Cracks in a Butcher Block

Woodworkers consider why cracks would open in a butcher-block cutting board during orbital sanding. January 8, 2010

I made a bunch of end grain butcher block cutting boards for Christmas presents this year. All were about 2" thick, 14" x 16". I was sanding the last one (random orbit, 120g) and most of the interior squares started cracking. Not to the point of falling apart - it was still sound - but aesthetically appalling. I have built big countertops (7' long) in the same manner in the past and never had this issue. Any ideas as to why this happened?

Forum Responses
(Furniture Making Forum)
From contributor M:
I would guess the heat from sanding caused the wood to crack - the wood was probably not quite dry enough.

From contributor C:
I have come across this before in my furniture restoration business. I think it is probably down to shrinkage. When butcher's blocks are used, they are cleaned down with water and possibly a detergent. This would swell the wooden blocks, causing them to stay tight in their frame. I am thinking if you applied an oil finish, it might just swell the wood enough to close up the joints.

From Professor Gene Wengert, Sawing and Drying Forum technical advisor:
A crack is evidence of wood shrinkage. Sometimes the cracks are in the end of the wood but not seen; they re-open as the wood dries (with sanding heat or dry air). So, do we know if these are pre-existing end checks or new end checks? If new, then the wood is too wet for the air.

From the original questioner:
Thanks for the input. Initially, I thought heat or moisture issues were to blame. The maple shorts that I used had been sitting in the shop for months and my random orbital, it would seem, couldn't generate enough heat to cause stability issues. But maybe, I'm thinking, it was a combo of the two that together was just enough to cause the problem. At least they were just cutting boards and not a huge countertop for a customer.