Troubleshooting Tearout on End Grain
I have never had much luck getting a roundover bit to make a clean cut as it goes across end grain when cutting a radius, especially with maple. I am now trying to streamline some production work and would love to not have to go back to clean up the tearout that seems to happen. The work is children’s toys and has a lot of curves and 95% of the wood used is hard or soft maple. The tearout happens even with brand new roundover cutters. I am cutting the work on our CNC router and then rounding over the edges on a Shopfox shaper that spins at 14,000 rpm. I use different sized roundovers and they all seem to do it. Does anyone have any advice? If I could avoid this I would save huge amounts of time.
I have to round over both sides and so have never tried the CNC. I assume when you say back cut you mean feeding the piece in the direction of cutter rotation? Could you expound?
From Contributor O:
Counter-rotating cutters is a good strategy. One cutter rotates the conventional direction, the other rotates the opposite way. Cut with the grain and then switch to the other spindle to finish the cut, feeding in the opposite direction. This way, you are always cutting with the grain, and avoid cutting into the grain. You see big old two spindle shapers that were made for these types of operations. Some of the unique cabinet door making machines have counter-rotating spindles to do arched panel and rail work, and then there are the big tenoners that have counter-rotating spindles. If you are doing a bullnose edge of any quantity, you should be doing the entire 180 degrees with one cutter and a template. Then you can do half the cut, flip the template over, then do the other half, and lose the need for counter-rotating spindles.
From contributor K:
I think I would want to use a tool with higher rpm's, and as stated, climb cut, at least the parts where running against the grain becomes tangent on the outside turns. You can also sharpen your bits to have less hook angle, which may help, but requires more power.
From contributor R:
Climb cutting on end grain can be pretty dangerous, especially at the start of the cut. What radius roundover are you using? If it is over 1/4", I suggest lowering the bit for the first cut and then raise and make a traditional cut for cleanup. 14,000 is way too slow. Have you tried a Freud quadra cut?
Contributor R is right. I should have said climb cut on the CNC. Sorry for the omission.
From contributor D:
Use the CNC. Step cuts not all in one pass, with the last pass running 180ipm and 16K rpm and just nicking off the last 20 thousandths. If you are running production, do as much programming as you can versus hand machining and then let the machine work for you. For example, you can tab parts into a sheet and then flip the sheet and roundover the other side. Tearout is not an issue for me using the CNC - you can dial in your speeds and repeat them more accurately than just push parts about this fast. Also don't just roundover the perimeter of a piece. Plunge in and conventional cut the end grain first, blowout be damned. Then plunge in and climb cut the sides, which cut away or inside of the blown out areas completely.
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