Thread: Help with Jointer

Originally Posted by silentC

My apologies if I have misinterpreted your tone.


I suppose it depends on how easy you find it to locate TDC consistently. I don't have the means to do it, other than eyeballing it. I would say I'm pretty close, but as I say give or take. I establish one blade and then use a ruler to measure the distance from the edge of the outfeed to the back of the blade so that I can replicate the setting for the other blades. If you have a tip for reliably finding TDC then I would be glad to hear it.

Cliped here

Finding TDC
You mentioned that you wished you had the right gear to locate TDC of cutter. Well have I got good news for you. Just becauce I am a nice fella I will give you all you need to find TDC with 100% accuracy every time. Without going back through the posts I am sure you mentioned that you use a a rule on the outfeed table to check knife height, and I am pretty sure that you have eyes that are working. So here is my free gift just for you (Sorry just had to have a little fun there) I wont go into a lot of detail here as I am sure it would have been covered in here many times before. Do a search for 'carry method' as it is commonly called. During this process do not remove or bump rule. Place rule on outfeed table, rotate cutterblock untill knives start to move forward, place mark on fence/table, continue to rotate untill rule stops moving forward, place mark on fence/table. Measure half way between these two points and you have the location of TDC. Now you simply rotate cutter backwards till rule reaches middle mark on fence/table and your knife is at the top of its arc. Set your knives to this level and you will not have to adjust outfeed table after replacing knives. One of the reasos I use this method is because it is the easiest and works on all cutter blocks. Your method would not work on one of my jointers as it has skewed knives (don't run paralell across cutterblock).

Straightening a board
Just so as there is no confusion lets clarify a few terms

Bow - Curve on flat face of board from end to end
Bow up - Board laid flat on table and centre is up of table
Bow Down - Board laid flat on table and both ends are up off the table

Crook - Curve on edge of board from end to end

Cup - Curve on flat side of board from side to side

Wind or Twist - areoplane propellor

A lot of people call a crook a bow ( I know I do quite regularly). Regardless of whether you are planing a bow or crook the method is still the same so we will just call it a bow.

The majority of time you will be straightening a board longer than your infeed table. The principal is still the same regardless of just how much longer the board is than the table. The majority of 8" jointers which most people in here will have have a combined table length of about 1.8mts. If you are planing a 1.8 (double infeed table size) or shorter board it will require very little downward pressure while feeding board as the overhang will either be balanced or very close to being balanced over the end of the table. Your main purpose is to keep the board up against fence ( edge jointing) and to feed in a forward direction. This way if you do have a slip with your hands they will not be heading in the direction of the knives. Exerting unnecessary downward pressure, especially if you are working near the knifes only increases your chances of a serious injury if your hands slip. To me that is enough in itself to avoid having to exert more pressure than necessary.

Assuming it is a light timber and not of a massive dimension you can still handle a little more length with only minimal downward pressure. Anything longer or very heavy will require either another set of hands or rollers set up for support. .

For this exercise we will edge joint a peice of 200 X 25 X 1800 with a 12mm bow in centre which is in the shape of a perfect arc over the length. We could do a little trig (trickanometry) to give you exact measurements of what is happening where but that will add another 10 pages, so we will just use estimates.Set depth of cut on jointer to lets say 3mm.
Some people plane from both ends alternativly as the cutter stops cutting. This is not necessary. You should always feed in the direction of grain from end to end of board. You will loose no more timber than you would if feeding from both ends to roughly straighten before doing a final pass.

When you plane with the bow up the following happens
-front end passes over cutter and has 3mm removed from front end
-Trailing edge which is below the table now raises the centre of board off cutters as the tail end starts to climb up the end of the table
- cutters no longer cutting in centre
- trailing end now totally on table and starts to cut to a depth of 3mm at trailing end

Repeat above
This time the length of the bow section has been shortened from 1800mm to approx 1500mm. On this cut you will notice the the 3mm cut will extend further into the board before the board is raised by the trailing end and the trailing end will start cutting sooner

Repeat above
This time the length of the bow section has been shortened from 1500mm to approx 1200mm. On this cut you will notice the the 3mm cut will extend further into the board before the board is raised by the trailing end and the trailing end will start cutting sooner (why do I feel like I am repeating myself here?)



