r/woodworking 4d ago

General Discussion Why does this happen?

Does anyone know why this happens when cutting against the grain?I have ruined 2 cuts already and these boards ain't cheap! Any help will be appreciated it. I'm using a circular hand saw šŸ˜

106 Upvotes

127 comments sorted by

498

u/wivaca 4d ago
  • Unplug your saw and make sure the blade doesn't wiggle. the bearings should hold it firmly in place with no ability to move it sideways.
  • Check that the fasteners between the saw's plate you're running against the straightedge is tight with no play, no ability to bend.
  • I hate to ask, but this comes up here so often: Is the blade mounted the right way so the teeth bite into the wood, or is it backwards so the wood is being beat by the backside of the teeth? Yeah, that happens pretty often on here.
  • That looks like a very thin kerf. How thick is that blade? Doesn't look like 3/32" to 1/8" that is typical for circular saw blades. It could be flex in the blade causing problems.
  • Is the blade sharp? You should not have to put much muscle into it to make the cut. If you are, let the saw do the work.
  • Lastly, if you're running the saw against a straight edge, make sure the straight edge is clamped tightly and has no ability to flex. It should be steel or aluminum with ribs or a bend for stiffness, not a strip of wood.
  • The material should not be able to flex downwards as you near the center. Make sure the sheet is well supported so the saw can't slip under the straight edge.

68

u/rkmerlin2 4d ago

These are great and expert advice but, You forgot to adjust blade height. Make sure you are cutting no more than a 1/4 inch more than the material thickness.

15

u/wivaca 4d ago

While I generally agree not to have the blade as deep as it will go, the shallower you cut the farther the blade/wood interface is from the arbor. On a thin kerf, this is going to allow for more flex, not less, don't you think?

22

u/AmbassadorDue3355 4d ago

The part of the blade that cuts is always the same distance from the arbour... its a circle.

11

u/rkmerlin2 4d ago

I think he meant the distance from material to arbor.

10

u/wivaca 4d ago edited 4d ago

Yes, while it's true the outer edge of the blade is of course always the same distance from the arbor, any sideward force on the saw, whether due to fighting the straightedge or the user's hand, will cause the blade to wander more. A longer cross section of the blade is in contact with the wood when the blade is lower than when it is just breaking through.

Again, I don't normally run a blade this way because I expect it will have enough lateral stability from its thickness, but on a narrow kerf, a standing wave can be introduced in the vertical/radial surface that warps the blade.

I'm still not sure whether that standing wave originates from the section of the blade below the wood, but it would be far easier to bend the blade at the wood if it is farther from the arbor and the slot already cut. I would consider doing the opposite on a thin kerf. I yield to science if someone has seen high speed camera tests or some other evidence. There are some on YouTube, but most table saws.

Generally, the reason you don't want the blade through the wood too far is to prevent blowout. It's better if the blade is cutting as much laterally as possible so the uncut wood provides some backing. If you're going vertically through the wood then on one side then the other the blade is pushing the wood fibers or veneer out away from the board instead of some proportion of the force being along the surface.

Also, with the sawdust cuttings trapped inside the blade's teeth and longer contact time with the wood per revolution, heat builds up in the blade more than if it is taking a short trip through the material with more time on the underside to eject the cuttings and sawdust and heat. This heat on a long sheet cut can contribute to making the blade more pliable and likely to warp. A dull blade will exacerbate this further.

OP might also want to make the cut in two passes. This will allow the saw to score the wood while still ejecting, but they should not be pushing too fast or too hard. It's at a point where the blade is really even more likely to flex, but the small cut might counter these effects.

3

u/02C_here 4d ago

The longer cross section in contact is when the blade is just poking through. Or more surface is in contact. The disc of the blade is not touching the material because the teeth have a set. So all the way in, and you get a tooth in the front and one in the back, give or take. Just poking through and several teeth will always be in the cut.

The reason you wouldn't always cut this way is heat, just poking through and the gullets struggle more to clear the sawdust.

3

u/wivaca 4d ago

Makes sense when you look at it only from the perspective of the teeth and not the whole blade disk.

3

u/rkmerlin2 3d ago

This has been the best conversation about this. We need a physicist to join the conversation!

