Question on SCREAMING BIT

[ken_rychlik]

I bought some mortise comp centurion bits and tried the first one out today. It cut fine, but the scream/squeal ran me out of the shop. I tried to run faster, slower, changed router rpms and nothing helped. Is this just the nauture of the beast? I have just been running down spiral bits before this and they run quiet.

Thanks

Kenneth

[Gary Campbell]

Kenneth...
Let me guess... it is a 1/4" bit and you cant go below 12K rpm. Thats where they start the screaming. Can you increase your move speed?
Gary

[ken_rychlik]

I took it down to 10k rpm and no change. I sped up the feed speed to 3 ips ( it was at 2 )

So you are saying I need to push it faster? how much faster?

There is no sign of burning and I was running some of the same files that were fine with a down spiral bit with the same settings.

Kenneth

[Gary Campbell]

Kenneth...
Not saying I eliminate the noise, but usually cut around 10.5K @ 5-6ips, .700 per pass. Noise is lower and bit stays room temp.
Gary

[myxpykalix]

I had the same experience when cutting some mdf on the climb path of the cut, not sure why it was doing that.

[ken_rychlik]

I am wondering if the normal compression (non mortise) would do the same?? I am running prefinished ply cabinet parts, but I run the same stuff quietly with the down spiral bits.

I ran climb .68 deep and finish pass conventional, and it screams on both cuts.

[Gary Campbell]

Kenneth...
There have been other posts on the noise of 1/4" comression bits. I dont think its peculiar to the mortise compression or Centurion. The 3/8 make noise too, but mortise comprssions are by far the best tool for cutting PF plywood cabinet parts.

You can use a normal compression if you are not cutting dados. The standard compression has a higher up spiral section, and can actually cut outlines faster, but chips the surface when cutting shallower than the bottom of the downspiral section. Wear ear protection!

Gary

[ken_rychlik]

I have big radio muffs, but this noise still makes me want to use the cabinet saw. lol

[Gary Campbell]

Kenneth...
Use the muffs for the saw too! We both know that cutting those panels on the saw would be "just wrong"!
Gary

[ken_rychlik]

The cabinet saw is like a whisper compared to the compression bit's SCREAM. I've been "wrong" before, so that doesn't bother me much.
KR

[arouterman]

We deepen or enlarge the gullets , interrupting the air vortex, when circular saws scream. Could the screaming attribute to air vortex? But from your description, this happened at cutting, when bit was in the material, then air did seem not to be the problem???

Do you think make a cut or two cuts ( one or two line chip break) will make the scream go away, but making minimum sacrifice in finishing quality?

[arouterman]

Could be the in-balance of the bit? Causing vibration?

[gene]

Try running the bit @ 14000 and 6ips with a cut depth of .75

[ken_rychlik]

I did. Lost steps and made firewood out of the sheet.


KR

[harryball]

Look at the second post.

http://www.talkshopbot.com/forum/messages/29/40100.html

I finally wore them out. For my production cutting I stick with a brand name and I've found the geometry to be consistent as well as the noise levels.

Centurion bits are still a good value, but I use them for non-production, prototype work where I may break a bit or feeds/speeds are not tuned.

I could use some firewood, how much are you selling for? ;-)

/RB

[keithb]

Tools Screaming?? The tool is telling you it is not happy. When tools make noise, even in the corners, it is because the tool is not loaded adequately against the material being cut. The bit is experiencing an non-concentric orbit, and is trying to self feed. The noise is the vibration from the bit as it tries to spin true, but can't. The size of the wood chip being cut is way way too small. Are you making saw dust, or chips? You need to be making chips, and a certain sized chip in relation to tool diameter. The options are as follows: #1. lower RPM's. #2. Pick up feed rate. #3. Use a single flute bit, especially when feeds are slow or you have low Horsepower situations. Simply loosing one flute from a two flute bit down to a one flute will double the chip load of the tool and will transfer all the motor power down that one flute. It makes material penetration for the bit much easier. Your tool life will go way up too. There is a lot of psysical science used in building bits. Everything about the tool has purpose, and a specific range of performance. Learning how to properly load the bits will allow the user to experience the fastest possible production while getting still a good finish on the cut. The more flutes you use, the faster you need to feed to keep chip load correct, and the more power you need to drive it. With four H.P. that sets your diameter limits and your feed limits. High RPM is a Tool Killer if you don't match the tool to it's proper feed rate. More is not always better.

