hello all, new to this forum so first off hi!
secondly, ive been thinking of making a tt, and have been thinking about bearings.
Am i right in saying that the main problem with making a usual type bearing is the tight tollerence of machining needed between the center pole and the outer bush?
I was thinking about how to get it machined, and though about getting an engine shop to do it.
Then i realised, these parts already exist.
Has anyone tried using a valve from a cars head? These are very strong and very acurately made/machined with a very smooth finisg. If this was used, with the thin end machined to support the bearing and the wide end welded to a base to fix to the plinth, the bronze bush thats pressed into the head, the valve guide, can be used as the outer tube.
These two parts are already very free moving but very well fitting. After all a valve needs to freely move up and down with no sideways movement.
Does this make sense? im new to all this so im not sure how to describe things in ways you wil understand.
Has it been done before?
I probably wont be able to try this idea out for quite a while as im too busy, but thought i'd share the idea now.
secondly, ive been thinking of making a tt, and have been thinking about bearings.
Am i right in saying that the main problem with making a usual type bearing is the tight tollerence of machining needed between the center pole and the outer bush?
I was thinking about how to get it machined, and though about getting an engine shop to do it.
Then i realised, these parts already exist.
Has anyone tried using a valve from a cars head? These are very strong and very acurately made/machined with a very smooth finisg. If this was used, with the thin end machined to support the bearing and the wide end welded to a base to fix to the plinth, the bronze bush thats pressed into the head, the valve guide, can be used as the outer tube.
These two parts are already very free moving but very well fitting. After all a valve needs to freely move up and down with no sideways movement.
Does this make sense? im new to all this so im not sure how to describe things in ways you wil understand.
Has it been done before?
I probably wont be able to try this idea out for quite a while as im too busy, but thought i'd share the idea now.
A valve bushing is pressed into the cylinder head... becoming smaller in the process.
The bushing is then machined for a loose fit to the valve about 0.002-0.004" (0.05 - 0.1mm) this is to allow room for the valve to expand with temperature (more for exhaust valves).
A valve could make a good spindle provided the clearance to the bushing was greatly reduced... say 0.0006 - 0.0008 inches. Oil film will consume the gap and provide a tight yet smooth bearing.
You can purchase shaft, bushing and hubs though... not so expensive.
The bushing is then machined for a loose fit to the valve about 0.002-0.004" (0.05 - 0.1mm) this is to allow room for the valve to expand with temperature (more for exhaust valves).
A valve could make a good spindle provided the clearance to the bushing was greatly reduced... say 0.0006 - 0.0008 inches. Oil film will consume the gap and provide a tight yet smooth bearing.
You can purchase shaft, bushing and hubs though... not so expensive.
hmmm, thanx. More play in them than i though. I suppose all other parts will be the same. I was thinking of ways to use the center pin in the piston and the small end bearing, or cam shaft bearings, but they will all have larger clearences to allow for expansion.
Back to the drawing board for the easilt made, cheap DIY sollution.
Back to the drawing board for the easilt made, cheap DIY sollution.
wrist pins hey, ill look into it. Ive got access to loads of engine/car parts.
The other thing i was thinking is car wiper spindles.
On 60's beetles you have the assembaly that bolts to the windscreen scuttle and a spindle that runs through it.
When there new there is no play at all, but they spin freely.
I just chucked two out so cant look into that, however theres loads of jags over my friends workshop, they may yield something.
There must be options in automotive parts. You can get different size bearing shells for when you re-grind cams/cranks so you could make up and clearence you like. And they have oil ways to keep em lubed up.
Just a matter of finding ones of a suitable diameter to reduce drag and a long enough length to support properly.
I was thinking of looking into flywheel platters, and crankshaft journals but this is getting seriously too heavy duty
would look nice and industrial though.
The other thing i was thinking is car wiper spindles.
On 60's beetles you have the assembaly that bolts to the windscreen scuttle and a spindle that runs through it.
When there new there is no play at all, but they spin freely.
I just chucked two out so cant look into that, however theres loads of jags over my friends workshop, they may yield something.
There must be options in automotive parts. You can get different size bearing shells for when you re-grind cams/cranks so you could make up and clearence you like. And they have oil ways to keep em lubed up.
Just a matter of finding ones of a suitable diameter to reduce drag and a long enough length to support properly.
