3/4" blade on 14" Powermatic Bandsaw

[Brian Mahaney]

Hello all,

I bought a 14" Powermatic band saw a little over a week ago. I'm not that familiar with it yet. Today I picked up a 3/4" blade on sale at a local lumber supplier. I tried to install it a little while ago but ran into a few issues. It went on fine, or so it seemed. The lower bearing that rides at the back edge of the blade does not seem to have enough travel to allow the blade all the way in. It goes most of the way, but it does not seem possible to set it according to the owner's manual. In other words, it will always be touching the back of the blade and it touches it pretty hard if you know what I mean. To complicate matters, that bearing doesn't spin freely anyway. It's too stiff to spin like the rest of the bearings. I will tinker with it and replace it if necessary, but the travel issue is still a problem. The combination of the two problems resulted in a slightly hot bearing with a slight groove beginning to wear in the bearing. This was after a short test run.

Questions: Should I pull the blade off and just accept that a 3/4" blade simply won¢t fit even though it is supposed to fit? I seem to remember a recent discussion saying that fitting a 3/4" blade on a 14" saw is a common problem. I sure did like the result of the test run I made. Are there any adjustments that I am missing that would remedy the problem? Anyone familiar with this saw enough to tell me what I need to know to run a 3/4" blade in it?

Thanks, Brian

[cerskine]

At the risk of sounding like a wiseguy, how about posing your question to Powermatic? Especially if you may have a bad bearing.

mailto: [e-mail]

[George]

Well, you might have been able to move the blade forward with tracking, but if you're doing all right with other blades, do without. I've a Delta, and it does fine with the 3/4 blade, especially the thin one from Suffolk.

Never have been able to figure out why, if the upper thrust bearing was on an eccentric, the lower wasn't. Can lead to those kind of problems you mentioned if the blade was too far inside the rim, even if the bearing spins like a sweetheart otherwise. Remove and reverse the bearing, though you still might want to bitch and get another from Powermatic.

[David]

If the blade is riding where it's supposed to be, remove the table and adjust the lower guide mounting unit. It is attached to the frame with bolts--loosen the bolts and move the assy back. be sure to keep it aligned with the blade so that the side bearings are still perfectly parallel with the blade. I had to make this adjustment when my BS was new...

Dave

Brian Mahaney wrote:

[Hax Planx]

There are some simple adjustments to setting the thrust bearings. Like David said, there is another adjustment where the guide and thrust bearing assembly bolts to the frame. Running your saw in a bind the way you did was extremely unwise and dangerous, not to mention murder on your nice new saw (Wanna trade?). The damaged bearing should be flipped or changed. Don't use the damaged face anymore. Your saw won't perform well or safely if it isn't adjusted with care. The thrust bearings should be adjusted to where they just barely don't move when the machine is on, but will as soon as you start cutting a piece of wood and the blade moves a fraction of an inch (1/64 is the rule of thumb) and braces against them. Guide blocks should be adjusted similarly close, as close as possible without touching when the blade is moving, and behind the kerf of the blade. When I change blades, I move everything way out of the way, install the blade, tension it and then turn the saw on for a few seconds so that the blade finds its equilibrium. Then you can do the adjustments, turn on the saw and check to see if your adjustments need any tweaking. If you are lucky, your adjustments will keep, but you should keep checking them as long as you are using the saw, because if your saw is anything like mine, the blade will drift for a variety of reasons, including sawdust building up on the wheels. These should be thoroughly cleaned before using the saw. It may all sound like too much trouble, but that's the price of using a band saw. Your saw should run a 3/4" blade with ease, but most people stop at 1/2" or 5/8" for 14" saws. A 1/2" Timberwolf blade resaws perfectly adequately for my purposes. You should get the Duginske book. It will tell you more than you ever wanted to know about band saws.

[Brian Mahaney]

I did think of that. How do you know I didn't email them as well as this newsgroup? I can be a wiseguy also :) But seriously, when I think of a place to look for a broad range of real-world experience with woodworking machinery, I think of this newsgroup, not the customer service rep at a large corporation. I'm sure their help is great, but sometimes I like to mine many sources to arrive at a solution that works for me.

Thanks for the input, Brian

[Brian Mahaney]

I did try to move the blade forward with the tracking, but it was too far forward to be safe or practical by the time it wasn't touching any more. It was already pushing the limit of being "centered" when it was rubbing against the bearing. I'm still tinkering with it. I may have found a solution. I'll post it if I do.

Thanks, Brian

[Brian Mahaney]

On Mon, 06 Jun 2005 15:02:59 -0700, David wrote:

Dave,

I had to leave right after I wrote my post yesterday, but when I got home last night I was able to get a closer look at the problem. Taking your advice, I pulled the table and examined the lower guide. Sure enough it had quite a bit of adjustability. However, it was already adjusted back as far from the blade as possible. I loosened the two bolts that hold the assembly in place and pushed back on it just to make sure. It wouldn't go back any farther. I was able to see why the bearing wasn't spinning freely. When it is adjusted back as far as it will go, it rubbed against the body of the unit. It was touching just enough to cause a little friction. The bearing still turned, but not enough to let it spin at the same speed as the blade was traveling. So a small mark (I'll call it a scratch) was formed all the way around the circumference of the bearing. In order to buy a little space (not much was needed) I filed a couple of thousandths of metal from the area where the bearing was rubbing. Additionally I filed a couple of thousandths from the area where the mounting bolts go to allow the whole assembly to move back just a hair more. This did the trick. I bought just enough room to allow the bearing to spin freely. However, I would like the blade to be a tracking a little closer to the center of the wheel. It is close, but not where I would put it if I had the ability to move it farther back. Also, when I move the blade by spinning the upper wheel, the blade touches the bearing more often than not. It's just too close to be how it's supposed to be. I've actually considered tapping new holes to mount the assembly. I could easily mount it closer to the center of the adjustment range. Don't know why they didn't do that in the first place.

