HL850 Question

[Birdhunter]

I've got the HL850 planer mounted in the bench top fixture. Doing an ordinary planing operation works just fine.

I'm getting strange results when I try to cut a rabbit.

If I make one pass, the rabbit is perfect. If I make multiple passes to get a deeper rabbit, the sides of the rabbit are stair stepped. The width of the rabbit gets smaller with each pass.

What am I doing wrong?

 

[semenza]

That's weird. Without setting mine up and trying it I am trying to picture how that could happen. Just to be certain ...... you are only adjusting the cutting depth not the fence , right?

Is the stair step even and the same width difference each time?

What are the dimensions of the piece you are rabbeting?

Seth

 

[Birdhunter]

I'm not touching the fence and it is tight.

The stair steps are exactly the same.

 

[Birdhunter]

the wood is 3/4" pine

 

[Birdhunter]

This has to be something to do with the position of the cutter knife. The knife sticks out from the cutter head a lot more on the rabbiting side than on the other side.

 

[tbellemare]

90 degrees off?

Tom

 

[Birdhunter]

I don't understand the 90 degree question.

 

[tbellemare]

It would seem that if you are exposing more of the cutter with each pass and you are getting a stair step that the work piece is 90 degrees off. Maybe my thinking is off?

Tom

 

[Birdhunter]

The width of the rabbit is greatest on the first pass. The rabbit is slightly narrower on the second pass and even narrower on the third. So, the width of the rabbit gets progressively narrower.

 

[epicxt]

I've ran into this with my unit. I ended up finishing the rabbet on the router table as I was in a hurry and never got back to figuring out the root cause. In my mind it seems that the cutter head isn't quite out to the edge of the plane body.
I'll be watching this thread...

 

[Wenyce]

Could it be that the bench unit is allowing movement of the planer in its cradle? Or the blade isn't tight enough?

I have no idea if what I'm saying is making any sense, just offering up some suggestions..

 

[Birdhunter]

It is more like the wood is referencing off something other than the fence.

 

[semenza]

Is the first rabbet pass coming out at the correct width?

Are the steps  about 1/16" - 1/8"?

Can you post a picture of the bottom of the planer showing the blade, drum, and full width of the planer in the shot?

Seth

 

[Birdhunter]

I'd guess the steps are all about 1/32".

What I have noticed is the the fence is off square to the edge of the planer by about 1/32" measured at the two ends of the fence from the edge of the planer. The width of the rabbit on the first cut is also unequal from one end to the other by about 1/32".

Somehow, this off square error is added to each successive pass.

The front shoe lines up perfectly with the body of the planer. The cutter blade lines up perfectly with the side of the front shoe and the body of the planer.

The only thing that is not lined up perfectly is the fence.

It may well be that I am expecting too much from the planer/fence.

I have several other ways to do rabbits. It's just that I wanted to try rabbits on the planer.

 

[semenza]

    Sounds like you may have tracked it down. I was thinking the blade might not be centered. But if the fence is tilted away from the bed at the top of the fence. Then the reference point against the fence will be closer on each pass because it will be at a lower position on the fence on each pass.

Seth

 

[Birdhunter]

I do think the fence is the culprit. So, what should I do?

 

[tiralie]

I do think the fence is the culprit. So, what should I do?

You just get a shoulder plane, clean up the rabbet and move on.
BTW, how deep is the rabbet? Can you cut it in one pass?
Tim

 

[semenza]

I do think the fence is the culprit. So, what should I do?

I guess try realigning and squaring it?

Seth

 

[Birdhunter]

As I said before, expecting a sheet metal fence to consistently remain square to the planer's edge isn't realistic. So, I'll cut rabbits on my BIG Powermatic planer with a massive cast iron fence. I know it is dead nuts accurate.

The HL850 does a wonderful job doing what it was designed to do, flatten boards. The fence, even off square, produces true 90 degree angle edges.

I'm a little disappointed as this is the first of MANY Festool products that wasn't "just right" when I first used it. Oh well.........

 

[Birdhunter]

Problem solved!!!!!

There were two issues interacting to give me the stair stepped rabbits.

One, the fence was not square to the side of the plane. I shimmed the fence with a section of a plastic hotel key. That got the fence within 1 to 2 tenths of a mm measured at both ends. I still got a little stair stepping on the test cut.

I decided to move the cutter out from being flush with the side of the planer. The cutter now sticks out a tad past the side of the planer. Now, the reference surface is the fence and not the side of the plane.

I think the planer needs to be set up so the reference surface needs to EITHER the fence OR the edge of the planer. If the reference surface is the fence, the cutter needs to be just proud a hair from the side of the planer. If the side of the planer is to be the reference surface, the cutter needs to be flush with the side of the planer.

If I have this wrong, please correct me.

I don't think the HL850 will ever be my primary rabbiting tool, but I've finally got it to where it cuts rabbits that are perfectly square.