Jointer Bed Tolerances

[Mike Cruz]

This is a two part question:

What would you consider to be an acceptable tolerance for a jointer bed's flattness on a 20 year old machine?

At what point is, or what "gap" is unacceptable?

Your answer may vary between a new machine and a 20 year old one. If not, state that. If you would allow more for an old, and less for a new, state that.

The reason I ask is because I just got the rust off the bed of the DJ-20 I recently purchased and notice it is concave over the lenth of the outfeed bed. I'll wait to get answers before revealing my deviation...

Thanks.

[Dan Friedrichs]

Delta's spec on the DJ-20 was <0.008"

[tyler mckenzie]

If you can get the board flat, then your tolerances are fine.

[Van Huskey]

A .007 feeler gauge is the go-nogo for me new or old. Though my mind tells me I need better I can't find any issues in product until you get above .01. This is based on the full length of the in/out feed tables and on a long bed machine such as what you are looking at.

In your case I would joint a long board 5-6 times and plot the width about every 6 inches (mark the board before at the rough intervals so you are measuring at the same places each time) and see what level of variation you get then determine if that is acceptable to you. In the end nothing matters but the wood, although it is hard to convince ourselves of that sometimes.

[Mike Cruz]

WOW! .007! I put my straight edge on the outfeed bed and I could get the .003 under it, but not the .004, so I was guessing at .0035 and thought I was about to have to get it reground or something. The gap "looks" huge and can't imagine how a board could come out straight with such concavity.

But, if ya'll are okay with that, who am I to argue?

BTW, one thing I found odd about this jointer was that the infeed bed is 43 1/2" and the outfeed bed is 31". Don't know why, but I would have expected the opposite.

I'll go remeasure just to make sure I had it right.

[Van Huskey]

People get too freaked out over wood working machines they tend to treat them like we are metal machinists.

I was going to add in my post that I like to see sub .003 levels but I didn't want to freak you out and the reality is thats just a want not a need for ME. Again I suggest jointing a long board and plotting it out since that is what really matters.

In the end I truely think you can sleep well at night.

[glenn bradley]

Edge joint two 40" boards, place the jointed edges together as if you were going to glue them and hold it up to the light. If it is something you can live with, your good. I get really silly over specs and have to reign myself in now and again. If it is close and the result is good, move on.

[Dan Friedrichs]

BTW, one thing I found odd about this jointer was that the infeed bed is 43 1/2" and the outfeed bed is 31". Don't know why, but I would have expected the opposite.



Nope, this is correct. The infeed needs to be longer, so that any high spots on the wood are already (hopefully) up on the bed before the board hits the cutterhead. Otherwise, you could be jointing along, then a high spot on the board comes up onto the infeed table, and lifts the board away from the cutterhead.

[Mike Cruz]

Makes sense, Dan, thanks for explaining.

As for "trying" it out... I haven't yet for a couple of reasons. One, right now, I haven't hooked up the DC to it yet. I have to fabricate everything from the dust chute to the blast gates. The DJ-20 (or at least mine) doesn't come with DC hook up, just a chute. Second, I have a Byrd head to install in it! :D

[Mike Cruz]

I wanted to point out that I don't usually get all worried about thousandths of an inch and stuff. But I saw light and it looked like a lot. My reaction was...how the heck could you get a straight board with the bed like that! But, maybe I never really looked at my tools closely enough to realize they all are like that. We'll see how it does...

[Van Huskey]

I wanted to point out that I don't usually get all worried about thousandths of an inch and stuff. But I saw light and it looked like a lot. My reaction was...how the heck could you get a straight board with the bed like that! But, maybe I never really looked at my tools closely enough to realize they all are like that. We'll see how it does...

Never question something that worls correctly too much, it usually results in lost sleep... :D

[Phil Thien]

Second, I have a Byrd head to install in it! :D

This entire thread kinda reads like a gloat. :confused: :D

[Van Huskey]

This entire thread kinda reads like a gloat. :confused: :D


True, even the main question. Ever see someone post and ask something like "my blade/miter slot parallelism is out by .00000000001" is this OK or do I need to contact XYZ corp and complain... :eek:

[Mike Cruz]

Absolutely. The thing is, I may have been putting the cart before the horse here. I bought this thing from a...wait for it, wait for it...pawn shop/broker that said he knew the guy who owned it and it was just sitting in his storage/garage for years, usnused. So, he was selling it for him. Seems like a fishy story to me, but he had not only a bunch of other stuff that looked to be wwing/shopish and from the people that kept stopping by that he seemed to be "close" with (by that, I mean it didn't seem unreasonable the he "knows" a lot of people from being in business there for some time) that it "could" happen.

Anyway, he fired it up. It started, with some coaxing of the start button. And it took a few seconds to wind up, but seemed to hit max rpm...eventually... I attributed that to the fact that he cranked it up for me from a 100 foot 16 gauge extension cord... So, when I got it home, I changed the plug and rewired it from 110 to 220. Not exactly sure how this motor was running, but it didn't look like it was wired according to the motor wiring diagram. I correctly switched all the wires, got a new switch, and it fires right up, is quite, and doesn't shake.

