Weird "Ripples" in Bandsaw Cut

[buckeye95]

All,

I just started using my bandsaw (Sears 21400 10" rebadged Rikon bought on CL) and have been seeing these odd ripples in the cuts I have been making. Unfortunately I was under the gun to get a Pinewood car done on time, so I was forced to buy a Craftsman blade (no time for a Timberwolf, etc. to be shipped), but I did tune it up per the Woodscrub blog directions others here have recommended.

The symptoms are that I find the blade to go through rather slowly (not "like butter" as I have heard others comment should occur with a properly tuned bandsaw). Additionally, when I look at the finished cut, I see a defined ripple in it. This ripple effect has a definite period to it (distance between peaks and troughs are consistent), and is not just visual; you can feel a distinctive ripple in the wood that must be sanded out. I have attached a picture for reference.

Does this sound normal? Any clues as to what might be causing this (cheap blade, user or setup error, etc.)?

Thanks in advance,

Pete

[LCHIEN]

probably an incorrect blade tension issue.

[tommyt654]

And possibly a dull blade as well, How much time on the blade?

[Mr__Bill]

Here's the question, now mind you I'm not insinuating anything by this but, is the blade on the right way? I ask because I have done it in the past and it kind of sounds like my results in cutting were similar to yours.



Bill
Over the course of my life I have come to realize that only the really smart people make really stupid mistakes, for the rest of the people it's just par for the course.

[buckeye95]

LChien - I considered that, but tried to set up the blade as close as possible to the blog instructions people recommended.

Tommy - the blade I am using is brand new. Not the highest rated brand (Craftsman), but it was new out of the box.

Mr_Bill - I think you may have hit it. Looking at my saw, the blade has one part of the tooth at 90 degrees to the movement of the blade and another at an angle. The way the blade is set up now, the part of the tooth that is perpendicular to the blade movement hits the material first. This seems wrong to me - I think the angled side of the tooth should go into the material first. Can someone confim the correct way the blade should be oriented (sorry for such a basic question).

Regards,

Pete

[leehljp]

I get that all the time on my old 12 inch Sears with blades 1/4 inch and larger. In reading in other places and from my experience, BS smaller than 14 inches in general do not have the tension ability to match the job that most hobbiests hope for. I do think that the Timberwolf would probably do a better job.

[LCHIEN]

LChien - I considered that, but tried to set up the blade as close as possible to the blog instructions people recommended.

Tommy - the blade I am using is brand new. Not the highest rated brand (Craftsman), but it was new out of the box.

Mr_Bill - I think you may have hit it. Looking at my saw, the blade has one part of the tooth at 90 degrees to the movement of the blade and another at an angle. The way the blade is set up now, the part of the tooth that is perpendicular to the blade movement hits the material first. This seems wrong to me - I think the angled side of the tooth should go into the material first. Can someone confim the correct way the blade should be oriented (sorry for such a basic question).

Regards,

Pete

No it sounds like you have the blade on the correct way.

the 90 degree edge does the shaving of the wood.

since the front of the blade goes downwards, the hook of the blade should look like someones nose.

If the tension may be incorrect, try some other tensions higher or lower than what you get "by the book" - experiment.

here's a pic of the correct tooth orientation (the teeth travel down in this pic):

[Bill in Buena Park]

Pete,
Not sure what kind of blade you're using - but there's a fair amount of things to check, including blade orientation, sharpness, tension, tracking, guides, etc. For your question on blade orientation, I've attached a pic.

[buckeye95]

Thanks guys - looks like the orientation is correct.

I'll keep fiddling...

Pete

[Uncle Cracker]

I'd suggest that, before you tweak your saw into oblivion, you try a different blade. You may have just gotten one where the teeth were not "set" properly from the get-go.

[mpc]

I used the 10" Craftsman bandsaw (also looks like a Rikon clone) with the Sears blades. It worked okay... but was far far better with other blade brands - like the Olson blades from Woodcraft. See if you have a Woodcraft or Rockler in your town; if so the Olson blades they sell are a step up from your Sears blade.

I don't know the details of your saw... does it have a blade tension indicator? Try this test anyway:
* saw off & unplugged
* raise the upper blade assembly to nearly its maximum position
* loosen the guide bearings/blocks (the ones on either side of the blade) and the rear "thrust bearing" and pull them away from the blade - get them well out of the way. Do this for both the upper and lower bearing/block assemblies.
* loosen the tension until the blade is visibly "rounding" rather than being straight from wheel to wheel. This is a very "slack" tension obviously.
* Pluck the back of the blade like a guitar or harp string. It'll be really dull sound
* Increase the tension a little
* Pluck again.
* Repeat adding tension & plucking. At some point you'll hear the blade start ringing. When the sound is a nice even tone (not a thud) see what the tension scale reads.
* A high-pitched ringing is typical of decent tension.
If your saw has a blade tension indicator, don't go more than 1 pointer "notch" above what it thinks is correct for your blade.

