Resawing Tropical Hardwoods

Resawing dense hardwoods like Bubinga, Cocobolo and Swartzia requires special care. October 1, 2009

Question
I would appreciate any advice on resawing seasoned 6"-10" wide boards of the following species for a customer, on my WoodMizer sawmill: cocobolo, bubinga, and swartzia. He's got 8/4 boards and is hoping to get either three half inch boards or four 3/8" boards out of these. That doesn't leave a lot left over. I realize I'll have to rig a baseboard underneath as the mill won't cut 3/8" off of the bed rails. But are any of these which will be so hard that they won't be a match for a new DoubleHard blade?

Forum Responses
(Sawing and Drying Forum)
From contributor S:
I don't have any experience with these particular woods, but I have resawn a good bit of material, using both my bandmill and my horizontal resaw. From my experience and what I have heard from others, resawing expensive, dense, dried tropical hardwoods should only be done on a horizontal resaw equipped with an air hold down system that will keep the boards flat. I've also heard of using carbide tipped bandaw blades for this. The blades cost $200-$300. If your customer only has a few boards, he may be alright with you trying to resaw on the sawmill, but if you waste a bunch of his wood he's not going to be a happy camper. I would suggest that you pass this job off to someone with the right equipment or if this guy has a lot to do, and consider getting a horizontal resaw of your own.

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From contributor T:
I have resawn plenty of barn beams without resawing attachment, but thinner lumber like this needs accuracy, and pressure rollers of some kind to keep control of the boards warping during a cut. If this does not work maybe you can still take on the order, but find a place capable of handling it and sub contracting it out.

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From contributor S:
My first resaw was designed for resawing pallet cants and had simple pressure rollers that used the weight of the roller itself to push down on the wood and against the feed belt. I have a better resaw now that uses air cylinders that can pretty much straighten out a 4/4 and sometimes an 8/4 board, I crank the pressure up to about 100 psi. If your lumber is all really nice and flat the simple pressure rollers will probably work fine.

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From Gene Wengert, forum technical advisor:
You do need wood that has the drying stresses removed (also called casehardening). Make sure that you cut the standard prong test to check for stresses. If there is stress, you will not be able to resaw without bowing and cupping. As mentioned, the high density makes this job very difficult with a small saw and poor hold-downs.