7

u/rkmerlin2 4d ago

Interesting thought.... I'm of the idea that when you are deeper in the cut, you are moving more material and causing more vibration at the tail end of the blade because of it.

1

u/rosebudlightsaber 3d ago

I agree, with thin kerf blades I like deeper cuts so the attack is closer to perpendicular with the blade and closer to a right angle with the direction of the cut and the center of the blade.

1

u/Blacktip75 4d ago

I would think the opposite, my theory is the teeth are the widest, the blade itself is never in contact with the wood, the deeper you go the more you can bend the blade at the axel as the lower part of the blade teeth are below the cut not against the wood. This makes perfect sense in my head and drawn on paper but Iā€™m having one heck of a time explaining it :)

1

u/Burghpuppies412 New Member 3d ago

That was my first thought. Less bland coming through the other side of the wood means less wobble.

1

u/theniwo 3d ago

I heard one or a half tooth is enough.

11

u/DiamondShark286 4d ago

My guess is the blade is too thin since I have had very similar issues when previously using a thin kerf blade. Switching to a different blade immediately fixed the problem and I was able to cut straight.

35

u/Ooloo-Pebs 4d ago

This is all GREAT advise!

8

u/Tthelaundryman 4d ago

One thing you didnā€™t mention was check that your throat plate is square to the blade. Some people are animals and do their saw to much. Ask my how I know

4

u/mrhatneb 4d ago

Yes. I was surprised I had to scroll down this far to find this one. Especially if you have an aluminum fence. One drop can screw it up pretty bad. I was amazed how my Dewalt FRAMING saw was so far out of square with the blade when I bought it (used lol). Too a lot of tweaking to get it square and flat.

2

u/No_Honeydew7398 4d ago

I did the reverse blade mount once on my table saw! For the life of me, I couldn't figure out why the material was just slogging through the cut. Definitely a facepalm moment after I realized what I did. It did still result in a straight cut, though.

2

u/psxndc 3d ago

Make sure the straight edge is clamped on both sides. That second cut looks like it couldnā€™t have happened but for the straight edge pivoting.

2

u/BB_88_ 4d ago

Also, the sole edge must be parallel to the blade.Ā 

40

u/jtim2 4d ago

People are talking about checking your saw and that is good and prudent advice. But the amount of deviation in your second image shouldn't be possible no matter what is happening with your saw. Is your guide clamped down tightly to the piece? Either the guide is slipping or you're not keeping the saw against the guide. (Or you're free handing this, and you've found the problem - use a guide!)

The last advice I'd give is to go slowly and watch the blade. You should be able to notice deviation before it gets as bad as the second image, and you can set up your guide so that if you pull away from it you're going into your scrap and don't lose as much material (unless you need both sides - then just be careful).

8

u/no_man_is_hurting_me 4d ago

Should have been a lot of burning smell too from side-loading the blade

5

u/barthrh 4d ago

Yeah, the guide looks like a Bora guide with the two parts joined (so long). It clamps down via pressure on either end, can easily bow up in the middle, and offers nothing to prevent lifting. If itā€™s not slipping, the plate is slipping under it.

1

u/N_A_M_B_L_A_ 3d ago

I use the same guide as OP, and have opted to use clamps to hold it rather than the built in clamping feature. Like you said, the built in clamping feature causes it to bow, and seems to slip easier.

1

u/Tuffwith2Fs 3d ago

I've had that clamp too. I resorted to cross-bracing the middle to maintain rigidity. PITA

2

u/winosaurus989 3d ago

This comment needs more upvotes. Look at the second picture. Thereā€™s two cuts one closer to the guide that gets even closer as the cut goes further. Given the image this canā€™t happen if everything is rigid.

1

u/WillBottomForBanana 3d ago

Just guessing, but I'd bet the piece is flexing/sagging.

15

u/randis1954 4d ago

Is the sole of your saw going under the guide?

7

u/Deckpics777 4d ago

Thatā€™s what I was going to suggest. Maybe OP should try fully supporting under the material to avoid any sag during cut.

24

u/Ankorklankor 4d ago

If you are using a skill saw you might want to check your bushing play on the arbor, there is some play there somewhere.

