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Crosscut sled help, please

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Forum topic by Courtney posted 02-15-2013 09:21 AM 1189 views 0 times favorited 10 replies Add to Favorites Watch
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Courtney

49 posts in 709 days


02-15-2013 09:21 AM

Topic tags/keywords: crosscut sled beginner help

Hi, I’m VERY new to woodworking, as in just using a table saw for the first time not too long ago, still learning the language, and on and on. I decided to pause the build of my first little mini workbench to build a crosscut sled for my little Bosch table saw. I loosely following the Wood Whisperer’s video. It was going fairly well—I fixed the 1/2” ply to the runners (2 I bought from MicroJig) and afixed the front piece of hardwood. I cut the kerf, but didn’t cut all the way through to the back before trying to sqare up the back “fence”. I thought I had it square (used a framing square) to the blade, but when I make test cuts, they are thicker in the back. I moved the back fence forward on the right side to compensate. Then I moved it again. And again. And again. Pretty soon I had moved it about 1/2” and there really wasn’t a big change in my off cut—still leaving more wood at the back of the cut. There is no play in the miter slots and the fence is nicely perpendicular to the plywood base. Where am I going wrong? Why isn’t there more of a change when I move the fence? The only thing that has changed on the sled was that, after I made the kerf throughout the whole thing (this first time I screwed the back fence in and made my first test cut), the plywood on the right side of the blade protrudes about 1/8” towards the back. That has stayed consistent during each test cut, and I don’t think it has anything to do with the inaccuracy of my cuts.

-- It's very common for people to separate things they do from the things they need. - Jogge Sundqvist


10 replies so far

View kdc68's profile

kdc68

1979 posts in 933 days


#1 posted 02-15-2013 11:53 AM

Courtney – It’s very possible that your framing square isn’t square. Try a drafting triangle or a good machinist square, or a digital protractor. I have one of those digital protractors which works well. Get some feeler gages from an auto parts store and a caliper (digital). Use these to make your fine adjustments
After making the 5th cut take the differnce between the measurement at the back versus the front and divide by four. If your test piece is about as long as your fence, use a feeler gage as a guide to adjust the fence forward or back by the number you got from the math. Do not use the same hole to re-fasten the fence. Make a new hole otherwise the old hole may pull the fence out of adjustment. It is much better explained in the video below

http://lumberjocks.com/thewoodwhisperer/blog/22879

Now if your test piece isn’t about as long as your fence, then the math is a little different. After making the 5th cut take the differnce between the measurement at the back versus the front and divide by four. Take that and divide it by the length of the test piece. This will give you how for its off per inch. Take that number and multiply by the length of your fence and use that number to make adjustments. It is much better explained in the video below

http://lumberjocks.com/wnwoodworkingschool/blog/28570

Good luck !!

-- Measure "at least" twice and cut once

View lumberjoe's profile

lumberjoe

2833 posts in 905 days


#2 posted 02-15-2013 04:39 PM

ditch the framing square. It’s not doing you any favors. Follow this and you will be as accurate as can be:

http://www.thewoodshop.20m.com/fivecutmethod_swf.htm

-- www.etsy.com/shop/KandJWoodCrafts

View PurpLev's profile

PurpLev

8476 posts in 2305 days


#3 posted 02-15-2013 04:47 PM

since you moved and moved and moved your back fence and still getting same results, this might not be related to your square at all…

is your blade square to the table?

-- ㊍ When in doubt - There is no doubt - Go the safer route.

View CharlieM1958's profile

CharlieM1958

15698 posts in 2875 days


#4 posted 02-15-2013 06:02 PM

Something just doesn’t add up here. As PurpLev said, the framing square might not be the problem.

What kind/size of board are you cutting as a test, and how are you measuring the result? I see no way that moving one end of your fence by 1/2 inch wouldn’t have some serious affects on the squareness of your cut.

