End mill woes while milling Aluminum.

Kevin M.

Kevin M.

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I have a small hobby end mill that I use from time to time for projects whenever I decide to get creative with my firearms. I'm far from a machinist but I do have at least a decent grasp of milling operations on a hobby scale.

My projects have ranged from modifying magazine wells for bolt actions to building ammo can mount brackets for my beltfed 1919, and a ton of stuff in between.

Currently I am playing with some aluminum block for a magazine well prototype I wanted to try, and have been having running into serious issues with my end mill cutters becoming dull very rapidly, as in between 5-10 minutes of cutting time. I follow the recommended RPMs per bit size while cutting aluminum pockets, but the lowest part of the cutter always rounds out in a very short period of time, so I figured I would see what you guys think.

At the moment I am just using busy bee tin coated 2 flute cutters. Are these bits insanely low quality? Should I be using carbide or HSS instead? Or am I perhaps feeding too slow or fast? When I feed too fast it causes chatter because it is just a small machine, so I obviously want to avoid that.

Thanks for your help fellas.
 
If the cutters are dulling that quickly on aluminum they are not very good cutters. Even heat treated aluminum should machine fine with a decent HSS cutter.
 
The busy bee endmills are crap.

Buy some (decent) HSS or carbide endmills and your problems will magically disappear.
 
ShawnC6 said:
Carbide bits would last a hell of a long time on aluminum. Not all that expensive when it comes down to it.

You using coolant?
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No full time coolant but I do give a good spray of light oil like WD40 to keep the chips flowing on a frequent basis.

Good to know that it is likely just the end mills I am using.

What would you fellas recommend for end mills and where to buy them? I don't really use anything bigger than 1/2", most of my work is 3/8" and 1/4"
 
Problem is not you are using HSS ( although the quality of cutter makes a difference ) , but rather the lack of rigidity on those small mills

You will "round off" a carbide cutter just easily

No way a HSS ( even non cobalt ) should wear that fast .

Generally when you are loosing a edge in a dramatic fashion, its not from wear , but rather you are trying to take a climb cut with a machine that does not have the rigidity . Even a heavy climb cut on a Bridgeport with NON ball lead screws ( ie there is some lash ) you can knock the teeth . The backlash of non ball lead screw or non "backlash eliminator" leadscrews will cause the workpiece to be pulled towards the cutter

Conventional cutting is the way to go with these small machines, not climb milling

Good end mills are not expensive....try KBC . I generally stick with Niagra, SKF , Dormer , Do All , Nachi

For your application you should look at a high helix ( a off brand from KBC , 1/2" dia is only $15 )

IF you are milling pockets in solid blocks, part of the problem is chip control . Look at a coarse tooth roughing cutter (especially with limited power machines like yours ) .

I have a huge 40 taper spindle machine and I still use roughers for applications like that

Problem with carbide is you need to run relatively high speeds and feeds . I use indexible carbide end mills / face mills and I run my mill up to over 3000rpm ( my max spindle speed ) even for 1" end mill

You need to have lots of machine rigidity as well
 
TRG-42 said:
Problem is not you are using HSS ( although the quality of cutter makes a difference ) , but rather the lack of rigidity on those small mills

You will "round off" a carbide cutter just easily

No way a HSS ( even non cobalt ) should wear that fast .

Generally when you are loosing a edge in a dramatic fashion, its not from wear , but rather you are trying to take a climb cut with a machine that does not have the rigidity . Even a heavy climb cut on a Bridgeport with NON ball lead screws ( ie there is some lash ) you can knock the teeth . The backlash of non ball lead screw or non "backlash eliminator" leadscrews will cause the workpiece to be pulled towards the cutter

Conventional cutting is the way to go with these small machines, not climb milling

Good end mills are not expensive....try KBC . I generally stick with Niagra, SKF , Dormer , Do All , Nachi

For your application you should look at a high helix ( a off brand from KBC , 1/2" dia is only $15 )

IF you are milling pockets in solid blocks, part of the problem is chip control . Look at a coarse tooth roughing cutter (especially with limited power machines like yours ) .

I have a huge 40 taper spindle machine and I still use roughers for applications like that

Problem with carbide is you need to run relatively high speeds and feeds . I use indexible carbide end mills / face mills and I run my mill up to over 3000rpm ( my max spindle speed ) even for 1" end mill

You need to have lots of machine rigidity as well
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I only do conventional milling, never climb, as I know that with these little machines that can rapidly cause issues.

I'll take a look at roughing bits, as I have not tried those before.

