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My sliding miter saw cuts a slight curve

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Forum topic by Robert Newport posted 06-11-2011 04:43 AM 7216 views 0 times favorited 16 replies Add to Favorites Watch
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Robert Newport

21 posts in 2003 days


06-11-2011 04:43 AM

Topic tags/keywords: miter saw accuracy adjustments

I just got a 10” sliding miter saw that is a huge step up for cutting larger pieces, but I am baffled about something that it’s doing and I’m hoping that someone here can help me pin it down. I aligned my fence to the blade so that the blade cuts square for the entire travel of the slide. When I put a framing square on the finished piece, both ends are square to the side that was against the fence, but there is a “curve” that starts right at the beginning of the cut and reaches about 1/32” at the center of the cut and then curves back out until the cut is again square when the blade reaches the end of the piece. This takes place over a distance of about 12”. If I leave the fence set up for a 12” cut and then I cut a 1×4, the cut won’t be square because of the “curve”. I’ve marked on the table where the left side of the fence needs to be (the right side is stationery) when cutting 3 different sizes (normal, large & maximum slide), so I can just adjust the fence depending on what size piece I’m cutting, but that doesn’t seem right, and when I’m cutting a full capacity piece of wood, I’ll still get this curve in the middle, which doesn’t seem right either. Can anybody out there point me in the right direction for adjustments? My bevel is accurate, my miter is accurate and my blade is at 90º when the bevel is at 0º. Any suggestions will be a big help. Thanks!


16 replies so far

View MedicKen's profile

MedicKen

1610 posts in 2923 days


#1 posted 06-11-2011 07:25 AM

It sounds like you may have a bent arbor shaft. I would take the blade off and put a dial caliper on it and see what the run out is.

-- My job is to give my kids things to discuss with their therapist....medic20447@gmail.com

View childress's profile

childress

841 posts in 3003 days


#2 posted 06-11-2011 07:44 AM

”maybe the problem is your work is creeping during the cut.”

+1

And also possibly, the blade is deflecting??? you using a thin kerf blade?

-- Childress Woodworks

View dbhost's profile

dbhost

5604 posts in 2693 days


#3 posted 06-11-2011 08:34 AM

I tried a thin kerf 12” blade on my slider, it would deflect and cut a curve on a level cut. Full kerf blade fixed that.

-- My workshop blog can be found at http://daves-workshop.blogspot.com

View Loren's profile

Loren

8296 posts in 3109 days


#4 posted 06-11-2011 05:27 PM

Put a groove about 1/4” deep in a 3/4” board. Don’t cut all the
way through it.

Is the cut line curved or straight in a non through-cut?

If the line is straight, your saw is probably sliding straight and the
problem is with your blade, arbor, or technique. If the line
is curved, the rails may be bent and that’s non fixable.

View Robert Newport's profile

Robert Newport

21 posts in 2003 days


#5 posted 06-11-2011 07:05 PM

Guys,
Thank you for all the suggestions.
August and Childress: I clamped the test piece, so I don’t think it’s creeping. The adhesive sandpaper is a great idea.
DBHost & Childress: I just put an 80 tooth on and it IS a thin kerf. The blade that came with the saw is also a thin kerf. Each measures about 3/32” on the kerf instead of 1/8”, so I’ll look into a full kerf blade.
MediKen: I don’t have a tool to measure arbor runout, but I’ll keep that on the list of possible causes.
Vonhagen: I truly hope you’re wrong about the twisted rails, but the heeling is a possibility that could be caused by a bent arbor. The saw slides as smooth as can be, but that may not be an indication of accuracy.
Loren: I’ll try your test and post the results.
I’ll also look into a full kerf blade. I’ve had a similar problem with my little 5.5” 18v circular (very thin kerf) and had to switch up to my 7.25” circular to get square results on clamped straight edge cuts.
Thanks again to all of you for taking the time to respond!
I’ll follow-up with the solution if I can ever find it.
Robert

View jim C's profile

jim C

1467 posts in 2560 days


#6 posted 06-11-2011 07:23 PM

Possibly the rails that the saw slides on are bowed.
What brand/model is it?

-- When I was a boy, I was told "anyone can be President", now I'm beginning to believe it!

View Robert Newport's profile

Robert Newport

21 posts in 2003 days


#7 posted 06-11-2011 07:41 PM

Hi, Jim…
It’s a factory reconditioned Ryobi. Model TSS100L. Certainly not the best available, but a huge step up from my 15 year old Delta non-slider. Only had it for a couple of months. Never dropped or handled without care. Slides like greased lightning. Completely adjusted on all angles to be square and true. But it still cuts a slight (1/32” deep) curve when cutting a 12” piece. Several replies think the thin kerf is the problem and I’m thinking that’s probably the answer. The test piece was clamped and the saw is bolted to the workbench, so I don’t think the test piece “creeped” at all.
Any thoughts are appreciated.
Robert

View Loren's profile

Loren

8296 posts in 3109 days


#8 posted 06-11-2011 07:58 PM

You are pulling, plunging and push-cutting, right?

That’s the best way to do it with a slider in my experience.

View Robert Newport's profile

Robert Newport

21 posts in 2003 days


#9 posted 06-11-2011 09:59 PM

Loren,
Actually, I’m plunging, pulling and stopping before raising the blade. It didn’t occur to me to try it the way you mentioned, but I’ll give it a try and see if it makes any difference.
Thanks for sharing that little tip…it all helps!
Regards,
Robert

View jim C's profile

jim C

1467 posts in 2560 days


#10 posted 06-11-2011 10:19 PM

Pulling a saw through is called “climbing” and can be dangerous. Routing that way is also a no-no.

-- When I was a boy, I was told "anyone can be President", now I'm beginning to believe it!

View Robert Newport's profile

Robert Newport

21 posts in 2003 days


#11 posted 06-11-2011 10:30 PM

Thanks, Jim…I wasn’t aware of that. Good tip!
I’ve got WD-40 and Duct Tape, too.
Robert

View Robert Newport's profile

Robert Newport

21 posts in 2003 days


#12 posted 06-11-2011 11:17 PM

Loren,
I just tried your suggestion of pulling, plunging and push-cutting.
PROBLEM SOLVED!!!
Now I get a straight and accurate cut on all sizes of wood.
Thanks very much for that, and also to everyone who responded with suggestions. Very much appreciated!
Jim: I’ll remember your suggestion when I get a router.
Robert

View jim C's profile

jim C

1467 posts in 2560 days


#13 posted 06-12-2011 12:53 AM

That’s what we LJ’s are here for. Glad we could help.
I always find an answer here when I’m stumped!

Stay safe and keep the WD and Duct tape handy

-- When I was a boy, I was told "anyone can be President", now I'm beginning to believe it!

View Dark_Lightning's profile

Dark_Lightning

2632 posts in 2570 days


#14 posted 06-12-2011 01:39 AM

Climbing cuts can be performed using a router, and preferred in some cases. Chris Gochner has an article about it in the August issue of FWW.

-- Random Orbital Nailer

View CanadaJeff's profile

CanadaJeff

207 posts in 3071 days


#15 posted 06-12-2011 02:06 AM

My guess is the wood is creeping. If you have a hold down clamp tighten it good and make a test cut. Should be straight then.

If not, perhaps the blade has a warp in it, although that is a guess

showing 1 through 15 of 16 replies

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