Shaving off 8mm to 1cm from Bone Possible in Rhinoplasty?

What you are describing is exactly what is done as part of the rhinoplasty.   8 mm or more seems like quite a bit to lower a bridge, but I have seen cases that gave required that much.  Photos would really get helpful.  I would also suggest going on a few consults with surgeons in your area known for their rhinoplasty work.  Good luck.

You can certainly have the bridge of your nose lowered, and have the tip of your nose deprojected with Rhinoplasty Surgery. 1cm sounds like you want your nose significantly smaller than it is now. Significant reduction in size will lead to other changes in your nose like widening.
Seek several consultations from qualified, experienced Rhinoplasty surgeons, and view many photos. Feel free to post / email your photo (full face frontal, and profile), and I'll be happy to share my thoughts.
Best regards

 It is possible to make your nose smaller in all dimensions. It is important to see an experienced rhinoplasty specialist to evaluate your skin thickness as well as facial proportions.

Yes it can be achieved. However 1 cm seems to be too much. Look at your profile view and make sure you don't have a small chin. A  small chin can make your nose look bigger than it really is.
Also, reducing the nasal hump too much is more likely to lead to complications than a conservative reduction.
Regards

Newts UK, the amount of reduction performed on your nose really depends on a number of factors. One of the most important considerations is your skin type. If you have thick skin, there is a limit to how much your nose will 'shrink wrap' down following reduction of the underlying bone and cartilage. Thinner skin tends to shrink down more readily and is more favorable when looking to make the nose smaller in size. If you are able to reduce the nose by 8-10 mm from bridge to tip will ultimately depend on whether or not the final size is proportional for your face. This determination is best made through careful nasal analysis done by an experience rhinoplasty surgeon. The link below may be helpful in better understanding what goes into this type of analysis. It would be beneficial for you to undergo a personal examination followed by computer imaging of your nose to determine what would be the ideal direction and degree of change.