Bandsaw table flatness...

[Sam Joyce]

Hi guys

Recently purchased a Grizzly G0513 because I just didnt have the willpower to resist the sale. So it arrives and i get it mostly set up then check the table with my Veritas straightedge. Lo and behold it is out by almost 20 thou in the center. (incidentally it is perfect where the relief cut for the blade is)

So I email grizzly and they are very cordial in sending out a replacement. It arrives and i check it. This one is out 23 thou with a bow in the center this time. Now my question is this. How flat does a bandsaw table really need to be? Is it worth it to try again? It is only a 17x17 piece of cast iron so i figure it COULD be at least as flat as my table saw which is much larger.

But maybe it is not so critical?
If you guys have any opinions let me hear them
Thanks

[Tri Hoang]

The bandsaw is what I consider a coarse tool (in the coarse-medium-fine scale). I'd not worry about a 20 thous dip. Make sure you have the screw the bridge the blade-entry gap in place...it may help.

[glenn bradley]

Since you state that it is flat where the blade slot is I assume you are not falling prey to the frequent "forgot to seat the table pin" syndrome. If the pin is in and well seated I would inspect where the table is being tightened to the trunnions. Cast iron is softer than you think and can be pulled out of shape if the mating surfaces are not true. This would be easy to test by placing your straight edge on the table where you see your gap and then loosen the trunnion bolts.

I would consider a couple hundredths to be unacceptable. So you are saying that you can slip a .02" feeler gauge under the straight edge? That's too much for me; others are more tolerant. If you are resawing a 10" height, that small dip becomes a larger number. If you are only roughing out bowl blanks, you probably don't care. If you are doing bandsaw boxes, it would be a struggle. Determine how you will use the saw and that will help determine how important this is to you.

[Chip Lindley]

Maybe .020" IS a bit much! But I had rather have a crown, than a dip in my table. You now have one of each; maybe if Grizzly ships you another table, 3rd time will be the Charm!

[Gary Herrmann]

.020 and .023, right? Have you checked the flatness specs for your model's tables? It may be within spec.

.020 is a bit over 1/64". Try resawing something and see how the saw performs. I'd be surprised if you it caused you any problems.

[David Nelson1]

The bandsaw is what I consider a coarse tool (in the coarse-medium-fine scale). I'd not worry about a 20 thous dip. Make sure you have the screw the bridge the blade-entry gap in place...it may help.

I have to agree with Tri. Cast iron is rather soft, that's why you see webbing on the back side of fences and table saw tops and wing extensions etc. Having said that .0200 is a bit much for a surface that should have been parallel ground during manufacturing. Unless the saws blade (front and back) are not square with the table (check with a machinist square or equivalent) I wouldn't sweat it.

My B/S had the above mention default. Please refer to this thread for the SMC troubleshooting and results. Good luck with the new purchase

http://sawmillcreek.org/showthread.php?t=140191

[Van Huskey]

I would consider a couple hundredths to be unacceptable. So you are saying that you can slip a .02" feeler gauge under the straight edge? That's too much for me; others are more tolerant. If you are resawing a 10" height, that small dip becomes a larger number. If you are only roughing out bowl blanks, you probably don't care. If you are doing bandsaw boxes, it would be a struggle. Determine how you will use the saw and that will help determine how important this is to you.


+1 unlike Tri I consider a BS to be a "fine" tool at least some of the time, veneer is one of those times and 2 hundreths is too much. In the end I would not settle until they supplied me a table that was within their spec. (.02 is apparently not since they sent a replacement unless they did it to be nice) since they would not have settled if your credit card was out of spec... People often overlook woodworking machine specs since we don't work to .001 with our wood but every deviation adds up and ofetn multiplies.

[Sam Joyce]

Great feedback guys.
Yes I used feeler gauges and got up to .020 and .023 and the pin is well seated. I can actually rock the straitedge back and forth on the one with the crown.
Glenn, I pulled the table off the saw, rechecked and came up with the same results so I dont think it's related to the trunnions thankfully.

I was leaning toward trying again and I beleive I'm going to fall in that direction. The saw will be used for resawing(and veneer) and curvy work so I think its worth it to start out with something as flat as possible. So yup, hopefully third times the charm!

[Myk Rian]

Have Grizzly "Certify" the top before sending it out.

