Tolerances in dimensioning stock

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    Topic
  • #554179
    Chayne Rudolph
    Participant

    Hello folks,

    I am just getting started and have been trying my hand at surfacing stock for my workbench. However I can never seem to get a piece “dead flat”. I am usually within a 1/16th of an inch. Everytime I try to correct for it, I end up taking more than I need. Is being within a 1/16th acceptable?

Viewing 6 replies - 1 through 6 (of 6 total)
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  • #554193
    Edmund
    Participant

    @etmo

    It depends. Sometimes 1/16th is a far tighter tolerance than needed, sometimes it isn’t nearly good enough.

    The good news is that a workbench is a very forgiving thing — not a big deal if it’s 1/16th too long or too tall. So it depends what part of the workbench you’re making, and where you’re out of tolerance — be specific.

    Generally speaking, “flat enough” is determined by usage. If it’s a reference face and going to receive joinery, probably not. If it’s the underside of your bench top, and nothing will ever see or touch it, it’s plenty flat enough.

    It takes practice to get good at dimensioning stock, but I promise there will come a day when you’ll laugh at all the struggles and you’ll regard it as easy, if you follow what’s being taught by Paul and other master woodworkers (such a Chris Schwarz’s video on stock prep by hand: https://www.youtube.com/watch?v=2_96gNMMc_g).

    If you’re always ending up taking more than is needed, it’s very possible the problem is simply that you’re not checking your progress often enough. As a beginner, check your progress very often, on everything. Eventually, you’ll develop a feel for various operations, but until then, trust in your straight edge, winding sticks, square, tape measure, etc.

    #554195
    Colin Edmondson
    Participant

    @cedmondson

    Not sure if I can add much to what Edmund said. I agree with all his comments, but as a relative beginner myself who built a bench last year (my first true woodworking project) two specific points spring to mind.

    #1 Sometimes inaccuracies or tolerances cancel each other out but sometimes they multiply. If everything is 1/16th out, you may be disappointed with the outcome. I aimed for much finer tolerances but still found the odd instance where two or more ‘errors’ combined to create angles or dimensions I couldn’t live with and needed rework.

    #2 If you view your bench build as an exercise in skill building (as I did) then maybe it’s worth aiming for a bit more accuracy than you might strictly need. I must confess I took ages to complete my bench but I don’t regret the time I spent at all.

    Good luck and hope you enjoy both the process and the outcome as much as I did!

    #554196
    Tim Ridolfi
    Participant

    @obscurious

    If you’re ripping stock to size, 1/16″ is great as long as you’re on the waste side of the line. If you do need accuracy, planing off the last little bit is simple.

    #554197
    Ed
    Participant

    @ed

    @chayner Tell us more about what you mean about not closer than 1/16″ of dead flat. Does that mean it is flat, but you are 1/16″ off your dimension? Does it mean it wobbles here and there away from flat as much as 1/16″? If it is that, is it random or is there a pattern, like the near edge is always 1/16″ too low or the far edge is 1/16″ too low, etc.?

    • This reply was modified 2 months, 2 weeks ago by Ed.
    #554228
    Chayne Rudolph
    Participant

    @chayner

    Thanks for your replies guys. Hello Ed, my situation is that the width of one face may be off a 1/16th from its opposing face and yes I do have tendency to dig into one end or another especially when dealing those areas around knots. I have had the opportunity to work on the legs the last two nights and got a bit better especially with a No.7. I think I will leave the 4-1/2 to smoothing until I get better at it.

    #554250
    Ed
    Participant

    @ed

    Cutting too much on the near or far end is really common when you start (and, embarrassingly, for much, much long after starting in my case). A sharp plane doesn’t need much pressure to cut, but to the extent that it does, you wan to put pressure on the knob to register the plane on the near side as you start the cut. It’s easy to let the heel of the plane hang or to put pressure on the heel of the plane as you start, so that the near side cuts more quickly. On the far side, you want to remove the pressure from the knob and focus pressure on the heel of the plane to keep it registered on the work as the knob/toe moves off the work. It is really easy to keep pressure on the knob as it goes off the work, causing the far side to cut more quickly. The end result of all of this is being too narrow/thin on the near side, the far side, or both (making a hump in the middle). You may be using pressure incorrectly just as part of learning or you may be compensating for not being quite sharp yet. If you are making a hump in the middle, you can try to get rid of it by making partial passes, maybe 1/3 the length of the work. In other words, the toe and heel will never leave the work. You’re digging a hole in the middle portion of the work a few thousandths deep to remove the hump. You then lengthen the stroke to 1/2, 3/4 the length and then take a full pass. Ideally, on the first full pass you’ll get shavings at the near and far side and nothing in the middle (because of the hole you dug) but then on the next pass or two you’ll get a continuous shaving, telling you that you’ve cut end to end and may be flat at that point. This is in contrast to having a hump in the middle that you ride up, over, and back down, again getting a continuous shaving, but not being flat/straight. Depending upon the size of the hump, you may need to repeat.

    • This reply was modified 2 months, 2 weeks ago by Ed.
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