Jointer noob

[Andrew Hughes]

Andrew, Enjoyed your movie,but don't think those adjustment levers are much good for moving something a thousandth
at a time. But it might be useful for moving rubble off earth quake victims.

I hear ya Mel. The levers would be a waste of time and should be removed once the knifes are set for a perfect cut. So some clown doesn't change the setting.
The Dj 20 has adjustable cams or bushing to level the tables.If they are good and flat it's worth the time and set them right.
Good night Sir

[jack forsberg]

I also think Jacks knife sharpening video is silly and pointless.

Good luck

I would agree not something needed now a days . much faster for me to do this than change out the knifes as this is my edge joint planer /jointer .

[David J Blackburn]

Yes, this. I said the same thing the other day, but I wouldn't fiddle with the settings based on what's in those pictures. You're likely to make things work. You have a board with a lot of cupping at the back end, and when you run it over the jointer, it's cutting in the other parts, and not there.

Joint something already flat and see if it takes even cuts. It doesn't even have to be perfect- as Steve said, just find a board that lays flat on flat surface, run it over the jointer and see if it stays that way.

[Andrew Hughes]

Yes, this. I said the same thing the other day, but I wouldn't fiddle with the settings based on what's in those pictures. You're likely to make things work. You have a board with a lot of cupping at the back end, and when you run it over the jointer, it's cutting in the other parts, and not there.

Joint something already flat and see if it takes even cuts. It doesn't even have to be perfect- as Steve said, just find a board that lays flat on flat surface, run it over the jointer and see if it stays that way.

David Blackburn the furniture maker? We met at the Oc fair sometime ago I'm also a big fan of your work. Just wanted to say hi and that I'm still plugging along.

[Steve Demuth]

I'd like to see someone do the actual math on the scallop depth idea. The flaw in that idea is the presumption that the user is feeding fast enough to leave each peak intact before making the next cut.

There are some approximations in this, but nothing that invalidates the point.

A typical small jointer, like the Powermatic 54a has a 3" diameter cutting head running at 6000 rpm, or 18000 cuts per minute. If you feed stock at 18 feet per minute (a reasonably brisk hand feet rate), you're making 1000 cuts per foot. The arc of each cut is therefore .012" - 12 thousandths of an inch - wide. A little trigonometry will will tell you the depth of the arc is just over .00001" - one hundred thousandths of an inch. To get a .0015 - one and a half thousands - depth of arc, you'd have to move the board fast enough to get .19" per cut width - roughly 3/16" - which at 18000 cuts per minute is 285 ft per minute. That is, you'd have to run a a 4' board through your jointer in under 1 second. Power feeders can do that. Humans probably can't, and certainly typically don't.

I corrected an earlier arithmetic mistake in which I indicated the .19" per cut width equated to 135 fpm.

[jack forsberg]

There are some approximations in this, but nothing that invalidates the point.

A typical small jointer, like the Powermatic 54a has a 3" diameter cutting head running at 6000 rpm, or 18000 cuts per minute. If you feed stock at 18 feet per minute (a reasonably brisk hand feet rate), you're making 1000 cuts per foot. The arc of each cut is therefore .012" - 12 thousandths of an inch - wide. A little trigonometry will will tell you the depth of the arc is just over .00001" - one hundred thousandths of an inch. To get a .0015 - one and a half thousands - depth of arc, you'd have to move the board fast enough to get .19" per cut width - roughly 3/16" - which at 18000 cuts per minute is 285 ft per minute. That is, you'd have to run a a 4' board through your jointer in under 1 second. Power feeders can do that. Humans probably can't, and certainly typically don't.

I corrected an earlier arithmetic mistake in which I indicated the .19" per cut width equated to 135 fpm.

UnLess the knives are jointed you can only assume a one knife cut from the head . At 30 feet feed rate it would be less than 17 kmpi

https://www.mr-moulding-knives.com/i...ng-knife-marks

[Jim Morgan]

Isn't it also possible that there may be some amount of compression/springback with each cut? This would vary by species and be more pronounced with dull knives. In any event, this would suggest that the outfeed table should be set slightly below TDC to compensate.

