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Ask an Expert

Joinery, cabinetwork & furniture

Like to know what wood to use building a pergola or framing a barn? How about the difference between tung oil and polyurethane as a floor finish? How to revive decking or deal with merbau stains? Or how to meet the building code or bushfire standards? Or ask about the environmental advantages of wood or forest certification?

Q. I am wondering what are the best types of glue for gluing Spotted Gum in chair making. Any advice would be greatly appreciated.

Chairs are sometimes put under considerable stress, particularly if a person tilts back on the two back legs. There are many furniture glues on the market, but Selleys 308 is one that gives a strong bond. Spotted gum has a slightly greasy quality and if you have any difficulty achieving a bond, a reference in our library washing it with 10% sodium hydroxide (caustic soda) before gluing. Remember caustic soda is a dangerous chemical - you will find information on the net about safe handling procedures.

Q. I have a 5m x 3cm deep x 800cm wide blackbutt kitchen bench top. It has just started to warp is there anything I can do to save it?

If the benchtop is warping, that means the timber is changing moisture content - either gaining or losing moisture. We weren't sure whether the benchtop was glued up from strips of timber or whether it was one solid piece. If it is "glue laminated" it would have been kiln-dried before gluing and in that case presumably it is gaining moisture from somewhere. Perhaps the timber was not sealed on all surfaces, including cut-outs and underside, as recommended. If it's one solid piece it would be too big to kiln dry and might not have been thoroughly seasoned before installation. Apart from the moisture content of the timber, the other critical factor is correct installation. Timber benchtops should never be glued down and screw fixing must allow for movement as shown in one company's installation details, available via this link - http://www.dgi.com.au/bench2.html. You might want to take up some of these issues with your builder or supplier.

Q. I am looking at making a solid timber dining table. I would like to have Red Box in the middle with a Red Gum edge of approximately 100mm around the edge of the whole table. I'm concerned about the movement in the timber as we'll have red box running north/south and the redgum on both ends of the table will run east/west. I'm predicting there will be movement in the timber where the end grain of the red box meets the redgum. Is there a way of joining the timber at this point which will still allow for movement?

You are right to approach this with a great deal of care. Since wood only shrinks and swells across the grain, any movement in the red box will be restrained by the red gum fitted at 90° each end. Ideally if the wood is nice and dry and the table is kept in a stable environment then movement will be minimal. However if the wood is not fully dry, or the table is subjected to a change in moisture content, the red gum at each end will restrain the red box and may cause it to split. The easiest way to resolve this would be to only fit red gum on the sides parallel to the red box, not on the ends. If you particularly want the neater finish of red gum running all the way round, it would be advisable to find a way of allowing the central portion to move independently of the red gum edging. Perhaps the red gum could be fitted to the red box with a tongue and groove joint that is not glued but is tight enough to hold the edging in place. Note that the red box section of the table must be fitted to the frame in such a way that movement is possible, for example with table clips rather than screwing and gluing. There's a good explanation of this on the net at http://www.finewoodworking.com/pages/w00173.asp.

Q. I'm a year 12 Design & Technology student and I need to purchase timber veneer for the finish of my project. Are there any reasonably cheap yet aesthetically pleasing Australian timber veneers on the market? And also, are there any major suppliers that I could purchase the material from?

If you go to the website of the Timber Veneer Association of Australia (TVAA) and click on the tab that says "How to Find Us" you will find a list of veneer suppliers around Australia. One of the TVAA members in your State should be able to help. Veneers vary in price but Australian species should generally be more economical than some of the exotic species. Perhaps Tasmanian oak (mountain ash/alpine ash) would suit your project.

Q. I'm building a dining room table using tallowwood (eucalyptus microcorys). I glued up the table panel using Titebond II glue, after washing the joints with a 10% sodium hydroxide solution (as suggested on a couple of timber advisory websites). However, the glue failed. Which glue should I use? The table is for indoor use. I have read contradictory advice. Some say use a two pack epoxy, others say use Titebond III. Any advice would be appreciated.

It's hard to say why your joints failed. Tallowwood can be difficult to glue due to its greasy nature (hence the name tallowwood). However, you have followed the recommended procedure in washing it with sodium hydroxide so it should have been OK. Perhaps the glue went off too quickly? Titebond III gives a longer working time than Titebond II and that, combined with its greater strength, might do the trick. Before you have another try we suggest you phone for some technical advice from the distributors of Titebond. They provide technical support on this number: 1300 133 439.