I was thinking of looking into flywheel platters, and crankshaft journals but this is getting seriously too heavy duty
would look nice and industrial though.
sure would. Use a beetle engine and you could still carry it around.Who needs a electric motor, just run the engine. Might spin it a bit fast though.
I am sure theres something in the automitive world that will work, just not sure what yet.
I have access to a metal lathe anyway, so ill sort something.
graeme uk said:
Who needs a electric motor, just run the engine. Might spin it a bit fast though.
I am sure theres something in the automitive world that will work, just not sure what yet.
I have access to a metal lathe anyway, so ill sort something.
Does me think of the Lirpa’s steam turntable
If you Google around on it you will find some interesting reviews.Hi,
I wouldn't wish to stifle any enterprise here, but, if you really wish to end up with a good result, I think you need to look elsewhere than automotive engineering for your solutions.
Turntables are remarkably sensitive to their main bearings, and I cannot think of any automotive parts which would help you here.
If by 'wrist pins' this refers to 'small ends', you don't have any way of resolving the end-thrust, or axial thrust with these, and this is the most important area to get right. Also, the last time I looked at small ends, they were case-hardened, so any machining will not be easy with these, whether you have a lathe or not.
I mean no offence, but wiper blade bosses are just a joke as far what is needed here, as they are in an entirely different league from an engineering aspect, and anything you do with these is going to disappoint you.
I think you need to consider tolerances and surface finishes more akin to instrument engineers, or clockmakers to end up with a good result, but the axial thrust is the most important to get right.
With a well balanced platter, there is very little side-thrust, just the 'pressure' applied by the pick-up (maybe one gram, or so) at the rim, but the entire mass of the platter must be supported by the end, or axial, thrust of the bearing.
Good luck anyway.
I wouldn't wish to stifle any enterprise here, but, if you really wish to end up with a good result, I think you need to look elsewhere than automotive engineering for your solutions.
Turntables are remarkably sensitive to their main bearings, and I cannot think of any automotive parts which would help you here.
If by 'wrist pins' this refers to 'small ends', you don't have any way of resolving the end-thrust, or axial thrust with these, and this is the most important area to get right. Also, the last time I looked at small ends, they were case-hardened, so any machining will not be easy with these, whether you have a lathe or not.
I mean no offence, but wiper blade bosses are just a joke as far what is needed here, as they are in an entirely different league from an engineering aspect, and anything you do with these is going to disappoint you.
I think you need to consider tolerances and surface finishes more akin to instrument engineers, or clockmakers to end up with a good result, but the axial thrust is the most important to get right.
With a well balanced platter, there is very little side-thrust, just the 'pressure' applied by the pick-up (maybe one gram, or so) at the rim, but the entire mass of the platter must be supported by the end, or axial, thrust of the bearing.
Good luck anyway.
could you explain axial thrust to me again, i dont quite understand what you mean.
I had already come to the same conclusion as you, and was looking elsewhere, thinking that there was nothing suitable in automotive.
Although someone on here has used a harley valve and valve guide. I checked this a while ago with VW valves and there was so much play it was silly!!
However, out of the blue yeaterday i found exactly whats needed, on a car.
Its part of the carb on an old su carb from an austin mini.
Its perfect, nearly, but can be got very cheap and moddified easily.
My other question is about the ball.
I will need to make two discs to sandwich the ball between, but what sixe/material for the ball, and what material for the discs?
Am i right in assuming the smaller the ball the better?
I had already come to the same conclusion as you, and was looking elsewhere, thinking that there was nothing suitable in automotive.
Although someone on here has used a harley valve and valve guide. I checked this a while ago with VW valves and there was so much play it was silly!!
However, out of the blue yeaterday i found exactly whats needed, on a car.
Its part of the carb on an old su carb from an austin mini.
Its perfect, nearly, but can be got very cheap and moddified easily.
My other question is about the ball.
I will need to make two discs to sandwich the ball between, but what sixe/material for the ball, and what material for the discs?
Am i right in assuming the smaller the ball the better?
There is one automotive componant that has the required tolerance, is freely available, and would need little change to become a good bearing....
The SU carburettor (fitted to pretty much anything british before 1992) has a critical componant that meters the fuel - the dashpot assembly and bellhousing. The dashpot has tight tolerance for using an oil damper, however, the bellhousing has a very tight tolerance with the dashpot (so tight it takes time for the air to escape when inverted). seperating these two componants from the remainder of the carburettor is easy, converting them into a usable componant is tricky.
