New 1/8" cutting bit causing serious overheating problem

[Digitalwoodshop]

Is the Software still throwing a fit when the 1/8th inch bit is not set to the CT bit length? Just curious...?

My next bit purchase I will seriously look at this..

Thanks,

AL

Still using 1.184... and happy with it... works... don't need to fix it...

[DickB]

I tried a very long bit and this short one - no issues. The firmware is the latest from Designer 2, although I used Designer 1.187 for the project.

I think the key to this application is that the bit has only two flutes and the spiral is not tight. It does a good job of ejecting most of the sawdust. I have not found a router bit like this in 3/4" cut length, but mscdirect has 2- and 3-flute 1/8" end mills in lengths up to 1" that I may give a try. I occasionally get a little burning on rounded corners such as gear teeth when cutting 1/2" or 3/4" hardwood like oak with the old Carvewright 1/8" cutting bit.

Of course the ER11 chuck is a great tool to allow the use of these other bits - a wide variety is available and the cost can be significantly less.

[DickB]

The Freud router bit is fine for 1/4" and 1/2" stock, but I've got to come up with something to cut 3/4" stock. I just ran this with the new bit, and you can see it burned all the cut edges. The old bit never burned like this.

[tierman]

Dick, I have found that if I am going to cut out a piece of 3/4" mat'l, I need to make sure that all of the sawdust is blown out of the previous cut path otherwise it is going to burn or possibly shift and even worse, break the bit. I do have dust collection but it does not get it out of the deep cut. My cuts depths are never more than .125 per path. This is why I use my CW very little to cut parts out. I have found that I can save myself time and money by making a router fixture for my router table. I know what you are cutting is quite complex but that's just my input.

[DickB]

The sawdust seems to be the issue, or at least a contributing factor. The new bit has tighter flutes and ejects little sawdust - most of it seems to get packed in behind the bit. On the third cut pass the sawdust itself also got bunt. My dust collection is also not powerful enough to suck the sawdust out - maybe Dan's dust shoe would do the job. I don't like to blow sawdust around in the machine, but as an experiment maybe I should rig up a compressed air nozzle on the spindle and see if I can blow the sawdust out to see if that makes a difference. Otherwise the bit is my focus. The Freud bit has only two flutes with more empty space and loose spiral, and comparing cuts in 1/4" material it ejected more sawdust. I am going to get some two- and three-flute end mills on order and give them a shot.

I haven't used my 3/16" cutting bit in a while, but it also has more open space and a looser spiral. I don't recall having any burning issues with it. For many projects the larger diameter is not an issue, but for clock gears and the like it is. Plus, when I'm working on projects for the Pattern Depot I prefer to stay away from the specialty bits and use only the two "standard" bits whenever possible.

I'm surprised others have not reported this problem - I can't be the only one. I'm concerned for unsuspecting customers of my clock patterns having issues and possibly starting a fire.

[Digitalwoodshop]

I know everyone is focusing on a "Bit Thing" and I even have my input above...

Do me a favor... Replace the Y Gearbox Bearings and try it again with the same setup.... I am starting to believe that a sloppy Y motion due to bad 685ZZ Bearings could be the cause of this... I know it is frustrating.... That Black Bit I had could have started a fire on me too...

AL

[DickB]

I appreciate the input, but recall that I measured bit temperatures back-to-back. The old bit (and new Freud) topped out at 130 degrees F, while the new Carvewright bit hit 180 and was still rising before I stopped the test. The bit has got to be a heavily-contributing factor.

[Rob Mulgrew]

I didn't get to read this whole thread yet but I recently bought a brand new 1/8 cutting bit from LHR and the very first project I used it on filled the whole shop with smoke and turned the bit black.
Them I tried another project and put the old bit I got on eBay for only $20 and it worked fine. I only cut 3/4 pine at a .25 pass depth so there is definitely a problem with the bits.

[DickB]

It would help if you could compare the two bits and describe any differences. I would like to know more about the eBay bit.

If I am measuring and calculating correctly, my old bit has a helix angle of about 20 degrees while my new bits that are giving me trouble are about 30. It seems that 30 is quite common in the industry. I checked with a couple of suppliers and could find bits of 30, 40, and more, but nothing less than 30 in 1/8" diameter and 3/4" or 1" length of cut. I was able to find 30 degree bits with only two flutes, which I am going to try. The Freud bit has only two flutes (I haven't measured it's helix angle).

[DickB]

New 2-flute bits arrived today. Same project, same machine, same wood - in fact, the adjacent piece of the same board! - no burning. (I did have a depth of cut issue unrelated to the quality of cut which I have solved). This bit ejects considerably more sawdust from the cut path. In the bits photo is my old bit at left, new Carvewright bit, and Kennametal 2-flute bit at right. Most of the discoloration on the new Carvewright bit came from running this same project and board. Notice how bright and shiney the 2-flute is after the same project run.

I also measured the 2-flute while machining the same gear as before, and this bit ran coolest of any - one spike at 121 degrees F but typically 95-105 degrees.