Blue chips

[wawoodman]

Patience has never been my long suit!

I wached Tom's video on speed, and I get that. It's the feed that throws me.

Practice, grasshopper...

[f350ca]

Its not the cabinet shop, the speed we can remove metal is trying after a bout upstairs. The feed comes with practise as you said, you'll develop a feel for it and the sound when the cutter is working right, same as feeding a piece through the jointer.

[wawoodman]

You're right, Greg. After 50+ years of woodworking, I know how to listen to the machines. Metal is an entirely different kettle of fish.

So, first, I get the spindle speed correct. If I move at a moderate pace, and the chips are blue. Do I go slower, or faster? In my mind, if I go slower, the cutter spends more time in a smaller area, and heats things up. But if I go faster, I'm risking chatter and a poor finish.

As a woodworking analogy, if I'm routing the edge on a piece of maple, if I go too slowly, it will burn. So, I move the router faster. If I go too fast, I'm straining the router motor. So then, I look for the sweet spot: move as quickly as I can control, without slowing down the router.

Is that what I'm looking for, here? That "sweet spot"?

[f350ca]

Like you I started woodworking then ventured to the dark side. I have no formal training so any advice is to be taken with a grain of salt.
The router is probably a good analogy, but when was the last time you used a HSS router bit. The trick with a milling cutter is to keep the heat out of the cutter. From what I gather a lot of the heat of cutting is removed with the chips. the work piece will remove heat as well. The burning you see in the maple is caused by the cutting edge rubbing the material, same is true in metal but you won't likely burn the metal, but no chips coming off no heat removal. That sweet spot is making chips heavy enough to carry the heat away from the cutting edge.
From what I've seen depth of cut has little to do with cutter life to the point where you load the cutter to the breaking point. Taking lots of shallow cuts to get to depth just wears the bottom cutting edge, cut as deep as you think you can. A rough rule of thumb I've seen is when making a plunge cut as in a key way go 1/2 the dia of the cutter in depth, or profiling from the side the dia of the cutter in depth. Get close to size then take a light finish pass to get a better finish.
The truth be I hardly ever use a HSS end mill in steel without flood coolant. Its messy but extends the life of the cutter by magnitudes.
Hope some of this helps.

[TomG]

Feed on a mill like yours, or pretty much any knee mill is by feel. You can go through the exercise of calculating chip load, but it's meaningless if all you have is a hand crank or a variable rate power feed. Just set the rpm based on material type and cutter diameter adjust your feed based on the color of the chip (for steel) and the sound of the mill. If you are getting blue chips or the mill is screaming at you and jumping around, then slow down the feed rate or reduce the depth of cut.

If you were using a 1/2" end mill with cuts that light and getting blue chips, either your end mills were dull or you weren't cutting 1018. And the fact that you damaged a new Niagara cutter with it pretty much makes it a slam dunk.

Tom

[wawoodman]

How can I identify the steel? I looked online, but couldn't find anything that I could do.

If I send any of you a piece, could you i.d. it?

[Vinny]

There's a method where you put the steel against a grinding wheel (spinning, of course) and the color and look of the sparks will tell you what you have. I'm sure someone here has a link to that, I can't find it right now.

[TomG]

Unfortunately there is no easy way to identify steel. There is the spark test as Vinny pointed out, but it's very difficult to use and will only give you a rough idea of the carbon content. Identifying a specific alloy would require a metallurgical lab.

Tom

[Sunset Machine]

I still think he should time himself with a watch. He's a woodcutter, like my buddies. Machines are supposed to make a bunch of noise and whizzz through materials, right? Just seconds to cross a sheet of plywood. Taking minutes to travel the mere width of a vice might not even show up on the radar.

[wawoodman]

Excellent point, Sunset!

Where in Washington are you? Anyplace near Seattle?