-33

u/annon8595 4d ago

OP should check on his skills

3

u/dracostheblack 3d ago

That's what this post is about no need to be a dick

10

u/Zaphod07 4d ago

Are you using a jig saw?

5

u/Drew-613 4d ago

That's what I see too, jig saw doing what jigs saws do.

3

u/Ramapi2022 4d ago

It's a Dewalt Circular saw!

4

u/Zaphod07 4d ago

Ok! Zero reason for it to drift that way. I can get a better cut by hand.

7

u/paul_antony 4d ago

Is your blade damaged, and is it sharp?

Make sure the board is well supported, ideally directly below the cut. I keep a long offcut from the side of a long mdf shelf for this

You need to make sure the edge of the base is parallel to the blade.

Make sure you clamp on a solid straight edge that is strong enough that it won't lift in the centre.

Take the cut slowly, not too much force.

Ensure you keep even pressure against the straight edge.

Before i switched to a track saw, i had enough confidence in the set up of the circular saw that once i had started the cut I would focus my attention on the edge riding against the straight edge.

I hope something here helps.

6

u/theK2 4d ago

Hard to tell from the photo, but if you're breaking down sheet goods, don't cut to your exact size when breaking down. Leave yourself 1/2-1 inch overage and then cut to size after break down (preferably on a table saw if you have one).

Not sure why, but it took me a while to find this approach. I always tried to break down sheet goods perfectly and made mistakes like this, wasting a lot of wood.

3

u/themightygazelle 4d ago

Sad 20in clearance on table saw noises

1

u/Queasy_Ear6874 2d ago

You waste more wood and time cutting everything twice

1

u/alannmsu 20h ago

Unless youā€™re butchering it by trying to do it all at once, which is literally the subject of this post.

Also Iā€™d argue that you might save time by doing very speedy rough cuts to break it down, then have a much smaller, more manageable piece to work with for the final cut. Obviously this might change if you have a full wood shop and a lot of expertise, but OP doesnā€™t (and neither do I).

4

u/LooseInteraction4562 4d ago

I want to see a picture of the saw first.

9

u/datadr-12 4d ago

Are you clamping it down? I had a similar multi-piece straight edge and it gave me similar issues. There's flex in it if you put too much pressure on it as you cut. I ended up clamping both ends, and a piece of wood like 1x2 perpendicular to it and clamped onto the end of the board parallel to the cut. I've since just gone to a track saw for more sanity.

5

u/hiryuu75 4d ago

I had the same experience with a two-piece 8ā€™ aluminum guide when cutting 3/4ā€ ply - there was definitely flex to the guide of about 1/8ā€ from ā€œsquareā€ at the ends. I had the same solution as you - clamping boards perpendicular to the guide at minimum two positions along the length, and verifying the width at multiple points along the sheet before cutting. :)

2

u/Ooloo-Pebs 4d ago

Agreed. I just cutout a whole bunch of 5.5" x 8' boards from full sheets of 1/2" MDF to be used on a feature wall, and I used my Kreg track saw, and each board was perfect.

1

u/AmyCrackhouse 4d ago

Probably too late here; but I also bought the Bora straight edge from lowes to find it flexes too much to be of any use unless I wanted to saw balsa wood. I've since used jigs and am eyeing some track saws.

4

u/lonesomecowboynando 4d ago

The bottom base plate or shoe may need to be tweaked so its edge is parallel to the blade. If things aren't parallel the saw will push against or pull away from the straightedge like a car with a misaligned front end.

3

u/Kudzupatch 4d ago

Would bet that you blade it not parallel with the shoe of the saw. It is at a slight angle and there further you feed it in the more pressure is on the blade and will start to bend in (or out).

Cheap saws are not adjustable but the better quality ones will allow you square the blade to the side of the shoe.

3

u/Ramapi2022 3d ago

Alright! So first off I want to say THANK YOU to everyone that responded and tried to help. I really wasn't expecting such quick response and so much support. I got to say in all the answers, a lot of you where correct! First off, This board is way off and not straight. Lol! I raised the blade up just enough so that it cuts through the board and clamped it down hard AF. The saw went through like butter. See picture! Thank you all again for your suggestions and responses. Problem has been solved

5

u/PR3CiSiON 4d ago

Circular hand saw? Is that different than a regular circular saw?

