Infeed roller causing scalloped finish on planed boards

SBAER · Oct 4, 2016

I have a 12" Poitras thickness planer with a 5hp motor, a three knife 4" diameter cutter head and a serrated steel upper infeed roller. The only way I can get rid of the shallow scallop marks ( they seem to be at the exact pitch of the serrations on the infeed roller)is to roll electrical tape around the infeed roller. The marks are there even when a 1/8" cut is taken, scallops are worse in hard wood than in pine.

I have sharp knives and they are set within 0.002" to the bottom of the infeed table, I have tried backing off the tension on the infeed roller springs.

Is this something left to try other than replacing the serrated roller with a rubber one?

Don Burch · Oct 5, 2016

Are you getting a scalloped surface or roller track marks? I have a Laguna 16" planer with the helical head. If I take to light of a pass, the surface is smooth but the cut is not deep enough to take out the infeed roller tracks. This be a cut of 1/62" or less I think.
I never had this issue with my lunchbox planers that have rubber/urethane rollers.
Don

SBAER · Oct 5, 2016

They are scallops not track marks, light cuts, heavy cuts it doesn't matter

stephen thomas · Oct 5, 2016

They are scallops not track marks, light cuts, heavy cuts it doesn't matter

The marks are there even when a 1/8" cut is taken, scallops are worse in hard wood than in pine.

This does not sound like a feed roll problem. More a work support or cutterhead problem.

Are your table rolls set too high? If so, the wood will vibrate under the cutterhead as each knife hits it; or some resonant frequency thereof coordinated with the feed speed.

I would normally say unjointed knives, but if it goes away when you wrap tape around the infeed, it sounds more like vibration. if a 1/8" cut in hardwoods still leaves "scallops" it is very difficult to imagine that they are from the feed roller on a smallish planer.

Assuming the outfeed roller is smooth?

Also, for smoothness in a planer make sure the chip breakers are dressed sharp, & in correct contact evenly, and that the presser bar setting is correct. If they are not making contact, vibration will occur. But no more pressure/copntact than book value, or wear and hard feeding will result.

smt

atomarc · Oct 5, 2016

I also don't believe the infeed roller is the culprit. If the machine has a variable speed infeed adjustment, I would eyeball measure the spacing of the marks you're getting now, then kick the feed way up and measure again. This will tell you if the pattern you are seeing is being generated by the head/knives or by a feed roller or holdown issue.

Does your planer have a onboard jointer on it?

Stuart

SBAER · Oct 5, 2016

I have made a 3/4" thick MDF bed plate that covers the bottom of the table, this helps with snipe but does nothing for the scallops. Maybe the knives are too long as the chip breaker is 1/4" away from the cutting edge of the knife if memory serves.

stephen thomas · Oct 5, 2016

Even an out of round infeed roller might cause the problem by bending (flexing) the board over the lower table roll cyclically. Though the period appears to match the corrugations. Tape would mask that by giving enough to even out the amplitude and damp vibration.

So again, check the setting on the table rolls and make sure everything else in the feedworks is correctly set.

I'm not saying the feed roll is not an initiating factor, but that the corrugations are not imprinting on the wood itself to the extent that the cutterhead would not clean them up in a correctly set up planer.

Is your infeed roll solid or segmented?

I have sharp knives and they are set within 0.002" to the bottom of the infeed table,

That is not nearly close enough to eliminate scallops from the knives. Essentially they have to be jointed. There is a good section in "Chisels on a Wheel" that addresses this and shows the math, and any moulder text describes it. A few tenths (.0001's) = scalloping. I hone the knives with a hand stone (obviously machine unplugged) over time, and they come into joint. You just hone the knife(s) with the most obvious wear tracks, the one that feels duller than the others and is not shiny near the edge.

smt

SBAER · Oct 5, 2016

The reason I tried the tape was that the scallops were not present in the last 4" of the board, this is the distance between the infeed roller and centerline of the cutterhead.

crzypete · Oct 5, 2016

Off the cuff guess, you knives are not sticking far enough out of your cutterhead. But, you really should get a manual and set everything up to spec. With my all my planers, doing a full set-up always brought things back to functionality. Every floor standing planer uses a seated indeed roller, replacing it with a rubber one shouldn't be necessary

Pete

stephen thomas · Oct 5, 2016

Every floor standing planer uses a seated indeed roller....

