Which steel?

[David Brown 9Participant @davidbrown9]

I need some steel for a 35mm pulley shaft (and also a 20mm one). The 35mm shaft will support a load of around 25kg, rotating at around 40rpm. Proably around 100cm long. I am going to use pillow block bearings. What steel should I get? I was advised to get precision ground mild steel for this shaft.

Metal Supermarkets have 'engineering steel' precision ground bar, EN8, EN 16 and EN24. Also 4130 and 4140 (just round bar).

Also 'bright steel' EN3A. EN3A (leaded), EN3B, EN8,EN24, EN16, EN19.

I am confused, which one would be best?The 20mm I will need to machine, the 35mm shaft I possibly may need to, I have a mini-mill.

David

[David Brown 9Participant @davidbrown9]

[John RuddParticipant @johnrudd16576]

Silver steel?

Which is also ground finished

[Thor 🇳🇴Participant @thor]

EN 3 should be Ok for your shaft if it is a good fit in the bearing. Precision ground bar may be a better fit in the bearing.

Thor

[Nigel McBurney 1Participant @nigelmcburney1]

In the request there is no mention of the centre distance between the bearings,or the position of the load between the bearings, or how much deflection the assembly can tolerate under load. commercial bright bar cannot be guaranteed to be straight and is usually 11/2 to 2 thou down on nominal diameter but is more economical than ground bar, en 8 bar 35 mm dia with bearings at 8oomm centres supporting a load of 25 kilos should be adequate, I think a loaded 20mm bar may be a problem . I would far rather machine en8 than en3a or b , en3 is horrible to machine,

[BazyleParticipant @bazyle]

Silver steel would be staggeringly expensive, even BMS in that size is pricey. I suggest using a cheap steel, thin as possible, and make a bush to fit whatever bearing you end up with. One source is a drive shaft from a rear drive car. The speed is a crawl so balance and straightness only a problem because it might influence the symmetry of the final product.

I suggest a major rethink to use a car front axle assembly with your table bolted to the brake disc. Apply the drive via a washing machine pulley fixed to the table and poly-v belt which is lighter, and more flexible than a v-belt. Also this will be taper rollers so no need for a thrust bearing. If you find you have a ripple related to the bearing being worn a new one would be far cheaper for a standard car fitting.

 

Edited By Bazyle on 25/11/2015 21:25:21

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