There are other sources of precision ground rods that can be made into a good bearing... probably much easier than what is currently proposed...
Owen
The SU carburettor (fitted to pretty much anything british before 1992) has a critical componant that meters the fuel - the dashpot assembly and bellhousing. The dashpot has tight tolerance for using an oil damper, however, the bellhousing has a very tight tolerance with the dashpot (so tight it takes time for the air to escape when inverted). seperating these two componants from the remainder of the carburettor is easy, converting them into a usable componant is tricky.
There are other sources of precision ground rods that can be made into a good bearing... probably much easier than what is currently proposed...
Owen
They are the parts im talking about. I see no problem modifying them into usable components, already got it all drawn out. A few different ways, depends on how complex i want to make it.
It'll be a while before i have access to any tools, so wont be able to start on it till spring, but that gives me lots of time to think.
Just need to clarify the actual ball requirements.
It'll be a while before i have access to any tools, so wont be able to start on it till spring, but that gives me lots of time to think.
Just need to clarify the actual ball requirements.
graeme uk said:
Hi,
No. (why we are not all raiding biro's for miniature carbide balls)
The critical issue is the area of the thrust contact patch,
and if the ball is harder than the thrust pad (which it usually
is) then the pad will deform to keep this area constant.
Consequently there is no engineering advantage in going for
a small ball and a considerable wear rate disadvantage.
Stick to a sensible size and everything should be fine.
/sreten.
TT bearing
Hi Graeme,
Axial thrust in this instance is basically merely supporting and taking the weight of the platter, which means there will need to to be some accurate machining in the 'end' of a small-end pin in order to locate the thrust ball which you have now mentioned.
As I said, the small-end pins I have seen over the years are usually case-hardened for durability, which means they cannot be machined in a lathe (normally). I think you would need to grind any such surfaces to make an impression on them, which was what I was getting at with my comments.
Some small-ends may well have a depression in their 'ends', already, but these are more 'accidental' and part of other machining operations, and are not necessarily finished very accurately or 'cleanly' (as opposed to the very well finished circumference of the pins), as there is simply no need for this in their intended application.
Here it is absolutely vital to have the ball located concentrically with the shaft's axis, or the thrust ball will follow a 'wandering' course on the bottom-plate or whatever it sits down on, and this unwanted additional friction is something which will badly affect the sound, and the wear on the parts concerned.
Thinking more about this, any depressions already in the ends of such pins are most likely to be there to 'centre' the pins when they are being finally surface-gound in production, so they should be reasonably concentric with the pins' axis, but I have my doubts over the finish here, and the depressions may already be too large (or small) for your chosen ball size. I would guess that some grinding to suit the size of ball chosen would be needed for a good result, anyway, unless you are very lucky in your choice of pin, but with the right equipment, this would certainly be possible.
It would need some kind of grinding arrangement set up in the tool-post of your lathe though, and not merely a simple centre- drill, or other 'cutting tool', because of the surface hardness of the pin.
Incidentally (in my own opinion) most automotive small-ends are larger in diameter than I would think are ideal for this application, and this will give greater 'drag' due to the larger surface area of the bearing. Also, there will be a higher 'sliding speed' between the two components, because the 'mating surfaces' are further away from the centre line of the bearing assembly with larger diameter shafts. Because the circumference of a shaft (i.e. the 'sliding' or 'rubbing' surfaces) increases by a factor of 3.14 X the increase of the shaft's diameter, any unnecessary increase in shaft diameter will increase these potential 'drag' problems considerably.
Large shafts are not needed for strength in this application (because there is so little side-thrust), and additional friction, together with the inevitable varying 'drag' due to temperature-related oil viscosity changes during operation, will not be good for the overall sound and speed stability.
This leads on to your query over the size of ball, and the same comments apply here. Ideally, for best performance, the ball should be infinitely small, for these same reasons of minimising drag/friction etc., and the least drag which can be obtained in the overall bearing arrangement, the better. However, for practicality, there will be a substantial downforce (depending on the overall weight of the platter etc.) and with a very small bearing area resulting from using a tiny ball, it won't last very long, unfortunately.
Most of those I have seen used commercially, and which I have experimented with, have been about 5mm dia., as a guide, and this seems to be a good compromise, but they do still benefit from having the ball replaced every so often (or the ball re-positioned to give a fresh bearing surface). So far, I have only seen and used 'normal' steel ball bearings, but I will try some ceramic types at some time in the future, and, as this entire area is so sensitive, I have little doubts that this will have some effect on the sound, but whether it is better, or not, remains to be seen from my point of view.