Working on our 12mm bow and 3mm cut you will probable need one more pass and then a final 'cleanup' pass.

Assuming there was no driver error lifting the board you should now have a nice straight edge on a 188 X 25 X 1.8m

The majority of 8" jointers which most people in here will have have a combined table length of about 1.8mts

I have a 6" jointer with a combined table length of 1100mm. I'm sure I mentioned that.

avoid having to exert more pressure than necessary

Already it has gone from 'no downward pressure' to not exerting 'more pressure than necessary'.

OK, well that's a reasonable explanation of what is happening. I'll try it and see if I can follow what is happening. I still don't have from you a reason for why my method (which was taught to me by someone along time ago) is wrong. I don't accept your assertion that it will rock and that has not been my experience.

This is what i do. A few passes of the back of the board first, then start from the front until its flat.

If it is a rail or something that has to be "straight" i wont apply preasure in the middle, but if it is for a panel or table top i will just to speed it up.

Having said that, if its for a table top or panel, i reckon its a waste of time joiniting it first even if its cupped or warped. Just bung it rough sawn straight through the thicknesser. Works every time

Well, I must have jointed about a hundred boards in my head last night and I concede that there is no advantage in doing it the way I have been all these years and that there may even be benefits in doing it the opposite way. I can now visualise what is happening with the opposite ends of the tables acting as pivot points and how the bow is gradually removed. I don't see any need to reverse the board and cut from opposite ends.

The person who taught me isn't here to defend himself, so I suppose I'll just assume that he had his reasons for showing me that method.

Yes Wongo, I'm admitting that I was wrong

BTW, searching for 'carry method jointer' brought up this thread and one other unrelated one, so if you'd care to share the full details with us, I for one would be appreciative. I understand how to locate TDC and how to set the table height using it, but I don't understand how you can also set the knives in the cutter head at the same time using it.

Originally Posted by silentC

I have a 6" jointer with a combined table length of 1100mm. I'm sure I mentioned that.


Already it has gone from 'no downward pressure' to not exerting 'more pressure than necessary'.

OK, well that's a reasonable explanation of what is happening. I'll try it and see if I can follow what is happening. I still don't have from you a reason for why my method (which was taught to me by someone along time ago) is wrong. I don't accept your assertion that it will rock and that has not been my experience.

We cant all be blessed with a big one! That you only have a combined table length of 100 is not a prob. It only means that you need extra support at a earlier stage. I used 1.8 on a 1800 o/a length simply because is demonstrates the principals of how it works without introducing the added problem of overhang into the equasion. Did you miss the part about if it was longer you should have extra support?

Nothing has changed in what I said, maybe just the way I said it. Any time you are handling anything to feed it you are always applying some downward pressure. Since we are taking everything down to the letter try this to demonstrate. Try sliding a small peice of timber across a set of kitchen scales and watch the scales. Although you are not deliberatly applying any downward pressure you will note that the scales are going up and down. So even feeding a piece 500 long through your jointer there will be some variation in downward pressure without you deliberatly applying it. Because you are working from above the tables you will always be exerting some downward pressure, but not deliberatly. Maybe I should have specified and pressures in Kg/M*. The point I am making is that as a general rule you should not be deliberatly applying downward pressure. There are allyays the odd exception in certain circumstances that you break the rules. With the methods you mentioned there is 2 safty issues raised. First is you are moving the guard manually back and exposting the head needlessly. Secondly you are exerting pressure towards the cutter increasing you chance of an accident. I am guilty of running a jointer without a guard to run large rebates on occasions but Why increase a risk level when it can be easily avoided.

