Twisted Kity Planer fence

[DigitalM]

I'm not entirely sure why, as it has been left on the machine and not abused, but my KITY planer fence has developed a slight twist. I'd been getting frustrating results when trying to true up against the fence, having already flattened on the bed. There's not much in it, but obviously it's not good. Has anyone else had this? How would I got about correcting it?

The measurements I've put in the photo are made up but to give you an idea what is wrong. It's probably about 2mm of rocking that I get when I place it flat on the planer bed and gently rock it - hence the figure I quoted - I haven't gone at it with feeler gauges or anything yet.

EDIT: I went carefully over the planer bed (which I was using as reference when checking twist) with a straight edge to check that was true, which it is. I also ran a mitutoyo dial indicator across the lower bed, to check that it was planar with the upper bed, and it is within 0.02mm across the width - I suspect that is good enough but haven't seen any figures quoted.

 

[MattRoberts]

Either replace the fence with a genuine part or an alternative aluminium extrusion, or alternatively fix a flat sheet of something on the fence (HDPE or similar) and shim it to be flat in the necessary places.

You might also be able to sand down the fence on the high spots - assuming there is enough meat in the fence and the disparity isn't too huge

 

[dickm]

Stick one end in vice and GENTLY twist the other end against the fault?

 

[NazNomad]

Stick one end in vice and GENTLY twist the other end against the fault?

That would be my first try too, it's not like you're going to f-it up, is it?

 

[custard]

I'd try shimming the error out before I did anything more drastic.

Also, instead of checking for an error with the fence removed you'd be better of doing it "in situ", replace the fence then check for 90 degrees at several locations along the fence with an accurate square, try and shim out those specific errors rather than any hypothetical error deduced for examining the fence in isolation.

Good luck!

 

[Racers]

I would try and straighten it by clamping it with packers under the high points and gradually increasing the force until it’s straight.

Pete

 

[DigitalM]

I'd try shimming the error out before I did anything more drastic.

Also, instead of checking for an error with the fence removed you'd be better of doing it "in situ", replace the fence then check for 90 degrees at several locations along the fence with an accurate square, try and shim out those specific errors rather than any hypothetical error deduced for examining the fence in isolation.

Good luck!

I've check with a starrett square already custard. Then I took it off to get a second perspective on what was going on.

I'm wondering about just unscrewing it and putting a plywood fence on, faced with something like tufnol. I pretty much never use anything other than 90 square - the adjustment has always been a hinderance. I don't like the fence mechanism at all, it's the weakest part of the machine IMHO. I'm assuming though that a plywood fence would be more dimensionally stable that this aluminium thing, and with less flex.

 

[Sideways]

I have the older 3636 Kity with the fabricated steel fence that came before the upgraded extrusion fence on yours. Mine was twisted too ! I screwed an inch thick piece of oak onto the face of the steel one, planed it flat and it's done fine for donkey's years.
Sorry to hear that the alloy isn't as rigid as I'd hope. If straightening fails, it might not be hard to replace the extrusion ? If I remember, it didn't cost me that much to buy a 700mm long x 200mm extrusion with multiple T slots on ebay last year. It's about an inch thick and weight s few Kg. Sounds like that could be an upgrade. I'm a fan of what the yanks call 8020 profile and Bosch Rexroth sell in europe for building workstations in factory production lines. It comes in many sizes and weights.
Thinking of using my piece to make the bandsaw fence to end all bandsaw fences ...

 

[Brandlin]

I'm a fan of what the yanks call 8020 profile and Bosch Rexroth sell in europe for building workstations in factory production lines. It comes in many sizes and weights.

its not the yanks, most of it is european in origin. the bosch stuff is expensive, but you're right you can get it many places fairly cheaply. just google 80x20 aluminium profile and you'll find lots.

 

[DigitalM]

And you chaps think this 80x20 will be torsionally more robust than the fence I pictured? My only concern is that there's a lot of "space" in it, but I guess it's designed to work like a sort of complicated I beam with T-slots?!

 

[Sideways]

I'm a fan of what the yanks call 8020 profile and Bosch Rexroth sell in europe for building workstations in factory production lines. It comes in many sizes and weights.

its not the yanks, most of it is european in origin. the bosch stuff is expensive, but you're right you can get it many places fairly cheaply. just google 80x20 aluminium profile and you'll find lots.

As you say, lots of this made in europe, but for a web search the American term will find you a lot of images quickly

The stuff is made all over the world in what look to be variations on the same concept (one of them is the Bosch design). I have some from Korea that is close to but not identical to the Bosch variant.

 

[Sideways]

And you chaps think this 80x20 will be torsionally more robust than the fence I pictured? My only concern is that there's a lot of "space" in it, but I guess it's designed to work like a sort of complicated I beam with T-slots?!

There are different "weights" in this stuff. Some of it is really heavy duty and yes, I think the heavier versions will be stiffer than your fence. Just measure the weight of your fence and look for something substantially heavier. Thicker metal or a wider section - either or both should improve stiffness.