increasing hole size in deck post.

[Lidfam]

Hello. I have a problem with increasing the size of the newly drilled holes in my decking posts. I decided to replace the old balustrades with rope, so drilled what I thought were the correct size holes, 25mm, but the rope is quite a bit thicker than stated on the packaging. So I am attempting to open out the holes in the 9 posts, to about 32-35 mm. My problem is, every drill bit type I use, judders badly as soon as it touches the wood and tries to throw the power drill to one side due to the existing hole. The fact that the posts are 4ft high and not totally rigid at the height I am drilling, doesn't help. My power drill only takes a shank of up to 12mm, so I am at a loss what to try next. Any help or advice would be very much appreciated to stop me tearing my hair out. Thankyou.

 

[gissle]

Can you remove the posts and drill them on a bench? That would be ideal.

You could also use a flat drill bit to bore a bigger hole.