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Forum topic by rulubos posted 05-22-2015 11:45 AM 681 views 0 times favorited 4 replies Add to Favorites Watch
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1 post in 1127 days

05-22-2015 11:45 AM

I am new to wood working so thank you in advance!

My friend and I are creating small, machined, wood products from pre-dried wood. Although we treat them with tung or linseed oil after machining/sanding, the components tend to crack after some time sitting in an indoor environment. I am looking for somewhat of a consultant to help me finalize a process that prevents cracking of various woods we used. I’m happy to pay for an expert to provide detailed explanations. Thank you in advance!

1. We use pre-dried woods (10% – 12% MC)

2. Wood is stored in a semi warm/humid environment (60% – 88% relative humidity)

3. Wood is machined (cnc and manual machines) in this environment

4. semi-finished parts are stored in this environment

5. Parts are sanded and treated with tung or linseed oil

6. finished product then shipped to customers. They are generally stored indoors (15% – 40% RH)


1. Best way to seal wood from expanding/contracting in low RH environments (absolute best way methods)

2. tips for machining

3. tips on storing wood prior to machining

4. tips on storing semi-finished parts (partially machined but untreated)

I know different woods have different properties. I am listing the woods below in hopes that someone has expertise with the different woods and can comment/help specifically.


4 replies so far

View TheWoodenOyster's profile


1317 posts in 1961 days

#1 posted 05-22-2015 11:55 AM

My sole advice that I think would get you almost all the way to a solution is to store, work, and finish the wood in a lower RH environment. 88% is pretty humid. Even thought the MC of the wood is low (technically) there is big difference in what wood does at 90 degrees and 80% RH versus 65 degrees and 20% RH. Using a polyurethane-type film finish might help a little bit, but the relative humididty at the front end during manufacturing is likely your biggest problem.

My wood expert consultant fee is $100 a word, so you owe me a new shop.

Just Kidding – Good Luck!

-- The Wood Is Your Oyster

View OSU55's profile


1700 posts in 2015 days

#2 posted 05-22-2015 12:14 PM

Agree with oyster. Other finishes will slow the moisture equalization process, but not stop it. You need to store the wood and manufacture the products in a less humid environment. You could probably store lumber and pre finished product in less humidity, and machine at current moisture levels. A somewhat airtight area, even sort of a “greenhouse” within a room, with a dehumidifier, would be my 1st attempt.

View barada83's profile


86 posts in 1212 days

#3 posted 05-22-2015 04:21 PM

I’m wondering about the cracking, are these glued up or cracking as single pieces? If they are cracking after being glued up, it could be a multitude of reasons but if cracking as single pieces, I would predict that dehumidifying would not help your situation. Wood typically cracks in single pieces as it dries. Wood is very wet when green and some of that moisture is held in the plant cells. As the wood dries, it shrinks and often cracks especially in edge areas as the wood literally pulls itself apart. Now if glue lines are cracking, that could be different as increases or decreases in moisture content can affect that. What I would do is try to acclimate your wood to your relative humidity for quite some time before working with it, like 2-3 months if possible. The humidity should stabilize. When you do work with it, mill it deliberately oversize and let it rest a day or so before final milling. I would highly recommend humidity control devices to reduce the fluctuations – humidifier and dehumidifier.

-- Mike

View pintodeluxe's profile


5705 posts in 2839 days

#4 posted 05-22-2015 04:51 PM

Try using kiln dried wood and see if that makes a difference. I have found that air dried lumber at 10-12% MC moves more than KD lumber at 6-8% MC.

You can mill the wood in stages (watch any Tommy Mac show for detailed explanation).

This all assumes that the construction techniques are sound. Obviously if you attach wood across the width of a board (ie wrapping solid wood table with edgebanding) you are going to have problems with seasonal expansion.

Good luck

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

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