Thread: Cupped Pine Boards

Rip it into 3x 90mm lengths to reduce the amount of cupping per width, then remachine them straight and square.

Its pretty hard to keep 290/19mm pine flat... near impossible actually!(we call it crapiarta here )
To get radiarta pine to not cup/twist at 290x19mm it would need to be quarter/riff sawn clears grade, plantation pine is usually harvested well before the tree's can grow that big and its rarely cut quarter/riff sawn.

Try damping the hollow side with water and leave it a day or so.
If it flattens use it immediately.

Thanks for that. It would seem that buying wider planks of pine is yet another trap for young players as we enter the world of woodworking ---- I'm not even sure what quarter/riff sawn is

If the wetting of the board works and the cupping is removed, when I assemble the bookcase (2000mm high -- three fixed shelves with biscuit, glue & screws) will that hold the timber straight or will the cupping pull the bookcase apart. I am trying to not have to cut the lengths into narrower sections and rejoin them.

Thanks

Stephen

Most likely the convex side already has more moisture than the concave side due to the way you had it stored.

So wetting it down till it straightens then screwing and gluing usually does the job.
As long as the air can get to both sides once assembled its likely to stay flat.

Señor Quixote


As Bob hints, if you placed the pine directly on the ground then moisture can move through the ground into the wood. If one side is wetter than the other the wood will cup. Wetting the dry side should reduce the cupping. In future you should put some battens between your timber and the concrete.



My wife is an academic so I have made heaps of book cases. The first were 300 mm deep, like yours, but very few books are so deep so the next were 200mm deep. Others have been 150mm (mainly for paperbacks). I also make my bookcases from pine that is 32mm thick:
* It spans greater distances without bending under the weight of books.
* It is less likely to cup or twist.
* It looks better, in my opinion.
* I think its easier to work with.



Anyhow Señor, welcome to the wonderful world of woodwork. If you make ten percent of the basic errors as me then you will do OK.


Cheers


Graeme
Worlds most creative stufferupperer.

Thanks Bob, I will give that ago.

Graeme thanks for sharing your experience. How far do you span with the 32mm thick pine. The bookcases lok great. Are they modular & movable? Being able to relocate them was one of SHMBO's requirements.

Stephen

For bookshelves also consider using MDF with a laminate. You can get full 8x4 sheets with a thin hardwood laminate on one or both sides. There are lots of choices in the laminating. You can then put a real hardwood front on them to hide the rough MDF edge, make the shelf look thicker and strengthen the span.

I enjoy making smaller pieces out of solid wood but larger items that have long or wide sections are more predictable when made from MDF as it doesn't move much at all.

Originally Posted by DonQuixote

Graeme thanks for sharing your experience. How far do you span with the 32mm thick pine. The bookcases lok great. Are they modular & movable? Being able to relocate them was one of SHMBO's requirements.

Stephen

I have spanned up to 1.5 metres. Those in the photo are 1.2m long and 195mm deep. All are totally modular - verticals of the same pine and shelves are held in place with sliding dovetails - absolutely no nails or screws. Finish is danish oil and those shelves are about 15 years old.

In practice I just took the length of the wall and divided it by 2, 3, 4 and five. Select the "optimal" span distance which always seemed to be between 1.05 and 1.35 m. The 1.5 shelves are beside a fireplace. It is very quick and easy to cut the sliding dovetails with weel made and accurate jigs.

I also mix the shelf heights to maximise the storage of variously sized books. Heights vary between 235 and 365 mm.

Cheers

Graeme

I have tried MDF but I have found that as I put a lot of books on the shelves the span has to be short (around 600mm or less) other wise teh shelves bow too much. That is why I am using pine.

Thanks Graeme. The finish looks great in the Danish Oil. My wife wanted straight pine but I'm not overly found of the colour.

How do you stabilise the book case -- are the vertices secured to the wall?

I just looked up on the net about the sliding dovetail joint but so far the jigs they refer to are difficult to see the detail on. The angle of your dovetail does not appear to be as great as that shown on some sites.

I wouldn't mind having a crack at sliding dove tail joint - would you be able to give me a couple of tips please. Really appreciate your help.

Stephen

PS: I used to live at Old Beach, I understand that the seasons first snow has fallen on Mt Wellington.

