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Help ! Fixing 8mm dia pully over 8 mm rod and so on..

Posted by viren 
Help ! Fixing 8mm dia pully over 8 mm rod and so on..
December 21, 2017 06:42PM
I am finding it difficult to put in 8 mm bore dia pully over 8 mm rod. Also some F688ZZ bearing are also not accomodating 8 mm rod. Seem 8mm rod is not actually 8mm rod but slightly more. I am tight on budget.

Any innovative ideas ?
Re: Help ! Fixing 8mm dia pully over 8 mm rod and so on..
December 21, 2017 06:47PM
sand paper much?


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Help ! Fixing 8mm dia pully over 8 mm rod and so on..
December 21, 2017 08:18PM
try heating/cooling the mating parts, you'll get a pressfit but wont really be able to tweak it.
Re: Help ! Fixing 8mm dia pully over 8 mm rod and so on..
December 22, 2017 09:21AM
Quote
Trakyan
try heating/cooling the mating parts, you'll get a pressfit but wont really be able to tweak it.

...Now, that would be an issue.. Any one please !
Re: Help ! Fixing 8mm dia pully over 8 mm rod and so on..
December 22, 2017 09:45AM
There are only so many ways to make parts that don't fit together fit. You either remove material from the outside of the part that's too big, or remove material from the inside of the part that's too small, or you try a thermal trick (but in this case it would probably destroy the seals on the bearing). Do you have a caliper with which to measure the parts? Do you have any tools? Put the rod in a drill, get a piece of sand paper. Spin the rod and grip it with the sand paper. Stop frequently to see if it will fit inside the bearing.

Cheap parts are made with poor tolerances. That's why they are cheap. Now you know what can happen when you buy cheap stuff. Think about it the next time you're shopping for parts. There's a reason for the expression "buy cheap, buy twice"...


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Help ! Fixing 8mm dia pully over 8 mm rod and so on..
December 22, 2017 09:22PM
Thanks digital dentist !

"buy cheap, buy twice"... True but sometimes the costs are astonishingly high such that you may like to purchase two cheap parts (95% times work) rather than one costly and may or may not work...

Anyhow, I likethumbs up your suggestion of grinding while spinning with drill....Many thanks...
Re: Help ! Fixing 8mm dia pully over 8 mm rod and so on..
January 04, 2018 09:42PM
Ouch ! while using drill and sand paper. I think I bent the a rod somehow. Is that possible ?

How much tolerance is accepatable for straightness of 8mm dia 350mm long rod.? How to measure this tolerance.

Please help !
Re: Help ! Fixing 8mm dia pully over 8 mm rod and so on..
January 05, 2018 02:26PM
It takes a lot of force to bend an 8mm steel rod.

Acceptable is whatever you define it to be. A bent guide rail will create a distortion in the print, assuming it isn't so bent that it keeps the axis from moving or causes the motor to skip steps. But you're going to be spinning this rail, so it's being used for power transmission and a little bend may not matter at all.

Edited 1 time(s). Last edit at 01/05/2018 02:29PM by the_digital_dentist.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Help ! Fixing 8mm dia pully over 8 mm rod and so on..
January 06, 2018 02:53AM
If you can see it is bent, then it is too much bent.

If you managed to bend it; it is crappy recycled steel from Lychee cans or your name is Bender smiling smiley


"A comical prototype doesn't mean a dumb idea is possible" (Thunderf00t)
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