-- Charlie M. "Woodworking - patience = firewood"

View kdc68's profile

kdc68

1979 posts in 933 days


#5 posted 02-15-2013 10:22 PM

Excellent point PurpLev. The blade must be in line with the miter slot. CharlieM1958 I reread Courney’s post and realized he was moving the fence a 1/2”. Wow. Moving the fence a small fraction of that would impact the squareness of cut considering it’s 4 times the error. Courtney regroup. Get a machinist square, calipers, feeler gages, and a dial indicator. Be sure to check alignment of the blade. If the blade is out then tune your saw. Watch the videos that I and PurpLev provided and good luck

-- Measure "at least" twice and cut once

View Courtney 's profile

Courtney

49 posts in 709 days


#6 posted 02-15-2013 11:58 PM

Thanks, everyone, for your helpful comments. I think “regroup” is great advice kdc68, and I really enjoyed the videos that you posted (incidentally, I’m a “she” not a “he” :)). I got the feeler gauges today, and ordered a drafting triangle and dial caliper from Amazon. Hopefully, I’ll be ready to try this again on Tuesday, when said items arrive. PurpLev, I did check the blade, but now I really don’t trust the square that I was using (it never occurred to me that me “square” wouldn’t be square – shows how much I have to learn). I’m going to hunt down a good machinist square (I think this would be a good one to use to square the blade, right?) and double check that. I also was thinking about it, and to CharlieM1958’s point, I think I need to use a different piece to do a test cut. The board I was using was fairly small (.75”x3”x8”) and had been jointed a couple days before, but when I looked at it again after reading that comment, really wasn’t perfectly square any longer after being in my basement. I’m going to use a piece of plywood for the test cut, and follow William Ng’s advice to use a longer test piece.
Thanks, again. I’ll post again how things work out.

-- It's very common for people to separate things they do from the things they need. - Jogge Sundqvist

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Courtney

49 posts in 709 days


#7 posted 02-16-2013 12:02 AM

As another aside, I also think I’ve learned that if you’re frustrated and things aren’t adding up at all and it’s getting late…it’s a good time to stop and sleep on it :). I’m sure I’ll have to learn that lesson again, but woodworking will probably accomodate my need to be taught this over and over…

-- It's very common for people to separate things they do from the things they need. - Jogge Sundqvist

View kdc68's profile

kdc68

1979 posts in 933 days


#8 posted 02-16-2013 12:24 AM

Courtney...first, sorry for implying you were a “he”. My excuse is I know both “he’s” and “she’s” that are named Courtney.
I posted a link below on blade alignment to the miter slot. There are several here at LJ’s to let you know. You can purchase a ready made fixture or make one of your own as seen in the link. Thats what I meant by getting a dial indicator in a previous answer.
To test a square for square, align one leg of the square against a known straight surface and draw a line along the other leg. Flip the square over. Keep the same leg tight against the known straight surface, and draw another line next to the first. If the two lines are “perfectly” parallel then the square is square. A lot of framing squares are not perfectly square. Any deviation from perfectly square will make aligning a sled very difficult. Or any other work that needs to be percise.
Try using a bigger test piece to cut on your saw. As big as you can cut safely on your saw. The bigger the piece, the bigger the error will be, which will be easier to detect and correct if your sled is misaligned.

http://lumberjocks.com/topics/19029

Good luck

-- Measure "at least" twice and cut once

View lumberjoe's profile

lumberjoe

2833 posts in 905 days


#9 posted 02-16-2013 03:32 PM

There are way too many variables on a cross cut sled to square it with tools. The only true way to square one that i have found is the 5 cut method. It’s pretty easy to do and you will be very pleased with the end result

-- www.etsy.com/shop/KandJWoodCrafts

View RogerM's profile

RogerM

447 posts in 1056 days


#10 posted 02-16-2013 04:04 PM

Sounds like your framing square is out of calibration. You can adjust it by following the instructions of http://lumberjocks.com/topics/449

-- Roger M, Aiken, SC

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