What should I expect for cast iron tolerance on new Grizzly 76” jointer tables?

Hey there,

I’m curious if what I’m seeing is below a reasonable level of tolerance on the outfeed table (just the cast iron, not involving cutter heads).

From front-left to front-right on the outfeed table (away from the fence) I get a .002” variation, which is great. From back-left to back-right I get maybe .005”, which I guess isn’t awful? But from front-left to back-right I see a roughly 0.011” scoop in the middle.

Measuring with a 36” straight edge that should be within .002.

I got the outfeed edge within .001 with the cutters from front to back (well, the cutter body, challenging to do on a helical head) using a dial gauge. It’s pretty flat for maybe the first 8-12 inches, then some of that scoop in the middle variance kicks in. I’m not sure how much I should worry about this.

You won't see any difference in any of those tolerances. And since you only know what your straight edge tolerance should be, the measurements might be off a couple thou.

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Originally Posted by Richard Coers

You won't see any difference in any of those tolerances. And since you only know what your straight edge tolerance should be, the measurements might be off a couple thou.

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Ok thanks. I had heard others seeing their tables having .002 tolerances all the way through so I was concerned.

I wouldn't worry about those numbers. I seem to remember something about jointer tables being around a hundredth for tolerance.

I knew some folks who owned a local shop that sold wood machinery (now retired). They said that most of the people that fiddled with new jointers to make them "more accurate" usually ended up making them worse than what they stared with, to the point where sometimes they would have to send someone out to fix them.

Does your jointer have adjustable gibs? You might be able to adjust the gibs to take out some of that dip.

Those tolerances are way off of what I personally consider to be acceptable. Most offensive is the .011” dip. I have a SCM jointer/planer that is flat to less than .002” over the whole surface.

The question to ask is, does it work? If it doesn't work, what can you do about it?

Start by setting the outfeed table even with or just below the knives. Joint a pair of flat 1x4s as long as the outfeed table and offer up the jointed edges to each other. Do that at the right, left and center of the machine. Can you get a tight joint? If not, adjust the outfeed table height in minor increments. If you can't get the results you want, beg, borrow or buy an accurate 6' straight edge and check that the tables are in plane. Adjust them as close as you can if needed and try again.

If you truly can't make the machine do what it is supposed to do, document your findings and talk to the seller. If it is out of their stated tolerances they should replace it. Grizzly has a decent reputation for customer service, but I suspect your machine may be within their standards. In my opinion .011" over 36" on a jointer table is pretty horrible and not likely to result in accurate work, but the proof is in the pudding.

On my grizzly, I'm within about .002 everywhere I can tell (I won't pretend I'm an expert at feeler gauges and a straight edge). I did however find the back left side of my outfeed drops .005 or so. When I'm edge jointing a glueup, I'll usual slide the fence to the middle to avoid that drop, since I generally have to check and resquare the fence every time I edge joint. That said, I've never noticed anything bad from my .005 drop, and I've found more issues are created from bad technique - if I'm not careful about how much (well, little is probably a better word to use) I can end up with a non-straight edge joint, but if I'm careful to just barely guide the wood through the machine and not push on it more than I absolutely need to I get better results.

Why do you think your straight edge is accurate? HAs it been stored correctly so it has not lost that accuraqcy?
Bill D

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Originally Posted by Bill Dufour

Why do you think your straight edge is accurate? HAs it been stored correctly so it has not lost that accuraqcy?
Bill D

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Yeah it’s been hung on the wall in the mountable storage it came in. Also checking against other flat surfaces (cast iron tops and granite countertops) I only see about a .002 degree of variance.

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Does your jointer have adjustable gibs? You might be able to adjust the gibs to take out some of that dip.

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I don’t know what those are to be honest. So I’m not sure if it does. This is the G0858.

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Originally Posted by Kevin Jenness

The question to ask is, does it work? If it doesn't work, what can you do about it?

Start by setting the outfeed table even with or just below the knives. Joint a pair of flat 1x4s as long as the outfeed table and offer up the jointed edges to each other. Do that at the right, left and center of the machine. Can you get a tight joint? If not, adjust the outfeed table height in minor increments. If you can't get the results you want, beg, borrow or buy an accurate 6' straight edge and check that the tables are in plane. Adjust them as close as you can if needed and try again.

If you truly can't make the machine do what it is supposed to do, document your findings and talk to the seller. If it is out of their stated tolerances they should replace it. I think Grizzly has a decent reputation for customer service, but I suspect your machine may be within their standards. In my opinion .011" over 36" on a jointer table is pretty horrible and not likely to result in accurate work, but the proof is in the pudding.

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Sure, I can try that. But for $2500, I have a certain level of expectations. I think I will give Grizzly a call and ask them about this.

