Jointer testing and set-up: What tools / gauges do I need?

[Mark Hennebury]

With a straight edge.

A straight edge and the understanding of how to use it is all you need.

Ideally you would have five precision buttons. they would all be the same thickness, you can anything that is the same thickness, bearings, tool steel, dimes, pieces of paper.. whatever in a push.
And a set of feeler gauges if you have them, or paper if not.
Set one button on each corner and one in the center of the table that you want to check.
Place your straight edge across the diagonals resting on the three buttons.
On a flat surface the straightedge would touch the three buttons across diagonals.... in both directions.
If it doesn't then you table is not flat. and you can see where and how it is not flat.
With feeler gauges you can precisely measure how much out your tables are.

Huh?


How do you check for twist?

[Allan Speers]

A related questiON:

Let's say I find that the tables are a bit off. And being picky, I want them a little flatter.

Assuming I have a very good reference, like the Lee Valley straight edge (I think I'm going to order one)

IS IT POSSIBLE TO CAREFULLY HAND-SCRAPE A TABLE, to something resembling machinist precision?



- Or is that akin to jumping off a high cliff, during a hurricane, into an ocean full of rabbid sharks?

[Brian Holcombe]

A related questiON:

Let's say I find that the tables are a bit off. And being picky, I want them a little flatter.

Assuming I have a very good reference, like the Lee Valley straight edge (I think I'm going to order one)

IS IT POSSIBLE TO CAREFULLY HAND-SCRAPE A TABLE, to something resembling machinist precision?



- Or is that akin to jumping off a high cliff, during a hurricane, into an ocean full of rabbid sharks?

Yes, if you're willing to buy a large, recently inspected granite surface plate and scraping tools. Theoretically scraped surfaces are the highest precision flat surface, in practicality that depends on whose doing the scraping and the caliber of inspection tools they have.

[Andrew Hughes]

I say yes it is possible. But you will need a second reference surface bigger and flatter then the table your scraping.
Plus you’ll need more tools,time and skills you may not have.

I hand scraped my Fence for my tablesaw it took a most of a day and lots of elbow grease.

Good Luck

[Allan Speers]

Yes, if you're willing to buy a large, recently inspected granite surface plate and scraping tools. Theoretically scraped surfaces are the highest precision flat surface, in practicality that depends on whose doing the scraping and the caliber of inspection tools they have.

I was thinking more of testing carefully with that precision straight edge, (and maybe Mark's "3 button" idea above, or precision winding sticks,
or....) Then marking all the high spots, and just SLOWLY taking things down. Is that viable?

Of course, if there's a low spot, I'm sunk, but I figure small low spots probably wouldn't affect lumber milling much, anyway. (unless right by the cutterhead.)

[Doug Dawson]

A related questiON:

Let's say I find that the tables are a bit off. And being picky, I want them a little flatter.

Assuming I have a very good reference, like the Lee Valley straight edge (I think I'm going to order one)

IS IT POSSIBLE TO CAREFULLY HAND-SCRAPE A TABLE, to something resembling machinist precision?

It's theoretically possible, and I'm sure they've done this in North Korea, at the instructions of Dear Leader. But for all intents and purposes in our country, it's probably not worth it. Better to suffer thru the use of shims, in the hope of getting the "global" alignment right.

[Brian Holcombe]

I was thinking more of testing carefully with that precision straight edge, (and maybe Mark's "3 button" idea above, or precision winding sticks,
or....) Then marking all the high spots, and just SLOWLY taking things down. Is that viable?

Of course, if there's a low spot, I'm sunk, but I figure small low spots probably wouldn't affect lumber milling much, anyway. (unless right by the cutterhead.)

I can’t imagine this approach doing anything but frustrating the user.

This type of thing works for hand planing becuase the hand plane itself is a long reference. Scraping is done with a small scraping tool which has no reference surface so i imagine it would be similarly difficult to flattening a board with a carving with a spear plane (long handled Japanese slicing tool), yes it can be done but without a big reference surface you may just be causing dips.

[Tom M King]

If it's old enough to have been from the time when they left castings out in the weather for several years before machining them, and has not been in a production shop with a feeder, I'd expect them to be okay.

[Allan Speers]

If it's old enough to have been from the time when they left castings out in the weather for several years before machining them, and has not been in a production shop with a feeder, I'd expect them to be okay.

Sadly, it's a 1980's Taiwanese Dayton. That's why I'm so concerned.
But like I said, the price is very good. And it has a USA 1.5 HP motor. And no rust. And one hobbyist owner since new. So.....


I know, I know, I should have jumped on that 8" General when I had a chance. Sigh ...

