Trying to slot several chunks of aluminum. 1/8" wide and hoping for 1/4" deep but I'll take what I can get. Like I said, material is aluminum and the end mill I have has two flutes. (1/8" end mill) Hoping to get an RPM and feed rate. If I have to do it in two passes that's fine... but I don't have a lot of time.
Yeah, unfortunately that isn't an option. I'm seriously down to the last few hours I have available to finish this project and well... I just broke one end mill and am down to the last one so... I guess I'll just take it really slow.
use lots of lube/coolant to keep it from loading up, and something that small you can go pretty high on the rpm, between 900-1100, and I'd probably try to do it in two passes to not side load a small diameter cutter like that. Also, whichever direction you are cutting, lock down the bed in the other axis, because if your mill is old like mine there might be a bit of play in the ways and you don't want it jumping around. Good Luck, I've been there and I'll keep my fingers crossed!
If you have a Bridgeport spin that baby about 4 grand, and feed it slow - forget the lube, blow the chips away with an air gun. Make a couple passes, and only go one direction. Good luck!
The formula for RPM is: (Cutting Speed x 4) divided by diameter. The cutting speed for Aluminum is 150-200 fpm. (150 x4) / .125 = 4800 rpm Set the mill to the highest speed,and let it rip.
4k Rpm and a 2 flute cutter, never use a 4 flute on aluminum...multiple passes in the same direction and slow feed will make it a smooth cut...or give me your mill and i'll make whatever you want whenever you want, hehehe
Use Lots of WD40 it makes toxic smoke but works. General rule of thumb for endmills is depth per pas =1/2 diameter of cutter.
You have to keep the chips out of the cut or you will break the end mill. I would make 4 passes with the cutter and turn it as fast as the machine will go. Feed it very slow, take about .003 per rpm. Chip clearing can be done by blowing air on the cutter. If you start to get any buildup on the end mill you are in trouble and will have to change one of the parameters. The air will also help cool the aluminum.
I'm right around 3900 and feeding 3 or 4" per minute... I think. It's working well though. Just blasting with coolant every few inches and the chips aren't packing up or anything. Thanks everyone.
You can get a holder for small diameter metal cutting saw blades. They work well if you can get the area to be grooved exposed - and supported - for the horizontally spinning saw blade.
Kevin, to confuse the issue farther, I plunge small slots. That is instead of going full depth and milling to the other end, I plunge to full depth, lift the quill, move the table about.02-.04 then plunge again., move , plunge. With enough caffeine you can get pretty proficient, useing one hand on the quill and the other moving the table. This way you don't bend the cutter, causeing a tapered slot, and it clears the chips. When I get to the other end of the slot I put go full depth and mill back cleaning up all the lumps. I would also rough in with about a .093 or .109 cutter then finish with the .125. Kerosene is a good fluid for aluminum too, but really stinks. Two flute only in slots. Been doing it that way for ne' on to 40 years.
For the inexprienced I would suggest, A)plenty of lubrication. B)Hand feed while watching and looking for chatter. C)Blow chips away frequently. D)Moderate cutter speed (not too fast ,not too slow)
I know you are most likely done, and good show! However, for the sake of others;as C9 said, A slotting cutter is the best way to accomplish this, if the parameters allow you to get the tool in there, or, sometimes in the design process you can for-see machining problems and avoid them by a design revision.
Not to go too far afield here - not that I've ever done that - I saw on one of the machinist boards that many preferred WD-40 for machining aluminum. I've been using it ever since I read that and find that it works well. I buy it in gallon cans and apply with a new acid brush. WD-40 doesn't seem to work well in pump oilers. It penetrates so well that it leaks out everywhere.
Too slow on the rpm increases the chip load per tooth, making it more likely you will break such a small cutter.
Once't upon a time an old machinist told me that's there's a correct cutting and feed speed for everything. Kind of a simple statement, but like he pointed out I was feeding the mill too slow and the end mill had more rub than cut....
Ive watched the old timers use Kerosene as a cutting lubricant for aluminum...... even when they had cans of tool oil and brown stinky cutting oil right in front of them.
Kerosene is marvelous stuff. I understand it's the base for more than a few commercial tap & drill lubricant's. Runs the garage turbine heater. Runs in diesel pickups. Jet airplanes. One of the best uses I've found for it so far is as a penetrant for rusted together stuff. It takes some time, but badly rusted stuff can be freed. I found a complete South Bend lathe tailstock at a junkyard that had been closed for about ten years. It was pretty rusty, but I took it home anyway. Tossed the tailstock into a small bucket of fresh & clean kerosene figuring I'd leave it there for a month or two. Kinda forgot about it and it was a year before I pulled the tailstock out of the kero. One interesting bit was that much of the external rust had flaked off. It still has a patina, but not the rubbing off on your hands rust it had before. Sure enough, everything had free'd up, but it was still operating slow. A few shots of PB Blaster and sitting overnight has it operational. It could use some disassembly and wire brushing, but since it was an experiment that's as far as I'm going to go.
So check this out: I gave up later that night. Snapped the third and final end mill. So I called Phil the next day to apologize for wrecking his stuff. He says, "Aw, no big deal on the end mills... say, why didn't you just use the slotting tool?" Silence He told me where it was, (right next to the three broken end mills) gave me some set up specs and a trick or two concerning clamping the material. Set it up last night and was done with all eight slots before I could have finished one the other way. I guess that's why Phil makes his living with those machines and I don't. Thanks, Phil
All part of the learning curve. My worst one was deciding I could cut some major depth on a piece I was turning in the lathe. Figured deep and slow would do it. Sorta along the lines of what the big lathes do. The cutting bit hung up, bent the 1 1/4" solid round steel piece enough so that it popped off the live center and made a helluva loud pop when it went. After I got things shut down, I thought the lathe was probably damaged and out of line. Ran a few checks and it was ok. Lesson learned; .025 is as far as I'm gonna cut on my 12" x 36" lathe on any material. Another lesson learned and this is more important than the screw-up above. I was using the lathe cut-off tool to cut a piece of metal to length after all the turning operations were finished. The cut-off blade jammed in the somewhat deep cut, got yanked out of the tool block and hit the ceiling where it left an interesting mark. Lesson learned there was don't try to cut solid stuff all the way through with a lathe cut-off tool Cut-off tools work best on tubing or workpieces with a hole through it in the cutting off area. Trick with solid pieces is to cut to a reasonable depth, shut off the lathe and use a hacksaw to finish the cut. Leave the lathe in the chuck, set the back gears so as to lock the lathe up. Put the wayboard or other protective device under the cutting area so you don't ding the ways with the hacksaw blade if it drops through the cut area unexpectedly. There are machinist sites much like the HAMB. A little reading will usually tell you what you want to know and there are guys who will answer the most basic questions and do a little mentoring as you go along. Books will tell you a lot. Get some reference stuff and read them. Lindsay's has one book about doing machine work from a 1930's viewpoint and it's an excellent reference for most of us home machinists who are working with 1930's type machinery. At the least, you got some good experience.
The Jalopy Journal
