Luke11CNC Build Log ,I'm so naïve

[Jonathan]

I got mine all machined to 25mm.

Lengthen the screw is not that hard if you access to lathe.

That'll be my lathe then.

I've done that before to add a handle to lathe leadscrew - drilled & reamed a hole in the end then machined a bar to fit. Put a straight knurl on the bar to make it grip, loctite and big hammer to 'press fit' it. Start by machining the bar slightly oversize, then after put the ballscrew in lathe, get it on centre and skim the bar the right size so that it is on centre.

Can't the whole screw be moved along and the bearing mount on the non driven end be moved?

[Swarfing]

Your almost right Jonathan? The screw is very hard and can easily crack (only the centre is soft). If this is added to the floating end then no need to knurl it, just go for a nice tight slide fit and let the loctite do it's job.

[Jonathan]

Your almost right Jonathan? The screw is very hard and can easily crack (only the centre is soft). If this is added to the floating end then no need to knurl it, just go for a nice tight slide fit and let the loctite do it's job.

The reason I knurled it is because that's what John S does. Well, says he does at least. Could anneal the very end of the screw to stop the risk of cracking, but that's probably taking it too far.

Putting the extension on the 'floating' end sounds good to me as all it's doing is stopping the screw whipping, not transmitting torque. The other end is probably easier though as the tolerances to fit the pulley are not tight as for a bearing. It depends how much we need to add?

[Web Goblin]

Jonathan,
I cant see how the nut will travel the whole length of the screw either. I think your idea of moving the "pulley" end bearing a bit further in towards the floating end and you can machine the plain section down for him to accept the pulley. I dont think lengthening the shaft would be agood idea particularly if you are going to fit a pulley on the lengthened section. Without some kind of support this will start to wear and wobble.

Ian

[Swarfing]

You wouldn't fit the pulley on the lengthened end? you would put it on the machines end end keep the nut housing to the side closest the belt end. That is how i have my arrangement and it allowed me to add a 90mm extension to the screw.

[Swarfing]

Jonathan the problem wih extending the belt end is as you have pointed out to is torque on the jointed section. As WG said that end can always be machined to allow for the pulley. An even easier solution is to just extend out the floating bearing housing with some ali round bar and mount the bearing in the end?

At the end of the day the KISS approach is always best, less to go wrong

[luke11cnc]

I haven't got a clue what your all taking about but I think I've solved the problem.

If I take the retaining nut off and have the pulley machined to slide over the threaded part and have 2mm machined of the pulley shoulder and fit a grub screw plus slide the other bearing right to the end and cut off the excess ballscrew material It will fit



what do you think is this a solution or am I making more problems for my self

James

[luke11cnc]

No one with any advice on my solution ??

James

[i2i]

I take it you're going to replace the bearing clamp nut with a thread in the pulley. If so you'll need a more positive location for the pulley, one grub screw just won't be enough. Possibly a pin right through the pulley and shaft when it's clamped up tight.

[luke11cnc]

Well after a lot of soul searching I've decided to take it down to my local engineering shop and have it rematched if it doesn't work I will have to buy a new one but I'm not going to cut corners to make it work now

and if it works they can do the other one (z-axis) as that is the same

James