Thanks for the advice. I'll post the ultimate solution when I arrive at something, Brian

[Brian Mahaney]

No it wasn't unwise or dangerous. It was not in a bind. The blade moved easily and was close to the center of the wheel. There was pressure on the thrust bearing, but it was no more than what would be encountered while pushing a board through. The slight damage to the surface of the bearing extended all the way around the bearing indicating that the bearing was turning. However, it was turning slower than the blade causing the blade to scratch the shiny surface. As it turns out, the bearing was rubbing against the assembly housing slightly. Apparently, the design does not include a stop other than the bearing hitting the housing.

The damaged bearing should be flipped

I will flip the bearing.

Don't use the damaged face anymore. Your saw won't perform

Duginske's book is on my list. I don't have a problem with tweaking a band saw. As you said, it's the nature of the beast. At this price point, I would have liked to see a little bit better quality control or design, whatever the problem was. Honestly, I like the saw, but other than the extra gadgets (light, chip blower), I don't see the price justification. The saw had no better fit or finish than my Grizzly table saw, or my Geetech jointer. There were chips in the paint right out of the box (this didn't bother me in the least); there was some overspray and some under spray of certain areas (no big deal to me). Although I can say it is slightly better than other equipment I have seen, it's just not enough from the quality perspective. Again, I guess the light and chip blower are what makes it cost more. I received a free mobile base with it. That was an incentive to me also.

Thanks for the advice, Brian

[David]

Brian, I'm glad to hear you were able to run with my suggestion on the lower guide assy. Sounds like on mine PM didn't secure the guide assy in the exact spot they should have, and in your case they may have drilled the holes off their mark. As I remember, I had to move the assy all the way back, so any slight error on another unit's bolt holes might require some machining.

Once you get over this problem, I bet you'll really enjoy the saw. Using my BS yesterday a lot, I congratulated myself for buying it, after a disastrous 1 week of owning a Delta. I esp love the blower and light.

Oh, I find that the 1/2" (or is it 5/8" - I'm not sure) blade I use is sufficient for the big cuts. Many books suggest NOT installing a 3/4 blade onto the 14" "Taiwanese" BS, due to the heavy tension needed.

Dave

Brian Mahaney wrote:

[Brian Mahaney]

I decided to try the 3/4" on a whim because I found it on sale. I already had a 1/2" on order. If it cuts as good as this 3/4" is cutting, I'll just leave it on for most cuts. I do like the saw. Even with the cheap blade that came with it, I like it. I'm even enjoying the light and mobile base that I got with it. I'm normally a no frills kind of guy, but went above and beyond for this one.

That reminds me. My wife made me promise to gloat about her because of her tool policy. She said I could only purchase this band saw if I extol her virtues to the world so here goes: my wife's policy for tools is that I should always get the best I can afford. She makes me buy the more expensive one most of the time because she says, "I don't want to hear you bitching that it isn't good enough." So, little by little as I can afford more, I go for the best I can find that will fit in my tiny shop. There it is. I see a new tool on the horizon for this.

Thanks again, Brian

[David]

:) Your wife attitude sounds identical to mine! She's prodded me into buying a bit more than I'd planned on. She's ordered a number of gifts from LV for me. The only tool I'm having trouble convincing her I should get is a drum sander. Father's Day is coming up, and for that I suspect there will be some more LV goodies! Xmas always nets me a few LV goodies too. Gotta love her!

What size is your shop, Brian? I see you say it's "tiny". Mine is in a

2 car garage and I wish it were at least 3 times that size so I'd have more room for stock, another workbench, and dedicated tall and short assembly tables. But hey, I'm still having fun with what I've got.

Dave

Brian Mahaney wrote:

[George]

Time to move the wheels forward the thickness of one washer....

[Brian Mahaney]

Now there's an idea. Elegant. Simple. Reversible. I like it. Might try it. I'd use machine bushings. They are more likely to be the same thickness. This sounds easier than drilling and tapping.

Thanks, Brian

[David]

Don't do it on a powermatic! I tried that after reading about coplanar theory. The unit is designed correctly and tracks all blades perfectly without being coplanar. I put washers in, thinking I was smarter than the mfgr, and fired it up with a wide blade. No good. Removed the washer and all my blades track well.

Dave

George wrote:

[David]

Brian, granted PM may have drilled the holes incorrectly for the lower guide, but they have the geometry correct for the wheels. I already tried making the wheels coplanar; it won't track correctly.

Dave

Brian Mahaney wrote:

[Brian Mahaney]

Hmm, were the washers the same thickness? Those things are stamped out of what ever thickness they have on hand. They vary greatly even when they come from the same box. That's why I would try machine bushings. Any other experiences with this sort of thing out there?

Brian

[David]

I can't remember exactly how much I shimmed it, but I think it was about a 1/16. It put the 2 wheels into the same plane, but it didn't track with a damn. Because of the tracking adjustment, it's not as simple as just aligned the two wheels with a straight edge.

Bottom line, if your blade tracks well, you shouldn't need to "improve" the design with shims.

Dave

Brian Mahaney wrote:

[alexy]

But if he puts the same number of washers on the top and bottom wheel, isn't he maintaining the original geometry, while moving the whole thing relative to the guides?

[Brian Mahaney]

That's what I thought. After all, I wouldn't be attempting to change anthing except how far out the wheels are. Using the same thickness of machine bushing would maintain that geometry. I haven't even had a chance to look at it, but I may do so tonight when I come home from work. Maybe he's right. Maybe there is something else there, but it sure seems like a great idea.

Brian