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View Full Version : I Got That Wood Grain Pattern Again..............



JoeLee
05-23-2013, 11:35 AM
A couple weeks ago I replied to a thread that someone started about tramming in the head of the mill. Someone mentioned that if your getting this Moire pattern it's an indication that the head is properly trammed in.
Someone else mentioned that it's caused by an interrupted cut. I say it's caused by vibration, which can also be caused by an interrupted cut.
However........ I was milling some soft cast iron the other day and noticed the patter again. I was only taking .0005 per pass, hardly enough DOC to cause enough vibration from an interrupted cut. I was using my 2" dia. shell mill with 3 dead sharp inserts.
The part is 1 3/4" wide and I had the part centered under the shell mill. There is some slight vibration in the variable speed head of the mill and my guess is that is what causes the pattern. I should have played around with the RPM's to see if the paattern changes in design or goes away, next time I will.

You know........ if I wanted to put this pattern on something I wouldn't be able to!!!!! Life sucks and then you die!!!

JL......................

http://i911.photobucket.com/albums/ac317/JoeLee09/Moire%20Pattern/Image006_zps788b35a1.jpg (http://s911.photobucket.com/user/JoeLee09/media/Moire%20Pattern/Image006_zps788b35a1.jpg.html)
http://i911.photobucket.com/albums/ac317/JoeLee09/Moire%20Pattern/Image007_zps5e51066d.jpg (http://s911.photobucket.com/user/JoeLee09/media/Moire%20Pattern/Image007_zps5e51066d.jpg.html)

A.K. Boomer
05-23-2013, 11:46 AM
There's something in relation to the crescent - if you look it's where the pattern line starts and stops on the other side,,,
it's actually quite beautiful - we'll take 4,000 of them by next tuesday....

Glug
05-23-2013, 12:48 PM
Spirograph!

You can get patterns like that, down to the microscopic level, when waxing a car. They can be fine enough to form a diffraction grating, and then it really becomes noticeable. That's why they say to wax using straight strokes and not circular.

So with that as an example, you can't expect a very light cut to eliminate the problem. I see similar effects when taking fine cuts on aluminum. In some ways it seems the finer cuts produce more diffraction.

If you were uh, bored you could measure the distance between the grooves and try and relate it to your rpm, feedrate and number of cutter teeth.

ranger302
05-23-2013, 01:32 PM
So does this effect mean your mill is trammed in correctly? I get this all the time on parts I make, even when using a fly cutter.
Please advise.

outlawspeeder
05-23-2013, 01:52 PM
It looks to be a pattern in the cast?? If you look close you can see the cut going across the pattern?
Just saying?

Fasttrack
05-23-2013, 02:17 PM
That's really interesting. Like AK says, it's actually really beautiful. You need to come up with some kitchen gadget or coffee table knick knack that highlights that pattern!

MotorradMike
05-23-2013, 02:44 PM
I get that often on a light finish cut.
My theory is that with the head in perfect tram, the leading side of the cutter does all the material removal, and the trailing side scratches whatever has sprung back.

bob_s
05-23-2013, 03:01 PM
The irregular shape leads me to believe that maybe the work piece was rocking as it was being cut.

JoeLee
05-23-2013, 03:04 PM
So does this effect mean your mill is trammed in correctly? I get this all the time on parts I make, even when using a fly cutter.
Please advise.
I don't know if this effect means that your mill is trammed perfectly or not, I think it's more vibration related. I suppose I could knock the head slightly out of tram and see what happens!!!
The pattern isn't in the cast, what you see at the right hand edge of the part is the original mill marks. The part was slightly out of square and I needed to square it up.

JL.........................

JoeLee
05-23-2013, 03:08 PM
Here is the picture I posted a few weeks ago in the other thread. This is a piece of 6061 alum. 3/4" in width.
It has the same pattern, I was also using the same shell mill. So this proves it's not in the cast.

JL......................

http://i911.photobucket.com/albums/ac317/JoeLee09/Image004_zps945da862.jpg (http://s911.photobucket.com/user/JoeLee09/media/Image004_zps945da862.jpg.html)

outlawspeeder
05-23-2013, 03:17 PM
+ one on it not being the cast. If you can do that down a knife blade you would have a seller.