Q. I have a raw edge Marri slab cut from just of centre of log, it is 2.8 mtr long by 1.1 wide and 50mm thick dressed.It has been air dryed over a number of years in a shed in South West of WA, unfortunately the 4 logs dressed from the same log didnt have stickers inbetween once stored back in shed after machining. My problem is that it has cupped by about 12mm since being in my Perth shed. My question is as this slab is going to be attached to very solid refectory base, could I pull it flat as I dont want to make it too much thinner by machining off cupping. What would be best method to hold it flat, taking into account expansion.Would sliding dovetails set into underside of slab running widthways, what size would they need to be to hold table flat.

The risk is that flattening your slab might make it split. However, 12mm isn't a great amount of cupping to remove over a width of 1.1m and wood is able to flex a bit. Having said that, a 50mm thick slab of hardwood is going to be fairly resistant to being pressed down flat! The usual way of achieving a curve or flattening out a cup (other than by steam bending) is to run one or more grooves on one face.  Frankly we feel it would be easier to machine your slab flat, but you could try the sawkerf method. It's described in more detail in this blog http://www.sawmillcreek.org/showthread.php?5559-Flattening-a-cupped-board.

Q. I'm a year 12 Design & Tech student and I was considering making an expandable coffee table out of cardboard then finishing it using a wood veneer, perhaps out of zebra wood. I was wondering if there are any particular adhesives on the market/techniques to fix the veneer to the cardboard and also, I was wondering what would be the most appropriate finish to use in order to waterproof/spill-proof the table. Thanks for your assistance

Wood veneer will bond well to cardboard with normal PVA woodworking glue. The hard part will be to keep it pressed flat while the glue dries. Maybe you could turn your kitchen table upside down, or use some other similar wide flat surface to press the veneer and cardboard together without any wrinkles. The best finish would be a floor-grade polyurethane. They are very tough and liquid resistant - obviously they are designed to be walked on, so they stand up well to wear and tear.

Q. I'm interested in any information you have about the recyclability of laminated cupboards. Not reusability but recyclability - ie breaking them down and reusing the wood in the production of new cupboards.

If in referring to "laminated cupboards" you mean cupboards finished with a laminate (eg. "Laminex"), we feel there would be limited opportunities for re-use. The majority of cupboards are taken out of service because they have suffered wear and tear and/or have gone out of fashion. Benchtops may have holes cut out for sinks and other services, which would not fit a new location. It is possible that some sections could be used for hidden areas, such as cupboard floors and shelves, but it is not likely that cupboard fronts or benchtops made from recycled laminated board would find a ready market. Solid wood doors and benchtops might be more marketable, although the labour in breaking down the cupboards and re-working the timber might make the end product more expensive than new material.

Q. Caribbean Pine | Pinus Caribaea - Is this product suitable for a reception desk top? Also what thickness does it come in. I have selected this for interior wall panelling and would like the desk to match the panelling. Could you please advise me, if this product is suitable?

Caribbean pine can be used for desks and benchtops, although it is not as hard as some of the denser timbers. However, we assume a reception desk will not be subject to denting or impact loads. Wearing qualities also depend on the coating, and we recommend a floor varnish for best results. The top will have to be made up by a joinery shop or specialist supplier by gluing planks or strips of timber together. Consequently, any thickness from 19mm to 45mm could be specified. You may wish to inspect the timber before the top is made to ensure that the quality meets your expectations. Correct moisture content is important to avoid shrinkage after installation. Your joiner should have a moisture meter and be able to ensure that the moisture content of the timber does not exceed 12%. One final tip - the top must be installed correctly and you may find this installation guide useful - http://www.dgi.com.au/bench2.html.

Q. Where do you buy nice wood to make a top for a fold singer sewing machine table top and the drawers. It was veneer stuff but I would like better than that. And what type of wood might be nice with nice grain.

Some timber merchants are mainly interested in supplying the building trade, whereas you are looking for furniture quality timber. If there is a Timber Merchants Association in your State they should be able to narrow down your search and point you in the right direction. Otherwise you will find some leads if you write "specialty timbers" in your browser. Regarding the type of timber, it's probably best to see what local suppliers have in stock and look at some samples, rather than have us suggest some timbers that might not be available in your area.

WoodSolutions

Did you know?

About 16% of Australia’s 147 million hectares of native forests are in nature conservation reserves.