LumberJocks

delta 14" bandsaw: resawing, blade cuts a cup into the workpiece

  • Advertise with us

« back to Power Tools, Hardware and Accessories forum

Forum topic by parchiba posted 10-15-2021 09:51 PM 1460 views 1 time favorited 19 replies Add to Favorites Watch
View parchiba's profile

parchiba

5 posts in 171 days


10-15-2021 09:51 PM

Kind of hard to describe.

I’m resawing some 2.5×5.5 redwood into fence pickets. I did about 75 of them the other day, no problem. But today I can’t get them right, and I don’t understand what is happening.

The blade is drifting out (away from the fence) on the top of the boards and the cut is ending up cup shaped, as though the blade is not staying straight as it passes through the wood. Across the cut board face its ending up about 3/16 low in the center of the board on one side and of course 3/16 proud on the other, so the pickets look warped.

My setup is a Delta 14” with a Kreg fence and resaw guide and a 1/2” bosch 4tpi blade. I have tried changing the blade, and tried both with and without the resaw guide, with the same results.

So, I just don’t understand what could be going on here. The blade is being pulled down through the wood, so why would it drift off the line at the top (and rub against the outside blade guide) and follow a curved path through the wood? It seems to defy physics.

The only thing I can think of is the the blade got dulled on one side and so is not cutting evenly. Maybe when I was experimenting with leaving the resaw guide off? I watched a video of a guy who mentioned that as the kerf opens up the board pushes away against the fence, which might cause one side of the blade to dull faster. Maybe?


19 replies so far

View Richard Lee's profile

Richard Lee

445 posts in 2059 days


#1 posted 10-15-2021 11:01 PM

Something may have moved, check your table alignment to blade.
Check your blade guides, might be pushing one way to much.
Check for blade squareness to table.

View Aj2's profile

Aj2

4134 posts in 3082 days


#2 posted 10-15-2021 11:23 PM

Is your blade clear from the guides. Your post does read like a dull blade.
Make sure the blade isn’t getting forced back into the side guides when you cut wood.
Good Luck

-- Aj

View wichman3's profile

wichman3

114 posts in 1905 days


#3 posted 10-16-2021 02:46 AM

Softwood will do this. Older softwood is worse. Higher tension on the blade is the only recourse, assuming the blade is sharp.
I see this frequently on my scrollsaw when making compound cuts. I just cut an ornament and the waste piece would not come out normally, I had to re thread the blade and cut the waste piece into quarters. I’ve never had this problem with hardwoods.

View Lazyman's profile

Lazyman

8229 posts in 2672 days


#4 posted 10-16-2021 04:02 AM

When this happens to me it, usually means the blade has become dull. A fresh, sharp blade always seems to fix the problem. I’ve had it happen when the blade has become really dirty with pitch or resin too so if it is dirty, try cleaning it before you replace it.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View RClark's profile

RClark

187 posts in 3469 days


#5 posted 10-16-2021 09:43 AM

I’ve had this happen on my 14” Delta.

Could be a few causes:

- Dull blade

- Something out of alignment; you’ll need to run through the tuning sequence and make sure it’s all right.

- Blade tension; might not be enough. My Delta is a 2001-ish model, one of the last USA-made Delta 14” saws. I think it’s spec’d for a max of 3/4” blade, but it really doesn’t do well going that wide. I really think a 1/2” blade is the max it can handle. You said you’re using a 1/2” blade, but even at that, the stock tensioning spring on these 14” Delta’s isn’t strong enough. The gauge on the back of the saw isn’t a very good indication of tensioning strength. A new, stronger spring for my Delta is on my to-do list. Until I get the new, stronger spring, resawing is not one of the tasks lined for that saw.

-- Ray

View Robert's profile

Robert

4786 posts in 2765 days


#6 posted 10-16-2021 11:27 AM

The most common cause of bowing is inadequate blade tension. If it’s not tensioned up enough the blade will bow when you push, worse with a dull blade. A dull blade also tends to follow the grain.

It always pays to occasionally double check alignment – blade square to fence, fence aligned to drift, guides all good.

Tension the snot out of the blade.

Don’t feed wood too fast.

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

View ManySplinters's profile

ManySplinters

25 posts in 64 days


#7 posted 10-16-2021 03:21 PM

Also, you’ll want to check wheel alignment and where your blade is tracking. Mark Duginske mentions cupping in his Band Saw Handbook and had those suggestions along with the ones already posted above. He also talks about feed rate, which probably is affected by blade sharpness as well.

Also saw (sorry about that pun) those things mentioned by a sawyer here. They talked about guide blocks being a factor as well.

But isn’t 450’ (assuming 6’ fence) of 5.5” cuts pretty good for a regular blade?

View parchiba's profile

parchiba

5 posts in 171 days


#8 posted 10-17-2021 11:14 PM

Good responses. Let me address them.

Dull blade? I have three blades, none feel dull. Not to say its impossible one side of the blade is duller than the other, but I honestly can’t detect a difference by hand. Dirty? That might be it, the same side of all three blades seems more sticky. I will try cleaning them and see if that helps.

Alignment? I will check, but I doubt its the problem. No reason to think it would change from one day to the next when I didn’t even move the fence. But I will check.

Tension? Yeah, this one seems possible. I will try cranking it up.

Softwood? Interesting, I wonder why that would be. I have tried flipping the boards around in different directions, and I don’t think its following the grain. I would think redwood would be pretty easy to cut.

