This machining thing is getting expensive. I broke End Mill number 2 and 3 of the four I bought for my combo mill\lathe today. I can understand the first one going last weekend as it was a 1/8" end mill. Then today I broke a 3/8" end mill. Was using it to cut through a chunk of aluminum when the drill chuck (MT2 taper) or something like that came loose on the taper when using the power feed from the lathe lead screw. The end mill went crooked and snap. Guess I need to get a proper End Mill holder and make sure it is snug more often. I ended up using a skill saw with 40 tooth carbide blade to cut through the aluminum, it cut like butter. Then I spent about 3 hours cutting fins into the aluminum heat sink I am building. I was using a 1/4 End mill and manually feeding it so it did not break. I then was cleaning up the groves with a brand new 3/16 Ball End mill and snap. Guess I was so used to the pressure of the 1/4 inch. Oh well, when I factor in the cost of end mills, this heat sink is starting to get expensive.
You can't run end mills in jacobs chucks. It doesn't work.
Jim
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I recently dug out the inside of a chunk of aluminum. It ended up lots easier to drill a series of holes with a plain old twist drill to remove the bulk material, then used the mill to clean up and make the edges nice. The tool and machine were both much happier that way.
What Jim said. Normal drill chucks DO NOT grip hardened objects well enough to be trusted.
The chuck coming out of the spindle is but another of the problems related to that type of holding system.
If you have no alternatives but to cut with your chuck, do these things:
Wipe each off with a dry cloth, until there is NO oil present, nor any lint or dust, the arbor and the socket in the spindle.
Using a block of wood against the table, or what ever you have below your spindle, set the chuck by bringing down the spindle hard against the wood block. Don't break anything, just tap it sharply a few times to insure it's well seated.
With the end mill in the chuck, tighten each of the holes repetitively. Each one tilts the scroll slightly differently and tightens the chuck ever so slightly better. Go around the chuck a couple times, using each hole alternately.
Try to not take full width cuts with the finish size end mill. Your rough cuts with the saw were a great idea. You are far better off to finish a
1/4" wide slot with a 3/16" end mill than you are using a 1/4" end mill. By using an undersized end mill in a roughed opening, you can cut one side at a time, preventing any climb milling. Climb milling is the most desirable way to take finish cuts, but not on a weak setup. It encourages problems, including breakage, when the end mill pulls the table along. You can always go back over a cut, climb milling, to clean it up after conventional milling. That usually works fine.
Make sure you lubricate the aluminum well while cutting. Use kerosene, or many guys recommend WD-40. I haven't used it, but it appears to have a solvent base with dissolved paraffin wax in it. It's bound to be good for aluminum. You can brush apply the lubricant, or use a spray dispenser. Brush is generally a little cleaner than spray, for obvious reasons.
Run your cutter as fast as possible. When cutting aluminum with such a small cutter, it's nearly impossible to over speed the cutter, and too slow is bad, really bad, where it comes to breakage. Very fast tip speed discourages grabbing and yields a much better finish, plus will accommodate higher feed rates.
Good luck. Don't give up, you'll get on to it. It requires that you become familiar with the characteristics of cutting tools, and your personal machine. You'll discover things that work and you'll have better luck in the future. My hat's off to you for trying.
It's not just the lack of grip. It's that the chuck assembly makes the tool's distance from the spindle way too long and flexible, and the tool will start to pull sideways in the slot and will end up taking too big a bite and breaking itself. A set of collets, rather than costing extra, will save much money. I think that the small combination mill/lathe is already too flexible, and anything that adds flex is going to make things worse. I once ran a cheap mill/drill machine, and it had the same problem. Not until we got a decent knee mill did we get good life out of cutters. The same went for lathes; I put a dial indicator at various places on the frame of a 10" Taiwanese lathe and got some astounding readings when cutting anything other than really small, light stuff. Fixed that with a 6000 lb Chinese 14" machine. Not much flex there.
My 2 cents worth: Are you using a 4 flute end mill? If so, you may have a chip interference problem in addition to the other problems that have already been mentioned. I'd recommend 2 flute end mills. If I were you, I would take your own suggestion to "get a proper end mill holder" ASAP! You already have the investment in the machine. Try to get a collet adapter and a set of basic collets in the range of your machine. If not, you can get individual Weldon tool holders for the shanks that you use most often.
Pete Stanaitis
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David De Vu> This machining thing is getting expensive. I broke End Mill number 2
"Appears"? WD-40 is chiefly a light fraction petroleum distillate (one MSDS names it as Stoddard solvent) like kerosene but lighter, plus that coconutty perfume. No waxes, a film of it evaporates at room temp over a vew days without any residue (thus, while it lubricates like kerosene, it doesn't last and for that is not sold as a "lubricant"). So it works fine for cutting aluminum, and smells great doing it, but is expensive compared to kerosene.
