Crosscut sled accuracy using the 5 cut method


barri

5 Cut accuracy  

17 members have voted

  1. 1. What was your accuracy over 24" (or equivalent)

    • under .002"
      5
    • under .005"
      7
    • under .007"
      4
    • under .010"
      1
    • over .010"
      0


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Marc quoted in his video that .005" error over 24" in the real world was good enough. I get .0067 over 24" and the large rectangle left over from the 5 cuts appears to have four 90 degree angles as well as a test cut, checked with a set square. I guess that if my sled can only cut to a bit more than 24" and current cuts of that length appear square then i should stop here and start enjoying my sled but I am curious as to where others have stopped and said that's good enough. By the way, I have almost no places to put more more screws as that was my 4th attempt.

Would you stop here or should I try to get under .005" over 24"? What is considered an acceptable figure to aim for? .008"? .004"? Where did other people stop?

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I am with Eric, you are close enough.  You and mother nature are going to make bigger errors throughout the project.  If you have a quality square and it can't tell the difference, you are there.  

 

I used to spend a lot of time worrying about getting my machines perfect, and found I improved my quality of work a lot more by simply building stuff and learning tricks along the way.  The time spent perfecting machines, in my opinion, can be better spent mastering the craft (or building stuff).  Get them good, but stop at good.  Perfect is an impossible dream!

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BTW Marc's error of .005" was after dividing by 4

And you'll notice he went back and dialed it in further.  He said "good 'nuff" after the first round of tests that yielded an error of .005"...but I'll assume that meant it's good enough for YOU if you WANT it to be.  Frankly I wouldn't settle for 5 thou out over a 24" span.  In real world it probably wouldn't be an issue very often, but I could see it causing some frustrations from time to time if you're an anal retentive type like me who would lose sleep over a tiny gap in something.

I thought you were saying your .0067 was BEFORE dividing by four, which would have made your actual number closer to barely more than one thou.  I'd definitely leave that.  But almost 7 thou?  I think you can do better.  I'd try.

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There should be.

Here's an example why that would bother me.  Say you're setting a plywood panel in the back of a cabinet, rabbeted.  You'll see that 5 thou gap at two opposing corners.

Granted, in this example it's just a back panel so you may not care because you can't see it, but it's not beyond possibility that you'll encounter the same issue on some show area in the future.  I couldn't live with knowing the gap is there, even on the back.  One thou I could probably handle...five?  Probably not.

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OK I'll have another bash and report back. I hope I can find spots for new screw holes. I will label the screw holes that I have now so that I can return to the current setting, which is pretty good, just in case I make it worse. I'm anal about this too.

Eric the .0067 error was AFTER dividing by 4. The above poll is for errors after dividing by 4 as that is the true error over the length of the test piece

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No problem, next time I replace a sled.... sometime in 2017... :)

 

Honestly, if you watch the Ng video and just augment the last few steps, you're there...

 

I am presuming that talking about inserting a brass piece inside the kerf cut and then using your square to reference against that.

551.jpg

Something like a brass setup gauge bar?

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I've got 4", 6" and 12".  Honestly, I use them all the time at the sled... The ability to get precise registration from the kerf is quite valuable and indispensable for TS-based joinery... I use the 4" when it's a small jig and 12" for sleds... Same goes for Engineer's squares -- from 2" to 18" -- small jigs to large sleds...

I also have some 1/4"t x 1/2"w x 2"l for the drawer bottom groove when transferring tails to pins on the Moxon (I built the BC-Moxon w/ tailboard shelf)... Registers the boards at the groove... And since the groove is 3/8" from the bottom....  That plus the 140 trick and you've got the pin boards nailed...

2c

Edited by hhh
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hhh, a good post.

I actually use a thin kerf blade (about 3/32") but I did use a framing square first and placed a metal ruler in the kerf ensuring it was jammed in straight using small wedges. That gave me a good start but maybe my square was out or my ruler wasn't straight in the kerf or I had too many drinks the night before.

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Another pretty simple way to get it dead on the first time, is to run the blade through the rear fence and right up to where the front fence would starts.  Place your square against the blade itself.  Square the fence visually, shoot some screws from the top to hold it in place, but back it up enough to shoot from the bottom and drill/tighten down. 

 

It requires a good machinist or precision square.  Just be sure you either have a long enough square that you touch both ends of the saw blade on the tooth or get one small enough to fit between the teeth. (Error larger if possible, much easier, and more accurate) 

I've never had to reset a fence using this method.  It's simplicity is why I keep using it.  

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Got to .0021" over 20". I'm happy with that but in real terms it made no difference. Before when it was over .006" I did a long test cut and it measured exactly 90 deg using a digital protractor. Did the same and it was still 90 deg. So for practical reasons a few thou makes little difference. For what I do this setting is fine. I am not doing precise engineering metal work.

I now understand Marc's comment about "in the real world .005" is good enough".

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