milling aluminum poor results 6x26 4 flute Tin coat

[VegasF6]

Was practicing with the 6x26 HF mill I purchased. I had some aluminum angle, probably 6061 in a vise and a 5/8 4 flute tin coat cheap end mill in a collet.
Consulted my feed chart and I started at full speed for the machine, 2885 RPMs. Was very unhappy with those results so I cut it in half to 1425 RPMs (or near there forget exactly) and I did have better results, but still not what i wanted.
Rather than cutting, the end mill is melting and pushing the aluminum out of the way, even coating up the end mill some and leaving a heck of a trail behind me.
For cutting fluid I was just using a little WD-40.

So, I am about to order a couple aluminum specific 2 flute cobalt end mills from Enco, but before I do I would like some advice on what the problem, or problems may be.

Spindle speed? Feed rate? (was pretty much feeding as fast as I could turn those handles, then tried slower for a finish pass) End mill choice? Do I need to use oil/kerosene/cutting fluid?

Here is the mill I have, but this one is converted to CNC and he is just cutting the hell out of aluminum in this video:
http://www.youtube.com/watch?v=eUcxRgJgikA

 

[gadget_lover]

That mill should be able to do a good job on that.

My first thought is that you have it running in reverse. That would explain the symptoms. Watch it as it spins down to check that. Chances are the cutter is toasted. If it's dulled, you do NOT want to try using it fir any agressive cuts.

My mill is similar to yours. They work really well.

Daniel

 

[precisionworks]

you have it running in reverse.

+1

Aluminum should cut like butter, and more rpm is better than less. Most "standard" tooling will cut aluminum, although optimized tooling does a better job - this article has good info:

http://www.moldmakingtechnology.com/articles/030702.html

 

[KC2IXE]

The other thin "cheap end mill" - Just DON'T - learned that the hard way when I was starting out. Bought some of those cheap sets that ENCO et al sells - they are TiN coated turds - just don't buy them - spend the money for a couple of decent end mills

 

[VegasF6]

My first thought is that you have it running in reverse. That would explain the symptoms.

I may have exagerated it somewhat, I don't think it is actually running backwards, but I will double check on this, thanks.

+1

Aluminum should cut like butter, and more rpm is better than less. Most "standard" tooling will cut aluminum, although optimized tooling does a better job - this article has good info:

http://www.moldmakingtechnology.com/articles/030702.html

Thanks for the link to the article. It is one of the ones that got me asking the questions to begin with.

The other thin "cheap end mill" - Just DON'T - learned that the hard way when I was starting out. Bought some of those cheap sets that ENCO et al sells - they are TiN coated turds - just don't buy them - spend the money for a couple of decent end mills

Yah, I am going to have to find a happy medium on that. I can't see paying $35 each for them, but then no point in paying for junk either. I have a 5/8 cobalt roughing mill that I tried and it sure did cut nicer. Any recomendations for decent, not super high end cutters? How about HSS, you can still get quality with it, right?

So, how important is lubrication, can I dry cut aluminum?

I am going to see if I can take a short video today and put it up somewhere, maybe you tube or my box.net account, I am just embarrased about my setup

 

[precisionworks]

Any recomendations for decent, not super high end cutters?

EBay, eBay or eBay

Almost all my non-inserted end mills are solid carbide, purchased on eBay. Quite a few of these should work well: http://shop.ebay.com/?_from=R40&_tr...w=end+mill+aluminum&_sacat=See-All-Categories

 

[VegasF6]

eBay, I get it! Hah. So, in this case I can get one specific to aluminum. Carbide, preferrably. Cobalt?
How about a set, or a few pieces anyhow for steel. They don't all have brand names, or even if they do, it may not mean much I guess. How about something like this? They say tin, carbide, and USA but no name.

On to much more important stuff. The good news is, yes the spindle was spinning the correct direction. However, the reversing switch is quite hinky. I tried it a few times and it broke. Into pieces. I will contact Harbor Freight about a replacement, but I don't have much hope. In the meantime, I have a project that I really really would like to get done next weekend so I need to engineer this thing to work in the meantime. It LOOKS like I could just fit any DPDT switch to reverse polarity, following for instance, this diagram. I could really use a confirmation on this though. I start having nightmares about terms like contactors and mag switches and I dunno what else. When the switch fell apart, it appeared to move a pair of contacts with round balls inside, and maybe something similar to spring steel. And it did appear burned, there had been some arcing going on inside

Alternatively, I could just jumper it for a temp solution, again, if that is safe enough? There is actually a wiring diagram on page 6 of this manual, but I am still confused.

 

[darkzero]

the reversing switch is quite hinky. I tried it a few times and it broke. Into pieces. I will contact Harbor Freight about a replacement, but I don't have much hope.

Good luck with that if you don't mind the wait. You would probably be better off with replacing it with something else & better. Or check LittleMachineShop, Grizzly, LatheMaster, not sure what mill you have but many others sell mills that are similar.

LMS actually lists replacement parts online for some of the HF machines & has them in stock (I've been there & seen with my own eyes). Grizzly lists various switches online (other search keywords might give you more results) that might work as a replacement. Bob at LM is a great person & helpful but not sure how he feels about supplying parts for HF machines over his machines. I've purchased parts from Bob but I never mentioned they were for a HF lathe.

 

[darkzero]

eBay, I get it! Hah.