A.K. Boomer
05-23-2013, 03:18 PM
Joe lee, Bob S brought up something along the lines of what I gave thought to earlier,,, except im not thinking the piece was actually rocking but being held tighter on one end than the other - this would set up different frequency patterns which would in turn show in the work, for me im actually trying to figure out why the pattern is progressive from one side to the other...

the bigger picture of why any of it exist could be anything from a loose quill to a multitude of other reasons...

checking a vise for stable clamping is easy - just lightly put the piece in and see if both sides hold the same - if one side is drastically engaged whilst the other is loose you may have a tweaked vise, this can happen from someone putting something in on just one side then clamping down hard on it, can also be the corrective measure although you can break something in the process...

john hobdeclipe
05-23-2013, 03:23 PM
I think your pattern comes from vibration introduced by the interrupted cut. It would have been interesting to see what would happen with changes in rpm or feed rate, or a change of cutter. I'd bet that if the work piece were taller or shorter the pattern would be different.

I run into a similar effect frequently when I make hard maple rolling pins on a metal lathe. A difference in grain density will set up a vibration in the wood cylinder that then creates a texture pattern on the cut surface. Usually the pattern will be a series of closely spaced helices. Sometimes slowing down the rpm will stop it, other times it works better to run it faster. Sometimes the only cure is to put on leather gloves and put some hand pressure on the spinning workpiece to damp the vibration. I haven't yet tried a follow rest.

A.K. Boomer
05-23-2013, 03:30 PM
Here is the picture I posted a few weeks ago in the other thread. This is a piece of 6061 alum. 3/4" in width.
It has the same pattern, I was also using the same shell mill. So this proves it's not in the cast.

JL......................

http://i911.photobucket.com/albums/ac317/JoeLee09/Image004_zps945da862.jpg (http://s911.photobucket.com/user/JoeLee09/media/Image004_zps945da862.jpg.html)


I have to tell you when you figure it out you need to let us know, there are items that something like that would look really neat on and now you have me wondering what anodizing would look like on that aluminum...

timbertoes
05-23-2013, 03:58 PM
I'd sell it on ebay as Old-Growth Aluminum recovered from Lake Erie. ;)

A.K. Boomer
05-23-2013, 05:09 PM
Forget the oak, im thinking tiger stripe 6061...

JoeLee
05-23-2013, 05:42 PM
A.K. the vise holds tight evenly across the jaws, it's not sprung or anything like that and the jaws are like new, I've ground the a couple times in the past.
The piece was stickimg up well above the jaws as it's 3" in height and the jaws are 1 1/2" tall, but at .0005 per pass there isn't enought force against it to do much of anything as far as vibration from an interrupted cut or any other type of movement. The aluminum block was settiing well into the vise with only about 1/4" sticking above the top of the jaws. As was mentioned, everything vibrates at a given frequency, if you change the freq. you'll probably see a difference in the pattern. I'm going to try some different speeds and feeds along with a few different cutters and see if I can narrow it down. I guess I have an exclusive here since no one can duplicate it. Remember I hold the rights, don't anyone try and infringe.

JL....................

JL.......................

A.K. Boomer
05-23-2013, 05:55 PM
Remember I hold the rights, don't anyone try and infringe.

JL....................

JL.......................


You better be careful or were going to start calling you Patsy Sherman around here... lol

JoeLee
05-23-2013, 05:58 PM
You better be careful or were going to start calling you Patsy Sherman around here... lol
OK, who's Patsy Sherman??????????? have I missed something???

JL....................

A.K. Boomer
05-23-2013, 05:59 PM
She invented scotchgard, completely by accident, lol

Zero_Divide
05-23-2013, 06:05 PM
Want to get rid of it?
Position your facemill not on the center of the part, but to either side.
The first rule of facemilling is to never go on center.

Always climb or convrntional.

Again this patented woodgrain screwup does not happen on rigid machines. It only happens on manual bridgeports and such.
I am looking at a part with similar finish right now, and beleive me guys at the shop dont spend too much time making sute tram is perfect.

The pattern is vibration based.
I bet if you do un-interrupted cut it ll be fine.

Mark Rand
05-23-2013, 06:58 PM
It's because you're using crown cut aluminum. Next time pay the extra for the quarter sawn billet.:p

john hobdeclipe
05-23-2013, 08:49 PM
I would really appreciate it if someone could teach me how to do that on demand. And how to make it look like various different species of wood.

Jess13
05-23-2013, 08:54 PM
So your using a shell mill like a fly cutter? I don think they are expected to be used in this way.

Does any other cutters give this pattern, fly cutters & end mills mainly?

If yes (other cutters do this), I would think it is either the spindle bearings, belts or electric motor bearings. Belts can cause some crazy effects at times. If only the shell mills then switch to a fly cutter or end mill. I don't think Shell mills are center cutting, which is the way I am understanding you to be using them (I may be understanding wrong).


