VPI TNT Bearing question

Very interesting and thought provoking responses.

I am not worried about aluminum threads stripping and suspect you could shear of the top collar of the bearing housing if you apply enough torque (consider the amount of material engaged in the threads compared to the amount of material in the flange).

Dgarretson has done some very nice mods. As I read more about turntables I had begun to wonder if more mass on the bearing housing would be beneficial and I think he is saying it is.

The feet are pretty slick also. Do I understand that the flex provided by the fingers of the cup which holds the ceramic balls is enough to give a bit of vertical compliance as the four balls on the bottom move in and out allowing the top ball to move up and down? Some more details on the foot construction would be nice.

Your AC supply for the turntable bears some research as I have been looking for something that would do that.

As to machinist, while I am not a pro I do have pretty good skills and a very well equipped shop in my garage so I can fabricate a lot of this sort of stuff.

Lots of food for thought...

I am not a machinist, but I can surely appreciate the precision required to make a bearing that must run true along with providing a 90 degree platform for the platter to rest. How much would a machinist charge for a stainless steel bearing similar to that of the TNT Mark V?

Brf,

It's probably very hard to say. You would first need to know the bearing clearances that VPI is shooting for (it will be a range). For instance, if the bearing clearances are 0.0010", is 0.0015" acceptable or does VPI try to keep it to within 0.0003 instead? Maybe they're going for 0.0002"? The price would change as the tolerances change.

Then there's the surface finishes of the bearing components. Better finishes will cost more money.

The cost of for a bearing with loose tolerances and poor surface finishes will be different than one with tight tolerances and better surface finishes.

If you ask a machinist for advice on what tolerances or surface finishes to shoot for, he may recommend something not even close to the quality that VPI offers as he probably doesn't know how these parameters affect the sound of the turntable. I think it's safe to say that he would not know unless he was a turntable manufacturer.

Thanks Ketchup. You have confirmed my suspicion that it sounds easier than it is…… plus you are taking a gamble that it will work and sound good. If I had machining skills and access to equipment, it would be a fun project to attempt with the only real cost being materials. I see a lot of threads on DIY plinths, outboard tone arm mounts, motor drives etc, but very few are attempting their own bearing and platter assembly (except for Dgarretson)

Yes it is a bit of a crap shoot but you really would not have much invested except time unless you use some super exotic bearing material such as rulon and even then you don't need much of it for a TT bearing.

I think making a turntable bearing for a one off is a bit easier than manufacturing them. On a one off you only need to get the clearance right, the absolute dimensions don't matter that much.

You would need a decent lathe with a tool post grinder and someway to ream or hone the bearing to fit.

I have not seen anyone attempting this task. As I understand it Dgarretson only made a weight to attach to his bearing, not the complete bearing.

I'm not sure what sort of clearance is involved but I have two VPI bearing / spindle sets and they are both pretty tight.