I bought them haha.
I'm gonna look around for making my own, and post if I have any success.
@jeff
I just looked up Linn on google, I'm afraid I have never heard of that name before, but they look impressive!
Yeah, I've been wondering about the horizontal bearings. The bearings I have are apparently have a contact angle of about 10 degrees or so. They do bind up if the set screw that holds them in place is too tight, but it isn't a nice progressive bind that one would expect from a 'over preloaded' bearing, they just grab stiff.
This makes me think that the 60 degree contact angle of those needle into cup bearings are a must.
I've come up with a small experiment that I performed on a Grace tonearm and the tonearm I've made with the 10 degree contact flanged ball bearings. The experiment is to see how long it would take the frictional forces of the bearings to eat away at the rotational inertia of the tonearm swinging in a vertical plane. The duration of time required for the arm to stop oscillating will be a measure of it's bearings performance. Of coarse weights are attached to the arms to make there respective COG and moments on inertia the same.
Lets just say the one I made stopped in about 1/2 the time the Grace did.
I must admit I wasn't paying enough attention When I purchased the bearings to get a grade of bearing, I know they were the best the shop could get at the time. I'm starting to feel like there not as good as I thought they were when I bought them haha.
I'm gonna look around for making my own, and post if I have any success.
@jeff
I just looked up Linn on google, I'm afraid I have never heard of that name before, but they look impressive!
This tonearm came out in 1976 and has a gimbal that uses ruby ball bearings. I doubt any current tonearm can match its low coefficient of friction. It's still fairly sought after today and cost $600 when it was introduced, which is about $2400 today.
Technics EPA-100 on thevintageknob.org
John
Technics EPA-100 on thevintageknob.org
John
The BCF series bearings are open allowing easy substtution of balls.
As I said before, I'll be using Si3N4 balls which reduce friction to around the same level as Al203 but have much better fracture toughness. Since these are going into a modified DV 505 I need the load carrying capacity - these suckers are heavy.
As I said before, I'll be using Si3N4 balls which reduce friction to around the same level as Al203 but have much better fracture toughness. Since these are going into a modified DV 505 I need the load carrying capacity - these suckers are heavy.
smallparts.com
Sapphire Vee Jewel Bearing .0469" / .0472" OD , Angle 75 / 85 Degrees , Thickness .0374" / .0374" , Vee Depth .0138" / .0177"
Price $12.09
Sapphire Vee Jewel Bearing .0469" / .0472" OD , Angle 75 / 85 Degrees , Thickness .0374" / .0374" , Vee Depth .0138" / .0177"
Price $12.09
Radius = .002" / .0033" so appropriate tip radius for the matching pivot is .001".
Using a typical bearing max pressure of 4 GPa* the maximal tip load by Hertzian contact theory is 10mN which is .001 kgF (eg 1 gram). OK for meter movements.
* Likely to be generous, the tips they sell are stainless and I know of no stainless steel which will handle 4 GPa.
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