Shear cut rebate block

[Doug71]

A joiner I know has just bought a second hand Felder spindle moulder, he has also bought a new Whitehill shearcut rebate block to use on it. He says the rebates are slightly rippled and asked me what it could be. I gave him a few tips but sounds like he is doing everything correct.
I am just trying to get my head around the geometry of a straight blade making a shearcut in a round block, I presume it should be okay or they wouldn't sell them?

I normally use a big old square steel block but do have an aluminium shearcut I hardly use so will try it later.

My Festool electric hand planer does a shearcut but the blade is curved to compensate for it.

Any thoughts?

Doug

 

[Trevanion]

Strange...

I've used almost exclusively 4 wing shear rebate blocks from Whitehill or OMAS for rebating and I've never had any rippling problems and always have a top standard finish. Is he perhaps feeding the material too quickly resulting in visible knife marks like a washboard effect?

I also don't understand how the geometry works either, I know on some of the old planer thicknessers like the Wadkins sometimes were fitted with a shear cutting head and those knives were curved. Perhaps it's such a small shear angle over a short distance that it doesn't matter.

 

[Peter Sefton]

I run a Trend shear rebate block on my Hammer F3 with straight cutters, never had any quality of cut issues.

The much bigger heads on old tenoners tended to have curved blades, but the shear was more pronounced than these small blocks.

I have seen poor finish for reasons including a rough sawn finish on a fence given a juddered feed.

Cheers

Peter

 

[Doug71]

Thanks guys, I thought the block should be okay but thought I would ask.

He has a workshop full of decent machinery so I presume he knows what he is doing but the spindle moulder is new to him. I will go round and check how he is using it but says he is feeding it slowly and using shaw guards etc.

I do wonder if there is some run out on the spindle as it is secondhand and think it was a bit rough when he bought it.

 

[Trevanion]

You'll tell right off if there's play in the spindle because the machine will want to take off down the road :lol:

 

[Adam9453]

Is he using a power feed?

 

[Doug71]

Is he using a power feed?

That is a good question. I know he has one but I doubt he was using it, I will ask him.