STD 305M main bearing question

snap, crackle and pop
Trio KD1033
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Re: STD 305M main bearing question

Post by Trio KD1033 » 26 Dec 2015 19:03

Ah! Great, thanks.
I'm probably going to try 3/16" first as that is the Rega size. Not the same bearing I know, but of comparable spindle size.

Andy

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Re: STD 305M main bearing question

Post by Trio KD1033 » 26 Dec 2015 19:17

Just tried quickly (couldn't resist) the 4.76mm (3/16") Rega ball in the STD and it didn't want to sit in the centre, despite coaxing. Also the spindle seemed too high in the housing. Perhaps it needs to be smaller than I thought. Also it caused there to be a lot of side to side play with the spindle. Mmm.
Andy

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Re: STD 305M main bearing question

Post by Copperhead » 26 Dec 2015 19:26

Trio KD1033 wrote:Ah! Great, thanks.
I'm probably going to try 3/16" first as that is the Rega size. Not the same bearing I know, but of comparable spindle size.

Andy
Whatever you put in there will be an improvement from the present arrangement. Smear a bit of grease around the ball and then fill the bearing with your chosen oil. You should be able to see whether the 3/16" sits in the concave tightly with your camera trick. I assume that slightly bigger is preferable to slightly smaller. The smaller one would "dance" about in the hole, making centering of the spindle uncertain.

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Re: STD 305M main bearing question

Post by Trio KD1033 » 26 Dec 2015 19:34

I think I'll order up a few sizes and report back.

Many thanks

Andy

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Re: STD 305M main bearing question

Post by Tonybro » 27 Dec 2015 16:10

OK, here's the inside of my spare 305S bearing.....

It 'looks' like there is a ball at the bottom but I don't think it is a ball bearing. I think there is a sealed ball at the bottom as the bottom of the bearing housing is covered in a semi-clear sealant with a circlip visible.

To me it looks like the bottom of the spindle sits on this raised area.
STD305S_BearingWell1.jpg
STD 305S Bearing Well (#1)
(106.29 KiB) Downloaded 194 times
STD305S_BearingWell2.jpg
STD 305S Bearing Well (#2)
(44.3 KiB) Downloaded 179 times
Excuse the pictures they were done on my phone and I've messed with the levels in Photoshop to make things visible.

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Re: STD 305M main bearing question

Post by Trio KD1033 » 27 Dec 2015 17:04

Tonybro wrote:OK, here's the inside of my spare 305S bearing.....

It 'looks' like there is a ball at the bottom but I don't think it is a ball bearing. I think there is a sealed ball at the bottom as the bottom of the bearing housing is covered in a semi-clear sealant with a circlip visible.

To me it looks like the bottom of the spindle sits on this raised area.
STD305S_BearingWell1.jpg
STD305S_BearingWell2.jpg
Excuse the pictures they were done on my phone and I've messed with the levels in Photoshop to make things visible.
Thanks for going to the trouble Tony!

Interestingly, it looks a lot more rounded and ball like than mine. My bearing also has the sealant and circlip at the base. Did you see my pictures near the beginning? Rather looks like something isn't right. I tried the rega ball in there and the spindle sat too high with the bottom of the spindle seemingly clear of it's support bush which resulted in bags of play.

Andy


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Re: STD 305M main bearing question

Post by Copperhead » 27 Dec 2015 18:31

The saga continues, that certainly looks like a mighty big ball! Could it be that there were two different designs?
Maybe the photograph is deceiving, but I can see a dimple in yours and a huge ball bearing in the other. Is there a dimple as far as you can tell? Seems a bit counter intuitive to assume that there would be such a big ball bearing sitting in a dimple on top of a domed surface. The dimple is either wear or a locating point, a ball bearing big enough to fill the well would not need a dimple to locate it.

Either there is no dimple, and I am misinterpreting the photo, or the big ball bearing is not as big as it looks in the first photo.

Measuring the distance from the top of the well to the top of the ball bearing, then comparing it to your's with the missing ball, would give you the ball's dimensions.

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Re: STD 305M main bearing question

Post by Trio KD1033 » 27 Dec 2015 18:48

Copperhead wrote:
The saga continues, that certainly looks like a mighty big ball! Could it be that there were two different designs?
Maybe the photograph is deceiving, but I can see a dimple in yours and a huge ball bearing in the other. Is there a dimple as far as you can tell? Seems a bit counter intuitive to assume that there would be such a big ball bearing sitting in a dimple on top of a domed surface. The dimple is either wear or a locating point, a ball bearing big enough to fill the well would not need a dimple to locate it.

Either there is no dimple, and I am misinterpreting the photo, or the big ball bearing is not as big as it looks in the first photo.

Measuring the distance from the top of the well to the top of the ball bearing, then comparing it to your's with the missing ball, would give you the ball's dimensions.
As close as I can measure it from dimple to flush with the top of the housing is 36mm.
The spindle is 39mm from tip to where it joins the sub-platter.

It must be quite a small ball though, as the rega one (which looks way smaller than Tony's) that I tried meant that the support bushes didn't line up correctly causing loads of play!

