Several questions all about finish quality.

[Chris64]

I've been doing some machining on aluminum and it's going good but the finish still isn't what I want. I'm hoping to be able to go straight from mill to finish product (or anodizing etc.). Is this realistically possible?

I'm not really surprised my finish isn't perfect...here's why;
I got a good deal on sharp mill ends...the only problem is that they're all 1/2 inch, 4 flute and 4-5 inches long. They seem sharp but when I use them they seem like they chatter (not sure if this is the right term). I'm guessing it's because of their length...probably not the right tool for the job. So even though they're sharp and new they leave a bad finish.

I have a few old smaller mill ends (1/4"-3/16" and about an inch of cutting surface). These cut great and sound really nice (no chatter). I did a couple finishing cuts with a depth of around .001. While this did look good...you good still clearly see the swirls from the cutter (although it was totally flat). I tried polishing it with some Mothers wheel polish and it went really shiny, but the swirls are still there.

Is the culprit for this more likely the cutter or the fact that I didn't use any coolant (or air for chip clean out)?

And, speaking of coolant, I have a Bijur Mist system that has never really worked right since I've had it...I looked into it and the oil looked like it was all coagulated (spelling?). In my efforts to try and fix it I must have screwed something up because the guage blew a gasket and began screaming as air shot out of it...that really woke me up. Should I bother trying to fix this system or get a flood system? Even though it's just a standard knee mill, I was thinking about getting a couple plexi plates and sticking magnetic bases on them so that I could set them up to deflect the coolant with each project...Does this seem possible or is it just too messy? Is it possible to use coolant that won't get stagnant from sitting around?

[Chris64]

BTW, I just took the whole spraymist system apart. I think the gasket that blew may have been one connecting the tank to the actuator. The whole thing needs a major rebuild though. New filters, gaskets, oil and a serious cleaning. And none of these parts seem like off the shelf parts.

[contractdesign]

I would suggest using a 2 flute hi-spiral high speed steel endmill. 1/2 inch is fine, but 1" length would be better. Coolant is a must, I use a spray mist at about 70 psi and a little extra mist at a fairly high speed. If you want a really good finish take a .010 final finish cut. I get lousy finish cuts with 4 flute end mills, It gets even worse with steel.

[Chris64]

OK...I'll get my hands on a 1/2 inch 2 flute endmill today. My spray mist is going to be out of commission for a while though it seems.

IF I were to get a flood system going...I'm worried about the whole "science project" part of it that I keep reading. Can anyone comment on whether this will prevent the stink or not: http://www.martinchemicals.com/trueblue.htm?

[HuFlungDung]

Chris,
My Wells Index also had one of those Bijur mist units on it. I also had problems with the bacterial growth in the coolant, and so on. It was quite a lot of work to maintain their system. It would spray all right when cleaned up, but if it sat for a week or so, it would get a skin growing, which could then gum up the works.

I went with a small submersible pump for flood cooling when milling and drilling steel with HSS. Just ran the whole system out of a plastic 5 gallon bucket, with a return hose from the table to the pail. This simplified cleanup issues somewhat. Flood coolant is quite messy on an open machine, though.

Milling steel with carbide is probably better done dry. Roughing operations using insert cutters can give a pretty good finish right off the tool, but size control is a bit more difficult with inserted tools, in a quill type machine spindle. I used 3/8 up to 3/4" Iscar insert endmills in my Wells with adequate results. The small insert endmills only have one insert, so this can make for slow going, although the feedrate can be fairly aggressive. Finish cuts with solid carbide endmills are preferable for good side wall appearance, but the results produced by the end of the tool flutes was often hit or miss, quality wise. If you never plunge with the tool, and never recut old chips, and thus preserve the extreme corners of the flutes, then you stand a good chance of getting a good finish on the bottom of a pocket.

I went with a Trico air-lube unit for milling aluminum. For the material removal rate of a small machine, I think the Trico unit is entirely adequate for aluminum, and finishing steel, but it does require an air compressor running quite often to provide even its relatively modest air requirements. It is not noisy, does lubricate the tool nicely to assist in the finish cut, and get the chips out of the cut zone.

The finish produced by the end of an endmill depends on the quality of the grind. I do not think any tool will cut without leaving the swirly finish, but an accurately ground tool should produce a finish that is not snaggy to the fingernail. Some guys set up a brush operation to refinish the surface to a uniform appearance. Some kind of light duty sandblast or tumbling operation might be the answer to complex surface finishing. Those all tend to remove the shine, but at least everything looks about the same.

Iscar makes special inserts for cutting aluminum, with a wiper edge and polished face. The finish produced by the end of the insert tool is superb. It needs lots of rpm though, so probably the 3/4" tool is near the minimum you can use on that machine, running full speed, and still get the good finish.

[bennett71]

two flute is definatly the way to go or you could also try a fly cutter

[big_mak]

If you are allowed Corner Rads, This may help improve your surface on the bottom of the part. The corners also tend to last longer.