barber pole

RocketQ

RocketQ

It's Not Rocket Science
Silver Member
An observations I made last night but don't know what causes it. The 4 spindle saw machine I have all 4 blades and spindles rotate at the same speed travel at the same longitudinal speed but 3 of the 4 cut smooth and one got the barber pole look. Any guesses as to why one shaft at an initial cut would do this and none of the others? It is not common to any particular spindle so I am thinking it has to do with the wood. Any guesses?
Not always 1 gets goofy sometimes none.
John
 
Too much pressure on centers

I've had the same problem (doing them one at a time on a lathe) and I have a theory. I'm beginning to believe that, if I put the least bit too much pressure on the shaft when I mount it between centers, it bows ever so slightly. This would cause the "barber pole" finish as the shaft wobbles during the cut. I plan to check this (with a dial indicator) the next time I cut shafts.

Just a theory:confused:
 
Bill the Cat said:
I've had the same problem (doing them one at a time on a lathe) and I have a theory. I'm beginning to believe that, if I put the least bit too much pressure on the shaft when I mount it between centers, it bows ever so slightly. This would cause the "barber pole" finish as the shaft wobbles during the cut. I plan to check this (with a dial indicator) the next time I cut shafts.

Just a theory:confused:
Click to expand...
Climb cut vs conventioanl cut is prob the reason
 
I'm not so sure.

TellsItLikeItIs said:
Climb cut vs conventioanl cut is prob the reason
Click to expand...

This wouldn't explain why one has "barber pole" and the next doesn't.

I do agree with BarenbruggeCues that a dull cutter will also cause this due to the "push off" that results from a dull cutter. However, it will happen "consistantly" when the cutter dulls.
 
Make sure that blade is sharp and that the blade is on center with the center line of the shaft.
 
Try again

The barber pole is not isolated to any single spindle. then end pressure is no where near too high. This is a first turn from square. Little spring holding in place. I am thinking it is something to do with the density of the wood.
 
I've had some barber poling too.
Usually disappears with sharp cutters and/or putting more pressure on the separate spring that pushes the drive spur ( which is separate from the dead center ).
I think the wood is slipping in between centers then it looks like it got threaded.
 
Bill the Cat said:
This wouldn't explain why one has "barber pole" and the next doesn't.

I do agree with BarenbruggeCues that a dull cutter will also cause this due to the "push off" that results from a dull cutter. However, it will happen "consistantly" when the cutter dulls.
Click to expand...
It might. The OP is using a 4 spindle machine. Wouldnt all 4 blades be in the same condition or does he sharpen them one at a time?

Contrary to what some might think every piece of maple does not cut the same. Even if its from the same tree or branch it can cut different.

Like the other posters said it could also be one of several things.
Dull blade(s)
Off center
Too fast on the feed
Too deep a cut
A combination of any or all the above
Not holding your tongue just right
 
RocketQ said:
The barber pole is not isolated to any single spindle. then end pressure is no where near too high. This is a first turn from square. Little spring holding in place. I am thinking it is something to do with the density of the wood.
Click to expand...

The spring tension on that particular dowel is to weak on that shaft. The cause for this can be a couple of reasons. Probably, the center that has been put into that shaft is not deep enough so that there is not enough friction so the shaft doesn't turn at the same speed as the drive or the shaft is a little shorter or the spring tension may need to be tightened a little more for that depth of cut. My spring tension is adjustable on my machine and I tighten it up when I'm making my initial heavy cuts and lighten them on later, on finesse passes. However, whenever this happens to me I normally just drill the center a little deeper making it wider at the same time for increased friction.

Dick
 
slippage

The way that my centers are set up if they slip even a little they will just spin in the wood and the shaft will stop rotating. It is all or nothing with this. The centers will not slip and then pick back up. If it was the same one all the time I would say yes that has to be it. Al of the centers are drilled the same depth with a #4 center drill. What I am seeing is not caused by slippage or dull tooling. I can hold more pressure on the center and it still does the same thing. This is why I am scratching my head. could it be the wood? Could those particular pieces of wood have bad harmonics? I can't be the only guy that has seen this.

John
 
RocketQ said:
The way that my centers are set up if they slip even a little they will just spin in the wood and the shaft will stop rotating. It is all or nothing with this. The centers will not slip and then pick back up. If it was the same one all the time I would say yes that has to be it. Al of the centers are drilled the same depth with a #4 center drill. What I am seeing is not caused by slippage or dull tooling. I can hold more pressure on the center and it still does the same thing. This is why I am scratching my head. could it be the wood? Could those particular pieces of wood have bad harmonics? I can't be the only guy that has seen this.

John
Click to expand...

It's obviously a bad machine, I'll be over to get it out of the way for you and let you put another one in it's place.

Happy I could be of service! :D
 
ive seen this. when im turning wood round or in early passes i go fast and sometimes get this effect. i think your traveling too fast. try to go as slow as possible. i always cut router fastest and powerfeed slowest on my final passes.
 
You have ask yourself how many times has the cutter touched a piece of wood? I assume.......(we all know about that)....you are talking about your 4 head cutter? Are you just cutting shafts only or exotics also?
A bushel of things can come into play here. Did it just start doing it recently? Has it always done it? Make any changes on anything before it started?
If I were a gambling type person.......I would have to stick with the cutters losing their edge. Contrary to popular belief, it does not take long for a carbide cutter to diminish it's razor sharpness and start pushing off and causing weird things to happen. When this happens, the hardness difference in some pieces of maple will react differently on the same cutter.
I know you don't want to hear me say, this but it's prolly time to take those blades somewhere that has a cnc sharpener, get your wallet out and be happy about it!


<~~~just mark the cost up in your next 4 cues................

EDIT...because I'm not so good sometimes..........
 
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I think it is a harmonic problem. How often does this happen, how often is it the same shaft. How long down the cut does it take for this to happen?
You could try having the blades running at slightly different rpm's.
They have to do this on multi engine aircraft, othewise the harmonics can destroy the aircraft. Try a little bigger or smaller drive pulleys. In aircraft they are continually raising and lowering the engine rpms so that no two engines are in the same rpm range for more than 3 seconds.
Neil
 
blades

BarenbruggeCues said:
You have ask yourself how many times has the cutter touched a piece of wood? I assume.......(we all know about that)....you are talking about your 4 head cutter? Are you just cutting shafts only or exotics also?
A bushel of things can come into play here. Did it just start doing it recently? Has it always done it? Make any changes on anything before it started?
If I were a gambling type person.......I would have to stick with the cutters losing their edge. Contrary to popular belief, it does not take long for a carbide cutter to diminish it's razor sharpness and start pushing off and causing weird things to happen. When this happens, the hardness difference in some pieces of maple will react differently on the same cutter.
I know you don't want to hear me say, this but it's prolly time to take those blades somewhere that has a cnc sharpener, get your wallet out and be happy about it!


<~~~just mark the cost up in your next 4 cues................

EDIT...because I'm not so good sometimes..........
Click to expand...

lol yep it's probably time... But But But they still cut clean... Clean cut crawl cut the same thing happens only on certain pieces of wood. it's weird out of 60 squares I only have about 6 that did this. Dunno I am going to buy a new set from Forrest products. Not cheap but very accurate. I just don't want to have to re shim my spindles so they all cut the same again.. Now that is a pia.

John
 
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