I don't mean to offend anyone, but I have to strongly disagree with Tina R. By placing your child (or grandchild) in your lap and holding her arms down--you are teaching her that your body is a place of punishment! You do not want your child to associate touching you or sitting on your lap as punishment. Your lap and your body should be a place of love, protection and support.
I would suggest figuring out what your daughter's "currency" is. Every person has something that they would be very upset to lose--whatever that is for her (maybe a toy, a stuffed animal, a video--her VERY favorite thing) you need to figure it out. Then you sit her down and talk to her BEFORE she hits and explain to her that if she hits again, she loses that thing. Then when she hits, follow through. Show her the object, put it away in a cabinet or other place, and explain to her that she lost it for hitting. Tell her she will earn it back if she doesn't hit.
A couple hours later, make a big deal about giving the item back to her. Explain to her again that if she hits, she will lose it again...and follow through! It may take a few times, but if you truly are taking something away from her that means a lot to her, then she will most likely change her behavior.
Hitting and biting at this age are very common. At 14 months, children know more words in their mind than they are able to speak. Give her the tools to put words to her feelings. Teach her phrases like "I don't like that!" or "That makes me mad!" She is hitting because she is frustrated that she can't express how she feels in a way that you will understand.