When you figure it out let us know, it would be interesting to be able to repeat this at will.


Jess

lugnut
05-23-2013, 08:56 PM
It would appear that you have found something really great, Now you need to learn how to control it ;)

A.K. Boomer
05-23-2013, 09:01 PM
Hmmm, what is the distance between the cutters of the shell mill?

is one cutter entering the middle section when the other starts getting involved into the outer edge???

Highpower
05-23-2013, 09:31 PM
I guess I have an exclusive here since no one can duplicate it. Remember I hold the rights, don't anyone try and infringe.

JL.......................

Not! ;)

Upper: HSS
Lower: Brazed Carbide
Both 6061

I was thinking backlash in the splines on my mill because the HSS cutter hammered quite a bit more than the carbide. Changing feed or speed didn't eliminate it. :confused:

http://img.photobucket.com/albums/v82/Highpwr/Shop%20Projects/P7280085.jpg

http://img.photobucket.com/albums/v82/Highpwr/Shop%20Projects/P7280088.jpg

vpt
05-23-2013, 10:11 PM
Rare billet!

Zero_Divide
05-23-2013, 10:13 PM
Can you ckeck if you have axial backlash in your spindle?
Put an indicator on it and try pulling it up and down.

JoeLee
05-23-2013, 10:37 PM
It's because you're using crown cut aluminum. Next time pay the extra for the quarter sawn billet.:pIs this supposed to be a joke?????? Maybe I should look for rift cut aluminum next time.LOL

JL......................

bobw53
05-24-2013, 12:29 AM
Is this supposed to be a joke?????? Maybe I should look for rift cut aluminum next time.LOL

JL......................

I do believe that would be straight faced sarcasm. An inside joke at best. A comment to be taken very seriously on lookhowmuchshinyoverpricedbilletcrapIcanboltonmysl owloudobnoxiousvehicle.com.

Zero_Divide
05-24-2013, 01:03 PM
I think i have figured out the answer to this "important" issue.
And i can even replicate that.

First of all i was wrong: it is not a product of vibration, but in fact a product of good tramming AND variable chipload.

A cutting edge creates a circular groove. When the same edge goes over that groove it creates intersecting arcs that look like a grid.
The problem is near the center of the tool grooves are parallel to each-other. Arcs simply dont intersect.
So that creates a zone where there is no grid, but parallel lines.

What causes this woodgrain pattern is variable chipload.
Either because of uneven crwnking of the handle, or variations of spindle RPM spacing between grooves varies and it causes circles to intersect in different places.

Here is a part flycut on a bridgeport.
http://zero-divide.net/index.php?page=FrontPage&shell_id=151&view_attached_image=117
http://zero-divide.net/index.php?page=FrontPage&shell_id=151&view_attached_image=118
Here i replicated the pattern on a CNCMill simply by varying RPM withing 10%
http://zero-divide.net/index.php?page=FrontPage&shell_id=151&view_attached_image=119

JoeLee
05-24-2013, 02:40 PM
ZeroDivide, thanks for you help on the issue but I think you hit the nail on the head when you said to move the shell mill off center. I tried that and the pattern did not appear.
My spindle speed was 500 RPM and the table feed was set to aprox. 15 inches per min. in all my photos.
I did run the speed up to 1200 R's and still got the pattern however it changed slightly in size, more of a condensed version of all the previous ones. The intersecting arc is an interesting thought, however I think it's part of the pattern combined with vibration.
I also checked my spindle for end play and I got zero, I knew that wasn't the problem. When I indicate the head to the vise and pull down with a few pounds of force I see about .0003 deflection. I know that the BP's aren't as solid as some mills are.
Here are some pictures of the finish with the spindle off center.

JL.................................

http://i911.photobucket.com/albums/ac317/JoeLee09/Moire%20Pattern/Image008_zps28ad67d8.jpg (http://s911.photobucket.com/user/JoeLee09/media/Moire%20Pattern/Image008_zps28ad67d8.jpg.html)
Center cut
http://i911.photobucket.com/albums/ac317/JoeLee09/Moire%20Pattern/Image010_zpse853d4e9.jpg (http://s911.photobucket.com/user/JoeLee09/media/Moire%20Pattern/Image010_zpse853d4e9.jpg.html)
Off center cut

JoeLee
05-24-2013, 02:44 PM
Notes to above pictures.............
I didn't make any difference which side I off set the cutter to but it had to be off set by a substantial amount or the pattern would still show up. I haven't tried putting a wiper insert in the cutter to see what effect that might have as far as wiping out the intersecting arcs.

