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deannos
12-10-2011, 09:39 AM
This is probably a stupid question, but does it matter which end of the lead screws the motors are mounted:redface:. I can see the direction of rotation will alter depending on which end they are mounted, but can this be changed in the software or something

John S
12-10-2011, 10:13 AM
Not in the least, whatever fits best.
Direction can be changed in software but it does pay to get the main load / thrust bearing assembly at the motor end, support bearing at trailing end.

Web Goblin
12-10-2011, 10:16 AM
I dont think it would make any difference to the operation of the screw, but are the ends of the screw not machined differently? One end should be machined to fit a bearing block and the other would be to fit the motor. I would say that the end with the longer machined down section would be for the motor.

Ian

deannos
12-10-2011, 10:23 AM
Not in the least, whatever fits best.
Direction can be changed in software but it does pay to get the main load / thrust bearing assembly at the motor end, support bearing at trailing end.

Thanks for this John


I dont think it would make any difference to the operation of the screw, but are the ends of the screw not machined differently? One end should be machined to fit a bearing block and the other would be to fit the motor. I would say that the end with the longer machined down section would be for the motor.

Ian

The ends are machined differently, but i would turn the screw with motor mounted round

JAZZCNC
12-10-2011, 06:45 PM
This is probably a stupid question, but does it matter which end of the lead screws the motors are mounted:redface:. I can see the direction of rotation will alter depending on which end they are mounted, but can this be changed in the software or something

Hi Dean,

The others have answered your Q but one thing you may not know or be aware of is one end should be fixed (the thrust end John refers too) often this end will have a threaded portion.!
This end will usually be clamped thru 2 angular contact bearings mounted into a bearing mount or plate, reason: so the screw doesn't float back n forth effectively causing backlash. The other end just goes into a normal bearing and is referred to as the floating end.

Knowing the machine you intend to build I think you'll find it's not designed to take 2 angular contact bearings like I describe but a single STD bearing. This will work but there could be some end float, you may want to think about making a slight modification so it use's 2 STD bearings with a slight gap between the outer races then when tightened together it preloads the inner race to the outer removing any float. Or buy the more expensive angular contact bearings which are designed to run this way.!!

Cheers

Jonathan
12-10-2011, 07:11 PM
float back n forth effectively causing backlash

Just in case Dean reads up on this it's generally referred to as end float, and often mistaken for backlash.


Knowing the machine you intend to build I think you'll find it's not designed to take 2 angular contact bearings like I describe but a single STD bearing

STD bearing, is that 'STanDard' bearing? If it's the one of the two screws I think it is then it's one of two cases. Either thrust bearing and standard bearing, or a double row angular contact bearing or pair of thrust bearings.

JAZZCNC
12-10-2011, 07:22 PM
STD bearing, is that 'STanDard' bearing? If it's the one of the two screws I think it is then it's one of two cases. Either thrust bearing and standard bearing, or a double row angular contact bearing or pair of thrust bearings.

Yep STD in my world means Standard.! As in STD Deep grove bearings.

Believe the screws are the ones you sold him so you should know best which they were machined to use.?

Thou to be honest I was just trying to make him aware one end needs to be fixed with a simple example of a cheap way to do it. . . .(Knowing because I cut some bits for him that they didn't look like they were designed for 2 bearings.? )

Jonathan
13-10-2011, 01:55 AM
Believe the screws are the ones you sold him so you should know best which they were machined to use.?

Thought it might be those. Have a look at the first post in my build log to see how I did the shorter screw with a single thrust bearing and 'STD' bearing:

http://www.mycncuk.com/forums/showthread.php/2288-1.7*0.74*0.4m-Mill-Router-building...

I did the Y similarly but with two thrust bearings. Easier to use double row angular contact. Didn't I include some bearings / mounts with it? I forget...

deannos
13-10-2011, 09:14 AM
Hi Dean,

The others have answered your Q but one thing you may not know or be aware of is one end should be fixed (the thrust end John refers too) often this end will have a threaded portion.!
This end will usually be clamped thru 2 angular contact bearings mounted into a bearing mount or plate, reason: so the screw doesn't float back n forth effectively causing backlash. The other end just goes into a normal bearing and is referred to as the floating end.

Knowing the machine you intend to build I think you'll find it's not designed to take 2 angular contact bearings like I describe but a single STD bearing. This will work but there could be some end float, you may want to think about making a slight modification so it use's 2 STD bearings with a slight gap between the outer races then when tightened together it preloads the inner race to the outer removing any float. Or buy the more expensive angular contact bearings which are designed to run this way.!!

Cheers


Thanks Jazz,

This makes for some interesting reading, and endfloat is the same as found in crankshafts etc. I do like the simple idea of 2 STD bearings tightened up, but i only nead this on the Z axis as the others will be using bearings etc supplied by Jon.
cheers ,

Dean

deannos
13-10-2011, 09:21 AM
Thought it might be those. Have a look at the first post in my build log to see how I did the shorter screw with a single thrust bearing and 'STD' bearing:

http://www.mycncuk.com/forums/showthread.php/2288-1.7*0.74*0.4m-Mill-Router-building...

I did the Y similarly but with two thrust bearings. Easier to use double row angular contact. Didn't I include some bearings / mounts with it? I forget...


hi Jon,

Yes your memory is correct and you did supply bearings and mounts for X and Y axis. In my original question i actually meant fixing the X axis motor to the other end of the table