Buy servos with dual-ball bearings on the output shafts with metal gears. Sure, it's a lot more expensive up-front to do this; but with a biped and the load (lots of side load) on the shafts, if you don't, your decision to go "cheap" may end up costing you more in the long run than if you had spent the money on the more expensive option in the first place.
IOW - don't be "penny wise and pound foolish".
Thnx for the advise ..... No doubt you are right but unfortunately my budget will not allow...I live in India where such servo is not easily available moreover if a servo is $10 here they sell for $ 18 and Indian rupees have less value than dollar . And if I buy from other online site like robotshop.com and other the import duties are double of the cost.
I think I should not be needing so much high quality as my robot will weigh 1-2 kg and small in size.