Retired Trucker Scroll Saw Pattern.

This 10" X 8" portrait style pattern is for all the retired truck driver out there. This style of pattern is often cut from 1/4" or 1/8" thick Baltic birch plywood. Baltic birch plywood is a high quality void free board. Not many big box stores carry this plywood. You can find it at many hardwood supplier, Woodcraft stores and online.(Heritage Wood Specialties)

Because of the extra void free plies it cuts very well and is strong and suitable for intricate fret work. Cutting very thin 1/8" ply can be a challenge because there is little resistance to the blade. This makes it easy for the blade to get away from you. To combat this it can help to stack cut more than one at a time. 

What follows is the feedback I ask for from Tim at Heritage Woods Specialties regarding wood movement. This is great stuff right from an expert in the field. It corrects and enhances my comments from the earlier post. A must read for any woodworker.

Information: From the owner of Heritage Wood Specialties. Tim Worms.

Hi Steve,

Thanks for the opportunity to provide some feedback on this issue.  

Regarding cupping or warping, most of what you say in your attached article is correct, in my opinion.  Talking about the rate of moisture exchange can be misleading.  While the rate can have an effect, the amount of moisture exchange is far more important than the rate.

Some facts as I understand them:

All wood gains and loses moisture, period.  It is usually through water vapor in the air, but also can be from direct contact with liquid water. When wood gains moisture, it expands, and when it loses moisture, it contracts or shrinks. If a board gains or loses more moisture on one side than the other it will warp, cup or bow.  Stresses in the wood can also cause wood to move, but moisture exchange is the most common cause.

A board can warp even if it gains or loses moisture evenly on both sides, due to the grain.  Flat sawn boards will expand or contract more on one side than the other.  This is a characteristic of wood grain and is not a defect, and cannot be eliminated.  This is why quarter sawn boards are more stable than flat sawn boards.  It is also why we glue narrow staves together to make wide blanks, and we try to alternate the end grain direction whenever possible.

Hardwoods are almost always kiln dried to 6-8% moisture content, which is in equilibrium with a relative humidity of 30-40% at 70 degrees.  That means that if wood that has been dried to approx. 7% moisture content is stored at 35% relative humidity, it will not gain or lose any moisture – it is in a state of equilibrium with its surrounding environment.

Softwoods are generally kiln dried to approx. 8-12% moisture content, meaning they almost always will dry out when placed indoors in a 30-40% relative humidity environment. Air drying will only get most woods to approx. 15-18% regardless of relative humidity conditions.  It takes the heat of the kiln drying process to get down lower.  Air dried wood is always much more prone to warping and cracking when used for indoor wood projects, and I do not recommend it at all.

Knowing these facts, we can begin to develop some best practices with handling wood.  All wood will move to equilibrium with its surroundings when placed in a new environment.  It will either gain or lose moisture depending on the original moisture content of the wood, and the humidity of the environment.  The best environment is one that is 30-40% relative humidity.  We want to keep all surfaces exposed to the air during this time, as much as possible or practical.  Stickering, as you say, is one way.  Standing the board on edge so both faces are exposed will also help.  

Finishing the wood with a good quality paint or varnish will slow the exchange of moisture giving the board more time to reach equilibrium, and the slower movement is less likely to cause warp or cracking.  If a board laying on a table, cups, it can be corrected by simply turning it over for a similar 

period of time.  Adding moisture  and/or weight to one side may speed the process, but does not offer much if any additional benefit.  

Unfinished wood will reach equilibrium in a few hours or a day if it is thin, or a few days or weeks if it is thick. 

Regarding thin Scrollsaw blanks, we tell our customers that they may warp or cup a little, but that is sometimes unavoidable, despite all our efforts and best practices.  It is wood after all, and wood moves.  If it is easily flattened by a light push with one finger, we do not consider it a defect, as it is still usable for the intended purpose in almost all cases.  

If it is warped much more than that, or it is not usable, we will replace it at no charge, but we may ask the customer to be responsible for the cost of returning the original, or at least to send us some pictures. They can give us a call or send an email and we will be happy to hear there feedback.

This turned out to be a long winded answer, I hope it helps.

Thanks,

Tim

Information:
Yesterdays post included a secret word video giveaway. You had to watch this video and submit the secret word that flashed on the screen. Some of you got the answer wrong because you did not watch the full video. If you want to try again I will just delete any entries more than one. Oldest first. You will have to go back to yesterdays post for the rest of the rules. A couple of people used the wrong email address. I'm trying to make this easy but you have to follow the rules. It's a random drawing but I want everyone to have a chance so try again.

If you missed yesterdays post go back and give yourself a chance to win.

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