Cut my first piece of steel on my mill today

[gto7419]

Basically I cut a few pieces of practice wood on my manual rf-45 clone, and all went smoothly. So I felt it was time to start making a few metal chips.

Unfortunately the clamping kit I bought with the mill, didnt fit in the table... GRRRR... I had to grind the first two t-nuts so I could clamp the vise down, and THEN, I started to remove the excess metal off the other t-nuts using a 1/2" 2 flute HSS tin coated end mill - YAY, my first project!!!

First, I dont have real cutting fluid, which I am going to order tomorrow, but I was using some sort of slightly viscous oil I had laying around. (Im also learning how important a set of parallel blocks are...)

I now understand what people mean when they say chatter. Only, I was at the lowest speed ( 90 rpm ) and I was feeding the piece at a pace which must have been a record for slow feeding.... From what I have read on this forum, I understood that you should be moving pretty slow for steel. I was only removing at most .10.

I kept increasing and messing around with the speeds and feeds to get a feel of what works (Im really new at this), and the chatter ONLY mostly went away at 670 rpm. Is this normal?

Also, is it ok to start cutting without locking the gibs? I tried both locking the gibs and leaving them loose, and could not notice a difference even though Im sure its probably there...

Danny

[widgitmaster]

Firs off, you will get a better result with a 4 flute end mill, depending on the size of your mill, the small diameters may work better! Steel is best at 500 rpm when feeding freehand! Also, its nice to have a little cup of pipe threading oil and an acid brush handy, its a good cutting oil for steel!

Regidity is the most important ingredient when milling steel, if your not moving it, lock it!
Eric

[widgitmaster]

Oh yea, I forgot to mention that if you are milling with the end of the endmill, you should grind the points to a small radius, then stone them smooth. This will give you a much better finish, even in steel!

Eric

[gto7419]

I have the Machinery Handbook, but a lot of what Im reading still doesnt make sense. Should I be using a 4 flute end mill for harder steels, and 2 flute for softer metals to avoid heat damage?


Also, why would a smaller end mill help things? My machine is the same size as the IH mill - Its the PennToolco mill with the swivel base DM-45R.


Thanks for the help Eric, I really do appreciate it!!!!!!

Danny

[gto7419]

I was actually just looking through you webpage. Are you an emt?

[sanddrag]

100 thousandths per pass in steel? I'm no machinist by trade but I've done my fair share of tinkering and that seems a bit excessive. There is sort of a tradeoff, heavier cut and slower feed, or lighter cut and faster feed. I prefer the latter. Probably easier on tools too.

[gto7419]

Originally Posted by sanddrag 100 thousandths per pass in steel? I'm no machinist by trade but I've done my fair share of tinkering and that seems a bit excessive. There is sort of a tradeoff, heavier cut and slower feed, or lighter cut and faster feed. I prefer the latter. Probably easier on tools too.

I didnt know between 1/8" and 1/16" inches was so excessive? Especially on the side of the cutter and not the face???

[Runner4404spd]

i usually try and take about .030 per pass on steel and .050 on aluminum with my R-45. it might be somewhat conservative but it works for me.

[Mcgyver]

100 thou by itself is not a heavy cut, depends on the cutter dia and if the mill can handle it. Rule of thumb is depth of cut can be up wards of 50% of the mill dia, but that's really what the cutter can handle, whether this works or not will depend on chip per tooth and mill rigidity (ie if this is a benchtop machine, it's not going to have he same removal rates as a full size machine)

Getting a proper chip per tooth will reduce tool wear, but if it means only cutting on the bottom 1/16 of the mill, and you don't have the facilities to sharpen, you're not getting much out of the tool. I like to use as much of the side of the mill as i can in one pass rather than the bottom 1/16 over many passes.

sdantonia post this good summary of feed/speeds a day or so ago, read it and you'll understand feed/speed. keep in mind feed and speed calculations are theoretical, usually the practical is something less as machine rigidity, less than perfectly sharp tool, set up etc etc come into play

http://www.cnczone.com/forums/attach...chmentid=17528

as far as cutting fluid goes, you'll get lots of opinions. the objective is to remove heat and lubricate, my preference is soluble synthetic oils like cooltool. mix it 30:1 or so with water use something like an windex squirt bottle. the gallon you buy for $30 will last years. not as nice as flood, but works imo

[tobyaxis]

Using a smaller tool will produce less cutting force. As mensioned earier in this thread feeds and speeds have to do with Machine, Cutter, and Part Rigidity. In other words you have to aquire a FEEL for the Cut. That is why the best CNC Machinists were the Good Manual Machinists of days long past.
You will develope your own feel over time and be able to look at a Machine, set-up, and know what Feeds and Speeds to start at. A word wisdom, HSS takes less HP and Torque to run over carbide on manual machines. LOL, I use carbide anyway, because, I like too. You will develope your own methods and ideas. As long as you can make a good part in reasonable time, your fine.

Just my 2 cents

tobyaxis

[phantomcow2]

.1 off per pass is not much. With a bridgeport I can go 50% the diameter of the endmill okay. With the X3, I've been taking off .125" off per pass with a 1/2" endmill, a good amount of cutting fluid. 4 flutes makes a difference though, I'de suggest it.