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OK, I admit it - I'm early in my woodworking skills development. But now that I have acquired a great tablesaw and superb blades for it, plus high quality routers and bits - I have noticed that my "parts" often come together with a variance from plan of 1/64" to 1/32". This often leads to small gaps and misalignments. Don't get me wrong, if I can cut the parts against the saw's fence or use a jig or sled - they all come out the same size. But if I cut the two sides of a cabinet and then cut separately the top and bottom to fit into the rabbets - they can easily end up a small amount off in length. I realize that some of this can come down to doing things in the correct sequence - e.g. mill all the parts that share a dimension at the same time. That's not always possible, though. But that's not what I fear is my biggest problem: measurement. By that I mean when I go to measure a dimension I make my mark and work from it. But, how fine should the line/mark be? Does one always "take the line", or do you "keep" the line? If, due to physical constraints you have to cut from the "part" side of the line or the "scrap" side of the line, how do you ensure accuracy/consistency? Do you always use the same measurement tool, rather than switching between multiple ones?

Perhaps I'm just being AR, but when you put together multiple parts these little measurement variances add up! Thanks in advance if you have some methods to share!
 

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Most important thing is to always use the same tape, ruler, or whatever to measure with on the same project. Lots of variances between tapes. Always cut the mark the same way, whether you cut centerline, left or right, always the same. Don't forget the thickness of the cutting blade. For tablesaws, I keep my fence fine tuned for accurate cuts. I fully trust the gauge on my saw.
 

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I agree with "papadan" A good layout ruler is a must. Agood tape measure is also a good idea. I prefer a flat back tape in the shop. Doing bookcases or tall cabinets I like a story pole and that way I have all my pertinent measurements at my finger tips. For critical measurements, calipers are great also, but always make a cut on scrap first. There have been times when I have almost made a project out of scrap as I cut pieces for certain cabinets.
 

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What you mark with can easily make a measurable difference as well. In the cabinet shop the boss always insists on a well sharpened regular pencil not a "carpenters club" as he calls it. I personally prefer a 5mm mechanical pencil for rough measurements and a marking knife for marking cut lines.
 

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I try to measure once, then use a stop block for repeatability. If possible, it helps to get consistent length if you crosscut first then a rip multiple boards to width. Be sure your stock is flat and straight to start with, be sure your inserts aren't flexing under pressure, and that your fence and miter gauge aren't moving on you. You may find that the end dimensions don't need to be within 1/32" as long as everything's consistent.
 

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A fence that alows you to set and cut accuretly is a requirement.

I also cut my parts oversize and let them age for a while and I'm then able to trim to the correct size and yopefully use the same equipment setup.
 

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Another thing to remember is that wood doesn't always stay the same size after you cut it. It will expand and contract according to the humidity. You can get two different measurements on two different days.

I always use a pair of 6" dial calipers for small parts.
 

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I have a story on this very subject at the link below. This is a very common question at my site and sort of a right of passage for woodworkers. Practice is a big part of it but so is establishing good techniques ands ticking with them.

Cutlines Story
 

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If you can avoid measuring at all you ahead of the game. Many times you dry fit pieces together and your able to put pencils marks were your cut ,dados or whatever. If you can mark out were you need to do certain
operations without measuring at all you can avoid mismeasuring or transposing numbers or a very commend mistake were you measure off the 1" mark(also referred to as burning an inch) and forget that's what you've done when you mark you work
 

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if you are cutting multiable like pieces you only measure the first and then use it to mark up the second, third etc.
A lot will come with practice but, as we all have to learn the flaws are usually in the measuring and/ or set up. Most of us have had to learn by trial and discover. all of the things listed above are true. when you discover something work on it, practice. Don't practice on good wood, the best kind is free, or scrap etc. Do invest in good measuring tools and marking tools. If you will start with a #2 pencil with a very sharp point, you begin on the right road. Throw away mechanical pencils are better.A small pen knife or a razor knife will do for a marking knife for the time being. Stop thinking about 1/8 inches and think about 16th or 32 nds. AN Incra rule will measure to the nearest 64th. If you have trouble with fraction's and a lot of people do, go metric or use inch's by the hundredths (metric measures are readily available and are often included on the same tools that we use for English measurements. Most of all watch this web site You can learn more here that if you subscribe to every woodworking magazine in the country AND you can always ask.
 

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I don't like to measure because all the little fractions confuses me. I just butt, mark, cut. Lots of time, I use the knife to mark since it cuts the fiber of the wood on a cross cut. Then I cut to the right, so I'm left with a cleaner cut.
 

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When I first moved to Norway I had to get used to the metric system. I can well understand the difficulties in converting to a new system and I'm not advocating anyone to do it, but in my experience the metric system is a lot better and easier to work with. So basically I just feel sorry for you guys that are stuck with the imperial system.
 