[Steve Demuth]

UnLess the knives are jointed you can only assume a one knife cut from the head . At 30 feet feed rate it would be less than 17 kmpi

https://www.mr-moulding-knives.com/i...ng-knife-marks

With respect, Jack, I can put a machinists' dial indicator on my jointer after I set the blades and verify that I've got circular uniformity to within less than half a thousandth. No jointing necessary. The fact that my knives dull reasonably uniformly further proves that they are all cutting.

But even if you are running an effectively one-knife cutter head, the math is still not going to justify the theory that the outfeed table offset below the knife height corresponds to the scallop depth. When you adjust the math above, you'll have 28 cuts per inch, and you're still going to get a scallop barely .0001 - one ten thousandth - deep. And that's pushing the board through at 18 fpm. A hobbiest using a small jointer looking for the best finish or glue joint will probably run at half that speed.

[Mel Fulks]

As I wrote earlier, most jointers I've seen in commercial shops DO have the outfeed tables set slightly below TDC. But it serves no purpose beyond making sure the material does not climb and leave some of the edge unjointed. When the jointing is being done to make a surface fit for edge gluing the ends will be open....making an unfit ....misfit,likely to pop open after being glued.

[Matt Mattingley]

With respect, Jack, I can put a machinists' dial indicator on my jointer after I set the blades and verify that I've got circular uniformity to within less than half a thousandth. No jointing necessary. The fact that my knives dull reasonably uniformly further proves that they are all cutting.

But even if you are running an effectively one-knife cutter head, the math is still not going to justify the theory that the outfeed table offset below the knife height corresponds to the scallop depth. When you adjust the math above, you'll have 28 cuts per inch, and you're still going to get a scallop barely .0001 - one ten thousandth - deep. And that's pushing the board through at 18 fpm. A hobbiest using a small jointer looking for the best finish or glue joint will probably run at half that speed.

Steve, what is the diameter of your head, what is the diameter of your cutting Circle, what kind of knives are using? What is your 90° attack angle of your knife? What is your knife material made out of and Rockwell value? Are your knives Straight, skewed or helical and what are your in feed and outfeed table lengths? Each machine manufacture considers these important values.

First, most good bearings have a unloaded lash +- .0001. As soon as you apply a workload to it, there goes that lash.

My outfeed table is set to 0.0005 below the knife circle. I have a helical head and I use carbide inserts with 78ish Rockwell.(Rockwell value is a test hardness of the cutting material). Carbide dulls quite a bit slower than HSS, A2, D2 & M2. (there is the difference between carbide inserts and carbide knives and there is also a difference between insert manufacturing heads)I can send 1000 feet of IPE and it simply grinds my cutting circle down to 0.0003 above the outfeed table. I still have plenty of horse power to keep cutting and the inserts are still razor sharp. I have about 50 inserts in my head that run $6 apiece. But, that is $1.50 per cutting edge or $75 per full rotation. It is only A two knife head 12 inches jointer.

A 3 inch radius 0.0002 worn will still cut paper razor sharp.

Most people like to do indicating with brand new razor sharp blades. Most of the time there is a grinding bur that should be folded over with two or three swipes with a 2000 grit stone (you can actually even use a Real copper penny).

I hope you got your pennies worth with this post.

[jack forsberg]

Steve, what is the diameter of your head, what is the diameter of your cutting Circle, what kind of knives are using? What is your 90° attack angle of your knife? What is your knife material made out of and Rockwell value? Are your knives Straight, skewed or helical and what are your in feed and outfeed table lengths? Each machine manufacture considers these important values.

First, most good bearings have a unloaded lash +- .0001. As soon as you apply a workload to it, there goes that lash.

