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  1. #1
    Join Date
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    Default Seasonal movement question.

    I am doing a fair bit of laminating using shop cut laminates. Finished thickness of laminates is generally at or about 2 mm.

    I was thinking of the next job, which is an entertainment unit, a wedding present for my niece. I will laminate camphor laurel laminates over 16 mm MDF for the top, sides and doors of this unit. My question relates to the top.

    I will glue timber lips onto the MDF before laminating. They will be about 25 mm wide. This allows me to rout a profile onto the edge of the top. The pic is a small bedside table made earlier this year. On this piece, none of the lips are end grain, but I reckon the sides would look better if the lips were done with end grain timber, and the timber for the lips cut so the grain is a reasonable match for the laminates.
    IMG_2042.jpg

    My plan was to use end grain lips on the short edges of the top of the next unit, so I could match the grain on the top laminates. However, I am concerned that even with a unit only 450 mm wide that I may suffer from wood movement issues. The lips on the long edges are fine, because wood movement is minimal longitudinally. However, for the lips to the ends the seasonal movement will be greater in these lips if the lips are in end grain.

    Any advice gratefully accepted.

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  3. #2
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    Default

    Hi John

    I can see that you have really taken to laminating ...

    for the unit you are planning I suggest you go with a solid wood top. There's lots of simple ways to attach the top to the carcass -- construction rails and screws in slotted holes are possibly the simplest
    regards from Alberta, Canada

    ian

  4. #3
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    Default

    Thanks Ian,

    Construction rails with slotted holes is the method I generally use for solid wood tops.

    However, for this job the laminates are already chosen, cut and sanded. Here is a mock-up of what the top will look like when finished. The doors are prettier still.

    Top of cabinet.jpg

    Right now I am a bit kinky for book leafed veneers. More importantly, my niece has asked for this effect, having seen it in the cabinet made for her sister as a wedding present (see pic below), so book leafed veneers it is.

    Top grain.jpg

  5. #4
    Join Date
    Jan 2013
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    Default

    I don't think you're going to have too much of a problem. Here's why:

    it'll be in service in a house. Despite the fact that there are seasonal moisture shifts externally, for the most part the inside of a house is reasonably constant. It does shift but not to as great a degree as the outside environment. There are a whole heap of caveats around that statement regarding airconditioners and heaters but generally speaking a modern climate controlled house is far more stable then some old joint with moisture running down the walls in summer and a roaring wood fire in winter. I've got fine veneered furniture thats stood 50 years of the later environment and still looks good, but it has been looked after for that 50 years: ie it gets a hit of teak or cedar oil or Mr Sheen (depending on if its an oil or wax based finish) twice a year.

    The other is that where I have seen well done veneer peeling its always a coating failure that gets it, or water damage to the substrate. To actually swell the veneer wood the moisture has to get through the coating surface from one side or the backing substrate (which has its own coating surface) to get at the wood right? Modern coatings are quite water repellent compared with traditional oil or wax coatings. If some of these heirloom bits here have stood 50 years of service with moisture tricking down the walls in summer and a fire roaring away in winter with just a regular hit of oil or polish then what will be the life of a modern twopack epoxy that doesnt scratch or naturally allow moisture intake?

    The weak point so far as life expectancy is concerned will be the MDF, not the veneer. This old stuff I inhereted was all on a good quality marine ply backing, and I wouldnt think MDF would have stood up nearly so well.

  6. #5
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    Default

    I can see what you are saying and I agree, it may be a problem. But with the grain pattern of the bookmatch a long grain lip might look ok. I don't think I would like to risk it.
    I don't have any experience with veneers but how would the veneer mate to the lip? Is it just glued on top of the lip? I'm trying to envisage a worst case scenario. A split in the veneer?
    Those were the droids I was looking for.
    https://autoblastgates.com.au

  7. #6
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    Default

    Thanks guys.

    The lips are glued to the MDF and the sheet is sanded flat. Then the veneers are glued over the MDF and the lip and then a profile is made on the edge of the top. It will be a similar profile to the earlier pic of the bedside table.

    Actually I am more concerned about the bond between the end grain lip and the MDF than I am about the bond between the veneer and the lip.

    MDF is stable ... it barely moves at all. If I glue end grain lips onto the MDF I am concerned that the lips will want to move a lot more than the MDF; will want to grow or shrink in width (across the top) whilst the MDF will pretty much want to stay where it is.

    When I first started wood working I did some pretty terrible things in failing to allow for wood movement. By and large I seem to have got away with it, probably because I have habitually used wood that has low movement (cedar and NG Rosewood) and because as John.G said the pieces are inside a modern house in Brisbane.

    NCArcher is right about this piece. Because of the nature of the grain I will likely get away with long grain to the ends of the top, but for future pieces It will help if I can use end grain lips on the sides ... but am I asking for trouble?

  8. #7
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    Melbourne
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    Default

    Quote Originally Posted by John Samuel View Post
    MDF is stable ... it barely moves at all. If I glue end grain lips onto the MDF I am concerned that the lips will want to move a lot more than the MDF; will want to grow or shrink in width (across the top) whilst the MDF will pretty much want to stay where it is.
    A good, strong polyurethane or epoxy glue should hold it pretty well. There's always the risk of a small amount of movement, but as mentioned by others, it will be in a controlled environment.

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