# Why I like having a REAL Mill



## KC2IXE (Apr 30, 2009)

I've owned 3-4 mills - A sherline (which I still have, and will be CNC'd some day), and a ?? Brand Horizontal with a verical head, and of course, now the Millrite

Today I had a "as wrought" piece of Fortal Plate I needed to face down on both sides, and bring it to 1/2 inch. It was 14mm (the standard thickness - .551 in inches). Note, the other day I squared the edges, so...

I clamp the 6" long, 3.65 wide piece in the vise, whack it down with the deadblow, and skim off the first side - two very thin cuts with a 2" wide 1 flute fly cutter (a Metalmaster MM200 - which I think highly of BTW) - just enough to clean up that side.

Mic the plate, now at about .540 if I remember right, flip the plate, whack it down again, touch off the cutter, dial in a .035, make my 2 passes, re-mic, dial in what's left, and come out at .4995 - good enough

I'm still mentally in sherline mode (which is what I've done most of my hobby work on - despite owning the Millrite longer (I did say the shop was inactive for a few years). There is NO way I could have burried even a 1" fly cutter .035 into a block of 7075 and made a cut - it would have taken 3-5 passes.

Horse Power, and the cast iron to back it up is SO nice

I do want to get a nice 2-3-4 stagger tooth face mill that can take a wiper, to really improve the surface finish.

One day I have to add power feed to the mill


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## gadget_lover (Apr 30, 2009)

I know just what you mean. Being able to take a big bite with no strain is such a great feeling. .035 depth is almost nothing!

I was looking at power feeds today. After 600 for a DRO, 150 for a power feed is not quite out of the realm of possibility.




Daniel


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## KC2IXE (Apr 30, 2009)

Well, IF I decide to add Power feed, I'm gonna go "all the way" - and homebrew a power feed that uses a stepper motor, and maybe even change out the X axis to a ball screw

OK - you can see where THIS is leading, right?


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## wquiles (Apr 30, 2009)

KC2IXE said:


> Horse Power, and the cast iron to back it up is SO nice
> 
> I do want to get a nice 2-3-4 stagger tooth face mill that can take a wiper, to really improve the surface finish.
> 
> One day I have to add power feed to the mill



Ditto on the HP/weight. I came from the mini-mill (X2) to the knee mill, and I am still in adjustment mode, finding it hard to believe how much easier everything is on the "real" mill 




gadget_lover said:


> I was looking at power feeds today. After 600 for a DRO, 150 for a power feed is not quite out of the realm of possibility.



Please do let me know what you end up buying. And are you only doing the X one, right? I of of course have seen the power feed for the Y, but recently saw one for the Z in our knee mills :naughty:

Will


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## gadget_lover (Apr 30, 2009)

I see cables and computers and cad in your future.


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## gadget_lover (Apr 30, 2009)

wquiles said:


> And are you only doing the X one, right? I of of course have seen the power feed for the Y, but recently saw one for the Z in our knee mills :naughty:
> 
> Will



Yes, I'm currently thinking only of the X axis for nice, smooth finishes, but the Z axis is also attractive for fast tool changes. Even with the big handle along with well lubed ways and jack screw, the knee is less than fun to move frequently.

Daniel


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## KC2IXE (May 1, 2009)

Cad is already here


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## cmacclel (May 2, 2009)

Only .035.......my RF-31 would do that no sweat 

Mac


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## gadget_lover (May 3, 2009)

cmacclel said:


> Only .035.......my RF-31 would do that no sweat
> 
> Mac



I could do that in my micro mill with a 3/8 inch end mill. Let's see, 6" long, 3.65 wide piece at .100 per revolution of the hand wheel... 12 passes = 720 revolutions of the handwheel.

 But KC2IXE was using a 2 inch fly cutter. I thought that .035 was supposed to be a good depth for a 2 inch fly cutter. 

I was just in the garage doing a .300 deep x .500 wide slots in 6061 in two passes with a 1/2 inch end mill. The first pass .295 deep and the clean up pass .005. Since the exact width was not critical I cheated with the 1/2 inch end mill instead of multiple passes with a 7/8 inch mill.

