LumberJocks

5 cut method - how good is good enough?

  • Advertise with us

« back to Power Tools, Hardware and Accessories forum

Forum topic by garlandkr posted 01-18-2016 01:03 AM 976 views 0 times favorited 14 replies Add to Favorites Watch
View garlandkr's profile

garlandkr

57 posts in 971 days


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”
Bottom of 5th cut, B = 0.656”
Length of off-cut = 18.4375”
Distance from pivot point to point of adjustment = 44”

(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

View bonesbr549's profile

bonesbr549

1176 posts in 2534 days


#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.

View Kurt T. Kneller's profile

Kurt T. Kneller

104 posts in 831 days


#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.......

View WoodNSawdust's profile

WoodNSawdust

1417 posts in 643 days


#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

View garlandkr's profile

garlandkr

57 posts in 971 days


#4 posted 01-18-2016 01:23 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.

- WoodNSawdust

I figured it was 0.019” to bring it to 0 in my case, but then how is the deflection across length calculated?

View Loren's profile

Loren

8314 posts in 3115 days


#5 posted 01-18-2016 01:24 AM

Plywood cases go together twisted a little anyway. There’s
usually a little persuasion and compromise involved. I
emphasize making the front of the case square and let
the back opening be crooked if it needs to be. You
won’t succeed in tuning this kind of everyday carcase
twist out of your work by making your cuts square to
within 1/64th tolerances. There are methods to make
cases come out more square of course, but they have
to do assembly methods and tools like pneumatic case
clamps and wood-welders to set the glue in a few minutes.
This is beyond the scope of what you need to do working
on a small volume of material in a small shop.

Where it gets interesting, if you want to go there, is
tuning and fitting up smallish cabinets and chests
of drawers so everything looks and works just so,
fitting drawers nicely and things like that. Handwork,
really.

1/64” squareness error over 12” is very acceptable
in general, imo. I’ve found it difficult to get my
panels squarerer than half that error, which comes
out to a 1/32” error when doing a 5-cut test on
a 4’ square panel.

View garlandkr's profile

garlandkr

57 posts in 971 days


#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.

View hotbyte's profile (online now)

hotbyte

844 posts in 2442 days


#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.” :-)

View MadMark's profile

MadMark

978 posts in 920 days


#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 - Madmark2150@yahoo.com Wiretreefarm.com

View TheFridge's profile

TheFridge

5765 posts in 953 days


#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.

View lateralus819's profile

lateralus819

2236 posts in 1356 days


#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.

View rwe2156's profile

rwe2156

2198 posts in 948 days


#11 posted 01-18-2016 12:49 PM

What bones ^ said.
Get a good, accurate square and then eyeball it you’ll be close enough for ww’ing.

.002, .004, “settling” for .005?

FYI, 1/64 = .016 & 1/128 = .008

-- Everything is a prototype thats why its one of a kind!!

View BJODay's profile

BJODay

514 posts in 1410 days


#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

View garlandkr's profile

garlandkr

57 posts in 971 days


#13 posted 01-18-2016 05:55 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

- BJODay

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.

View Pezking7p's profile

Pezking7p

3097 posts in 1118 days


#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

Have your say...

You must be signed in to reply.

DISCLAIMER: Any posts on LJ are posted by individuals acting in their own right and do not necessarily reflect the views of LJ. LJ will not be held liable for the actions of any user.

Latest Projects | Latest Blog Entries | Latest Forum Topics

HomeRefurbers.com