JL......................

A.K. Boomer
05-24-2013, 02:46 PM
I can understand that part of it - but im still fixated on the progressive grain pattern, WTF is causing that?

JoeLee
05-24-2013, 03:03 PM
I'm not sure on the progressive part of the pattern either. It isn't the feed rate because I was using the power feed, not the hand crank.
It must have something to do with cutter engagement across the surface??

The progressive pattern kind of resembles the shock wave of a bullet in flight.

JL.....................

JoeLee
05-24-2013, 03:18 PM
I just tried this with a 1" 4 flute end mill, cutting down the center and I got no pattern at all, the finish is like glass.
So I gues this pattern only shows up with a shell mill type cutter.

JL......................

Mark Rand
05-24-2013, 05:27 PM
How about Zero_Divide's Moirre patterns as the cause of the optical effect, but the variation being produced by the shell mill and arbour flexing back and forth in the direction of feed? If the back teeth of the shell mill get pushed up a fraction as the rear of the mill comes on to the work, that would cause the front teeth to cut a fraction deeper in response, when the rear teeth get to that point the front teeth rise up etc. A bit like the patterns you sometimes get on bandsawed stock due to the set of the teeth 'echoing' along the cut.

The height differenced might be only a tenth or so, but still produce an obvious visual pattern.

There's got to be a market for it. :)

Zero_Divide
05-24-2013, 06:02 PM
Yeah it looks cool. And its obvious as a defect too.

To get it you need an insert with a radius and without a wiper.
As far as i know it even happens with 1 flute fly cutters.

The fact that OP was able to get rid of it shows that it has somethi.g to do with vibrations.

At the same time i was able to resemble that finish by varying chipload while in the cut.....

Wtf.?

Norman Bain
05-24-2013, 06:10 PM
Highpower in post #27 has a photo with a pair of parallels being attached to long blue bars. Not sure what they are; but do those bars just "hang out"? Not saying they cause the patterning in JoeLee's case but bars hanging out will add to the vibration.

Sometimes when I use large g-clamps to hold stuff I find draping a wet towel over the ends of the clamp screws reduces vibration.

Cheers,
Norman

Elninio
05-24-2013, 06:22 PM
Cutter flex and vibration propagation; cutting on center causes cutter flex, and vibrations propagate so much that they can be since in these very dense materials. Higher stiffness decreases propagation length. A carbide endmill would decrease them if it was single point as the same diameter as the flycutter. Small diameter tools don't have this vibration problem, because they are so small that vibrations cannot propagate noticeably. If you cut a wall with noticeable depth with an endmill, it will vibrate and produce this pattern VERTICALLY along the axis.

ammcoman2
05-24-2013, 06:25 PM
I read somewhere that one should actually set the tram just a little off "perfect". And then let the low side do a trail cut.

Another item: I didn't notice in the posts if you have been locking the quill. After getting advice from a seasoned pro, I now always lock it and use the knee feed.

Geoff

Elninio
05-24-2013, 06:25 PM
Yeah it looks cool. And its obvious as a defect too.

To get it you need an insert with a radius and without a wiper.
As far as i know it even happens with 1 flute fly cutters.

The fact that OP was able to get rid of it shows that it has somethi.g to do with vibrations.

At the same time i was able to resemble that finish by varying chipload while in the cut.....

Wtf.?

Just because he got rid of it, doesn't mean it has to do with vibrations -- since maybe he covered it up somehow by recutting those edges, as would happen with a wiper. Of course in the general sense of everything, we can say it has to do with vibrations, but that's not saying much at all. It has to do with cutter flex and vibration propagation. Just because you can't bend your tool by beating the crap out of it doesn't mean vibrations can't propagate through it.

Chip recutting, or curling in the chip formation is a good way the average person might cover it up, thinking he dampened his tool by changing the cutting speed, which is wrong. If you changed your RPM by 2x doesn't mean you dampened your tool.

Elninio
05-24-2013, 06:29 PM
That prevents recutting in non-rigid or elastic (they're not the same thing) of the back side as the mill is travelling. Better yet, that person should use a wiper insert so the recutting happens under the wiper edge, and remain flat.

In the lathe we can remain off center by raising/dropping the tool barely, since another cut can get to the desired dimension. In a milling machine, the 2D nature of a cut means that adjusting a size in one dimension can offset other. It's not a good idea to go by what you see with the eye. I can't think of any real world examples where this is a problem, since I lap by surfaces when I need to get good flatness. I'm sure it could cause seizing of butterfly dyes in the paper punching industry for example.