It's GOOD to have a large (er) mill. 

Daniel


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## precisionworks (May 3, 2009)

> I thought that .035 was supposed to be a good depth for a 2 inch fly cutter.


Using a 2" face mill, with 3 or 4 inserts, in mild steel (hot rolled, cold rolled, etc.), these machines will take .100" DOC with a moderate feed rate, or .050" DOC with a pretty fast feed. Surprisingly, an inserted face mill works well in the 1000-1500 rpm range in mild steel - as long as DOC is no more than .100". The sfpm is off the chart, but inserts last a long time. When you don't have lots of spindle hp, you can sometimes use a higher spindle speed with a (fairly) shallow DOC.

A fly cutter uses only a single cutting point, and .035" isn't a bad number. Also, since a fly cutter is NOT a balanced tool like a face mill, spindle speed is limited by out of balance vibration.


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## gadget_lover (May 3, 2009)

gadget_lover said:


> I was just in the garage doing a .300 deep x .500 wide slots in 6061 in two passes with a 1/2 inch end mill.
> 
> Daniel




Every once in a while I have to be reminded of the basics....

I did this cut using whatever speed the mill was set for. That turned out to be 450 RPM. I got a great finish but it cut much slower than I thought it should.

Today I finally got around to printing up a chart with the proper speeds (RPM and feed) for various metals, cutters and tool diameters. I was surprised to see the RPM for 1/2 inch mill should be around 3,500 rpm and the rate of feed was many, many inches per minute.

Sure enough, I bumped the speed up to 3400 and ran a test piece again at .300 depth. I could not even feel the resistance from the cutter as I ran through an inch in less than 10 seconds. The finish was beautifully smooth (as expected  ).

The moral is to check the charts (or at least do the simple math) before starting to cut. 

Daniel


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## KC2IXE (May 3, 2009)

gadget_lover said:


> ...snip... But KC2IXE was using a 2 inch fly cutter. I thought that .035 was supposed to be a good depth for a 2 inch fly cutter.
> 
> ...snip...Daniel




.035 is nothing to brag about, but it's all I need to remove to leave a finishing pass - still, based upon the recommened cuts, that's near max for the cutter


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## StrikerDown (May 3, 2009)

gadget_lover said:


> Today I finally got around to printing up a chart with the proper speeds (RPM and feed) for various metals, cutters and tool diameters.
> Daniel


 
Any chance you found the chart on the web? Link link link... I mean, hint hint hint 

Folowing the guidlines in most things eliminates many of the random results!


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## KC2IXE (May 3, 2009)

The problems with Feed/Spped/DOC charts is that they change

Machinery Handbook Gives you SOME information, and works great for HSS and generic "carbide", but if you use insert carbides, it's usually best to look at what the manufacturer has to say - grades, insert geometries etc are constantly changing


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## gadget_lover (May 3, 2009)

StrikerDown said:


> Any chance you found the chart on the web? Link link link... I mean, hint hint hint



I'll be glad to share the spreadsheet. It's nothing fancy. I just took the formulas found in my Mill's manual for HSS and applied them to the endmill sizes I use most often. I figured that way I will be more likely to set correct speed.

The PDF is at http://home.earthlink.net/~dbsuthe/hss_speeds.pdf
The spread sheet is http://home.earthlink.net/~dbsuthe/hss_speeds.xls in case you want to make changes.

For carbide, double the RPM.

Daniel


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## StrikerDown (May 4, 2009)

Thank you Daniel, that is much better than shooting in the dark!


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## HarryN (May 8, 2009)

gadget_lover said:


> I know just what you mean. Being able to take a big bite with no strain is such a great feeling. .035 depth is almost nothing!
> 
> I was looking at power feeds today. After 600 for a DRO, 150 for a power feed is not quite out of the realm of possibility.
> 
> ...



You are almost there Daniel - we can CNC it with a few motors, boards, and an extra pc. Of course, where on earth would you be able to find an extra PC at your house ?


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