Tool Break
December 9th, 2009Get Some Swarf Between Your Toes
I’m very excited because I’m going to get to use my fly cutter today.
As reported yesterday, I am trying to mate my cross slide table to the table on my drill press. The best method I’ve come up with involves making two aluminum plates, screwing the cross slide table to the plates, and bolting the whole mess to the drill press table. But in order to do that, I had to make aluminum plates.
I had a 3 1/2″ x 3 1/2″ bar of aluminum. I cut a 6″ piece off the end, and then I put it in the band saw sideways and cut two 5/8″ slices out of it. Now I have to clean them up.
Last night I got started. I stuck a 3″ cobalt fly cutter in the mill and ran one of the plates through it. At first, all was swell, but on later passes, the swarf got sandy and the finish got gritty. I tried going to higher RPMs and slowing the feed, but that didn’t help.
It’s hard to know what’s going on. I’ve determined that the right speed is about 400 RPM (hope I’m right), and I’m going to give it another shot today.
I can see how various things would cause this problem. A fast feed would give you big spaces between the cuts, adding up to ridges and points on the finished product. A shallow cut would result in narrower grooves which would not blend into each other well, giving the same problem. A slow tool speed would make for bigger spaces between cuts, just like a fast feed.
I thought maybe a piece of aluminum had welded itself to the tool, but I didn’t check. I’ll take a look. I doubt that’s the problem. I buried the work in WD40. And I also had finish problems with a piece of steel.
In any case, it’s wonderful to have a little time to make the metal fly.
I could use an end mill, which would be very easy. I can’t help myself. I love watching a fly cutter.
I’ll say this. The mill appears to be in excellent tram. The finish on the first pass was beautiful.
It’s surprising how challenging this job is. The two tables relate to each other in ways that make a simple solution impossible.
The slots in the cross slide table will take 5/8″ bolts, but I can’t believe that kind of hardware is needed. I assume they make big slots in case the tables are used for milling, which exerts lots of lateral force. Surely a couple of 3/8″ machine screws in aluminum will suffice to hold the table down and keep it from spinning. I can’t imagine a small 1-2 HP motor breaking screws this big.
Next, I need to may covers for my mill table. I keep piling junk on it, and I already have one ding. One is too many.
December 9th, 2009 at 12:00 PM
WD-40 is NOT a cutting fluid. It may work in some cases, but that’s the luck of the draw. Buy cutting fluids for the material you’re cutting. The fluid for steel is different than the fluid for aluminum.
You’ll be surprised at the difference it makes.
December 9th, 2009 at 12:26 PM
The reason I use WD40 on aluminum is that Darrell Holland recommends it in his milling videos. Bad choice?
December 9th, 2009 at 12:54 PM
WD-40=useable for steel, good waxy base.
For aluminum you want to go to with faster speeds and feeds.
400rpm is ok for mild plate steel milling.
Try 1000-1200 rpm and adjust your feed accordingly.
Aluminum is funny stuff to mill, too slow and you get a poor surface, too fast and it starts getting gummy and you will end up with built up edges on your tooling.
If you have a machining supply store, see if you can get a gallon jug of Mobiloil cutting fluid.
About 4 ounces to a gallon of water prioduces an excellent cutting fluid for aluminum.
Since you are going all out with Mill and lathe, may I suggest you obtain a current copy of “The Machinist’s Handbook”
It will become your second bible. HTH
December 9th, 2009 at 1:01 PM
I use aluminum where-ever possible (although I stay away from the harder to machine alloys such as 5052).
.
It’s almost effortless.
.
Surprisingly, I also mill a lot of Delrin (which is self-lubricating)…but you probably don’t have a use for it.
December 9th, 2009 at 3:00 PM
And here I was getting excited about using fly *paper* today.
December 9th, 2009 at 4:52 PM
WD-40 is excellent for milling aluminum. Did your cutter get dull?
Look at a feed/speed chart to make sure you’re running the fly cutter at the correct RPM.
December 9th, 2009 at 6:35 PM
I find WD-40 (and I know others who do also) to be excellent for aluminum. I agree with Milo about speed and feeds, but I suspect something is wrong with your cutting bit. Perhaps it’s duller than you think or is set wrong so there is no relief on the heel. Post a picture?
“finish got gritty” seems to indicate “tearing” of the metal, not a speeds issue.
December 9th, 2009 at 8:49 PM
You’re right about the metal tearing. The odd thing is, this seems to be an on-and-off issue. Maybe the answer is to put the tool on the grinder, but it looks as sharp as ever.
.
I looked up the speed, and I came up with about 400 RPM. On the other hand, I got very good results at 250, and a very knowledgeable machinist at Chaski says go as fast as possible.
December 9th, 2009 at 11:24 PM
WD-40 is perfumed kerosene. Kerosene is excellent for machining aluminum. Your toolbit can be razor sharp and still tear aluminum if it is the wrong shape.
Machinery’s Handbook.
Gerry N.
December 10th, 2009 at 1:04 AM
WD-40 works fine with Aluminum. Is it as good as flood coolant? No. Is it acceptable, cheap, and easy to find? Yes.
400RPM is low – try Milo’s suggestion. I used to run a 4″ face mill at 3000RPM, but that was in a big VMC with Flood coolant using carbide inserts
Pictures are a big help, so please post them – both of the cutter and the part
Don’t waste your money on the current edition – most of the updates are for CNC and exotic processes – any of the last 5 editions is fine, and can be had much cheaper on Ebay.
December 10th, 2009 at 9:01 AM
As for the bolts – maybe they’re big so that they’ll resist breaking when someone tries to take them out with a 10 foot breaking bar and a 5lb. sledge
December 10th, 2009 at 9:49 AM
“Don’t waste your money on the current edition”
.
Too late. I got it months ago, before I knew the CNC stuff was a problem. But thanks. The tip will help other people.
.
I think instead of being industrious and posting photos, I’ll just regrind the tool. My guess is that I need a little more relief behind the cutting edge.
.
The tearing problem is not a big deal. The parts are already sized, and I can remove the burrs with an end mill.
December 10th, 2009 at 10:53 AM
When I was young, my father worked a second job as a machinist for a family friend’s business. Later on I worked there for a summer. (Ever see those blue rubber stoppers that catch the vacuum cylinders at some Wachovia branches? I made those.)
Anyway… I recall one year we added large pieces of swarf to our Christmas tree as decorations. They resembled icicles.
December 11th, 2009 at 2:33 PM
My fodder when I was a kid used to bring home magniesium shavings from Boeing I think. We used to burn those all over the place. They were great and probably not safe for children!!!