[Will Blick]

Of course, there rarely is specs on BS table flateness. In a ww magazine, I recall reading that of many major makers, Sears had the flatest tables...go figure. My MM20 was .02" low in the middle as well... it bothered me considering its a $3k machine. But with no spec. its hard to argue, it sure was nice of Grizz to send out another table. I suspect their thinness is part of the problem as others have mentioned.

As an alternative, considering building a top to go over it, it serves the purpose of giving you more working room as well.... then you can achieve the flatness you desire. Of course, in most cases, this will not be a problem... as mentioned by a previous posters, BS's are considered rough cut machines vs. precisioned machines...

http://images.rockler.com/rockler/images/24504-01-500.jpg

[Pete Bradley]

+1 unlike Tri I consider a BS to be a "fine" tool at least some of the time, veneer is one of those times and 2 hundreths is too much.
Well it might be -- if that was the variation in the veneer, but it's a variation in the table. How much impact that has on an actual cut is questionable. Slices like veneer mostly depend on how parallel the fence is with the band and the technique of the user. On a standard cut against the table, the angular distance amounts to .02 over half the width of the table. I think that would be hard to measure on a bandsaw cut, and whatever was measured would change in a day anyway.

I've never found a need to put a straightedge across my bandsaw table, not sure I ever would.

Pete

[Sam Joyce]

As an alternative, considering building a top to go over it, it serves the purpose of giving you more working room as well.... then you can achieve the flatness you desire. Of course, in most cases, this will not be a problem... as mentioned by a previous posters, BS's are considered rough cut machines vs. precisioned machines...

This is an interesting fix but as lazy as it sounds im not sure i want to get into rigging up anothef type of fence when the saw already comes with a decent one.

There seems to be a mix of replies. I might just have a talk with Grizzly customer service a little more thoroughly then i did last time and see what they say. To be honest I'd rather not go through the hassle of getting another table as i have the original all set up.




I've never found a need to put a straightedge across my bandsaw table, not sure I ever would.

Pete

And Pete your probably better off for it. As it goes ignorance is bliss.:)

[Pete Bradley]

And Pete your probably better off for it. As it goes ignorance is bliss.:)
Most woodworkers would be better off for it. It's actually not ignorance, it's having the knowledge and experience to know what really doesn't matter. Don't get me wrong, when I'm rebuilding a machine there are places where I'll use precision tools, but this magazine-fueled notion of putting a straightedge to a brand new table must drive manufacturers batty.

Here's an illustration of why it is unlikely to matter: do the trig to calculate the variation at the top of a 2" thick crosscut, assuming the end at the workpiece at the band rises a full .02" during the cut (unlikely). Now go to the machine with a piece of hardwood and do that actual crosscut changing feed speed in the middle (or stop feeding for a moment so you can see the effect better), then put the cut face across your straightedge with a light behind it. This measurement method is crude at best, but unless the band is minty fresh and the stars are aligned, you'll find far more variation from technique than the few thou you calculated due to table flatness variation.

[michael case]

I bought a 14" Powermatic BS and the table is not truly flat. I had a Powermatic 66 and that table was way out. I finally ended up belt sanding portions to true it up. I read a Fine Woodworking tool test on 8" jointers. The test found Powermatic jointers had the least flat tables. This certainly dovetailed with my real-world experience with PM. My point is that you can pay big money and still get untrue tables. By the way, Grizzly jointers tend to have really flat tables. On a jointer I personally consider table flatness critical. But as Pete Bradley has explained, on a band saw the table flatness is not so critical. My bet would be that Griz along with many others does not bother that much with BS tables. The tables a split anyway and as others have pointed out the iron has a lot of give. If you find the inaccuracies interfere with your work, you might take one of the two tables you have and belt sand it a bit and true it up. I know this is not ideal, but it shouldn't take long.

[Pete Bradley]

The measurements in the FWW jointer review, like a number of other "precision" measurements in reviews of that time period by the same author, were very misleading. That same author even claimed that band saw table flatness measured with the pin out was important. What's important is not just what can be measured, it's what level of precision can actually affect the quality of the final product.

[John Thompson]

Again Pete.. I'm with you on your thoughts on BS table flatness. You and I both know who that author was that measured the BS table with the pin out which is essentially BS. I have a dip in the rear of my table about .020. About 10,000 linear feet re-saw across the table in 4 years and not one ruined piece of veneer as it simply is not going to matter re-sawing. The fence is much more important in the case of a BS..