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

[Bob Spryn]

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.

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.

[Alex Zeller]

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.

[Myles Moran]

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.

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.

[Ken Fitzgerald]

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.

[Bob Spryn]

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.

[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

[Curt Harms]

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

Excellent advice Rod.

[brian zawatsky]

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.

[Andrew Seemann]

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

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

[Bob Spryn]

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

LOL!!

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

Thanks folks!

[Keith Outten]

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.

[Bob Spryn]

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.

[Mike Stelts]

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".

[Erik Loza]

...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.

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