[Doug Dawson]

Sadly, it's a 1980's Taiwanese Dayton. That's why I'm so concerned.
But like I said, the price is very good. And it has a USA 1.5 HP motor. And no rust. And one hobbyist owner since new. So.....


I know, I know, I should have jumped on that 8" General when I had a chance. Sigh ...

Just start using it, then. Everybody needs a scapegoat. :^)

[Paul F Franklin]

If it's operating, another approach would be: take a wide flat board a few feet long with you (you know, from Home Depot's flat board section) and take a few passes and see if it's still flat....

[Robert Hazelwood]

I think you could do the scraping with a straight edge as your main reference. You won't be able to get ten-thousandth accuracy without a large plate, but one thousandth might be doable. A smaller reference plate could be used to assist to find local low spots.

There is a technique scraper hands sometimes use called "blind" or step scraping, I think. This is kind of a roughing technique to get the workpiece to sit flat on the surface plate before beginning the spotting and scraping process. Suppose you have a concave surface along the length, measure the extent of it. Say it's 0.005" deep at the center. Divide the surface into a number of equal parts along the length with a marker. Knowing that a scraper removes about a third to half a thou per pass, on the outer divisions need something like 10 passes, and the center section just one pass, the increasing numbers of passes for the intermediate sections as you move away from the center. Each pass is just an even series of strokes across the surface, keeping a consistent pattern. A similar concept to tapering a stick with a handplane.

If you have a lot of time on your hands I think that could work. A true madman might even create his own woodworking surface plate, maybe a 1'x4' MDF torsion box with the top flattened to 0.001" with planes/sanding blocks. Seal it good and spot with that.

A handscraped finish should have an additional advantage in reduced friction compared to a surface ground table. But really if your jointer tables are bad enough to cause problems then just take the top assembly to a shop that has a big surface grinder or blanchard machine and get the tops ground together while attached to the center dovetail part. That way you get flat tables and guarantee parallelism (which you could not easily do with the shadetree mechanic scraper method). An 8" jointer shouldn't be too expensive to get ground, and afterwards it should be better than any new jointer.

[Mark Hennebury]

You can do it, and you don't need any special tools, you can improvise and use whatever you have. You just have to ask yourself if it's worth it.

The sliding table on one of my tablesaws was out by 0.020" , so i got it to less than 0.002" with a disc grinder and a die grinder using a good straightedge. The saw is at least usable at those specs, when i get around to rebuilding it i will handscrape it in on the surface plate, but then i have to do the guide tracks and mitre slots etc, Its a lot of high precision ( time consuming ) work. Fun if you enjoy it and have the time.

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[Allan Speers]

Just start using it, then. Everybody needs a scapegoat. :^)

LOL.


Built-in excuses can be very helpful !


I got a good dial indicator package, plus I ordered that LV straight edge today. - It's actually only 99 bucks in US dollars, so that' really not bad at all. I guess I'm good to go, for the moment.


Thanks, all. Great stuff.

[Allan Speers]

Well, that 8" Dayton jointer is in my shop.

What a nightmare getting it in my truck.
(Hint: Don't forget a set of large metric allen wrenches! Oh, and don't pick up heavy machinery in the pouring rain.)

Maybe I'll post all the things that went wrong in a separate thread. It might save some future shlub the agony I just went through. Couldn't take it apart (the fence only comes off with an allen wrench & the tables won't come off if the fence is still on it), broke the fence mount picking it up with the hoist, had to slam on my brakes on the way home and broke the windows in both my cap and my truck, then the broken window let rain pour onto the tables for the 2 hour ride home & now they're covered in surface rust....
------------

BUT THE GOOD NEWS IS:

Thanks to all the ideas here, I was able to determine that the tables are dead-flat (not even a .005 gap anywhere) coplanar, no twist, etc. - Same for the fence.
The head is perfectly parallel and the bearings feel like new.
Not bad for 1987 Taiwanese.

The US Dayton motor runs great, the cutterhead bearings seem perfect, the tables move easily .....

I have to weld that broken fence mount before I can try it here, but it worked great at the sellers house. It seems like a VERY nice machine, actually. I think Grainger must have had pretty tight specs back in the day, and used an ISO 9001 factory.

I'm going to do a ground-up restoration, as most of the bolts are somewhat rusty. (I also hate the color.) When I do that, I'll try to do a write up on this model, with pictures. It's kinda' your standard Taiwanese Delta clone, but has nicer fittings than some of the others I've seen. (Bridgewood, etc) Plus, of course, it has those lovely table extensions.

It could be a great choice for guys on a tight budget, like me.
(Even tighter, now that I have to replace two broken windows. )