Roundover finishing - what's causing this..?

[Wal]

Hi,

I was making a little wooden ornament for a friend earlier and I noticed a bit of 'roughness' on the final round-over pass.



It sands out reasonably well, but I'm curious to know what's causing it - I thought it might be a conventional/climb issue, but the weird thing is that it happens in the same places regardless of whether I'm climbing or cutting conventionally. The areas where it isn't happening are nicely finished and the parts which bear the rougher finish have one thing in common (and this surely has to be a clue) - they're oriented the same way...

So, is it feeds/speeds, is my round-over bit a bit rubbish (admittedly it is), or is the wood itself contributing to the finish?

Cheers!

Wal.

[Ger21]

It's called end grain. Welcome to woodworking, where every piece of wood can act differently on any given day. :)
Generally, softer woods will tend to give the results you're seeing. The harder the wood, the better the cut. Tool sharpness can help. Increasing rpm/lowering feedrate may give better results, at the expense of tool life.
If the bit is bad as you say, a new sharp one will probably cut better.

[Wal]

End what?

Only joking - so, when you hear about wood-workers using grain filler, is it this effect that they're fighting - that is, will softer woods/open grained woods always misbehave a bit and need treating with a filler prior to finishing?

Wal.

[Ger21]

Typically, grain filler is used on flat surfaces to fill the pores, not tearing of the endgrain. Often when one would like to achieve a smooth non porous finish with a wood like Mahogany.
I normally prefer clear finishes, and would always try to sand out defects rather than fill them.

[longy]

Imagine that your length of wood is made of a load of straws all stuck together running from left to right. you want to cut a " V Shape " out of the wood as the cutter cuts downwards the straw below is longer and supports the straw being cut and the cut is cleaner, as the cutter moves upwards to form the other side of the " V Shape " the straws being cut are longer and supported by a shorter straw, the lonest edges get pulled away and cause the fluffing on the grains edge.

You can reduce the fluffing by using spiral fluted cutters for strait cuts but yet to find a spiral round over for rounding. try doing the same cut on some softwood and the fluffing will be 10 times worse. Edging 90* end grain is cleaner but remember to use a scrap block and the end of the cut to stop breakout. Have fun working with wood as it can be very rewarding when it goes right and warming when it goes wrong. I burn my mistakes.
Mike :)