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Forum topic by garlandkr | posted 01-18-2016 01:03 AM | 15814 views | 0 times favorited | 14 replies | ![]() |
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01-18-2016 01:03 AM |
After watching the William Ng and reading a few comments over on his site, it seems 0.001” is the ideal tolerance. Now that I’ve given it a few tries and growing tired of measuring and re-adjusting my crosscut fence I’m asking myself, how good is good enough? My latest measurement is 0.019” across a length of 18.4375” which to use the formula is: Top of 5th cut, A = 0.625” (0.625 – 0.656) / 4 / 18.4375×44” = 0.019” Seems good enough to me. In what conditions would I see this measurement of error cause problems? The maximum length my crosscut sled can handle is 24 inches, which means I would see a -0.014” deflection. ( My math could be way off, please be gentle. ) Thanks! |
14 replies so far
#1 posted 01-18-2016 01:11 AM |
Dude, crosscut a piece throw a good precision square on it. If you don’t see daylight, it’s good to go. -- Sooner or later Liberals run out of other people's money. |
#2 posted 01-18-2016 01:12 AM |
In a way it is a personal thing. I have spent a lot of time on my woodworking machines to try to have them dialed in as much as possible. This is a good and bad thing. I agree with asking the question “when is good enough good enough”. I guess that is a tail I still catch myself chasing. Wood is alive and will move, right? For me it is about eliminating guessing where I went wrong. If I know my sleds, or machines are dead-nuts, I do not have to look at them for blame in my errors. You would probably never notice the errors you are talking about. With that being said, I only had 4 test cuts and 15 minutes when I did my sled I got mine to 0”. -- Start with ten, end with ten....... |
#3 posted 01-18-2016 01:19 AM |
I think your math is wrong. I think the 0.019 is the amount you need to adjust the fence to bring it to zero. To be sure I would have to go thought the video again and then try it in my shop. I got my fence dialed in to around 0.004. I found that I had more inaccuracy in pushing the sled along the miter slots. -- "I love it when a plan comes together" John "Hannibal" Smith |
#4 posted 01-18-2016 01:23 AM |
I figured it was 0.019” to bring it to 0 in my case, but then how is the deflection across length calculated? |
#5 posted 01-18-2016 01:24 AM |
Plywood cases go together twisted a little anyway. There’s Where it gets interesting, if you want to go there, is 1/64” squareness error over 12” is very acceptable |
#6 posted 01-18-2016 01:41 AM |
Ok, so I think I’ve figured out that my deflection is at a rate of 0.0017” given my current alignment. Using the slope formula. Again, I suck at math so I could be wrong here. That’s more than acceptable to me. Given the maximum cut capacity in my sled is 24” I would see a difference of 0.042” between the bottom and top of the cut, or 5/119ths in other words. Thanks for indulging my random drivel as I scurried down this rabbit hole. |
#7 posted 01-18-2016 02:00 AM |
Somewhat related…I love the old adage “measure with a micrometer, mark with chalk and cut with a chainsaw.” :-) |
#8 posted 01-18-2016 03:50 AM |
.042” is more than 1/32” or about 1mm. Incra fence cuts to 1/32”+-.005” or .5mm _every time. M -- Madmark - [email protected] Wiretreefarm.com |
#9 posted 01-18-2016 04:02 AM |
4.2% of an inch is too much for me. I got mine to .002-.004 over 24” using the same method. It was confusing at first but after 1 adjustment it was close enough. -- Shooting down the walls of heartache. Bang bang. I am. The warrior. |
#10 posted 01-18-2016 11:12 AM |
I settled for .004/.005 too. Took me abit. It gets pretty finicky at times. Even with feeler gauges. Hard to know how hard to clamp against the feelers. Good luck. |
#11 posted 01-18-2016 12:49 PM |
What bones ^ said. .002, .004, “settling” for .005? FYI, 1/64 = .016 & 1/128 = .008 -- Everything is a prototype thats why its one of a kind!! |
#12 posted 01-18-2016 05:48 PM |
I wrestled with mine for a while and got it to about .005”. That is about the thickness of a sheet of paper. I always allow a little wiggle room when cutting and gluing up cabinets. If I try to cut everything the exact size desired, then something as simple as a burr of a tiny wood chip can throw it off. I think you have to cut yourself some slack. BJ |
#13 posted 01-18-2016 05:55 PM |
This is the exact number I ended up on today. I decided to go back and give it another go and now I’m at 0.005” and calling it done. For now. ;) I’ll make another sled another day and do this all over again with a bit more experience and knowledge, hopefully getting me closer to 0 next time. |
#14 posted 01-18-2016 06:18 PM |
OK, you have 0.031” off on your off cut. That is an error over 4 cuts, so your error is 0.031/4 = about 0.008” off over 18”. That’s not great. I personally would shoot for less than 0.005” in 24”. Very do-able with a set of feeler gages. I can’t remember if I used william ng’s video or the wood whisperer’s video, but I know one of them lays out the procedure for making the correct adjustment. If you follow the guide, you should hit near perfection after 1-2 tries. I know a lot of guys say “it’s just wood, wood moves naturally, etc etc”, but trust me, when you start fitting together multiple pieces and frames, a few thousandths adds up quickly. There is enough variability in wood anyway, 90 degrees is one variable I like to remove. Things start to fall together quickly and without fuss when everything is flat, straight, and SQUARE. EDIT: Dang, you responded while I was typing. Nice job and cheers. -- -Dan |
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