Planer Blade Setting Device - Method Tools

[cumbrian]

Just revisiting this thread and I'm thinking about wrightclan's delightfully simple jig. Unless I'm missing something, the magnets (other than those over the blade) serve to keep the jig in position on the table - and seem like the ideal solution if the table is iron. However, for those with ally tables, would the jig not work equally well if it was clamped or weighted onto the table?
As I said, maybe I've missed something.....

 

[Newbie_Neil]

Hi Cumbrian

Brad's jig is indeed very simple and I'm speaking as someone who made one.

The only problem is that you don't want the top of the blades to be exactly level with the outfeed. The blades should be slightly higher to give you an even cut.

IIRC, as it was explained to me by a certain woodworking superstar, the cutting action of the blade is a sort of scalloped motion and to get the best results the blades should be slightly above the outfeed table.

Cheers
Neil

 

[wrightclan]

... for those with ally tables, would the jig not work equally well if it was clamped or weighted onto the table?...

Why not? :-k #-o

Brad

 

[Noel]

Hi Cumbrian

Brad's jig is indeed very simple and I'm speaking as someone who made one.

The only problem is that you don't want the top of the blades to be exactly level with the outfeed. The blades should be slightly higher to give you an even cut.

IIRC, as it was explained to me by a certain woodworking superstar, the cutting action of the blade is a sort of scalloped motion and to get the best results the blades should be slightly above the outfeed table.

Cheers
Neil

Gotta disagree with that point. Top of the blades should be exactly level with the outfeed table at TDC. If they are higher how can you use the outfeed table as reference? You'd get a slight, no matter how small, rocking action as the timber dropped to the outfeed table as it travelled along, not to mention a concave surface on the timber.

 

[Steve Maskery]

Gotta disagree with that point. Top of the blades should be exactly level with the outfeed table at TDC.

Hmm. This is my reasoning for disagreeing with your disagreement!

The traditional way to set blades is with a block of wood resting on the outfeed table is it not? This can only be dragged the requisite 3mm or so if the blade is slightly higher than the table. It's been done like this way for a century so it'sdifficult to see that WWs have been wrong for this long.

So why should it be necessary?

The cutting action of the blades gives us a scalloped bottom. See your local GP for treatment.

mmmmmmmmmm

if that makes sense. The slower the feed rate the smoother the finish because the scallops are finer.

Now when the workpiece reaches the outfeed table it is the BOTTOM of the scallops which should contact the table, so the bottom of the scallops should be in line with the table surface. Therefore the top of the scallops should be slightly higher. Very slightly, yes, but higher. If the top of the scallops is in line with the table then the workpiece will ride up onto the outfeed table and the board will be planed convex.

I hope that makes sense.

 

[mailee]

I agree with you Steve that it must be slightly higher or the old wooden batten trick just wouldn't work. If it was level with the outfeed table it wouldn't move the batten. :wink:

 

[wrightclan]

In reality, with my jig, it leaves the blades just enough higher, but in exactly the same plane as one another. Even if it didn't leave them slightly higher, you could then set the outfeed table down by a quarter turn or whatever leaves you with a straight edge and no or minimal snipe.

Brad

 

[Scrit]

Gotta disagree with that point. Top of the blades should be exactly level with the outfeed table at TDC. If they are higher how can you use the outfeed table as reference? You'd get a slight, no matter how small, rocking action as the timber dropped to the outfeed table as it travelled along, not to mention a concave surface on the timber.

Overall the surface of a piece of timber passing across a rotating cutter block is not perfectly flat but consists of a series of flattened elipses which are percieved as "ripples" on machine planed work run at high speed through a planer/moulder (e.g. PAR pine from a timber yard) The smaller the cutter block diameter the the greater the "depth" of the elipse (and the more obvious the ripples) and therefore the need to ensure that the outfeed table is fractionally below the level of the top dead centre of the cutter. The timber going onto the outfeed table actually rides on the "crests" between these eliptical troughs which are obviously below cutter TDC. If you don't believe me draw it in a CAD package......

Industrial planers actually have a micrometer adjuster on the outfeed table so that you can adjust the amount of outfeed table offset (from TDC) to suit the feed speed and the species being planed. In any case the timber should then be passed through the thicknesser not only to obtain a consistently spaced ripple pattern but also the flatten out any slight deviations from the manual planing process

Scrit

 

[Lord Nibbo]

The traditional way to set blades is with a block of wood resting on the outfeed table is it not? This can only be dragged the requisite 3mm

Thats exactly how I was taught, I might add to check both ends of the blade.

 

[David C]

This is of course correct.

It is unfortunate that Knapp technical manual writers do not get this right, to name but one firm who ought to know better.

David Charlesworth

PS Their engineers do not appear to understand dust extraction principles either.......

 

[engineer one]

dc now you are being a real optimist

manual writers who know what they are doing, and
some one in the design department who can make an
extraction system that is cheap enough for the accountants :lol: :twisted:

paul :wink:

 

[Noel]

Hi guys, I'm obviously swimming against the current here. As I mentioned I disagree with the notion that the blades should be be slightly proud of the outfeed table. I'm in no way saying that it is wrong, simply that I disagree that it is necessary. It may be the traditional way when using a batten or aluminium block but I find it totally unnecessary and I'm very happy with the result.
I've been using glass (and other solid man-made materials) and magnets for a long time and it works for me.

Noel

 

[Jake]

That method works fine if you do want the knives slightly raised - you just need a sheet of paper or two between the outfeed table and the 'jig'.