Popular Woodworking 2002-02 № 126, страница 17
a ratio of three parts mineral spirits to one part polyurethane. We asked our finishing expert and contributing editor Bob Flexner for his advice: "You can thin it with water. The problem with doing this is that you reach a point where there aren't enough emulsifiers to combine the added water with the resin, and the finish separates or beads. Brands are different. You just have to try different mixture ratios. If it works, great. If the finish separates, thin with less water until it works. The first coat will probably be fine no matter how much you thin it because it soaks into the wood. It's the next coats that will separate if there's too much water." Should I be Worried About My Tabletop Warping? I want to build a kitchen table using 3/4"-thick oak. The dimensions are not final (about 36" x 96"). Can I make this size tabletop by edge-gluing boards without a big concern of warpage? Should I put cross pieces on the bottom to keep it from warping? Rob Doty via the internet There are concerns, but if you've done your prep work correctly you should be in good shape. First, use quartersawn lumber, which has less risk of cupping and warping. Make sure the wood is dried correctly by checking the moisture content (around 7 percent is preferred). If you have the opportunity, run the boards to thickness and allow them to sit for a day or so. If any of them warp, set them aside in your scrap pile. Lastly, remember to attach the top in a way to allow the wood to expand and contract during changes in humidity. (For more information on this subject, see Lonnie Bird's article in this issue regarding wood movement.) — David Thiel, senior editor Why Oval Holes to Attach a Top? In the $175 Workbench (February 2001, issue #120) you attached the bench's top to the base through cleats. Why did you make the screw holes in the cleats oval shaped? Ralph Knox via the internet The top expands and contracts more than 1/s" a year. The oval-shaped holes prevent the screws from snapping as the top moves. PW — Christopher Schwarz, senior editor 15 Circle #115 on Reader Service Reply Card |
