round shaft selection

[smarbaga]

hello
- i have some 1" id linear bearings and blocks.
- i am looking to buy shafting for these bearings
about 48" in length, double supported 3" apart at both ends.

- would it be ok to use tooling steel or stainless steel ?
- would this stuff flex more than the expensive stuff ?
- wear out much faster ?
- what kind of round tolerance do u think these thompson
linear bearings need?

- i plan on hanging a die grinder on the end of my
once completed xyz for routing wood and plastic.
- i see that this stainless and tooling is 1/2 the price of
shafting like thompson. ( 1" stainless (304) 54" long, $26. )
- i do know that any peice of equipment is only as good as its weakest link.
thank you all, for your advice

[mwp]

Stainless steel or drill rod is much softer than the Thomson shafting. This will lead to the other "shafting" being worn out at a much increased rate compared to the thomson as the stresses under the ball bearings are quite high. I believe that the tolerance required for the thomson bearings works out to +.0000 -.0005 but check the thomson catalog. If you manage to use drill rod or other steel, the "flex" will be equivalent to using the thomson rod as the stiffness (EI) will be practically equivalent in all cases for any steel (maybe slightly different for the stainless). Personally, I would buy the Thomson linear shafting because it is guaranteed to fit and should wear well.

Good luck!

[Mcgyver]

what mwp said. any + tolerance can wreck the fit and the hardness will give better performance and wear

[andy_ck87028]

Buy stainless / drill rod now and retrofit thomson when and if you get a problem.

Alternatively keep replacing with stainless / drill rod. You might even find that wear is limited to only part of the length in which case, you might be able to double the life. (that's what I'll do).

Design with a view to not locking in to one or other.

I have gone silver steel because I can't afford or get access to Thomson.

Andy

[smarbaga]

thank you all for your input.
i suppose that if stainless last for a year and the machine works well,
wel thats not a big investment.
i would rather spend my xtra bucks (lol) on getting good drive screws than top quality shafting, untill i see how the entire system preforms.