What Bolt's grade should be used in linear rail mounting?

[Zaher]

Hi guys

Can I get a recommendation on the Bolt's grade should be used to mount HIWIN rails knowing that the bolt size specified in the manual is M5 and tightening torque 883 N-cm (or 90 Kgf-cm)

is Grade 12.9 suitable in this Case?

[davereagan]

12.9 is as strong as you can get commercially. Allen bolts are always the strongest grade. Stainless is what you want to stay away from. Weak, not even on the C scale for 18-8.

[Zaher]

thanks davereagan

yes I am using Allen bolts but they are Stainless because I am using them in WaterJet Machines where rust may occur easily and I wasn't paying much attention before to the bolt's grade issue

do you have a better option instead of stainless bolts for WaterJet's rails ?

and do any one has experienced a recommended bolt's grade for a similar case?

[davereagan]

There are several options. You can get zinc plated alloy steel allen bolts in grade 12.9, part number 95263A388, box of 25 for $5.88 The stainless bolts in metric seem to have higher tensile strength, minimum 101,000 psi, so that is an improvement. If going with stainless, you might as well go with 316, which has 2% molybdenum and can resist salt water and other contaminants that 18-8 can't handle. That would be part # 92290A242, box of 25 is $9.17 I'm just guessing a 20mm thread length. Another possibility if you have total design control and can spec the threads being tapped in the base is to go with #10-24 or #10-32 American threads, which are .187", only .008" smaller than 5mm. That gives you many more choices for the surface finish. There is an Ultra corrosion resistant bolt that is full 180,000 psi Grade 8 strength. That part number is 91274A112, box of 50 for $8.08, #10-24 x 3/4 thread length, page 3075. This is all in the McMaster Carr catalog online. www.mcmaster.com

Dave

[Zaher]

these are a lot of options Dave, thanks for the fast reply

I'll take a look on the bolts you mentioned and see what fits