My outfeed table is set to 0.0005 below the knife circle. I have a helical head and I use carbide inserts with 78ish Rockwell.(Rockwell value is a test hardness of the cutting material). Carbide dulls quite a bit slower than HSS, A2, D2 & M2. (there is the difference between carbide inserts and carbide knives and there is also a difference between insert manufacturing heads)I can send 1000 feet of IPE and it simply grinds my cutting circle down to 0.0003 above the outfeed table. I still have plenty of horse power to keep cutting and the inserts are still razor sharp. I have about 50 inserts in my head that run $6 apiece. But, that is $1.50 per cutting edge or $75 per full rotation. It is only A two knife head 12 inches jointer.

A 3 inch radius 0.0002 worn will still cut paper razor sharp.

Most people like to do indicating with brand new razor sharp blades. Most of the time there is a grinding bur that should be folded over with two or three swipes with a 2000 grit stone (you can actually even use a Real copper penny).

I hope you got your pennies worth with this post.

lots to consider there .

its not like you can not get a good cut with one knife .

[jack forsberg]

With respect, Jack, I can put a machinists' dial indicator on my jointer after I set the blades and verify that I've got circular uniformity to within less than half a thousandth. No jointing necessary. The fact that my knives dull reasonably uniformly further proves that they are all cutting.

But even if you are running an effectively one-knife cutter head, the math is still not going to justify the theory that the outfeed table offset below the knife height corresponds to the scallop depth. When you adjust the math above, you'll have 28 cuts per inch, and you're still going to get a scallop barely .0001 - one ten thousandth - deep. And that's pushing the board through at 18 fpm. A hobbiest using a small jointer looking for the best finish or glue joint will probably run at half that speed.

as others have said you can get this simple machine to work in a number of ways . i never have had good results with the Rear table at TDC. just sharing what works for me

[Steve Demuth]

Matt,

Of course all the things you ask and then assert are relevant to the performance of a jointer. And, I was in no way arguing that you don't want to set the outfeed below the cutting circle of the head. You should, and If you don't, you'll generally get a tapered a cut on most machines, as many posters here, including myself, have pointed out. All I was saying in answering Johnny's question about someone "doing the math" on the scallops is that the depth of the scallops from even a small cutter head at hand feed speeds, is indeed very shallow - much less than the outfeed clearance you want for a uniform cut on a hand fed machine.

My answer to Jack was simply to say that this is true, whether or not you joint your knives. I don't, because I don't have to, and because jointing produces an inferior cutting edge. A jointed head, unless you start out with nearly perfect concentricity and do minimal material removal as a result, easily ends up with one or more knives having an excessive (to my likes) land width, with the result that at hand feed speeds, you burnish your cuts excessively.

Since I am in the shop mostly because I love being in the shop and working with the machines - no deadlines, production targets or particular budget restrictions - I prefer to spend a bit extra time getting very sharp knives, and setting them precisely. I in no way suggest that I'd take the same approach if I were in any sort of production.

[Steve Demuth]

as others have said you can get this simple machine to work in a number of ways . i never have had good results with the Rear table at TDC. just sharing what works for me

Jack,

I didn't say you don't want clearance between the cutting circle and the outfeed height. Quite the opposite - I agreed in other responses that you do. I was just pointing out that the depth of the scallops per se, is not the reason, and in my response to you later that unjointed cutters aren't an explanation.
I suspect, but have not done the work to completely justify my suspicion, that compression of the wood at the cutter head and leading edge of the outfeed table, and subsequent relaxation down table, is the biggest factor driving the need for clearance. If so, then jointed knives if anything increase the need. Jointed knives are certainly going to pound the wood at the lands more than unjointed.

[jack forsberg]

Steve if done properly stoning is not an inferior edge . its not a way to correct knife setting its a way of maintaining the edge and surface finish . the knifes i set are as you say within 10th of a thou and you my have a good point about the wood .


see here how careful i set fresh knifes
https://www.youtube.com/watch?v=k87WRWWFV_s

this video is after careful setting and the stoning



setting is now with the Wadkin setting stand i just rebuilt

image_114469.jpg

https://www.youtube.com/watch?v=8niha1LAUog

how is the cut

https://www.youtube.com/watch?v=O-ItjKtCFIg