I think Robert nailed my biggest question, which was why the blade would follow a curved path. I can see how pushing too hard on the workpiece could cause the blasé to deflect, and if its a bit dull that would encourage pushing harder.

So, tomorrow I’ll check the alignment, clean the best blade I have, tension the blade and try again. In the meantime I’m going to order a couple of new blades. Lowes ran out of the Bosch 1/2×4tpi. Im going to search elsewhere on the forum for brand recommendations.

Thank you guys.

View johnstoneb's profile

johnstoneb

3183 posts in 3457 days


#9 posted 10-17-2021 11:22 PM

That might be your problem. I have used Bosch from Lowe’s and there seems to be a quality issue they seemed to dull quicker and sometimes the set on one side was off and they cut crooked out of the package.

-- Bruce, Boise, ID

View JAAune's profile

JAAune

2056 posts in 3601 days


#10 posted 10-18-2021 12:19 AM

A curved cut can be caused by over-heating (warps the blade) which can be caused by a dull blade (replace it) or clogged gullets. If the gullets can’t clear the chips it might be that they are sticking (try cleaning and maybe applying paraffin wax to the blade if the wood is gummy) or you’re feeding faster than the blade can remove the sawdust (decrease TPI or slow feedrate).

-- See my work at http://altaredesign.com

View parchiba's profile

parchiba

5 posts in 171 days


#11 posted 10-20-2021 04:18 PM

thanks for the heads up on the bosch blades. lowes is only 10 minutes away, so that is where is usually start my search. got a wood slicer arriving today.

View Lazyman's profile

Lazyman

8229 posts in 2672 days


#12 posted 10-20-2021 04:24 PM

The Wood Slicers give a fantastic finish and cut effortlessly well when sharp but in my experience they tend to dull a little more quickly than courser cutting blades. They should only be used on dry wood.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View therealSteveN's profile

therealSteveN

9228 posts in 1859 days


#13 posted 10-20-2021 08:19 PM


Good responses. Let me address them.

Tension? Yeah, this one seems possible. I will try cranking it up.

Just reading your title this was my take away.

I think Robert nailed my biggest question, which was why the blade would follow a curved path. I can see how pushing too hard on the workpiece could cause the blasé to deflect, and if its a bit dull that would encourage pushing harder.

The thing to test here is that curved path, ALSO the same path the grain takes.

If the answer is yes, then I double down on not enough tension.

- parchiba

All of the suggestions are easy enough to do. I’d start with tension. If you are using the indicator for tension, set it for 3/4”. All of the Delta’s, and the clones are tough to properly tension, In every case you can start simply by moving the tension to the next stated setting. You have about as big a blade as that saw type can properly tension. I think you just need to get to that proper amount.

I’ve been having real good luck with the Starrett blades they sell at WoodCraft. Nice blade stock, great welds, and a low price. WoodCraft has them on sale two to three times a year. Get signed up for their email alerts, and you’ll see them. Goofy thing is my local store hardly stocked them. Since I have been buying them the Owner started to put them out, they are flying off the shelf, outselling the Olson, and Timberwolf by a large margin. He just smiles and says he’s getting a lot of repeat business

-- Think safe, be safe

View wichman3's profile

wichman3

114 posts in 1905 days


#14 posted 10-21-2021 02:49 AM


Softwood? Interesting, I wonder why that would be. I have tried flipping the boards around in different directions, and I don t think its following the grain. I would think redwood would be pretty easy to cut.

- parchiba

Re: Softwood

Recently while cutting some compound patterns with my scrollsaw in 1 3/8×1 3/8 redwood, I noticed that while crosscutting the grain there was a noticeable difference in the hardness of the thin dark grain line (harder) and the wide lighter colored grain (softer). When I turned the piece 90 degrees and started cutting along the grain (a rip cut) the blade did not want to cut the thin dark grain line, it wanted to drift into the wide (softer) lighter part of the grain. The blade wants to follow the path of least resistance, so the blade will bend inside the cut (cup). All the other issues will be magnified by this. Because most of the hardwood we use has much tighter grain it doesn’t affect the cut as much. :)
Please let us know what you find and how you fixed it. :)

View Ed Weber's profile

Ed Weber

82 posts in 167 days


#15 posted 10-21-2021 02:02 PM


– Blade tension; might not be enough. My Delta is a 2001-ish model, one of the last USA-made Delta 14” saws. I think it s spec d for a max of 3/4” blade, but it really doesn t do well going that wide. I really think a 1/2” blade is the max it can handle. You said you re using a 1/2” blade, but even at that, the stock tensioning spring on these 14” Delta s isn t strong enough. The gauge on the back of the saw isn t a very good indication of tensioning strength. A new, stronger spring for my Delta is on my to-do list. Until I get the new, stronger spring, resawing is not one of the tasks lined for that saw.

- RClark


+1

Blade tension,
Operator pushing too hard.
As mentioned, just about all Asian import 14” bandsaws have weak tension springs, (a riser block makes the effect worse). If the blade is not tensioned enough. it, will try to bend out of the way rather than cut as you feed into it, this creates the cup
Even with a replacement spring, you still may need to tighten far beyond where the mechanism indicates.

If the blade won’t cut, pushing harder also bends the blade out of alignment and creates the cup.

showing 1 through 15 of 19 replies

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