I keep three 1-quart Sure-Shot sprayers in my shop: naphtha, WD-40, and K-1 kerosene. The first and last can't be had at all in a spray can. WD-40 is cheaper in the loose gallon can, and their spray cans often malfunction.
Did the chuck come loose from the adapter or did the adapter come loose from the mill spindle? If the former, clean both the chuck and adapter tapers, assemble and give rap with a soft face hammer. If the later, is your mill spindle hollow to take a draw bar? Were you using it? A draw bar is a threaded rod that screws into the end of the Morse taper and has a nut and washer that is tightened down on the top of the mill spindle. There's no way that arrangement will come loose.
You can also break end mills by taking too heavy a cut. Start light and listen. Gradually get more daring as you learn. You'll still break a few (don't ask!) but far fewer than if you start out by going at it too heavy.
I said that due to a recent experience in which I had coated my little Wells A-7 saw with WD-40 to retard rusting. The saw was being housed in a less than desirable environment and it was all I had at hand. Needless to say, due to it's ability to evaporate quickly, it took a few applications to keep it from rusting. Each time it got sprayed it left a tiny amount of something behind, which had the appearance of paraffin. Not much of it, mind you, but enough that it required a good wiping down when the saw was finally moved to better quarters. I'm not convinced WD-40 is just a solvent. We both agree on the smell. Quite pleasant compared to kerosene.
Do NOT, repeat NOT rely on wd40 to prevent rust. It will have the exact opposite effect. The solvent will rinse off any oil that is present on the surface and you will be sorely disapointed at the results.
Purchase a small quantity of LPS-3 from MSC and you will be much happier - and your machines will remain, blissfully, rust-free.
I suspect your order to MSC might cross mine, for some dressing sticks.
Jim
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We use a Sure-Shot for Brake and Parts Cleaner, a real handy solvent that cuts grease real quick and dries fast and is best n-not used in con-conf-confined spaaaaaaces....zzzzz
I think they're gonna have as much success as the original poster with that. Which is to say, um, not much.
Jim
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I strongly agree. But there *will* be a waxy film on the equipment that will have to be cleaned off before you use it. That film is why LPS-3 works so well to prevent rust, ie it blocks oxygen and moisture from contacting the metal.
Stoddard solvent Mineral oil, petroleum based LPG Gas (propellant)
NOTE: NO 'water' as some continually suggest.
When the light solvent evaporates, a film of oil is left behind. This DOES result in a gummy film deposit with time. It has some ability to resist rust, but is not especially good at it.
Also note that applications of WD-40 can get REALLY troublesome at low temperatures. The residual oil apparently thickens up, or turns to a wax. A friend shot his car doors full of it, and couldn't get anything (latches or windows) to work right again until spring! The windows set up near solid.
Should the circumstances arise again, use CRC-3-36. While building the new house, I did not have room in a protected environment for everything and figured my anvil could best stand the weather. I sprayed it with the CRC stuff and let it sit out in the wind, rain and snow all winter. Any time I used it for hot work, I wiped off the top and gave it a light spray of CRC. It survives the winter with nary a rust spot anywhere. BTW, Mitutoyo recommend it for cleaning and lubricating their digital calipers. It's also pretty good penetrating oil.
This will be controversial but I use it on my Smithy for lubing ways, etc. I have tried heavier and found things don't slide any easier but the swarf sticks much "better" with heavier lubes.
The CRC stuff is available in aerosol cans but I bought a gallon of it and a Shure Shot sprayer for the cost of half a dozen spray cans. One fills the Shure-Shot and pressurises it with shop air.
Thanks for the great information. I was going through some of the links to find info on speeds for cutting different materials but could not find the info (impatient, wanted to get cutting). I was using 4 flute end mills (though I broke a 2 flute ball end mill as well) I was only using 400 RPM, stepped it up to 600 rpm and it seems better. Sound like I can go much faster. I was also not using any cutting oil and was inpressed with its ability so should be even better. I am working out of a 10'x10' insulated shed so will stick to WD40...thanks. The end mill does not appear to slip in the drill chuck, but I think I can see the chuck flexing. It was the drill chuck that slipped off the taper. Tapered unit appears fixed to the mill with a long bolt that goes up to the top of the spindle. Pay day this week so will look for the mill holder (and a few new end mills eh!. Dave D.
No you can't, unless the Jacobs chuck runs as true as the proper holder. Any eccentricity will force one or more teeth to carry the brunt of the load... thereby dulling more quickly and causing the results described by the original poster. This practice may be applicable to blacksmithing, but cannot be justified (1) in precision machining or (2) by those wishing to maximize tool life.
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