Unless you can fix the 'upper' disc firmly to the shaft, and arrange for a suitable depression in it (which is absolutely concentric with the shaft) to locate the ball, I would not contemplate using two plates. Otherwise, the ball will simply 'wander' around as already mentioned.
For the lower plate, the hardest and best finished material is going to be the choice here, and if you are auto-orientated (as you appear to be), what about trying out some OHC valve shims, perhaps?
I used some in a Lotus Twin-Cam engine (over 30 yrs ago) which would appear to be ideal for this, but there are many engines nowadays which probably use similar shims. The ones I still have are about 12/15 mm dia (from memory), are extremely hard with truly parallell sides, and are well polished on the two flat surfaces. If they will take the hammering they get in their intended use with so little wear, I guess they would last very well in this application, and they should be available in different thicknesses, mostly suitable for this use. When they show signs of wear, they could be reversed to give a fresh 'bearing surface', as well!
If you are able to arrange for a suitable concentric depression in the underside of the shaft, because the ball will be pressed to this around a much larger (surface and diameter) contact area than the 'pin-point' where the ball rests on the bottom plate, the ball should remain 'static' in the bottom of the shaft, which is ideal. All 'relative' rotation, and therefore potential friction etc., in the axial plane (which is by far the highest loaded) will be centred on a very small area which will soon polish up to an excellent bearing surface.
In your comment on SU carburetters, I guess you are referring to the dashpot piston in an SU carb., and for certain the accuracy and finish on the piston is very good on these. I don't now recall very well the diameter or the kind of bushing in the dashpot, though, but I think it was probably larger than I would consider ideal.
Michell Eng. shafts are only 10mm dia. approx., to give you an idea of what I would strive for, but this is not critical, and in such cases it is a question of finding the best overall compromise from parts which are obtainable, as you obviously already know.
In fact, I think that some other TT manufacturers may well use larger dia shafts, anyway, but bear in mind what I said about drag/friction etc., especially when you come to consider driving the TT, possibly via a flexible belt.
I have every respect for Charless Altmann and his inlet/exhaust (?) valve, but the bushing worries me a little here. The shaft would be very good, and of a suitable diameter, but the valve-guides I have been familiar with usually need to be reamed out after installation, unless more modern methods have changed, and this could be a problem, especially with the final surface finish. Maybe with Harley Davidsons (of which I know nothing) the position is different (possibly because of an alloy head etc.) but auto valves are really intended for reciprocation rather than rotation, and they work at much higher temperatures usually, both of which are very different from your intended application.
If you are prepared to consider H/D type valves (as opposed to whatever you can source more readily), I would get in touch with Charles, because I am sure his result would have been satisfactory in the end, and it may be that you don't need to ream these out finally, and that working clearances (when cold) will be quite OK.
As I originally said, I wouldn't wish to deter you in any way, and almost *anything* could be made to work after a fashion, but this is a very critical area to get right. Even different manufacturers' oils of the same nominal viscosity will change the 'sonic' results in my set-up, and time spent now in careful thought and thorough investigation, will hopefully avoid too many disappointments for you, as well as wasted costs.
Good luck, and if there is anything else I might be able to help with, I will do my best.
EDIT. I started a reply immediately after seeing your post with these queries. Family matters then distracted me for some hours, and when I later finished these comments and sent the post, I see you have added to your earlier comments, especially on the carb issue.
Hi Graeme,
Axial thrust in this instance is basically merely supporting and taking the weight of the platter, which means there will need to to be some accurate machining in the 'end' of a small-end pin in order to locate the thrust ball which you have now mentioned.
As I said, the small-end pins I have seen over the years are usually case-hardened for durability, which means they cannot be machined in a lathe (normally). I think you would need to grind any such surfaces to make an impression on them, which was what I was getting at with my comments.
Some small-ends may well have a depression in their 'ends', already, but these are more 'accidental' and part of other machining operations, and are not necessarily finished very accurately or 'cleanly' (as opposed to the very well finished circumference of the pins), as there is simply no need for this in their intended application.
Here it is absolutely vital to have the ball located concentrically with the shaft's axis, or the thrust ball will follow a 'wandering' course on the bottom-plate or whatever it sits down on, and this unwanted additional friction is something which will badly affect the sound, and the wear on the parts concerned.