Elninio
05-24-2013, 06:33 PM
http://doktori.bme.hu/bme_palyazat/hallgato/bachrathy_daniel/bachrathy_daniel_en/images/dgk3xjf_88cmj8d9f2_b.jpg

Deflection is cyclical
http://ars.els-cdn.com/content/image/1-s2.0-S0890695506002604-gr4.jpg

Cutting thickness varies because of this
http://ars.els-cdn.com/content/image/1-s2.0-S0890695506002604-gr2.jpg

The result is a (simulated) vibration pattern along the direction of the profile in the material as a poincare plot.
http://ars.els-cdn.com/content/image/1-s2.0-S0890695506002604-gr11.jpg

Jaakko Fagerlund
05-24-2013, 06:47 PM
Kind of OT, but Elninios pictures of the workpieces remind of one turd at work, he is a CNC miller and leaves that kind of finish on mold inserts and pockets and everything. Guess who gets to clean up those with hard handwork by files, stones and generous use of an angle grinder, with high hopes that the customer doesn't check/care for flatness...

JoeLee
05-24-2013, 07:12 PM
Highpower in post #27 has a photo with a pair of parallels being attached to long blue bars. Not sure what they are; but do those bars just "hang out"? Not saying they cause the patterning in JoeLee's case but bars hanging out will add to the vibration.

Sometimes when I use large g-clamps to hold stuff I find draping a wet towel over the ends of the clamp screws reduces vibration.

Cheers,

Norman
Any thing that hangs out too far from it's holding source, be it a chuck or a vise will vibrate but that results in a chattered finish.

JL...................

JoeLee
05-24-2013, 07:15 PM
I read somewhere that one should actually set the tram just a little off "perfect". And then let the low side do a trail cut.

Another item: I didn't notice in the posts if you have been locking the quill. After getting advice from a seasoned pro, I now always lock it and use the knee feed.

Geoff
That may be OK for milling but boring and drilling will result in error, very noticable error the deeper the hole is. I would prefer to be as perfectly trammed as I can get it.

JL................

Zero_Divide
05-24-2013, 07:49 PM
Okay when you are using power feed how do you make sure feedrate is constant?

My guess is you dont
The force required to move x axis along the slides will vary depending on weight distribution and wear patterns that would affect feedrate.

Slight variation in chipload will shift grooves ever so slightly to create the woodgrain patterns

From the patterns i observed through a microscope i can tell for sure the distance between those grooves was slightly varying and that must have led to those marks.

Again on cnc it only happens when spindle speed or feedrate is jumping up and down. Which happens rarely enough unless you are trying.

Elninio
05-24-2013, 08:00 PM
Kind of OT, but Elninios pictures of the workpieces remind of one turd at work, he is a CNC miller and leaves that kind of finish on mold inserts and pockets and everything. Guess who gets to clean up those with hard handwork by files, stones and generous use of an angle grinder, with high hopes that the customer doesn't check/care for flatness...

The dothead immigrants who can't speak english working for barely (or below) minimum wage? The pictures of the millwork are separate from the study which was a simulation.

Elninio
05-24-2013, 08:02 PM
The spinning head has momentum which normalizes the varying chip load, it's the resonance that's the problem (or the blessing, if you consider woodgrained on metal an act of god).

Zero_Divide
05-24-2013, 08:34 PM
Head-maybe.
But powerfeed is just a simple motor that moves slower if higher resistance is encuntered.
Also because its gear driven it will have not smooth motion , but there will be jerks in the movement.

A.K. Boomer
05-24-2013, 09:23 PM
Highpower in post #27 has a photo with a pair of parallels being attached to long blue bars. Not sure what they are; but do those bars just "hang out"? Not saying they cause the patterning in JoeLee's case but bars hanging out will add to the vibration.

Sometimes when I use large g-clamps to hold stuff I find draping a wet towel over the ends of the clamp screws reduces vibration.

Cheers,
Norman

All that stuff needs to be considered - including the length of the leads that work the X axis getting shorter or longer with the loaded side as its being ran through the centrally located lead nuts and mounts...

Zero D. I don't think you get to say that word on here... :p but now you have to leave it up so people know what im referring too...