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I guess everyone has their own way of insuring accuracy and consistency. I work a lot like Barry. I still make some mistakes, but for the most part everything turns out the way it should. You just need a way of measuring that you feel comfortable with. Our brains are all wired a little differently, that's why there are so many methods and they all work when applied consistently.
 

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Ralph,

One of the techniques I teach in my Fundamentals classes is to use layout sticks or story boards. Do all your measuring, and double checking, on the layout. Use the layout to transfer the marks directly to the pieces that need to be cut to size. If you're cutting the top and bottom of a case, square one end then hold the layout stick in place and transfer the mark. Set a stop block and cut both pieces at the same time. If you can't set a stop block, then use the layout stick to transfer the mark to both pieces thus giving you a baseline measurement (you're not compounding a problem by cutting one piece and then trying to use it as a pattern…I've seen pencil lines make pieces magically grow). If none of this is clear, let me know and I'll try to do a short video or blog post about it.

Good luck.
 

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Lots of great advice given. Also, try to use the same edge to referance the whole time. I mean use the same edge to to referance or go against the rip fence, miter gauge or edge guide. Pieces don't stay perfectly square and they don't do it the same rate in the same board. It's off by 1/64 here but 1/16 there type of thing. If you use the same edge for referance the whole time, it's a least consistent. That way all those little 1/64 and 89.8 degrees don't start multiplying.
 

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I think one thing that escapes people's mind when working with plans, is the purpose of the plan - and that is, to help the woodworker visualize the parts in question. NOW. once you actually start cutting - I think it's rare that things actually follow the plan within 1/64" - some cuts gets shorter, some parts have to be recut, and the dimensions eventually will change from the original plan.

point is- once you cut your 1st part. everything else needs to follow and match that part, so use the plans for general dimensions, but do the actual cut based on the already parts you have to work with. measure against those to get your actual cut line.
 

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Ditto what everyone has said, and especially PurpLev above.

And remember that wood is not steel. Variances creep into your work from all sorts of places. If you milled all the parts for a project accurately to within 1/128th, then went back next week to assemble them, I can just about guarantee that everything will not fit together perfectly.

A large part of the art of woodworking, in my opinion, is learning to adjust to the imperfections of the medium we work with.
 

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Discussion Starter · #18 ·
Wow, great responses! Thank you all so much - great food for thought. Here's what I think I "heard":
  • whatever method you use, such as take the line or leave the line - always do it the same way. Become familiar with and consistent in your approach
  • use the same tool for all measurments if at all possible
  • use good tools - a sharp pencil, a quality tape or rule, an accurate square or protractor, a quality miter gauge and fence for the table saw.
  • at the table saw use the fence or a stop for as many cuts possible.
  • ensure your tools - table saw, tape measure, square, fence, square, etc - are aligned, adjusted, etc. for accurate measurements. Check them before starting a project!
  • try to use the other parts of a project to "measure" a piece, not use the tape or other measurement.
  • when possible, use a "story pole" with all the key measurements on it to size pieces
  • remember that we're working with wood, which varies and changes (BTW, here in Reno the humidity is always 10-20% so this is reduced, but never zero. And temperature range plays a role too, doesn't it?)
  • remember to reference off of the same "edge" when working on multiple pieces
  • something I didn't see mentioned, but I think may be relevant, is to develop little finish/trim approaches that allow one to cover up minor variances and allow for seasonal movement. An example might be a shoe molding at the bottom of a baseboard to cover the gap between the flooring and the baseboard; or having a haunch/shoulder on a rabbeted or sliding dovetail joint.
  • and the old "measure twice and cut once" was I believe brought up too, and appropriate
  • use a marking knife when appropriate. Dovetails comes to mind
  • cut all the parts with a common dimension at the same time or at least before moving/changing the saw or other tool setup
  • be prepared (and skilled) in making hand tool adjustment/refinement of pieces for the final fit
  • move to anywhere outside the US where a sensible measurement system (metric) is used! Sorry, can't consider that one - but NZ is awful nice any time of year…...

Did I miss anything?

Finally, a related question: My current table saw fence can only go out to 25-26". How do you make parts larger than that with consistency? (I have the longer rails already, but need to build the cabinet that would support them and be a router table too)
 

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Discussion Starter · #19 ·
CharlieM, I think that may be the most important point - it's WOOD, not metal. It's a "live" material, know it will vary and develop approaches that handle that. That's where I have LOT to learn.

Oh, and Purplev - I think that's an important point I meant to include in my summary above - use the plan (and cutlist, too) to design the overall project, but once you get started work to the project, not the plan, for measurements.

Thanks everybody!
 

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If your table and miter gauge slider will support it, I'd make a 48" miter gauge fence and clamp a stop block at the appropriate length. Another solution would be to clamp a straight 1X4 to the front edge of the saw table, against the fence runner, and clamp the stop block to that.
As a last resort, measure and cut one and use it to gauge succeeding cuts.
 
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