First cuts

[no priors]

I am a newbe benchtop machinist with a Seig II tuned and trammed great. I'm making light end cuts on 6016 1 1/2 X 1/2 with a 3/4 4 flute Tin coat from LMS trying to see how smooth I can get. I have modified with LMS belt drive and do OK at about 1/3 rpm. I get small vertical wavy pattern on surface. Am I way to slow? Do I lubricate? My goal is perfection. Do I set the belt to higher speed pulleys. Cuts are smooth to touch with some shine and are perfectly square. How would you do it on this machine.
Thanks
No priors (honest)

[tobyaxis]

Originally Posted by no priors I am a newbe benchtop machinist with a Seig II tuned and trammed great. I'm making light end cuts on 6016 1 1/2 X 1/2 with a 3/4 4 flute Tin coat from LMS trying to see how smooth I can get. I have modified with LMS belt drive and do OK at about 1/3 rpm. I get small vertical wavy pattern on surface. Am I way to slow? Do I lubricate? My goal is perfection. Do I set the belt to higher speed pulleys. Cuts are smooth to touch with some shine and are perfectly square. How would you do it on this machine. Thanks No priors (honest)

First off, send some of that, "Shine XXX Over Here", and it better be like Grandpa used to make.

Seriously though it's a kind of feel when cutting anything. There is no proven science to Feeds and Speeds for any specific application. Lubrication is a good idea. You will never get a perfect surface unless you use a Precision Grinding Machine. What you might be seeing is "chatter". Chatter is the tool bouncing instead of cutting because the feedrate is too slow and the RPM too high. Try lowering your RPM a little more and using a bit more feed. I realize your cranking a handle. Also try lightly stoning the tips of the end mill (Flute Corners) and be careful not to cut yourself or take too much off. Try taking a less depth of cut. I hear about using Soapy Water for Lubrication (I have to get used to this). Try some soapy water and in my opinion make it thick. I have been a Machinist for almost 15 years and to be honest, I'll never use soapy water. That will be left up to you.

There is a new book out that has a few interesting points about machining. It's called "Machine Shop Trade Secrets". I borrowed this from a friend when I was bored and actually found some uselful information in it. I believe it's $40.00. Try Amazon.

Have fun with your mill and learn as much as you can.

Welcome to cnczone!

[fpworks]

A 2 or 3 flute endmill will usually finish better in aluminum. (than the tool you are using) Also, make sure that you are taking a finish pass with 0.005 finishing stock, climb mill (if possible), cut dry (if you're cutting on the outside of the part), use high rpms and prepare to get chips thrown at you.

For your feed (handle turning), practice and try to "time" a chip load of 0.001-0.002 for your finish pass. This might help you since you're just starting out and [probably] don't have a mentor. This may help you establish that "feel" that Toby is talking about.

Good luck!
Justin

[no priors]

Thanks Toby and Justin,
I think the feel is the goal. Justin I have tried a two flute 3/4 climb mill and it was good. Do I run this at 1700 or 4200 rpm? Thanks for the handle turn info which seems confusing when I read books and charts that say 600SFM. If i'm practicing on the end 1/2 " 6016 x 1 1/2" am I going to make this pass say counting thousand one, thousand two etc., up to three or six or ten? My point is I just don't know how to gauge what is a slow or fast feed. I'll look up chip load .
I truly appreciate the replys.
Thanks
Greg
(aka: no priors)

[solgood]

try using wd-40 for lube it works great on AL

[fpworks]

Greg,
I'm guessing that you're using a HSS tool (rather than solid carbide) so I would use 1700 rpm. It would be better to run a solid carbide tool at 4200 rpm.

The 600sfm means 600 surface feet per minute. It is simply the velocity of the cutting tool at it's perimeter.

Calculated sfm by: tool dia [inches] * pi [constant] * rpm [rev/min] / 12 [inches/foot]

So, in your case, 0.75in * 3.141 * 1700 rpm / 12in/ft = 334 ft/min (sfm)

A bit on the slow side, but too slow is better than too fast. Your finish may suffer, but you won't destroy your tool. If possible, you should adjust your rpm to attain the recommended surface feed from the tool manufacturer. Watch out for feeds/speeds found in the Machinery's Handbook. They really don't apply to small mills and generally assume optimal machine and setup rigidity.

Chip load is simply the size of the chip that each flute will take. This is more useful in CNC, where there really is no feel and you have to input a number for how fast to feed the tool through a cut.

Lets use a chip load of 0.002" per flute and a speed of 1700 rpm, with a 2 flute endmill

feed = (chip load) * (# of flutes) * (spindle speed)

= 0.002in/flute * 2 flutes * 1700 rpm = 6.8in/minute (this is how fast your cutter should feed through the workpiece)

My advice (although abstract) was to figure out how fast to turn the handwheel to get the above feed rate. I was hoping that you might be able to find a relationship, like turning your handwheel 1/2 turn per second, or something like that. That part is up to you! At least you will learn the proper feel, then you won't have to worry about that stuff again, until you break down and convert your mill to CNC

Justin

[no priors]

Thanks Justin,
So at 6.8in/minute a 1 1/2" piece of stock should travel through in about fifteen to seventeen seconds. Thats what I needed, a reference to what is fast or slow. I'll use the formula as a start basis.
Thanks again
Greg

[no priors]

Justin
Using your sfm formula, dosen't 334ft/min equate to 5.6ft /sec. and that is considered slow?
Before I get to CNC I want a lathe!
Greg

[fpworks]

Yes, that is on the slow side. On my VMC, I typically run my carbide 2 flute 0.5" endmills at 6000 rpm and feed at 120-150 inches/min. (for roughing aluminum)

However, 6000 rpm on a 0.5" endmill is only 785sfm, and that is still too slow. If my machine could run 15,000 rpm at 300+ inches/min, I would run it like that for production work. But it can't go that fast

Some tool manufacturers do not impose surface speed limitations on their tools in aluminum, such as SGS and their Ski-carb endmills. Sadly enough, I don't have any experience with those speeds, but I will when I buy my next machine

Justin

[no priors]

I'm looking at the LMS Mini mill power feed. Fastest speed is 12"/min. Is this OK, good, great or a waste of money? (Seig II)
Greg