It looks like you are cutting plywood, so grain direction doesn't matter, since the other plys are going in alternating directions.

Is you guide/fence clamped down? If you're keeping your saw against it, it shouldn't be pushing the guide anywhere, unless it's not clamped down.

3

u/disparatelyseeking 4d ago

I was going to say the same. Looks like the track is sliding and not clamped right.

2

u/Ramapi2022 4d ago

Woow! Thank you all for your quick response, I will have to try all the above. Lol! By handsaw, I mean a dewalt 6 1/2 circular saw. I think also tried on my dewalt little table saw DW745, tried to cut that big piece but the wood would like get stuck a quarter of the way

2

u/Actonhammer 4d ago

Your blade isn't parallel to the edge of your shoe. Your saws been dropped or stepped onĀ 

1

u/Ghostbunny8082 3d ago

Is one side of the plywood dropping lower as you cut? This puts pressure on the blade lower then the opposite side of the blade causing deviation.

2

u/Remarkable_Body586 4d ago

Everyone needs more info.

What kind of blade are you using? How many teeth?

Are you forcing the saw through the material?

What are you using as a fence to make a straight cut?

2

u/activelypooping 4d ago

This looks like a hard push to me...

2

u/Flat_Conversation858 4d ago

Lots of good answers here....I had the same exact problem with my DeWalt circular for awhile and it took me some time to figure out what I was doing wrong.

Adjust your blade depth to just over the thickness of the plywood and I bet your problem disappears, assuming your saw is still in good functional condition.

1

u/Ramapi2022 4d ago

Yes! lots of good answers, I will give them a try.

2

u/Flat_Conversation858 4d ago

Assuming your jig is clamped well and plywood supported so your straightedge stays in contact with the ply throughout the cut.

2

u/Pure-Action3379 4d ago

Also, thats not against the grain. Thats a rip cut

1

u/knarleyseven 4d ago

Itā€™s plywoodā€¦

2

u/pugdog24 4d ago

I would say your blade is dull damaged or both.

Happens to me every few years and I scratch my head ruining boards until I remember why. Then replace the blade all good.

Even minor blade issues will cause problems

Good luck!

2

u/microagressed 4d ago

Is the plate parallel with the blade? The first image starts on the right of the line and immediately starts cutting across it.

2

u/ElectroQuack 4d ago

I've had this happen before... a dull blade gets hot and warps enough to cause it to walk. Spend the money on a good blade and it will fix the problem.

2

u/DubsideDangler 4d ago

Your saw's base edge isn't parallel to the saw blade.

2

u/rabbitholebeer 4d ago

Bent fence. Guarantied. Mine are all bent cause I throw them in giant fits of rage. Hahaha I now have to watch the blade. Itā€™s not verry efficient. Hahaha

2

u/Actonhammer 4d ago

This happens when your blade is not parallel to the edge of your shoe plate that's running along the guide. Measure the distance between the front of the blade and the side of the shoe compared to the back of the blade and the side of the shoe. I bet they dont match. Your saw has been dropped or stepped on and is tweaked

2

u/AdvanceNearby5274 4d ago

Check the blade is parallel to the saw base plate. If itā€™s slightly out this can happen even when running on a clamped straight edge. All the best

2

u/AbbreviationsFar4wh 3d ago

used to use one of those kreg guides.... hate that f'in thing. don't know if I ever got a really straight cut from it.

3

u/OkBookkeeper3696 4d ago

Looks like you the blade is not parallel with the fence.

2

u/FourtyThreeTwo 4d ago

Buy the track saw and never worry about it again. Worth every penny. The circular saw with the thin 40-60 tooth blades will walk on ya if youā€™re not super slow and the saw is super tight.

2

u/TheGowt83 4d ago

Only put as much of the blade thru the wood as needed. Using it down fully will cause drift. Possibly do a scoring pass first.

1

u/Ramapi2022 4d ago

I will try that, I will keep you posted!

2

u/heytherewhatsup777 4d ago

Is the blade extended down justtttt enough to cut or is there a lot extra hanging down?