Thanks, Keith B.

[keithb]

One way to help dial in your chip loads, is to use a set of calipers and actually measure the thickness of your chips being cut then adjust accordingly.

Every tool manufacturer makes their cutters to perform through out a particular spectrum. The geometry of the tool must be hard set by its maker. It can not vary. If you are on one side or the other of that spectrum, you will experience nastyness, ie. noisy bit, broken bits, short tool life.

All tool manufacturers make great tools these days. There are NO bad tools. It is up to the user to find and use that particular tools range of performance spectrum. When in doubt call for tech support. Contact me if you like it's FREE here.

Your machine is a HUGE variable. It has the ability to make a great tool run crappy, or a crappy tool run pretty good. Changing tool suppliers when you have poor results is really not going to help much. You are relying on pure chance to find a slightly different performance spectrum that just happens to match your selected programs that may be mismatched to that tool.

Consider changing tool suppliers when a supplier has made important scientific advancements in tool strengths, and hardness that will equate to higher sustained feed rates and edge retention than usual. Once dialed in with a super alloy you have the world by the rear end with a down hill pull. Ah! life is good..KB.

[gene]

Hi Keith,
I liked the bits that i got from you and cant wait to get the next 3 bits in from you . Waiting to cut some with the new .375 compression bits. Hope to get them soon. Gene

[keithb]

Final Thoughts for the day: I don't mean to come off as an arrogant know it all with all my postings today. It's just that your exposure to tools and why they do, or don't do is mostly based on your trials and shared thoughts. I am offering a tool makers perspective for your consideration and review. After reading a number of postings I think you fellas have a collective excellence in trouble shooting. Just thought I would add some more input to my already long winded postings if I may? Down cut bits run quieter because the shank end of the cutting edge enters the material first where leverage force is lowest and tool strength is at maximum. Up cut are opposite where the tools end corners penetrate first where leverage at that point is the greatest relative to cutting length, and tool rigidity at it's weakest point. More likely to squeal. Down cut also-assist vacuum by pushing downwards against your material towards the table creating further rigidity and vibration dampening. Mortise compression bits do this as well. Compression bits usually cut faster than a regular spiral bit of same flute number because the flutes are split where only part of the cutting edge is in play at any one time. It is essentially acting more like a single flute bit. It is freeing up H.P. and transferring the new total H.P. directly to the cutting edge. It is also relocating the lever force further towards the shank area. The short up cut section does not have time due to it's shortness to create much of a lever load. That is why mortise versions can work better than the standard length end sections do. Compression bits are basically a down cut tool. They are the most universal tool on the planet. Lastly-Climb cutting: First off a regular cut has a bit orbit similar to a tightly wound spring with coils pressed tightly together. Maximum tool contact with the material. On a climb cut, the bit orbits in the same direction as it's feed direction. The orbit is now like the spring streached out. There is less tool contact with the material at the same feed and rpm setting. It's like an ice skater running across the ice on tip toes rather than on the flat blades surface. Less ice contact on tip toes. Need a little slower feed or a little more RPM for climb cutting. Most likely slower feed if your bit is already noisy. Higher RPM contributes seriously to noise levels. The bits should cut rather quietly. Your tools should be throwing a rooster tail of chips, not saw dust, and making noise. I hope this helps you guys a bit? No pun intended.
Thanks a lot. KB.

[keithb]

Thanks Gene..KB.

[jay_d_wyant]

I have found the Whiteside 1+1 .25" compressions to be the best single bit for cutting cabinet parts. Extremely quiet, great edge quality, no "chirping" when drilling holes, and I have cut 30+ sheets with very little noticeable change in cut quality. These have become the bit that I use almost exclusively when I need a .25 straight cutter(works well in melamine and hardwood too).

I have used a lot of Centurion bits, and still do use some of there others, but I no longer use the .25 compressions.

Anyone who hasn't, should give the 1+1 a try.

I get mine at http://www.woodworkersworld.net

[harryball]

I thought I'd report. I got a few of the extended life bits from Keith, here is my report.

The bits arrived very well packaged and professionally shipped.


3436

The bits themselves looked very clean and have the part information laser etched into them.