My 10" saw doesn't have a tension indicator; I did this "tension & pluck" test over and over until I found a tension that seemed to make good cuts. I've mentally noted the sound of a decent tensioned blade. I also busted a blade or two by over-tensioning... but repairing them is fairly easy - Woodcraft's little kit works fine though it's expensive for what it is.

Oh, how thick (not deep) is the blade? Bandsaw blades typically come in two thicknesses, just like table saw blades that come in regular and thin kerf. If the blade is thick for it's depth it'll take more cranking on the tension knob to properly tension it - the tension indicator may be calibrated for "thin" blades, not thick blades. Does the saw manual have any mention of blade thicknesses?

Did you adjust both the upper and lower (under the table) guide bearings properly? The under-table ones are harder to do and easily forgotten. The bearings/guides that rub against the flat sides of your blade need to be moved forward/aft (relative to the teeth of the blade) so that they are BEHIND the gullets (the cutouts in the cutting edge of the blade). The blade teeth are bent left/right (as you face them) in a "set" just like a handsaw blade's teeth. If the bandsaw's blade guide bearings/blocks are adjusted too far fowards (i.e. too close to where you stand when feeding the workpiece) the blade set will be hitting the bearings causing the blade to bounce around. Then, the blade guide bearings/blocks should be close to, but not quite touching, the blade when it's tensioned. Some folks like to use a dollar bill to check clearance. I spin the wheels by hand and make sure none of the bearings/guides ever touch the blade as it moves. The "thrust bearing" (the bearing that supports the backside of the saw blade) should also be a dollar bill away from the blade.

Check the guide bearing/block clearances when the blade guide assembly is lowered to just above your workpiece. Ideally that part of your bandsaw moves up/down perfectly straight but not all saws are that well built... you may find it's angled ever so slightly... so you have to re-adjust the guide bearings/blocks each time you adjust the height.

Also, when you spin the wheels by hand (saw still unplugged) watch for the weld/brazing joint of the blade. A poor joint will cause a bump, leading to a ragged cut. If you have to space a guide bearing/block just to miss the joint that means the joint sucks.

mpc

[LCHIEN]

i still put money on tension issues. The blade is obviously fluttering - the period is indicative of that. Any blade imperfections would result in a wide kerf and not ripples.

P.S. Also as ATQCPAUL suggests, check and make sure your top and bottom blade guides are set right. The top guide is adjusted to just above the workpiece so it just clears. The left and right guide blocks are close - dollar bill thickness of space, and the thrust bearings are backing up the blade just a few thou away. These will limit flutter in a sawblade under cutting forces - but you still need adequate tension.

[atgcpaul]

i still put money on tension issues. The blade is obviously fluttering - the period is indicative of that. Any blade imperfections would result in a wide kerf and not ripples.

The blade is fluttering. Make sure your guide blocks are close to the blade. I
make the gap 2 PostIts thick on my saw. Then tension your blade more.

About the incorrect blade/teeth direction. Isn't it only possible to have the
blade teeth facing you or facing away from you with a rigid steel band? Is it
even possible to roll a bandsaw blade inside out so that with the teeth facing
you, the teeth would be pointed up instead of down? If the teeth do point
up, instead of down wouldn't that mean the manufacturer welded the band
inside out?

[gsmittle]

Isn't it only possible to have the
blade teeth facing you or facing away from you with a rigid steel band? Is it
even possible to roll a bandsaw blade inside out so that with the teeth facing
you, the teeth would be pointed up instead of down? If the teeth do point
up, instead of down wouldn't that mean the manufacturer welded the band
inside out?

It's possible to roll a bandsaw blade inside out. DAMHIKT.

g.

[SARGE..g-47]

I have no experience with a 10" BS but have with from 12" up to 24". You failed to mention what the width of your blade is and the tpi or number of teeth. Assuming you have the guides set correctly and the blade does not have a bad set in a tooth or teeth which will cause the blade to wander aim-lessly.. try cranking the tension a bit higher.

Forget what your tension guage says.. just crank it to the proper tension mark for blade and then crank a tad more and experiment. For that matter you can go down to see if it gets worse. And.. depending on the teeth which you didn't mention.. adjust the feed rate. I am going to dis-agree that a BS will cut like butter. Jointer knives.. planer knives and to a degree TS blades will cut like butter but not necessarily a BS.

The most common reason for ripple when re-sawing which I do a lot of is feeding to fast or slow if the saw and tension are set correctly. If you are using a high tooth blade the feed must be extremely slow to remove waste as you don't have much gullet to help. Try adjusting the feed rate and see what happens. BTW.. try not to stop and start during the feed but keep it one continous flow..

Gottta get back to the shop.. good luck!