[OP]
Contributor
So I'm not much of a furniture maker, but I do have a project coming up that I'm thinking of using piston fit drawers on. Now, what I don't quite understand is what happens when you build it in the summer and winter time comes around. Everything suddenly loosens up, no? Or the other way around, the drawers will stop working, right?
I know that can't be right but I'm not sure what keeps everything working with such a tight fit. What's the secret?
Member
Don't make them fit too tight,or they will jam.
Member
I'm curious too. I have Rob Cosman's video on drawer fitting, and I just read an old Fine Woodworking article by Alan Peters on it... One thing that's clear is they tend to use solid wood for the components and follow good contruction rules (grain orientation in the right directions) which I suspect helps ensure everything is expanding and contracting at the same rate -- as best it can.
Member
John,
Rob does a really nice explanaition of this in his video, and Jamie is dead-on in his post. In essence you do it by running the grain vertical on the ends and cross-wise for the horizontal pieces with the exception being the drawer stringers. For those you constrain the drawer stop with the front rather than the rear of the drawer. This keeps the front relief at or near constant.
There are other nuances Rob discusses in his video to avoid seasonal binding but since I'm not that far along in my neander work yet, I have not committed them to memory. As a Neander-noob (but very experienced engineer) I really appreciated not only his coverage of seasonal binding but also his focus on which portions of the fabrication were most critical to a good fit.
He takes the time to tune the cabinet and build and tune a piston-fit drawer in "real-time" start to finish in the 2-hour video, explaining every step as well as how he'd do it differently if he were making a multi-drawer cabinet.
Be aware that success involves proper case tuning (as well as fabrication) in addition to drawer construction.
Just $0.02 from a "video-expert".
Jim
One can never have too many planes and chisels... or so I'm learning!!
Member
A nickel's worth of free advice: take a deep breath and tell yourself 'piston-fit' is not an appropriate standard for functional drawers.
Piston-fit demonstrates your ability to work to very tight tolerances; a drawer's job is to open and close easily.
In a recent class with Stewart Crick, he exposed us to a different standard: you should be able to close a drawer by pushing it with
one finger on any of the corners. This requires good fit, but not piston-fit.
I know a turner who is renowned for the piston-fit of the lids on his turned vessels. His wife refuses to use any of these.
When she lifts a container's lid, she wants it to come off.
Of course, YMMV.
AKA - "The human termite"
Member
John - your instinct is correct; you can make a drawer a piston-fit in the lengthwise direction, but you cannot make a drawer exactly fit its opening in the height direction and have it function in all seasons. It's for that reason that I choose to do something that, in my opinion, is a bit more sophisticated (and a heck of a lot harder to do). I make the cabinet carcass such that the opening at the front of the case is just a hair smaller than the rear of the case. One can then "piston fit" the drawer to the opening in the front, but when in use the drawer will open/close easily until it gets to be about 4/5 of the way open, at which piont it tightens up.Originally Posted by John Coloccia
Member
Could you say more? I'm not quite getting where the binding occurs in the "piston fit" case, and what part of the drawer tightens up at the 4/5 open position in your approach.
(I have a feeling I'm about to have one of those 'Duh, so simple!' moments soon...)
Last edited by jamie shard; 07-08-2011 at 1:40 PM. Reason: typo/clarify
Member
The tightening at 4/5ths open is because of a tapered fit. The drawer moves easily when you start to open it and the fit becomes tighter the farther it opens. This also helps prevent the "locked until next season" syndrome if it should actually swell too much.
The one thing that hasn't been mentioned so far is that some allowance should be made for the season in which it's made, i.e. fully expanded, fully contracted, or somewhere in between. I'm fortunate that where I live there's not much seasonal variation, so less planning is required.
Member
I built a night stand for my daughter from solid ash. Unfortunately, I built it in the spring from what was sold to me as kiln-dried wood at 8%. More unfortunately, I built it to tight tolerances. Later that summer she asked me why she couldn't open the drawer on the blasted thing. I knew exactly, and it took a Stanley Wonderbar to crank that drawer out. I needed only to take off a little, but I took off 1/16" just to be sure and she has not had a problem since.
Bottom line: piston-fit drawers are a nice ideal, but they don't work very well in MN where the humidity swings are huge. Maybe it would work in the desert southwest, but I wouldn't chance it even there if you're using solid wood. Plywood is a different story.