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Originally Posted by Myles Moran

On my grizzly, I'm within about .002 everywhere I can tell (I won't pretend I'm an expert at feeler gauges and a straight edge). I did however find the back left side of my outfeed drops .005 or so. When I'm edge jointing a glueup, I'll usual slide the fence to the middle to avoid that drop, since I generally have to check and resquare the fence every time I edge joint. That said, I've never noticed anything bad from my .005 drop, and I've found more issues are created from bad technique - if I'm not careful about how much (well, little is probably a better word to use) I can end up with a non-straight edge joint, but if I'm careful to just barely guide the wood through the machine and not push on it more than I absolutely need to I get better results.

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Interesting. I’ve seen advice to put pressure on the outfeed side once it passes over the cutter head. I’ve not heard people explain to put minimal pressure on that side, although that does make some sense so you aren’t forcing the wood into a position it doesn’t naturally want to be in. I have used that technique with some thin boards on my little bench top jointer I had.

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Originally Posted by Bob Spryn

I don’t know what those are to be honest. So I’m not sure if it does. This is the G0858.

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That is a parallelogram style jointer as opposed to a design with inclined ways with gibs. Each table is supported on four adjustable points so it is possible to make the infeed and outfeed tables coplanar and parallel to the cutterhead. One can twist the tables slightly in this way, but adjusting out a major dip in the length of a casting is not going to happen.

Joint two four foot pieces of wood on edge near the back of the jointer.

Put the two jointed edges together, if you have no gaps, or a few thou gap in the middle, you are good.

Repeat the test in the middle of the jointer and agin near the operator position, if the above is true, no need to start fixing something that isn’t broken……Regards, Rod

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Originally Posted by Kevin Jenness

That is a parallelogram style jointer as opposed to a design with inclined ways with gibs. Each table is supported on four adjustable points so it is possible to make the infeed and outfeed tables coplanar and parallel to the cutterhead. One can twist the tables slightly in this way, but adjusting out a major dip in the length of a casting is not going to happen.

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Ahh ok. Yea I’ve been adjusting the 4 points to make the table coplanar with the cutter head. So unless I could add a dip like that by adjusting those as a novice (I don’t think so)… The four corners of the table are coplanar with the cutter head body. So unless it’s possible to twist the middle while also having those all be coplanar, I don’t think it’s user error.

My personal take is that some people expect perfection even when it's not needed. Ask yourself this. When jointing the face of a board does it really matter if it's off by .010"? For most of us, not at all. When it comes to gluing up two boards to make a wider one where a nice straight edge is needed when is the last time you've had a project that needed boards wider than an inch? In the last 5 years I've only done it a couple times. The last time was to make some 4" square posts for a bed frame out of 4 triangles. Even then they were only a foot long and getting an exact 90 degree angle so they all came together nice and tight was the challenge.

When facing a board it leaves the jointer, goes to the thicknesser, and then most times the board movement from the newly exposed edges causes a slight amount of movement. Maybe in a perfect shop with wood that's been dried to perfection and has had years to climatize to your perfect shop this may not be the case.

The G0858 is a parallelogram jointer so you can try to set the two closest bed adjusters to match the head, adjust one of the rear adjusters (with the other loose) to get the bed parallel to the infeed table, lock those 3 down, and then try adjusting the forth adjuster to force the table to be less twisted.

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Originally Posted by Bob Spryn

Interesting. I’ve seen advice to put pressure on the outfeed side once it passes over the cutter head. I’ve not heard people explain to put minimal pressure on that side, although that does make some sense so you aren’t forcing the wood into a position it doesn’t naturally want to be in. I have used that technique with some thin boards on my little bench top jointer I had.

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Correct, I am trying to hold the wood onto the outfeed table, but very gentle in the process. Imagine a cupped or bowed board that flattens out with pressure - you're right about you making it "flatter" for the jointer and it springing back after.

I can't remember if I had a concave or convex edge joint when I learned this, but the problem cleared up right away when I used a gentle touch.

This topic has been discussed/argued many times here at SMC. IIRC, most manufacturers have a tolerance of 0.015. Realistically, 0.011 is 1/90th of an inch. I'd say it's an unfair comparison to compare a Grizzly machine to say an SCM jointer/planer because of the price difference when they were both new machines. If I paid 2-5 times as much for a machine I would expect tolerances, fit and finish to be better too.

First, what is the accuracy of the straight edge? Second, I'd call Grizzly to see what their advertised tolerances are, (2) what they recommend and (3) then try edge and face jointing a board to see what the results are.