Thinking more about this, any depressions already in the ends of such pins are most likely to be there to 'centre' the pins when they are being finally surface-gound in production, so they should be reasonably concentric with the pins' axis, but I have my doubts over the finish here, and the depressions may already be too large (or small) for your chosen ball size. I would guess that some grinding to suit the size of ball chosen would be needed for a good result, anyway, unless you are very lucky in your choice of pin, but with the right equipment, this would certainly be possible.
It would need some kind of grinding arrangement set up in the tool-post of your lathe though, and not merely a simple centre- drill, or other 'cutting tool', because of the surface hardness of the pin.
Incidentally (in my own opinion) most automotive small-ends are larger in diameter than I would think are ideal for this application, and this will give greater 'drag' due to the larger surface area of the bearing. Also, there will be a higher 'sliding speed' between the two components, because the 'mating surfaces' are further away from the centre line of the bearing assembly with larger diameter shafts. Because the circumference of a shaft (i.e. the 'sliding' or 'rubbing' surfaces) increases by a factor of 3.14 X the increase of the shaft's diameter, any unnecessary increase in shaft diameter will increase these potential 'drag' problems considerably.
Large shafts are not needed for strength in this application (because there is so little side-thrust), and additional friction, together with the inevitable varying 'drag' due to temperature-related oil viscosity changes during operation, will not be good for the overall sound and speed stability.
This leads on to your query over the size of ball, and the same comments apply here. Ideally, for best performance, the ball should be infinitely small, for these same reasons of minimising drag/friction etc., and the least drag which can be obtained in the overall bearing arrangement, the better. However, for practicality, there will be a substantial downforce (depending on the overall weight of the platter etc.) and with a very small bearing area resulting from using a tiny ball, it won't last very long, unfortunately.
Most of those I have seen used commercially, and which I have experimented with, have been about 5mm dia., as a guide, and this seems to be a good compromise, but they do still benefit from having the ball replaced every so often (or the ball re-positioned to give a fresh bearing surface). So far, I have only seen and used 'normal' steel ball bearings, but I will try some ceramic types at some time in the future, and, as this entire area is so sensitive, I have little doubts that this will have some effect on the sound, but whether it is better, or not, remains to be seen from my point of view.
Unless you can fix the 'upper' disc firmly to the shaft, and arrange for a suitable depression in it (which is absolutely concentric with the shaft) to locate the ball, I would not contemplate using two plates. Otherwise, the ball will simply 'wander' around as already mentioned.
For the lower plate, the hardest and best finished material is going to be the choice here, and if you are auto-orientated (as you appear to be), what about trying out some OHC valve shims, perhaps?
I used some in a Lotus Twin-Cam engine (over 30 yrs ago) which would appear to be ideal for this, but there are many engines nowadays which probably use similar shims. The ones I still have are about 12/15 mm dia (from memory), are extremely hard with truly parallell sides, and are well polished on the two flat surfaces. If they will take the hammering they get in their intended use with so little wear, I guess they would last very well in this application, and they should be available in different thicknesses, mostly suitable for this use. When they show signs of wear, they could be reversed to give a fresh 'bearing surface', as well!
If you are able to arrange for a suitable concentric depression in the underside of the shaft, because the ball will be pressed to this around a much larger (surface and diameter) contact area than the 'pin-point' where the ball rests on the bottom plate, the ball should remain 'static' in the bottom of the shaft, which is ideal. All 'relative' rotation, and therefore potential friction etc., in the axial plane (which is by far the highest loaded) will be centred on a very small area which will soon polish up to an excellent bearing surface.
In your comment on SU carburetters, I guess you are referring to the dashpot piston in an SU carb., and for certain the accuracy and finish on the piston is very good on these. I don't now recall very well the diameter or the kind of bushing in the dashpot, though, but I think it was probably larger than I would consider ideal.
Michell Eng. shafts are only 10mm dia. approx., to give you an idea of what I would strive for, but this is not critical, and in such cases it is a question of finding the best overall compromise from parts which are obtainable, as you obviously already know.
In fact, I think that some other TT manufacturers may well use larger dia shafts, anyway, but bear in mind what I said about drag/friction etc., especially when you come to consider driving the TT, possibly via a flexible belt.
