The "Perils of Piston Fit Drawers"

Re: The "Perils of Piston Fit Drawers"

Steve Hamlin

>I wonder. For a piston fit drawer, when fitting to such fine tolerances, perhaps the greater tangential movement would be better oriented vertically so flat sawn may actually be better? Would exacerbate differential movement between sides and front, stressing the joints more of course.

Cheers

Steve (from a position of ignorance, but just wondering...)

I totally agree...

Scott Burr in Ben Lomond CA

>When I made my saw till the two drawers came out so well they were piston fit. This was long before I ever heard of the term. Completely frustrating because it took so long to close them. I got very tired of waiting for the air to escape while closing them I drilled a hole in the backs of the drawers so the air had somewhere to go. Not the best remedy for an application like yours, but for my saw till it works just fine.

I made a similar miscalculation

Bruce, a MN Galoot

>on the sliding doors on my headboard. I built the thing in the winter, in North Dakota, when the humidity is just plain nonexistent. However, there is more humidity in MN in the summer, and sometimes it takes considerable effort to slide those doors open. Oops! Next time there will be a little more expansion room.

Bruce

Re: The "Perils of Piston Fit Drawers"

Sgian Dubh

>Always a tricky one Bill. It's nice to do and, as you say, works pretty well on small drawers, ie, drawers less than about 75-85 mm (3 to 3.5") tall.

Even better if they're made in the summer when RH is highest. They end up a bit sloppier in the winter when they shrink in height a bit. Of course if the seasons of high humidity are reversed, ie, low RH summers and higher RH winters you'd look to make them a tight fit to suit the winter months. Also using radially cut material helps, but this may not be the preferred choice for drawer fronts even if it is for the sides and backs.

Taller drawers, as you've found are very tricky to get that piston fit thing. On the whole I find it's safest to make drawers just a little sloppier than piston fit.

I used to have fun when I lived in Houston. I had to make drawers tight, oversized even, stick the cabinet and drawers into the air-conditioned office, and wait a couple of weeks. Then I could fit the drawers. It never made any real difference what time of year the job was done. Everything shrank once it got from my all expenses spared tin shed workshop into a customer's house. That's because all the wood I worked was at least 10% MC, and usually more. The stuff may have been kilned to 7% up in PA or somewhere, but it was usually a few percentage points wetter by the time I used it. Slainte.

YUP!

George@Colonel's Workshop-Havertown PA

>Good Afternoon Bill,

I an hand fitting 7 drawers in a cherry chest-on-chest at present. Sloppiness is certain if I really work at it. :<) I'm not too concerned about how they will operate on the oak slides and guides. The drawer boxes are poplar and attaching front faces will be cherry with a surrounding bead. The drawer face perimeter bead and carcase faceframe is where I need the piston fit.

George

Re: YUP!

David Charlesworth

>Bill,

Sorry to hear that.

Drawer height is an issue, which must be adressed, width should not be.

However I would bet that movement of the carcase sides or drawer sides caused the sideways binding.

Drawer fronts and backs cannot change their length more than the material that a conventional carcase is made from, i.e. solid timber.

There are changes of length but these are a minute fraction of width and thickness changes. Mind you you have much greater changes of relative humidity than we usually get in the UK.

best wishes,

David Charlesworth