Otherwise, I do feel like rigidity is an issue with this machine, however I have already managed to find a few ways to work with it and increase the rigidity while milling as much as possible.
 
*MALICE* said:
The busy bee endmills are crap.

Buy some (decent) HSS or carbide endmills and your problems will magically disappear.
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I would say this ^^^^^

Some brand name (ANY brand name!) end mills and ferchristsakes don't waste money on coated ANYTHING, unless you now exactly what the coating does, and why you want it!

Literally, if you cannot write an essay explaining why you need a coated cutter, and explaining exactly the benefits of it, then, you are peeing away money on the stuff. But since you are getting end mills from Busy Bee...

If you are going to buy cheap Chinese end mills, get uncoated ones, and shop mail order from the likes of Richon Tool and you end up with the same cheap end mills for, well, cheap. For what Busy Bee charges, you can buy real end mills from real suppliers. Stay away from kits that have a bunch of different sizes, and just buy what you need.

Carbide End mills rock, and once you get past the bit where you have to learn not to bump them into things when they are not running, and you nut up enough to actually run the mill flat out AND push the feed rate up a bit, they will last almost indefinitely. Running them at slower than 'book speeds will actually increase their useful life, as long as you do not allow the cutter to rub.

Try to remember always, that the 'optimum' book speeds and feeds are all about making the shop owner the best return on his money, not on getting the longest life out of the tools. Most work in the least time, for the best return on investment. If you can afford to go slower, the tools usually last a lot longer.

Cheers
Trev
 
Speeds and feeds are essential. 2 flute carbide endmills. Only use coolant if you can flood the cutter as carbide will crack if you intermittently use coolant. But I never use coolant as it just makes a mess. Make the setup as rigid as possible and take small cuts if you have too.
 
Green Skull said:
Speeds and feeds are essential. 2 flute carbide endmills. Only use coolant if you can flood the cutter as carbide will crack if you intermittently use coolant. But I never use coolant as it just makes a mess. Make the setup as rigid as possible and take small cuts if you have too.
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You can get carbide pretty hot and hit it with coolant and still not have any cracking
 
Slop in the low end mills is definitely an issue, especially on the smaller units.

There may be another issue though in the case of the OP. He doesn't say where he got his aluminum from or what the number on it is. If he picked it up from a scrap dealer it may only look like aluminum but may actually be mix of aluminum/titanium along with something else thrown in to increase the durability of the material under different or extreme stresses.

I picked up a bunch of "aluminum" scrap blocks cheap at a scrap dealer several years ago. They were great at first sight. 2 inches square and I thought they would make excellent barrel vice bushings. Nope, not a chance. Those squares were lovely to look at but they were very difficult to drill as well as cut. HSS would bind even with very slow feed and high rotation speeds. Lube of any sort didn't make any difference either.

The stuff was light and tough as heck to machine. It was an aluminum blend material used in aircraft parts manufacture. What these blocks were used for I have no idea. Carbide tools worked well on it but I don't have many carbide drills. Luckily I have carbide tipped circular cutters. I ended up using carbide tipped end mills lubed with kerosene (lighter fluid) to drill holes into the blocks large enough so that I could get an internal cutter into them to machine the proper taper on the lathe. I didn't and still don't like the idea of using kerosene/lighterfluid as a lube. Not because it is to flammable but because the darn stuff creeps into every nook and cranny on the machinery and attracts all sorts of crap. The smell is something else as well. As CanAm says though it works and sometime you just do what you have to do. Ventilation is necessary.
 
There are H.S.S. End mills that are made specifically for Aluminum, get those. Normal H.S.S. roughers works pretty well. Use WD-40 to help prevent chip weld. On Aluminum I sometimes use cheap carbide router bits, they actually work very well.
 
Are you sure the endmills are dull or you might have some welded aluminium on the cutting end preventing them from cutting. This happens to me with aluminium sometimes if I am in a hurry and dont use as a lubricant , I take a pick and pop the little pieces of aluminium of the cutting edges and then they cut fine check it out under a bit of magnification to see better , reading glasses in 2-3X are all over my shop lol.
 
I would recommend Niagara end mills in HSS they are excellent quality and reasonably priced.
They are available ground specifically for aluminum as well.
There is a Thomas Skinner in Edmonton. I've dealt with them in B.C. and they are great.

Google: Climb Milling a definite "Do Not Do" with light duty hobby milling machines.

Terry
 
I'll echo virtually everyone else here. Start with a good HSS or, even better, carbide cutter. See if this fixes the problem. If not then there'll be other stuff to look at.
 
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