Do a search for (and download) "New Yankee Workshop Apr 05 09.avi" In this episode the woodworker makes a table out of some badly cupped pine, by sawing about half way through the pine. In this way he doesn't need to joint separate pieces.

I found it quite illuminating.

Originally Posted by DonQuixote

I have tried MDF but I have found that as I put a lot of books on the shelves the span has to be short (around 600mm or less) other wise teh shelves bow too much. That is why I am using pine.

Sagging shelves will be a problem if you don't design against it. All timbers will sag if you span too far without supporting them.

What I was getting at with the MDF is use the cheaper material for the shelves (where there is the most wood) and front each of the shelves with actual/real solid wood. If you have a wide span, use thicker timber to front the shelves to give more support. eg. instead of using 19x19mm to finish off the front of a shelf use 38x19mm which makes the shelf span much more solid, looks great and is much cheaper than just using thicker shelving timber.

You can span quite large distances with 19mm thick shelves by reinforcing the front (any rear for more support). Without support, you need to limit the spans.

To test this...get a piece of pine, 19x38x2400, put it flat on the ground and get a person at each end to bend it up (keeping the middle still on the ground). See how much flex you can get. Now put the timber on the side and repeat the test. There should only be minor flex. Cut the timber down to 1800 and repeat the test, then 1200. By the time you get to 1200 there should be very little flex with the timber on its side. Obviously the "wider" the supporting timber the less flex at length as well.

Anyways, just some thoughts to save you some money and finished weight in the project.

Originally Posted by DonQuixote

Thanks Graeme. The finish looks great in the Danish Oil. My wife wanted straight pine but I'm not overly found of the colour.

How do you stabilise the book case -- are the vertices secured to the wall?

I just looked up on the net about the sliding dovetail joint but so far the jigs they refer to are difficult to see the detail on. The angle of your dovetail does not appear to be as great as that shown on some sites.

I wouldn't mind having a crack at sliding dove tail joint - would you be able to give me a couple of tips please. Really appreciate your help.

Stephen

PS: I used to live at Old Beach, I understand that the seasons first snow has fallen on Mt Wellington.

Hi Stephen

The pine started light and darkened with age - keeps getting better. My walls are brick+plaster - just drilled a hole in the brick near the top of each vertical, put in a bit of green spaghetti and a panhead screw, another screw near the top of the vertical and twisted a bit of wire around the two screws - stabilised the shelves well and nothing visible from eye-level.

Picture of my sliding dovetail trench cutter jig (made from scrap, but effective) is below. I just clamp it across the shelf vertical and run the router - the space between the left and right fences determines the width of the trench. Its essential that the timber in the jig is at absolutely 90* as any error will be repeated in all cuts. Dovetail angle is as per Carbitool dovetail bit.

To cut the sliding dovetail tails on the ends of the shelves rather than building a horizontal router stand I stood the shelves vertical. I built a similar jig onto the top of a workmate and thereby clamped the shelf vertically. First I would cut one side of the tail, then I put a removable spline against that fence and then cut the other side of the tail. The spline set the width of the tail and overcame problems of minute differences in material thickness that was a problem when I first tried to use two fences.

Its easier to do than explain. Set up the jigs with some offcuts and adjust until everything works. Then as you are cutting keep testing that everything stays aligned. I had several instances of the router bit moving by 0.5 to 1.0 mm during cutting. My practice was to cut three trenches then slide a set-up tail into that trench: if it fitted well then everything was still sweet. Similar every third tail I tested with a set-up trench. The workmate is only about 600mm high and the shelves were up to 1500 long - to get enough vertical clearance I took a board out of my deck and hung the shelves through the hole.

It was not a difficult job and I am not a highly skilled woodworker. It is essential that all angles are at 90* - jigs, shelf ends, trenches - cut slowly so that you do not overheat the router bit. Spend the time on the set-up and the rest is real easy and quite quick.

Cheers

Graeme

PS: First dusting of snow was below the Springs - a refreshing 2* in town this morning!

Hi Graeme
Spoke to my wife and she has given the ok to try it in her office! I can follow most of what you are describing but have two questions:
1. What is a spline & do you use the same router bit to cut the tail.
2. Do you build in a kick board at the bottom of the shelf. If so how do you do it to maintain the easy knock style of the shelves.

Appreciate your assistance.

Regards

Stephen

PS With the wind chill in Hobart that would have been a cold day. The in-laws awhere shopping in Hobart today & said it was really cold.