To add, I see you are in Vegas. I frequently go to the Crossroads of the West gun show. They also hold them in Vegas & Reno. I forget the name but there's a vendor who sells cheap tools & bits in bulk. He has a bin of end mills & other various carbide cutters. If you dig around you will find stuff that is sharp & looks to be only used a couple times or so. I always leave with nice end mills (although I don't have a mill) & solid carbide drill bits. Your choice of 6 for $20-$25 no matter the size. Much of it is name brand too. Not sure if that vendor is at the shows in NV though.

 

[gadget_lover]

You can useable DPDT switch, but make sure you get one that can handle the amps. Startup amp is over 20 for a second. Mine read 28 amps when it starts with the spindle at the highest speed.

You can also use a spst and wire it for forward only.

Daniel

 

[VegasF6]

Awesome, I will check a few local places tomorrow for a switch like this one:
http://cgi.ebay.com/Rocker-Switch-D...tem&pt=LH_DefaultDomain_0&hash=item4cebf7aa6d

Also, Will, thanks for the tip on the gun show guy. I haven't been to a gun show in several years, and when I did it was usually Claudes, but I have hit crossroads before too.

And, it does look like Grizzly has a part # to order the switch and housing for the 6x26 knee mill.

 

[precisionworks]

Carbide, preferrably. Cobalt?

Carbide is nice because it is less flexible than steel or cobalt & it's harder. The gibs on the mill need to be snug & the setup should be as short & rigid as possible.

Cobalt is not as hard as carbide but somewhat more forgiving if the setup isn't perfect. Lots of aluminum is still cut with cobalt & HSS tooling.

a few pieces anyhow for steel

That's a good idea, as aluminum specific end mills don't do well with steel.

 

[VegasF6]

A wise man once told me I would need about 5 years to finish tooling. 1 year in, I am starting to think I need more time
http://www.candlepowerforums.com/vb/showpost.php?p=2979916&postcount=17

The other funny thing is I see the same usual suspects helping out time and time again.
Barry, Will, Daniel, and KC2IXE thanks yet again. And Mac. And everyone else.

 

[KC2IXE]

You're welcome.

I know why I help out:
1)I can remember being there. I'm a 'beginning pro" but long time hobiest, so I can remember
2)It makes me THINK about WHY I do what I do
3)I lean by watching what other folks post

I _Don't_ call myself a machinist, I have way way too much to learn to call myself that. I'm a hacker who usually can get what I want done the way I want. I've seen too many toolmakers and the like who make me look like a poor joke. Right now, I'm unemployed - I'd LOVE to spend 3-4 (heck sometimes 8) hours a day with one of these guys, just learning - you wouldn't even have to pay me

Great line from the story "The Secret of the Old Master" by Lucian Cary (one of the J.M. Pyne stories - republished my Guy Lutard - P.M. Pyne is losely based on Harry Pope)

The old man shook his head. 'There is no secret' He looked at Joe Hill over his spectacles and his eyes were friendly 'Except that you have to know what nice work is, and you have to be willing to take the pains to do it. You knew that when you came here - else I wouldn't have bothered with you'

 

[gadget_lover]

Like Charlie ( KC2IXE ) I share my meager knowledge just because I can. It's nice to be able to help others.

I get other benefits too. It helps put things in a different light. To explain a subject you sometimes have to research it enough to verify your understanding.

I learn a lot by thinking about the questions that others pose. When you get 20 of us wondering about things that are "normal" for the professionals, then you also get a chance to answer those questions BEFORE you need the answers.

Thanks for letting us help.

Daniel

 

[VegasF6]

Ordered a switch and switch box from Grizzly today. Backordered until at least July 5th

Had no luck locally either, so ordered this one from Amazon. Hope I can make it fit, and hopefully by this weekend. Could have had this part done at a machine shop for ~50 bucks, think I am into it about $300 so far this week. With economics like this I should run for President!

Anyone see any glaring reason not to use that switch? Surprisingly I couldn't find a 20A 240V DPDT at Digikey or Mouser even. Didn't try Jameco

 

[gadget_lover]

It will not last as long as a contactor. That's all. It's likely to arc a bit, but for short term that's bearable. Contactors have multiple contacts and they are heavy duty.

The biggest problem is that you want to be able to stop it immediately, and rockers are sometimes hard to hit when in a hurry.

Daniel

 

[VegasF6]

Thanks Daniel. I must admit, the contactor switch thing has me a bit confused.
Remember though, this switch only controls the spindle direction, and is only switched before the power switch is applied, which in turn has a big old emergency stop plunger.
With my limited experience I can't think of a single reason why I would even want to reverse the spindle, except maybe if I had a tapping head. What would be some legitimate reasons to do so?

 

[KC2IXE]

Another reason that contactors are required on modern machines is safety during power failures - the contactor will "drop out" and go into stop mode, and when power comes back, the machine will not startup - where a switch MIGHT be left in the run position, and then the machine would start running with no warning

 

[precisionworks]

I couldn't find a 20A 240V DPDT

You want to look for a "NEMA manual motor starter" ... which looks like a light switch on steroids About $20 at most electrical supply houses or online.

That one is a Leviton MS-302-S.

things that are "normal" for the professionals

If there is such a thing In a job shop, most every project is different. The same questions always come up - how will the part be fixtured (3-jaw, 4-jaw, 5C collet, faceplate, etc.) What's the sequence of ops (aka where does it start & where does it end). Is +/- .050" good enough, or does it need to be +/- .005". What's the best material versus what what is quickly available?

The people I've worked with who are really good are the ones who think outside the box.

Could have had this part done at a machine shop for ~50 bucks, think I am into it about $300 so far

Those are the ones where you'll learn a bunch. In my shop, every new job is a prototype, meaning it takes two tries to make one good part. The third part is a piece of cake.