I’m pleased to report that I’m a complete bonehead. I *did* manage to introduce that gap by causing a twist. After getting some sleep I went back out there and took a bunch of measurements and thought about the geometry and figured I would test if I could remove the gap. I’ve got it all back down to roughly .002, and now I’m trying to keep that tolerance while getting the outfeed coplanar to the cutting head. It’s pretty difficult to do with the helical cutter head, but the One Way tool is helping me find the high point.

I’m getting the hang of the small adjustments and checking all the different angles, but it takes time.

Ok. Spoke with Grizzly and ended up having to shim the cutterhead to get it where I could get the outfeed coplanar. Now I can’t quite seem to get these .004 gaps out in the middle of the table. If I make changes to address one, then another develops in a different measurement. I imagine at this is probably the point where I should just say it’s “good enough” and make some sawdust? (I know it might be silly that I spent a bunch of time trying to get it just right, but I just like things to be proper ¯\_(ツ)_/¯ ).

Here’s a video of where I’m at.

https://youtu.be/hb_3N8iY_W4

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Originally Posted by Rod Sheridan

Joint two four foot pieces of wood on edge near the back of the jointer.

Put the two jointed edges together, if you have no gaps, or a few thou gap in the middle, you are good.

Repeat the test in the middle of the jointer and again near the operator position, if the above is true, no need to start fixing something that isn’t broken……Regards, Rod

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Excellent advice Rod.

The real test is whether or not the machine can accurately produce flat faced stock & true straight edges for glue joints. Have you run any wood across it yet? The proof - as they say - is in the pudding.

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Originally Posted by Bob Spryn

Ok. Spoke with Grizzly and ended up having to shim the cutterhead to get it where I could get the outfeed coplanar. Now I can’t quite seem to get these .004 gaps out in the middle of the table. If I make changes to address one, then another develops in a different measurement. I imagine at this is probably the point where I should just say it’s “good enough” and make some sawdust? (I know it might be silly that I spent a bunch of time trying to get it just right, but I just like things to be proper ¯\_(ツ)_/¯ ).

Here’s a video of where I’m at.

https://youtu.be/hb_3N8iY_W4

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I watched your video. Stop adjusting your jointer and start using it:)

You are at the point where any adjustment you make will likely be offset by something else flexing or moving. There is a limit to how accurate you can set up a machine of that size, weight, and design, and you are probably at it.

I've used metal working equipment that had more inaccuracy due to wear. Once, I was complaining about one set of ways on a WWII horizontal mill to the shop foreman, and he said "If it was good enough for MacArthur, it's good enough for you" and walked away:)

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Originally Posted by Andrew Seemann

I watched your video. Stop adjusting your jointer and start using it:)

You are at the point where any adjustment you make will likely be offset by something else flexing or moving. There is a limit to how accurate you can set up a machine of that size, weight, and design, and you are probably at it.

I've used metal working equipment that had more inaccuracy due to wear. Once, I was complaining about one set of ways on a WWII horizontal mill to the shop foreman, and he said "If it was good enough for MacArthur, it's good enough for you" and walked away:)

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LOL!!

Ok fair enough! What a PITA process, but I’m glad I learned about it.

Thanks folks!

Four thousandths of an inch is the diameter of the average human hair. If you feel that your woodworking projects need to be to that kind of tolerance you should keep the temperature at 68 degrees F which is the constant temperature of a calibration lab.

I ended up figuring out my issue! I was very close to calling it, but had a bit of an epiphany that the only reason I would be getting gaps in the middle that would switch back and forth when I adjusted for parallel near the cutterhead would be if I was causing twisting. So I adjusted it to remove all the gaps (which meant my table wasn’t parallel to the cutterhead,) and realized that the solution was to shim the cutterhead even more than I previously had!

Essentially one end (operator) of the cutterhead wasn't high enough, but I could get the corners of the table near the cutterhead to parallel by tweaking the eccentric bindings to extremes which would cause a bit of a twist.

Once I shimmed the cutterhead up even more (0.02 total), I was able to keep the table dead flat (< 0.0025 gaps) and get it parallel.

I know the .005 gaps probably would have been fine, but I just had the sense I wasn't quite doing it right, or I was missing something. I feel better having figured it out. Now I'm adjusting the infeed table.

I've finally become proficient enough to work at tolerances ~1/64" (0.0156"). Unfortunately, I can't confirm this because my eyesight has degraded to >1/64".

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Originally Posted by Keith Outten

...If you feel that your woodworking projects need to be to that kind of tolerance you should keep the temperature at 68 degrees F which is the constant temperature of a calibration lab.

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This is actually the best response I've ever heard. I know that our techs can calibrate a jointer on a cold morning and if it's a hot afternoon, guess what happens? Gonna' have to remember Keith's answer for the next time someone gets fussy about this.

Erik