I have every respect for Charless Altmann and his inlet/exhaust (?) valve, but the bushing worries me a little here. The shaft would be very good, and of a suitable diameter, but the valve-guides I have been familiar with usually need to be reamed out after installation, unless more modern methods have changed, and this could be a problem, especially with the final surface finish. Maybe with Harley Davidsons (of which I know nothing) the position is different (possibly because of an alloy head etc.) but auto valves are really intended for reciprocation rather than rotation, and they work at much higher temperatures usually, both of which are very different from your intended application.
If you are prepared to consider H/D type valves (as opposed to whatever you can source more readily), I would get in touch with Charles, because I am sure his result would have been satisfactory in the end, and it may be that you don't need to ream these out finally, and that working clearances (when cold) will be quite OK.
As I originally said, I wouldn't wish to deter you in any way, and almost *anything* could be made to work after a fashion, but this is a very critical area to get right. Even different manufacturers' oils of the same nominal viscosity will change the 'sonic' results in my set-up, and time spent now in careful thought and thorough investigation, will hopefully avoid too many disappointments for you, as well as wasted costs.
Good luck, and if there is anything else I might be able to help with, I will do my best.
EDIT. I started a reply immediately after seeing your post with these queries. Family matters then distracted me for some hours, and when I later finished these comments and sent the post, I see you have added to your earlier comments, especially on the carb issue.
Some great info there, i have a few more quieries though
I like the dash pot and center piece. Its very cheap (probably free) and easily got.
It is however quite wide, the center rod is about 20mm from memory.
If i can make it well, could i machine the center of the rod so only say the top 1cm and bottom 1cm are running in the tube?
Does that make sense? This will reduce the friction surface back to a reasonable level.
Also, the center rod will actually be another tube. I like this, as it can be filled with something so the center rod will have very little ring to be transfered to the platter.
As it is hollow, i can lathe a plug to press into the end, with a hollow to take the bearing. But what shall i machine the plug from?
Ive been reading about ruby balls, much better than steel?
Ive learned alot from the diy tt thread, been reading it for quite a while.
My plan is to try and build the platter/bearing/plinth as cheaply as possible, with as little compromise as possible, so i can spend all the money on a good motor and a great arm (mainly arm)
I like the dash pot and center piece. Its very cheap (probably free) and easily got.
It is however quite wide, the center rod is about 20mm from memory.
If i can make it well, could i machine the center of the rod so only say the top 1cm and bottom 1cm are running in the tube?
Does that make sense? This will reduce the friction surface back to a reasonable level.
Also, the center rod will actually be another tube. I like this, as it can be filled with something so the center rod will have very little ring to be transfered to the platter.
As it is hollow, i can lathe a plug to press into the end, with a hollow to take the bearing. But what shall i machine the plug from?
Ive been reading about ruby balls, much better than steel?
Ive learned alot from the diy tt thread, been reading it for quite a while.
My plan is to try and build the platter/bearing/plinth as cheaply as possible, with as little compromise as possible, so i can spend all the money on a good motor and a great arm (mainly arm)
coincidence ...
Hi Graeme,
I had the same idea. Winter time is DIY time
http://www.altmann.haan.de/turntable
Charles
Hi Graeme,
I had the same idea. Winter time is DIY time
http://www.altmann.haan.de/turntable
Charles
as for the reaming...
... you don't have to ream after installing the valve-guide. Since you just snug it into the wood with a little glue, it will not deform.
Deformation is the main reason that you may ream an automotive valve after installation (in a cylinder head). You have to press it in with quite a high force.
The valve-guide - as it comes - mates very well with the valve, although it is not the tightest fit. However, after oiling it, there is no detectable play (in any case less play compared to my Garrard 401, which I like very much btw).
The centering of the steel ball is an issue, as we do not have the precision of a professional made bearing. In my case the ball is offset from the center ca. 1/10 mm.
I have seen TT bearing designs, where an offset ball is a feature of the bearing construction... so I just don't care about it.
Charles
... you don't have to ream after installing the valve-guide. Since you just snug it into the wood with a little glue, it will not deform.
Deformation is the main reason that you may ream an automotive valve after installation (in a cylinder head). You have to press it in with quite a high force.
The valve-guide - as it comes - mates very well with the valve, although it is not the tightest fit. However, after oiling it, there is no detectable play (in any case less play compared to my Garrard 401, which I like very much btw).
The centering of the steel ball is an issue, as we do not have the precision of a professional made bearing. In my case the ball is offset from the center ca. 1/10 mm.
I have seen TT bearing designs, where an offset ball is a feature of the bearing construction... so I just don't care about it.
Charles
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