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brake rotor material

brake rotor material

(OP)
I am looking for advice on material selection for machining brake rotors.  For a small buget, i am looking into grey cast iron, or some steels.  I've considered 1018 colded drawn, or 1080 steel (i believe its the same as on most motorcyles), I haven even a slight interest in 4130 as a past friend has succesfully used this.  As far as the grey cast iron goes, i'm finding it hard to find a specific type to look at.  

Any tips or suggestions would be appreciated, I am working on a limited buget and do not wish to consider Al-MMC or any ceramics because of cost.  But overall some direction would be appreciated.  Thank you.

RE: brake rotor material

Gray cast iron has long been the material of choice for brake rotors, both solid and ventilated. But for a small dollar, low volume operation, you probably can't afford to have castings made. Any of the steel grades you mention will work, but just not as well as cast iron. You will also need to experiment with brake pads to find one that works to your liking with a steel rotor.

RE: brake rotor material

(OP)
Thanks for the responses.

I am now actually consider machining cast iron plates for rotors.  After reading the sae.pdf and some other resources I think I'd like to use the gray cast iron (seems like most grades will work with little differences between them).  

I will be modeling the rotors to work with a single piston (dual action) caliper, like on most motorcycles, so i wont need the rotors to float or anything.  I do not have the space for vented disks and the are pricey to manufacture anyway.  Does anyone know of any references on cooling theories for rotors?  

Lastly, i am aware that i will need to find pads with a specific friction coeficient depending on the rotor material used.  Again, does anyone know of any sites or references?.. I will continue searching.

Thank you in advance

RE: brake rotor material

hopkid929--what is the source of your cast iron plates? All cast iron is not created equal. Brake rotor iron requires specific graphite morphology, carbon content and strength to work well.

RE: brake rotor material

Depending what you are tying to stop it might be cheaper to adapt good used motorcycle parts.  A disk brake rotor often must be made parallel < 0.001 inch with less than 0.005 inch runout.  Not much fun on a (non-brake) lathe, and easy to mess up with a grinder.

Here's a decent brake book.  Used to be a bargain but its out of print with craxzy prices on Amazon

http://www.amazon.com/gp/product/images/0895862328/ref=dp_primary-product-display_0/102-9223821-7815338?%5Fencoding=UTF8&n=283155&amp;s=books

RE: brake rotor material

(OP)
Thanks again to those who respond.  I found some good formulas at stoptech.com, i'll have to verify them though.

Our lathes don't have brakes, but the technician said he could do better than 1mil for the parallel surfaces and same for the 5mil roundout.  I looked into motorcycle rotors already but found the bolt pattern and geometry to only complex the current situation.  I think I am now interested in either mimicking a motorcycle rotor, but with my own geometry, or again, trying to find some gray cast iron with the correct graphite composition.

What grade of stainless are bike rotors made of... I cannot find this anywhere.  Any chance they are 304 or 316, i can get that real cheap.  Thanks again everyone, i really appreciate it.

RE: brake rotor material

I recently researched this to replace my warped and variable thickness motorcycle discs.  It appears that they use a "high carbon content 400 series (martensitic) stainless steel" or "420 stainless".

Sources:  http://members.ozemail.com.au/~smiley_b1/About.htm
http://www.braking.com/home.asp?sel_lingua=eng  (and select Products, Disks)
http://www.galferusa.com/MOTO.html  (and select Rotors)

Browse the first source and you will see how cheap they can be.  I am buying mine from the first source (being in Australia) and he will make any design as they are individually laser cut anyway.

The 2nd source is Italian and the 3rd is in USA.

Rick

RE: brake rotor material

Depending on what you're stopping -
---------------------------------------------
http://www.fcpgroton.com/images/083-1206.jpg
volvo 240 rear brake rotor - $20 - $56
http://www.fcpgroton.com/volvo240brake.htm
-----------------------------------------------
cute little mechanical disk brakes here -
http://www.mfgsupply.com/GoMiniBrakesDisc.html/mv_session_id=RVEiHt3j

A brake lathe is made to refinish brake rotors.  They cut both sides at once to help ensure good parallelism, which can be VERY challinging doing one at a time.

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