Member
What he means is that the back of the drawer is taller than the front. Make the back tall enough so that it BARELY fits through the opening and leave the front room enough to expand and contract within the opening. This way the drawer won't bind until the drawer has been opened nearly the whole way.
It gets a bit complex because you have to know the moisture content of the wood at the time of manufacture and estimate the expansion and/or contraction from there. Thus if you are building a piece in the winter (low humidity) you would have to leave a larger gap than if you were building it in the summer when the gap could possibly be almost nill assuming the wood is both dried and acclimated and assuming that conditions in the shop are similar to the place the piece will reside.
HTH
"History is strewn with the wrecks of nations which have gained a little progressiveness at the cost of a great deal of hard manliness, and have thus prepared themselves for destruction as soon as the movements of the world gave a chance for it." -Walter Bagehot
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I make my carcasses and drawers as perfectly as I can, then I plane just the drawers so only the drawer fronts (including any cockbeading) are a snug fit in their openings. I also use a fairly simple three hundred-year-old trick that ensures the drawer slides freely until the last sixteenth of an inch – I plane the top edge of the drawer front at a slight angle so the true fit is right on the outer edge of the drawer front.
Geo_I_chest-on-stand_drawer_1720_01a.jpg
Geo_III_oak_COD_drawer_1780_01a.jpg
Our forefathers also made the drawer sides fractionally lower in height to avoid any binding issues. The drawer backs were made lower again so they wouldn't catch on the underside of the carcase top or dustboard.
Sorry if I'm preaching to the converted, but sometimes the obvious is overlooked.
Last edited by George Neill; 07-08-2011 at 7:23 PM.
Member
Actually, that's not what I mean, but it's a completely valid way to accomplish the same thing. What I was referring to is making the carcass such that the drawer opening is slightly wider at the back than it is at the front. As the drawer is pulled out, the sides of the drawer impinge more and more on the interior case sides and it takes more and more force to pull the drawer out farther. This description is assuming that you're making a solid case where the drawers are captured by the case sides and there are no drawer runners.
If you're making a case where the drawers will slide on drawer runners, this technique is quite easy - one simply makes two gauge sticks to use while nailing the drawer runners into the case - one gauge stick is the precise width of the horizontal dimension of the drawer opening, and one gauge stick is slightly longer (I usually make mine about 1/32nd - 1/6th inch longer depending on the overall drawer width). The shorter gauge stick is used to space the drawer runners at the front of the case, and the longer one is used to space the drawer runners at the back of the case.
There is one drawback to manipulating the height of the drawer sides to accomplish the "tighten up" feature as you pull the drawer out. Because the height of the drawer sides changes with the seasons and the height of the drawer opening does not, the point at which the drawer "tightens up" will change with prevailing humidity. Depending on the wood's EMC at the time of construction, this might result in a drawer that "tightens up" only a few inches after it's pulled out, or the opposite extreme where the drawer doesn't tighten up at all.
Last edited by David Keller NC; 07-09-2011 at 11:32 AM.
Member
That's why I found Rob's solution so innovative.. a "duh" after I saw it but I don't know I'd have come up with it.
One can never have too many planes and chisels... or so I'm learning!!
[OP]
Contributor
This is all excellent information. Leaving the back of the drawers loose is a very simple and obvious modification (except that I would have never thought of it!).
Member
Gents:
I just took a class a couple weeks ago; this was the entire week - constructing a drawer with half blind, and through dovetails on a drawer with ' let go '.
Like Jon said, it is a tapered fit, to which you need to have both sides of the drawer opening accessible - you fit the drawer ( which is initially the same size as the hole + / - ) from the back.
What is critical is using rift / quarter sawn stock for the drawer sides and back, as well as acknowledging which season you are in ( and assuming properly dried stock to begin with ). This was the summer, which has the highest RH, so if a drawer is fit now, it should be fine in the lower RH winter season.
Sneaking up on the ' let go ' point is the trick; a couple extra swipes @ .001'' shavings can ruin the let go. Fitting the drawer bottom a little snug can restore it if properly done however. The point about a properly fitted drawer being non-binding regardless of which corner is pushed to close it was also demonstrated.
My goal now is to produce a couple Pennsylvania Spice Cabinets, with proper let go. They will be as much Neander as possible, but my shop time is limited, so ......
Dave Beauchesne
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