The point, I bought it without running a single board on it. And have yet to. So, when I saw daylight under my straight edge, I gasped and paniced. I really need to run two boards through and put them together. I imagine I'll be left with a .007 or so gap. We'll see. As long as it isn't a wavy joint and is a consistant curve, I can probably deal with it. I am a bit anal, so I expect a perfect fit from my jointer. That way, if it isn't perfect, I know it was user error, and don't end up looking at the machine cross eyed blaming it.

[Phil Thien]

I really need to run two boards through and put them together. I imagine I'll be left with a .007 or so gap. We'll see. As long as it isn't a wavy joint and is a consistant curve, I can probably deal with it. I am a bit anal, so I expect a perfect fit from my jointer. That way, if it isn't perfect, I know it was user error, and don't end up looking at the machine cross eyed blaming it.

I guess that is conventional wisdom, but I suspect it is wrong. Flatter is certainly better, but people have used the jointers that were .008" out for eons and they got flat boards somehow.

I think the important thing to remember is adjusting the outfeed table slightly will allow you to fine-tune your results.

And remember that once the board is past the cutterhead and substantially on the outfeed table, you start applying pressure on the outfeed side of the board, rather than the infeed.

[Mike Cruz]

Thanks, Phil. I agree that just because we "put up" with certain tolerances, doesn't mean it's right...

Also, thanks for the tip. Not to sound like a know it all, but I have moved a lot of wood through planers, jointers, TS and the like. I am quite experienced in using them. But this was all in my boss's shop. I didn't fool with the tools. I never checked them for flatness and such. They were his tools. When we noticed a problem, we told him and let him fool with it. Not because it wasn't our "problem", but because it wasn't my machine to fool with, if that makes sense. If the planer was creating too much snipe, or needed some kind of adjustment, had I worked on the machine, production would stop, and since I didn't know what I was doing, it would take me a heck of a lot longer to tweak it back to par than it would have taken him. Besides, I also could have done damage to it.

So, while I've used the machines substantially, this is the first time I have been in the position to have to work ON them.

Again, I'm not jumping down your throat for the comment. Just letting you know that I already knew that. You have no way of knowing what skills I have/don't have.

But a concave bed in the length of the outfeed bed is what threw me for a loop. THAT is the bed that I would think would need to be DEAD FLAT...with no tolerance.

[Mike Cruz]

You guys suck! If I am correct, I already did the gloat thing on this machine when I got it. And as I just posted in response to Phil's other comment, while I've worked WITH these machines, this is the first time (now that I have my own shop) that I am working ON them. So, seriously, I wasn't gloating about the tolerance of the jointer, I REALLY was worried about it...

[george wilson]

You may be seeing not only the gap under a straight edge,but also the reflection of the gap from the table. This makes the gap look twice as big as it really is.

Another thought: The eye can see as small as a .0001" (ten thousanth of an inch) gap between surfaces and a straight edge,if the object is lit properly from behind.

[Mike Cruz]

Thanks, that would explain it. I've heard of folks here talking about .001 this and .003 that, but never actually measured them before. So, I too, rolled my eyes when people talked about their machines being .003 out and concerned about it. .003 sounds SOOOOOO small, but when you actually see it, it looks big. The light reflection thing may be amplifying it, too, as you suggested.

[Van Huskey]

You guys suck! If I am correct, I already did the gloat thing on this machine when I got it. And as I just posted in response to Phil's other comment, while I've worked WITH these machines, this is the first time (now that I have my own shop) that I am working ON them. So, seriously, I wasn't gloating about the tolerance of the jointer, I REALLY was worried about it...

Mike, we kid because we love....:confused:


We knew you were worried about it, just having some fun.


What you should do is see how many gloats you can get out of the one machine. :D


I think the internet has spawned a whole new breed of woodworkers that want metal machine tolerances BUT I guarantee you we/they aren't ready to pay for them. The problem is we don't even know why we want them, we just know that even a HF $10 dial indicator tells us our machine is .00X away from being perfect, and we expect perfect! I have been trying to get away from too much measurement and look at the product especially when the tolerance is one I can't adjust. If you notice there are a lot of threads about someones new TS table being .00X out and they are concerned about it, then if you watch they never seem to come back and complain once they actually cut some wood. I didn't say all this with any negativety and certainly none directed at you, since you were just asking because you had never actually dealt with jointer bed tolerances.

[Mike Cruz]

I know ya'll were bustin' my chops, no worries.

As for the number of gloats off one machine, I'm working on two more. :D I have to say, I got a good chuckle out of that (your) comment.

I have to admit that I had rolled my eyes a little at the TS .00X discussions, too, for a couple of reasons. One because I guess I never realized how big .004 actually looked. And two, I don't see how .004 would matter as much on a TS.

I will refrain from commenting on variances less than .008 from now on. I everyone happy now? :mad: :D :D

I guess I should go check my TS now...:rolleyes: