Planer puzzle

[sunnybob]

I use my router table as an edge jointer by offsetting the outfeed fence, but something is happening that I dont understand.
The fence is a brand new UJK professional (but this used to happen on my old home made fence as well). I pad the outfeed fence with 2 pieces of flexible plastic that are 0.8mm thick. These were cut from the same sheet and I have measured them and swapped them around with no difference found.

When setting up I usually align the out feed fence with the cutter blade to start. If there is snipe on the end of the wood I adjust the infeed fence untill the snipe disappears. the result is a very good surface.

BUT...........

The finished cut takes off more one end than the other.
Starting with a piece of wood that has two parallel sides, every pass reduces the back end measurement by 0.5 mm.
If I were to pass the wood across (for arguments sake) 4 times. the wood measurements change by 2 mm. I can reverse the wood and counteract the angle on smooth grained wood, but sometimes the grain will not allow me to feed from the other end.

Why is this happening?

 

[CHJ]

Applying uneven pressure of stock against the fences over its length, pushing the back outer corner perhaps during feed with a push stick into the infeed table instead of just along its axis, and not keeping it tight against the out feed fence.

Getting snipe in the first place tells me you are pushing the wood into the cutter instead of just feeding past it.

 

[sunnybob]

I dont use push sticks for this as its usually quite large pieces of wood and my fingers are in no danger from the almost completely shielded cutting bit.
The snipe (if it appears) is only on the back end.

Quite often when starting, the wood will just tip the cutter and not actually feed across the out fence. Then I swivel the fence away on the left side till the wood slides along the fence.
Then when pushing the wood through I make a point of putting more pressure to the outfeed side, keeping it flat to the fence and merely using the right hand as a stop to prevent the wood springing away.

At that stage I move the outfeed fence if there is any snipe as the wood clears the cutter.
The wood behaves perfectly, and the face is dead flat and smooth.

 

[PAC1]

Check if your fences are parallel or co planar?

 

[MattRoberts]

Are you using a featherboard to ensure even pressure at the cutting point?

 

[sunnybob]

This happened on my old home made fence. My main reason for buying the new UJK fence was in the hope of solving this ongoing problem. It didnt. But this fence is exactly parallel and I really like it as it is.

No featherboards. Imagine a piece of wood 300 mm x 22 mm x 75 mm wide.

As soon as the wood reaches the outfeed fence most of my hand pressure is deliberately on the outfeed fence to keep the wood flat and level with it.
If the edge is sawn, it may take two passes to remove all the wavyness. By which time the leading edge measures 1 mm wider than the trailing edge.
regardless of condition of the edge to be cut, the trailing edge width always comes out 0.5 mm per pass smaller than the leading edge width.

 

[CHJ]

....Quite often when starting, the wood will just tip the cutter and not actually feed across the out fence. Then I swivel the fence away on the left side till the wood slides along the fence.

In other woods the output fence is not lined up with a sharp cutter periphery and you are not getting a .8mm depth of cut, so you move the whole fence assembly in relation to the cutter until you are getting .8mm cut.

In this state do you get the same depth of cut using a piece of softwood and a piece of hardwood? (Cutter sharpness?)

....At that stage I move the outfeed fence if there is any snipe as the wood clears the cutter.
The wood behaves perfectly, and the face is dead flat and smooth.

How can you move the outfeed fence alone and maintain .8mm depth of cut? and as Pac1 said maintain parallel fences.

And as Matt mentions hand pressure varies far more than you think constant feather board pressure is better.


Cutter sharpness plays a very big roll in material removal and applied pressures will never compensate for this.

 

[ColeyS1]

So by using two bits of 0.8mm you're hoping to remove 1.6mm per pass ? It sounds like you should pack the fence to 1.65 or 1.7mm without moving the infeed....I think.
I use the spindle moulder to do similar when I'm making beads. Instead of edging everytime on the planer, I set the spindle so it's taking a mm or so off, then adjust the outfeed fence to compensate. I'd hazard a guess that it's the outfeed fence that needs coming forward a tad more.


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[woodbrains]

Hello,

You don't set the outfeed fence level with the tip of the cutter, it needs to be a touch further back. The same as the outfeed table on a surface planer. The cutter removes a little scallop of material, which it cannot do if the outfeed support is level with the tip of the cutter. Set up with the outfeed level, you will actually produce a convex piece of work.

It is hard to do what you want without an independently adjustable outfeed fence. I would run my work across the infeed until the cut passes the out feed fence a fair amount, then adjust the outfeed to support it. This automatically sets the job up optimally without measuring offsets.

Perhaps you could try shimming behind the outfeed fence with shim stock, set up your thing as you have been and the remove the shim stock. It might take a bit if trial and error, with a few thou at a time, but once you get the set up, it should be repeatable.

Mike.

 

[sunnybob]

Chas... cutter is sharp. Type of wood makes no difference.
Sorry, my explanation isnt clear. after setting the bit level with the outfeed fence, if the wood does not clear it (maybe the cutter wasnt exactly at 90 degrees), I swivel the entire fence backwards a touch on the left hand side, with the right hand side locked down, effectively bringing the bit further forwards.

Coley... no, there is a 0.8 mm piece behind each end of the outfeed fence, making it still parallel with the infeed. All I am after is a smooth edge, actual measurements are not important as far as the problem is concerened.

Mike, The fence IS inedependantly adjusted. The 0.8 shims are behind the outfeed fence.
My understanding of the process may be at fault, but as far as I know, the wood moves from the right, into the cutter. The cutter takes off its shaving (say 0.8 mm as that is the shims thickness). As the wood leaves the cutter it should match with the outfeed fence and slide along parallel.
What I cant work out is that the finished edge is NOT cupped, or sniped, its as good an edge as I would wish to get. Its just that this angle thing screws up the width measurements on the finished piece.

I will try it next time starting set up at the infeed fence rather than the outfeed, and see if that eliminates the problem.
This new UJK fence actually has T slots so I can now make up some featherboards, so i will try those as well.

 

[custard]

What Coley said.

You're starting the cut pressing the workpiece against a metal fence, you're finishing the cut pressing against, "2 pieces of flexible plastic that are 0.8mm thick".

The outfeed fence needs bumping forward a few tenths.

 

[sunnybob]

Custard, I will certainly try what you say, but I think too much emphasis is being put on the plastic thickness.
The only reason they are that thickness is because I cut them from a single sheet of pretty strong flexible material, just so that I could be certain they were the same thickness. 1 piece is placed behind each end of the outfeed to maintain parallel with the infeed. i dont want to remove huge quantities of material, this is all just because I dont have the skill to use a hand plane on a board edge.

I doubt very much that material will compress, I certainly cant mark it with a fingernail, but I have nothing to lose and maybe something to gain.

 

[PAC1]

So are you trying to achieve a planed parallel piece of wood? From your description the cut is good and straight you just end up with a piece of wood that is slightly tapered?
If you want parallel they you would be better planing one edge as you are and then putting it through your thicknesser as you will never achieve perfectly parallel on the router

 

[sunnybob]

you have grasped the entire problem.
I have a thicknesser, but its the lunch box type. Trying to put a small piece of wood through there on its edge would lead to more problems than I already have. And I have also been unable to completely remove snipe from the thicknesser, so I would be right back where I started.
It seems I am chasing the impossible dream.

 

[PAC1]

Can you keep the pieces longer in future so if for instance you need 4 pieces 150mm long then plane up a piece 150x4 plus say 50 -100mm for snipe and cutting= 700mm long or two at 400mm long. That way you can plane up on the router table and then thickness the wood and lastly cut to length.
If there is a mitre key in your router table you might be able to set up the piece of wood so the far edge is parallel to the key and then use this to plane the wood parallel?

 

[sunnybob]

Sometimes I can plan, and sometimes I just make do with pieces, rather than scrap 50% or more of the wood.

For example, recently I need 4 sticks (for want of the correct word) that I could neatly cut out from a single wide off cut. I cut them on the bandsaw but that left me with only 2 smooth edges from 8 sides. the other 6 are the ones I need to put through this process.
I'm only a retired hobby wood warrior, I cant afford to just keep buying new planks. i need some way of making this work with powered machines because my arthritic thumbs make hand tools completely out of my scope.

The router table has a mitre track, but its a way away from the cutter so I would need to make another sled in order to be able to move thin pieces across the cutter. If i cant cure the fence problem, I shall have to try that.

 

[ColeyS1]

Sounds like a couple wispy shavings off a jack plane might be easier tbh.
Next time you have the same issue, put a couple pieces of folded up paper behind the outfeed fence and see if that helps

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[PAC1]

Bob, make the jig you will never get a repeatable parallel cut off the fence as there is no reference point to keep the wood parallel. The mitre key gives you the reference and repeatability.

 

[woodbrains]

Hello,

I think you should revert back to your lunchbox planer for this. You are trying to use your router table as a surface planer, but expecting it to thickness. I think you are on a hiding to nothing.

Have you tried a MFC table on your thicknesser. I had an Axminster branded one, which was actually a Jet, when Axi used to appropriate other manufacturers machines. It was even still in the (then) Jet blue colour and the instruction sheet was labelled Jet too.

Anyway, digression aside, I could get minimal snipe results from this setup, within sanding if you can't manage a handplane. The surface was actually very nicely planed, these machines often out perform their perceived potential. I could plane 3mm thick laminations with it, so it is doable. Mine didn't have a head lock, which probably would have made it even more precise.

Mike.

 

[PAC1]

A further thought, if you have a bearing guided flush trim router cutter you could clamp the wood on to a piece of ply or MDF and then use the edge of the ply/mdf to give you a straight parallel cut.