3437

3438

For cutting I did not tune my original file at all (but will need too). It was running at 14k and 6 ips cutting 1/2" ply in a single pass. The chip load may be a little high but you can clearly see chips not dust coming out. The sounds was different but no where the intensity of my "screamers".


3439

Youtube video
http://www.youtube.com/watch?v=h_6qxTSLHgs

The cut quality was better than the screamers which is all I'm comparing to here. The first photo is an edge from the screamer bit. What you see is in fact that rough. The second photo has similar tooling marks but not to the excess. All of the compression bits I've used cutting at these speeds leaves some kind of pattern, cut quality here is not my primary concern but painting the end cuts from the screamer bits was a pain.


3440



3441

I also have a 3/8" compression bit I've not chucked up yet. As I keep cutting and tuning I'll post more information. >>>So far<<< I'm pleased with the cost, bit quality and cutting results.

/RB

[keithb]

Hi Robert, I like your video. By the sound of the bit you can pick up your feed yet or reduce your RPM's. Our bit is making too much noise. It should cut fairly quietly. When chips are being produced you are on the right track. Thanks, Keith B.

[harryball]

I've finally gotten around to posting this from a pile of notes on my desk...

I am cutting 1/2" ACX plywood. Results will vary by material type and even batches. All bits are 2 flute.

Centurion 1/4" Mortise compression.
I found the screaming would go away in a certain band of chipload. It was reasonably quiet around 10k RPM and 5 ips or a chip load of about .015. Keeping the chipload the same and going to 12k at 6 ips yielded similar results.

At 12k and 5 ips (.0125) the noise picked up considerably and at 14k (.01) I was ready to leave the room. On the other side of things, 8k and 5 ips (.018) sound began to increase. At 8k and 6 ips (.022) the bit survived but the sound was loud though a different pitch.

In the range of .012 to .018 chipload the bit sound is reasonable with the outside of that range the loudest. The cut quality is very acceptable. The chipload range causes noise increases during ramping.


Centurion 1/4" standard compression bit.
Yep, I discovered that's what my previous "screaming bits" were when I dug them out of the dead carbide box. I found this bit in my material was not quiet enough to be acceptable at any chipload. Changing the chipload changed the pitch, but the sound was always too loud. I suspect the relatively thin 1/2" material with the full compression may have contributed to the problem. I was going to attempt a cut in 3/4" material but this bit did not survive the .02x chipload test in 1/2" material.

I suspect this bit would never be quiet in my application. Beyond that I had no problem with the cut quality around .015 chipload though it was not as good as the mortise compression.


Keith's 1/4" Mortise compression bit.
As Keith suggested I did vary the chipload and found similar results with noise changes. The range that was slightly wider. 0.010 to .0190 with the middle around .016 being the least noisy. This bit also did not survive the .02x chipload test.

Cut quality was very acceptable in the middle of the range.


Onsrud 1/4" Mortise compression bit.
I ran the same test and found the chipload range to be .009 to .019. As with the Centurion 1/4" Mortise compression it survived the .02x chipload. The noise would challenge the other bits when reaching the extremes of the chipload listed. I found the cut quality very good close to .015 and degrading at the 2 ends of the range. At the .022 range it was more of a chewed look and at the .009 range it was more stringy to burned at the corners.



The moral of the story is "CHIPLOAD" if you are not happy change it.
The larger range in the Onsrud bit is probably just the geometry of that bit in that material reaching "zen" and I got use to it. A different model bit from the same company would likely change that entire range.



I'll note I spoke to Fred with Centurion and he assured me they have taken measures to insure that the same bit ordered will have the same geometry every time. I have nothing negative to say about the bits or customer service.

I have not spoken to Keith recently but I have nothing negative to say about their bits or the customer service.

I did speak with an Onsrud rep as well. They have been helpful and do publish a chipload chart to assist with targeting the right chipload for each bit. Again, I have nothing negative to say about them.


/RB

[Gary Campbell]

Robert...
Thanks for taking the time to test this and post your test results. I echo your results.... CHIPLOAD!!!

And in case someone might still be wondering.... this is "chips" :D

[sailfl]

Gary

What bit did you use to get those chips?

[Gary Campbell]

Nils...
That was Sapele cut with a single O flute @12Krpm 1ips. (PRS std) As they went into production of the louver doors, a compression bit was used to achieve better edge quality. Pics are courtesy Steve Varrow, Jalousie, LTD Nevis, W.I.