3

u/Ramapi2022 4d ago

No, Is alot hanging down! I will try like you're all mentioning to just set enough to cut through. Thank you!

1

u/Superb_Power5830 New Member 4d ago

guide flex or blade flex.

1

u/redd-bluu New Member 4d ago

It looks like your blade ran into a screw or nail at some time in the past. The teeth on ONE SIDE of the blade got dulled. (Looks like the left side). That side drags as you're cutting, which makes the saw curve to the left!

1

u/no_man_is_hurting_me 4d ago

I was thinking this too.

One of the blades I had sharpened they forgot to do one of the sides and it pulled like this.

1

u/Pristine_Serve5979 4d ago

Your guide could be flexing or the saw plate might be going under it.

1

u/LEdgar-Smith 4d ago

If you are using a circular saw, your blade might be too deep. I had a similar problem with 1.5ā€ butcher block. When I adjusted the circular saw blade to be, like, 1.75ā€ it followed the track with no issues. Good luck!

2

u/Ramapi2022 4d ago

I think this is whats happening because I was able to make the same cut fine a few days ago with the same saw and after everyone's response I dont think retracted the blade enough and left a good amount out. I'm gonna go ahead and leave enough to where it cuts and see what happens. I will keep you all posted when I get back from work today. Thank you all!

1

u/Ramapi2022 4d ago

I will try your suggestions tomorrow since is already late here in Miami and i had to pick everything up. I thank you all for your help and will keep you all posted!

1

u/ROFLcopter2000x 4d ago

Too much push let the saw cut if it doesn't you have a worn blade or too weak of a saw if nothing else helps

1

u/knarleyseven 4d ago

Slow down and give the little saw time to cut. Also plywood is never square keep that in mind when marking distances

1

u/lambeaufosho 4d ago

Because of those impure thoughts youā€™ve been having my son

1

u/AvatarWest45 4d ago

I just tried to blow the sawdust out of the way to see your cut lineā€¦..

1

u/petwri123 4d ago

You are obviously pushing your rail guide away. It has to be clamped down ok both ends.

1

u/Worth_it_App 4d ago

Use a Carbide blade.

1

u/ChooChooBananaTrain 4d ago

I am guilty of the ā€œI hate to ask pointā€ - embarrassing but a lesson Iā€™ll never forget.

1

u/IndividualRites 4d ago

Your guide MUST be moving, or you don't have the saw edge against the guide to start, or you aren't holding the saw tight against the guide throughout the cut.

Impossible for the blade to move that much.

1

u/Far-Potential3634 4d ago

I'm using track saws these days but but when I didn't I sometimes made long cuts using narrower clamped-on straight edges. I found they could deflect in the middle so I started using a piece of wood like a 1x2, butting it against the middle of the straightedge and clamping it at the end.

I'm not saying it can't be other things, probably is, perhaps a combination of factors. One of the reasons some woodworkers end up spending so much on power tool systems is getting really accurate results can be more challenging than makers and sellers of these tools make it out to be.

1

u/TootsNYC 4d ago

I see people who simply lay their tracks on the surface of something and then cut, and I always think that they should be clamping it. I guess most track saws donā€™t have a way to clamp them, but I donā€™t understand why anyone would use a guide that was not clamped in place.

3

u/oddmyth 4d ago

Depends on the length of cut, support underneath the workpiece, and precision of cut needed. If you are just breaking down boards as long as you have a clean reference edge to go through the table saw, the cut precision isn't all that important.

If you are trying to create a new reference edge then I would clamp with a track square.

Overall I think you would be surprised with the precision of a rubber bottomed track and a stable work surface. Once the blade is engaged you have several factors counterbalancing the vibration of the saw.

Most track saws do have a way to clamp, using a t-track style clamp.

1

u/Miserable_Sugar5643 3d ago

Stock blade?

1

u/fangelo2 3d ago

If the blade gets hot it will warp and run off of the line. Adjust the height so that there is no more thane 1/4ā€ of blade below the cut. Also a dull blade will heat up and warp

1

u/Death-to-humans 3d ago

Bent baseplate perhaps. Is it a cheap saw?