Andy

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Re: STD 305M main bearing question

Post by Alec124c41 » 27 Dec 2015 18:55

I think that the ball at the bottom is the size of the well, and that heeps it centered.
If you drop a small ball in there, it will roll around the sides, and cause a lot of noise.
I'd say, put a dab of moly on the bottom of the spindle, and on the side, if you like, add a few drops of oil,
and go play some music.

Cheers,
Alec

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Re: STD 305M main bearing question

Post by Trio KD1033 » 27 Dec 2015 19:20

Alec124c41 wrote:I think that the ball at the bottom is the size of the well, and that heeps it centered.
If you drop a small ball in there, it will roll around the sides, and cause a lot of noise.
I'd say, put a dab of moly on the bottom of the spindle, and on the side, if you like, add a few drops of oil,
and go play some music.

Cheers,
Alec
It's not my main deck at present, that duty is taken by a Technics SL-1500 + SME 3009 series 2 improved with Shure ME97HE, so the discs are still spinning.
It's more a case of finding out if I'm going to cause damage by running a bearing with a missing piece! And don't worry, the music is flowing as we speak!

Andy

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Re: STD 305M main bearing question

Post by Copperhead » 27 Dec 2015 19:42

Alec124c41 wrote:I think that the ball at the bottom is the size of the well, and that heeps it centered.
If you drop a small ball in there, it will roll around the sides, and cause a lot of noise.
I'd say, put a dab of moly on the bottom of the spindle, and on the side, if you like, add a few drops of oil,
and go play some music.

Cheers,
Alec
Yes, the ball does look as if it just fits in the well. What is strange is the locating dimple on the second photograph. I assumed, from what Andy said, that the photo of the well shows a convex and a dimple. or is it just a dimple?

A small dimple, together with the weight of the platter, would keep a small ball in place. A bigger ball would still need a locating hole, as it would still be slightly smaller than the well's diameter. You should be able to find a suitable size.

I can't help thinking that you could improve on the design, there seems to be an awful lot of moving parts and metal to metal contact on rough surfaces.

Does the spindle spin on the ball and is the ball static, or does the ball spin on the well but not on the spindle, or does everything move? I dread to think how scored the bottom of that spindle, where the ball would sit, is.

A more elegant solution would be a POM thrust pad and a highly polished spindle.

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Re: STD 305M main bearing question

Post by Trio KD1033 » 27 Dec 2015 19:49

Copperhead wrote:
Alec124c41 wrote:I think that the ball at the bottom is the size of the well, and that heeps it centered.
If you drop a small ball in there, it will roll around the sides, and cause a lot of noise.
I'd say, put a dab of moly on the bottom of the spindle, and on the side, if you like, add a few drops of oil,
and go play some music.

Cheers,
Alec
Yes, the ball does look as if it just fits in the well. What is strange is the locating dimple on the second photograph. I assumed, from what Andy said, that the photo of the well shows a convex and a dimple. or is it just a dimple?

A small dimple, together with the weight of the platter, would keep a small ball in place. A bigger ball would still need a locating hole, as it would still be slightly smaller than the well's diameter. You should be able to find a suitable size.

I can't help thinking that you could improve on the design, there seems to be an awful lot of moving parts and metal to metal contact on rough surfaces.

Does the spindle spin on the ball and is the ball static, or does the ball spin on the well but not on the spindle, or does everything move? I dread to think how scored the bottom of that spindle, where the ball would sit, is.

A more elegant solution would be a POM thrust pad and a highly polished spindle.
It feels like a convex area with a dimple. As you say, I would much prefer a design like Thorens used for the TD-160. I had one and the bearing span for ever and didn't make a sound.

Andy

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Re: STD 305M main bearing question

Post by Alec124c41 » 28 Dec 2015 01:35

If there is a ball at the bottom of the well, kept in by a C-clip, it might be worn on the top. Removing it and turning, or replacing it, would give you a fresh point for the flat bottom of the shaft to ride on.
I can think of no other reason for there to be a circlip.
Have you looked at the bottom of the bearing housing?

Cheers,
Alec

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Re: STD 305M main bearing question

Post by Copperhead » 28 Dec 2015 02:53

Alec124c41 wrote:If there is a ball at the bottom of the well, kept in by a C-clip, it might be worn on the top. Removing it and turning, or replacing it, would give you a fresh point for the flat bottom of the shaft to ride on.
I can think of no other reason for there to be a circlip.
Have you looked at the bottom of the bearing housing?

Cheers,
Alec
If you scroll up you will see a photo Andy has taken of the bottom of the well, according to Andy, this shows a convex with a a dimple in its middle. Pretty messy design, a ball sitting between two bits of metal with a locating dimple (or wear) in the middle of both.

The dimple in the spindle and bearing well would provide a locating hole so as to keep the ball centred. The fact the ball either spins on one surface or the other, or both, is hardly a great design. I also don't understand the need for the bottom of the well to be domed. Or the bottom of the spindle, for that matter. A simple dimple in both would suffice.