Screaming bits revisited...

[harryball]

I saw the cheap bit post and thought I'd share. You do get what you pay for...

I purchased three 1/4" 2 flute compression bits early last October for the MakerFaire demo. When I tried to use them everyone looked around because the bits were screaming like a banshee. Fortunately I had a rather worn major mfg bit that did the job.

I'd forgotten about the 3 bits until a few weeks ago when I decided to give them a try again. All 3 were screamers. I took one of them and varied the chip load dramatically. Never got a quiet cut. When I went to change the bit immediatley after a cut... it was HOT. I checked, 160 degrees hot. I also noticed the cut edges were burnished looking in appearance.

What was going on? I tried one of the other three repeating the chipload range... the temp was always well above 100 degrees. I reloaded my pricey cutter and gave it a shot... never over 90 degrees even with the small chipload.

I can only speculate the problem was the geometry. Something about it was causing rubbing on the wood. Like using a bit designed for plastic for wood etc...

I tossed the 3 bits ($60+ ouch). Thinking about it... it wasn't worth it to save a few bucks. The other compression cutter may be 2 or 3 times the price but they work well and last 2 to 3 times longer... at least in my experience.

/RB

[don]

/RB,

The rake angle are to low on those cheaper tools. You can have this increased when they are reground.
It may have cost $60 for those 3, I'm sure you could have had those reground for another $20 for the 3 and would have cut like the major mfg tooling.
That is if the regrind shop has that capability.
The guys with the cnc grinders do have that capability.
I know its easier to order a new tool, I've done it myself.
tool geometry (http://www.endmill.com/images/techdat4.gif)

[daski]

If you had used a 1/4" compression from Centurion, you'd have a great cut and your hearing at only $20 a bit. We use them exclusively for our cutting and are very happy.

[harryball]

I didn't care to try and revive them, I just considered it a lesson learned.

Dave, I won't mention the brand name on the forum... but I will shoot you an email.

/RB

[ken_rychlik]

I am running some that I got from sommerfeld tools. They are down spiral 1/4 inch and they were 10.32 each with free shipping. They are quiet and cut pretty smooth.

They have normal type straight two flute for a little cheaper, but they scream. They cut ok, but I can't stand the noise.

Kenneth

[gene]

I agree with Dave. I use the same 1/4 compression from centurion and they do a very good job.

[kc10flteng]

Echo the recommendations for the Centurion bits. Buy all my bits from them plus they have custom ground a few tapered bits for inlay work. These bits are headache free and an excellent value - and go like rockstars!

[wberminio]

DIDO on Centurion bits