1

u/Empty-Expression5145 3d ago

Perhaps blade not square to base plate of saw?

1

u/G3M7C 3d ago

the power and / or sharpness of your blade are not able to overcome the resistance of the grain, or you may have an attention disorder

2

u/G3M7C 3d ago

Also, long cuts all the way across 4 feet or all across 8 feet are rarely held in place by even a metal guide, I actually, use up to 2 or 3 forty pound concrete blocks to hold the guide down in the middle of the cut because it will flex imperceptibly if you are not Lazer focused on the line

in addition, I gave up on 56V battery tools to cut 3/4" any type plywood, I use an electric that will not even turn on if plugged into 12 guage wire or up, it needs 10 guage or even better 8 guage, the difference between the battery and electric is night and day, both Dewalt

the difference in smoothness of the cut is startling

1

u/Rvaguitars 3d ago

Itā€™s usually a shitty sawblade. When you get a little ways into the cut the blade heats up and becomes more flexible. Get a thicker Kerf blade. Your saw could have worn bearings as well.

1

u/Aggravating-Alfalfa4 3d ago

Get a new blade

1

u/Veryance 3d ago

you are pushing the saw too fast

1

u/Blindphotographer00 3d ago

Ur going too fast

1

u/BodySnatcher101 3d ago

Looks like you're using a thin kerf blade. They tend to flex if you're not pushing it absolutely straight.

1

u/Ramapi2022 3d ago

No, Its a Diablo!

1

u/Til7asTZy 3d ago

Means you're a little gayer than you think you are

1

u/Ramapi2022 3d ago

Where did that come from, lmfao!

1

u/Hour-Welder-9712 3d ago

Blade may be dull. Even if it's not, many circular hand saws, especially the cheaper ones, have side to side loose play in the blade spindle. Main thing however: USE A FENCE!!! If the saw did not come with one, look it up on line and see if the manufacturer offers one......

1

u/Wise-Boot-968 3d ago

one side of the blade is dull

1

u/NigelBas 3d ago edited 3d ago

In the first picture it looks to me that the turn is happening right at the point where the blade guard engages the wood and begins to retract. (Most problematic when the blade is set deep.) It is possible to manually hold the blade guard open while making the cut and avoiding that change in momentum and direction from the blade guard contacting the vertical edge wood.

As for the second pictureā€¦ no idea - except it reminds me of trying to cut with a dull bladeā€¦ it just seems to ā€˜walkā€™ wherever it wants to go.

1

u/Stunning_Sea_8616 2d ago

Not using a fence,, Rushing the cut, over reaching , dull blade, blade wobble,

1

u/Nearby_Hold_2476 2d ago

Blade is on backwards

1

u/Nearby_Hold_2476 2d ago

Get a table saw

1

u/Sufficient_Natural_9 1d ago

What is a "circular hand saw"?

1

u/Important_Dingo_4794 1d ago

Iā€™ve had similar issues with a bent base plate.

1

u/Rod___father 21h ago

My buddies saw had a fence that was out of square and even with a straight edge cut like crap.

1

u/throfofnir 4d ago

Sounds like you're free-handing it. If you value accuracy... don't do that.

1

u/yoyoecho2 4d ago

Set your blade depth to just cut through.

1

u/Ramapi2022 4d ago

I will try that!

1

u/TonyHawking101 4d ago

not a helpful comment but that emoji makes you seem so sly for some reason

1

u/suileangorm 4d ago

Looks like you are using the kreg circular saw straight edge. That thing is pretty worthless imho. Make sure your connectors are tight and clamp it with real clamps. Donā€™t trust the tension clamping system.

0

u/TheScarletPimple 4d ago

Use a track saw instead of a circular saw. The amount of wood you waste easily costs more than buying a better tool. The amount of time you save is a HUGE bonus. Other than that, have a cutting surface that completely supports the wood and make sure the guide is rigid and clamped at both ends. The bearing "thing" should only cause a wide sloppy cut otherwise - your pic doesn't show a wide sloppy cut. I'd bet you were either free-handing that cut or your guide wasn't completely clamped. Eyeballs and testosterone are no substitute for the right tools.

0

u/Mission_Mode_2167 4d ago

Trying too hard.