I did not say that your method will not work. It does work most of the time as you already know. But take a large bow and your method starts to fall apart. It is just not the best method or the standard method used in the trade. The bow up method gives you two reference points further apart at all times, Your method of sliding guard back and suppurting from rear table and in effect planing a small taper of at each pass will work but your reference points are always closer together. If you have a large enough bow, your length of reference in relation to the overall length is very small, thus making it more inclined to rock. Anything you do that reduces the error (bow) by the most minute amount will eventually remove the error. One of the points you are concerned about was your short length tables. What is concerning you there is the same principle that is happening with the board being able to rock of a short reference point. To demonstrate grab a board say 1200 long. Hold a stick in each hand about 100mm apart and try to balance the boord on top of them. Now do the same thing and this time hold the sticks about 600mm apart, repeat at about 1000mm apart. Which gives you the most control over balancing the board?
This is not a subject that can be easily explained in words alone and methods and reasonings can be easily misunderstood. I have already spent more time typing this than it would have taken to actually show someone how to set up knives and straighten a board. The easiest way for you to understand would probably be to have somebody else joint a board 1200 long so that you can actually watch the cutters and see the board rising and noting the path of the cutters.

Originally Posted by silentC

Well, I must have jointed about a hundred boards in my head last night and I concede that there is no advantage in doing it the way I have been all these years and that there may even be benefits in doing it the opposite way. I can now visualise what is happening with the opposite ends of the tables acting as pivot points and how the bow is gradually removed. I don't see any need to reverse the board and cut from opposite ends.

The person who taught me isn't here to defend himself, so I suppose I'll just assume that he had his reasons for showing me that method.

Yes Wongo, I'm admitting that I was wrong

BTW, searching for 'carry method jointer' brought up this thread and one other unrelated one, so if you'd care to share the full details with us, I for one would be appreciative. I understand how to locate TDC and how to set the table height using it, but I don't understand how you can also set the knives in the cutter head at the same time using it.

You snuck this one in while I was typing the last reply. So I am preaching to the converted now! I am glad you now understand the reasoning a little better. The carry method is probably best demonstrated with a few pictures and animations. When I have a little time to spare I shall see what I can do. I am honestly surprised that it hasn't been argued to death in here as it is one of the oldest and best(in my opinion) methods

Now go play with your jointer!
This way up
Feed this way
Not this way

Lots of good info on planning thanks,

just a note,
a good way to check the piece of timber your planning for striaghtness is to place three bits of timber (150X25X16 thick melamine) cross ways on the edge your checking (melamine sides facing up and down), a piece at each end and the other in the middle, then site from one end, if your timber isnt striaght it'll stand out like dogs b...

Originally Posted by teepee1

Lots of good info on planning thanks,

just a note,
a good way to check the piece of timber your planning for striaghtness is to place three bits of timber (150X25X16 thick melamine) cross ways on the edge your checking (melamine sides facing up and down), a piece at each end and the other in the middle, then site from one end, if your timber isnt striaght it'll stand out like dogs b...

Called winding sticks, sorry to steal your thunder but probably worth the reminder anyway, another option is 2 engineers squares used in much the same manner, the slightest gap also sticks out like dogs doo dads (although my dog lost his so he doesn't know what to look for anymore ).

as a general rule you should not be deliberatly applying downward pressure

OK, I've been thinking about this a bit. If what you say is true, I should be able to tie a piece of string to the end of a board and pull it across the cutter. I think this might work if the board was heavy enough to counter the uplift provided by the rotating cutter block, but if it wasn't, I think it would bounce and chatter it's way along. I think a light enough board would be flicked up into the air.

Also, when you are flattening a board that has wind along it's face, if you just allow the weight of the board to hold itself down on the tables, how do you prevent it from rotating about the axis of the twist as it passes over the cutters?