Highpower
05-24-2013, 10:02 PM
Highpower in post #27 has a photo with a pair of parallels being attached to long blue bars. Not sure what they are;

Cheers,
Norman

Just spring loaded keepers that hold the actual parallels against the vise jaws. Keeps the parallels from falling over when changing parts/material in the vise.

http://www.kurtworkholding.com/accessories/parallel_keeper.php

Elninio
05-24-2013, 10:24 PM
Head-maybe.
But powerfeed is just a simple motor that moves slower if higher resistance is encuntered.
Also because its gear driven it will have not smooth motion , but there will be jerks in the movement.

That's true, I know because I made a powerfeed once with a weak motor and my coupling wasn't perfectly centered, so every turn had a high and low spot.

JoeLee
05-24-2013, 10:31 PM
Okay when you are using power feed how do you make sure feedrate is constant?

My guess is you dont
The force required to move x axis along the slides will vary depending on weight distribution and wear patterns that would affect feedrate.

Slight variation in chipload will shift grooves ever so slightly to create the woodgrain patterns

From the patterns i observed through a microscope i can tell for sure the distance between those grooves was slightly varying and that must have led to those marks.

Again on cnc it only happens when spindle speed or feedrate is jumping up and down. Which happens rarely enough unless you are trying.
Well you don't but the power feed is more consistant than if you were cranking the table by hand, also how much chip load can there be when your taking .0005 per pass???? my guess is not much.

JL.......................

Zero_Divide
05-25-2013, 12:10 AM
Well you don't but the power feed is more consistant than if you were cranking the table by hand, also how much chip load can there be when your taking .0005 per pass???? my guess is not much.

JL.......................

Chipload is an advancement of a cutter per flute per revolution its not how thick the material you are removing is.

Powerfeed will give you slightest variations of tool advancemet that will give you a pattern, but will not be severe.enough to screw it up completely.

I dont have a better theory.

1200rpm
05-25-2013, 08:12 AM
i had a similar thing going on with my mill/drill - i wrote it off to it being a less than rigid machine.
then my drawbar threads started to strip so a made a new drawbar - the problem went away.

after looking closely at the old drawbar it was obvious the threads were cut really crappy and were not straight or concentric.

i think tightening it put some uneven stresses on the spindle/collet and produced a "pattern"

JoeLee
05-25-2013, 11:08 AM
1200, thats interesting about the draw bar threads but I can't see how that would cause vibration as long as the taper is seated in the spindle.

I milled the same piece of alum. this morning using my 3" shell mill this time. I ripped it right down the center and got no pattern.
So............ why is it that the 2" shell mill produces the pattern and the 3" does not???? I tried different speeds and feed rates and still no pattern. I was also using the same type inserts in the 3".


JL....................

Rosco-P
05-25-2013, 11:22 AM
Just a wild shot, could the 2" shell mill be unbalanced? Try mounting it between centers horizontally and spinning it by hand with no inserts. Does it come to rest at a random spot or is one portion always facing down?

JoeLee
05-25-2013, 11:35 AM
Just a wild shot, could the 2" shell mill be unbalanced? Try mounting it between centers horizontally and spinning it by hand with no inserts. Does it come to rest at a random spot or is one portion always facing down?
I doubt it's out of balance, it's machined out of a solid piece of round and all the cuts or pockets are the same in size.
I think that trying to balance something so small in dia. by using centers would cause enought resistance to allow the cutter to rotate.
Perhaps setting it on parallel rails and seeing if it rolls would be a better approach to checking balance.
But on the other hand fly cutters with one tool hanging out the side aren't balanced either.

JL.......................

Rosco-P
05-25-2013, 12:10 PM
I doubt it's out of balance, it's machined out of a solid piece of round and all the cuts or pockets are the same in size.
I think that trying to balance something so small in dia. by using centers would cause enought resistance to allow the cutter to rotate.Perhaps setting it on parallel rails and seeing if it rolls would be a better approach to checking balance.
But on the other hand fly cutters with one tool hanging out the side aren't balanced either.

JL.......................

Maybe it is too light to check static balance with home brew methods. Do you know anyone in the automotive machine shop biz that would static balance it for you? Is the face of the mill (and the bottoms of all the pockets) perpendicular to the shank?

If this is an import face mill, maybe you just got one of the bad ones.

john hobdeclipe
05-25-2013, 02:35 PM
Question for the OP:

Is this pattern merely visual, or can you actually feel an unevenness in the surface?

JoeLee
05-25-2013, 02:49 PM
It's mostly visual, the pattern isn't any deeper than your normal mill marks would be.
The shell mill is made by APT, I don't think it's a cheap import as I stay away from that stuff.

JL.......................