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End mill problem
http://luthiersforum.com/forum/viewtopic.php?f=10101&t=28929		 Page 1 of 1
Author:  JSDenvir [ Mon Sep 06, 2010 10:17 am ]
Post subject:  End mill problem
So the 1/32' end mill I got from LMI snapped off the first time I used it, and I don't know that I want to try again at $15 per.

That'll teach me to try to route a purfling ring in mahogany.

Any thought on other options/sources?

Thanks in advance

Steve
Author:  JohnAbercrombie [ Mon Sep 06, 2010 10:26 am ]
Post subject:  Re: End mill problem
What depth of cut were you pushing, and how fast were you spinning the bit?
Author:  JSDenvir [ Mon Sep 06, 2010 10:40 am ]
Post subject:  Re: End mill problem
Hi John, depth was 3/32" and speed was "too fast", I'm thinking :-)

Steve
Author:  tim88 [ Mon Sep 06, 2010 10:55 am ]
Post subject:  Re: End mill problem
Remember, slow and steady, let the bit do the work. It's better to start shallow and make a couple or three passes, instead of trying to cut the channel all at once. I don't care where you get the bit from, if you push it, it WILL break. Really you should plan on it breaking and always try to keep a spare. beehive
Author:  bluescreek [ Mon Sep 06, 2010 11:27 am ]
Post subject:  Re: End mill problem
Stew mac bits are too expensive. I do not use down cut bits, as a machinist /tool maker they will bind up a non cleared hole. These bits at this link are about 1/3rd stew macs price and will do a very good job. They are designed for high speed cutting. I use them at 70,000 rpm.
http://bqtool.com/cart/index.php check out square end mills , call them , they also carry a .020 bit.
Author:  Jim Watts [ Mon Sep 06, 2010 11:46 am ]
Post subject:  Re: End mill problem
3/32 is too much depth of cut for a 1/32 cutter in my opinion. It it might not even have that much flute length. You're rpm is fine, faster would be even better like john does, you can feed it to fast though, this is probably the actual problem.
Try making you cuts in a few passes instead of one. It'll go better.
Author:  jmpbuffalo [ Mon Sep 06, 2010 11:56 am ]
Post subject:  Re: End mill problem
Runout in your router (or dremel, or whatever rotary tool you're using) will also cause fine bits to snap.

Joe
Author:  Jeffrey L. Suits [ Mon Sep 06, 2010 12:02 pm ]
Post subject:  Re: End mill problem
JSDenvir wrote:
Hi John, depth was 3/32" and speed was "too fast", I'm thinking :-)

Steve


Way way way too deep a cut, for a 1/32" bit!
Author:  Howard Klepper [ Mon Sep 06, 2010 12:58 pm ]
Post subject:  Re: End mill problem
Right, way too deep a cut. The usual rule of thumb is not to cut deeper than the bit radius, so you were six times that. In practice you can go deeper if you keep the cut tightly controlled (i.e., you have a jig controlling the router motion and go slow). And get upcut spiral end mills from one of the industrial supply places like MSC for half the price; less when they are on sale which is often. Downcut bits are not intended for slotting. They pack the swarf down where it can't escape. And don't get a longer cutting length than you need; it just weakens the bit.
Author:  JSDenvir [ Mon Sep 06, 2010 1:58 pm ]
Post subject:  Re: End mill problem
Thanks everyone. Geez, at this pace, I'm going to run out of mistakes to make...nah, probably not :-)

Steve
Author:  weslewis [ Mon Sep 06, 2010 10:35 pm ]
Post subject:  Re: End mill problem
look on amazon.com ..I found end mill bits for 6.90 a piece for 1/32 and 5.40 for 1/16 bits..work great and very high quality!!
Author:  Mike OMelia [ Tue Sep 07, 2010 8:57 pm ]
Post subject:  End mill problem
I buy my skinny endmills on eBay at $10-20 per 10 pak. I've used mine a bunch in one year and have broken just one. Hope u have the Wells/Karol jig! The previous depth advice is excellent. Btw, these are mostly 1/8" shanks. I found a very good adaptor from Lee Valley, IIRC.
Author:  TimAllen [ Tue Sep 07, 2010 10:25 pm ]
Post subject:  Re: End mill problem
I would like to know more about how to buy end mills for working in wood. There's a big selection, and I'm at sea about what's the right type. :?:

Is this the type you recommend from CET Direct, Todd?
14003 - 1/16"4FL CARBIDE EM $4.98

And Mike, what do you buy on eBay? The refurbished ones? How many flutes?

Any other suggestions from either of you or other experienced users?

Thanks very much
Author:  Bob Garrish [ Tue Sep 07, 2010 11:35 pm ]
Post subject:  Re: End mill problem
In general you shouldn't use 4-flute cutters in wood, they have no chip clearance and so you're much more likely to either burn the work or break the cutter depending on if it's too big to break or not :)
Author:  Mike OMelia [ Tue Sep 07, 2010 11:37 pm ]
Post subject:  End mill problem
I dunno! I believe they are 2 flutes. Work great. Guess it makes sense they might be refurbished. Given our duty cycle, should not be an issue.
Author:  Stuart Gort [ Wed Sep 08, 2010 12:58 am ]
Post subject:  Re: End mill problem
Bob Garrish wrote:
In general you shouldn't use 4-flute cutters in wood, they have no chip clearance and so you're much more likely to either burn the work or break the cutter depending on if it's too big to break or not :)


Well yeah....at 20,000 rpm that's true but I've used the same .03", four flute cutter for the last two years and have cut a mile of inlay with it using the following numbers.

Cutting a groove in bloodwood. First cut .005" depth...second cut .01" deeper.....all subsequent depth cuts adding .015"......rpm 4000.....10 ipm on the first and second depths....15 ipm for the rest.

The cutting bit is a standard carbide bit used for milling aluminum.

http://www.mcmaster.com/#four-flute-end-mills/=8r3qzj
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