Just to be picky, if the above was supposed to say serated infeed roller; I don't think Newman's have, for a number of decades

They use either urethane covered steel, or pneumatic rubber tire feed rolls, or combinations, depending on the machine.

...replacing it with a rubber one shouldn't be necessary

Agree. OTOH rubber (urethane) rolls are really nice.

smt

SBAER · Oct 6, 2016

Thanks everybody. I think I have found the problem as a result of some of the ideas you brought up. This is not too flattering on my part but at some point I must have put the knives in wrong. The knives are on the wrong side of the slot in the cutterhead so the cutting geometry is way off. I have not had time to switch them but I imagine this will solve all my problems.

stephen thomas · Oct 6, 2016

Well that orientation will give less tear-out in gnarly grain, FWIW, lol!

But also with that set-up, the amount of scalloping per any given blade extension discrepancy is greater. Though perhaps not in accordance with how the blade extension is set and gaged.

Stresses on the machine are slightly greater, and blades will heat more and dull more quickly.

smt

atomarc · Oct 6, 2016

The picture shows the knives and gibs in the proper orientation, in my opinion...maybe the incorrect setup isn't shown!

Stuart

pri0ritize · Oct 6, 2016

I'll concur with Stephen. I've dealt with this problem multiple times and when you see obvious scallops like that it tends to be a bed roller issue. If they're set too high the board will flex and oscillate giving the scalloped finish. The scalloping stopping near the end makes me think this is the issue even more.

atomarc · Oct 6, 2016

As I posted earlier.. vary the feed speed while cutting and you will instantly see if it's a head issue or a hold down/feed roll issue. Takes seconds to do!!

Stuart

SBAER · Oct 6, 2016

That picture was the cutterhead as I originally had it. I have started flipping them around but have not finished. Here is a picture of how I figured the right way would be

I suspected the bed rollers being high but when I put a straight edge over them there is only a 0.005" gap to the bed. The 3/4" MDF bed plate should have helped with that too but it didn't.

dcsipo · Oct 6, 2016

atomarc said:
The picture shows the knives and gibs in the proper orientation, in my opinion...maybe the incorrect setup isn't shown!

Stuart

...i think not....The blade should go in the back of the slot with the gib against the back of the blade and the bevel pointing away form the direction of rotation. In the pictured setup there is no place for the chip. In the proper orientation the gib and the slot form a gulley in front of the blade allowing the chip to clear and not jamb between the back of the blade the lumber and the cutter head. Also that setup makes the blade hit the lumber at a more acute angle, causing it to dig in.

dee
;-D

atomarc · Oct 6, 2016

dcsipo said:
...i think not....The blade should go in the back of the slot with the gib against the back of the blade and the bevel pointing away form the direction of rotation. In the pictured setup there is no place for the chip. In the proper orientation the gib and the slot form a gulley in front of the blade allowing the chip to clear and not jamb between the back of the blade the lumber and the cutter head. Also that setup makes the blade hit the lumber at a more acute angle, causing it to dig in.

dee
;-D

Ooops..I was wrong, you're correct.

Stuart

CalG · Oct 6, 2016

When I read the original topic post, my first reaction was "he said the blades are sharp, but I think not. They must be hammering".

Which goes right along with all the vibration and support comments.

If the knives are truly sharp, (and installed properly) they pass through the wood with little resistance, and so do not generate Whoop ass forces.

Of course, even a keen knife will act dull if it contacts the wood with the wrong geometry.

SBAER · Oct 9, 2016

So I put the knives in right and the thing still leaves scallops in hardwood. For some reason the scallops and shallower and closer together in the high feed speed than in the low feed speed. I lowered the bottom feed rollers so they are barely above the bed and raised the top outfeed roller so that it is not putting as much pressure on the board. Snipe is pretty minimal so I am going to live with it for now.

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