[Potatohead908]

Can anyone please give me some input on this. Maybe speeds and feeds as well as setup. I haven't bought the end mill yet so tips on that would be good to. I mainly plan on doing aluminum but a friend asked if I can make this slot for him. It's less than 1in. in length and it will be all the way through a 1" disk of 304 stainless.

TIA

[pippin88]

Could be fun...

Consider drilling the majority of the material out then milling to shape.

[Fastest1]

Patience? I hate 1/8" tools

[gd.marsh]

+1 on pre-drilling most of the material out first ..
Just broke a 1/8" end mill yesterday trying to cut a 3/4" deep slot in aluminum. It was a 4 flute end mill (cause that's all I had on hand)
I did have both ends of the slot pre-drilled to depth .. taking .05 doc @ 7200 rpm & 13.8 fr - which is the recommended speed & feed in G-Wizard on conservative setting.
To get to that depth takes an 'extra long' end mill in 1/8" diameter .. which translates to 'extra tool flex' as well.
Be sure to buy more than 1 tool for the 304 job!

[wizard]

Can anyone please give me some input on this. Maybe speeds and feeds as well as setup. I haven't bought the end mill yet so tips on that would be good to. I mainly plan on doing aluminum but a friend asked if I can make this slot for him. It's less than 1in. in length and it will be all the way through a 1" disk of 304 stainless.

TIA

Fair warning this could be frustrating to the point of you throwing your mill out the window. If by the description you have above you mean a 1" thick piece of stainless it could get ugly and expensive. There are two distinct problems one being that Stainless work hardens real fast. The other related problem is that the chips are damn hard and will chip or break end mills real fast.

The recommendation to drill out the slot first might not be a bad one, but even with drilling you have to take special care and use good tools suitable for stainless. When drilling you will want to select a spindle speed well below what you would use for mild steel and feed the drill without stopping or hesitating. You stop or hesitate and you run a good chance of work hardening the surface you are trying to drill through. However it is very difficult to drill an 1/8" hole in just about anything with out clearing chips and the flutes. So you need a withdrawal technique that doesn't allow the drill to rub. As you can see just drill holes can get ugly.

You could mill the slot all the way through and you might have to if wall surfaces are important. The problem here being drill bit wander and deflection of the end mill as it tries to clear metal between the drilled holes. You might take the advice already suggested above of drilling two holes at either extremes of the slot and mill out the solid in between. The thing here is that the drilled holes will allow you to dwell a bit and adjust the depth of cut before actually cutting anything. More importantly it should allow you to completely clean the slot before each pass, as noted recutting chips is hell upon your end mills. When doing this do not use an excessive depth of cut as you want to be able to maintain a feed rate suitable for the spindle RPM, agan rubbing frm hesitation or dwelling can cause instant work hardening of the stainless.

In any case order lots of coated end mills suitable for stainless. If this is your first attempt at machining stainless it could get very ugly, epsecially when this is at best a bad operation to cut your stainless machining experience on. Oh before you even start find out how valuable this stainless piece is because honestly you may want to decline the opportunity to do this job for your friend. Everything considered it would be far better to learn machining of stainless on simpler tasks.

[bjones]

save yourself the headache, have your buddy send the part to a shop with EDM.

[wizard]

save yourself the headache, have your buddy send the part to a shop with EDM.

This makes a lot of sense and it is one simple sentence.

[tony978]

save yourself the headache, have your buddy send the part to a shop with EDM.

ya what he said ------^ you will thank us later !!!!

[Fastest1]

So will your friend!

[Potatohead908]

Thank you to all that replied. So for clarity it is only 1/8th inch thick 304 (or so he thinks), 1/8" slot less than an inch thick. It's for a finger/hand guard for a knife he is making. To make things worse I just converted my G0704 to CNC and am a total greenhorn to machining!! It's a small piece so not a big loss if I total it. The bit he has bought but we only have one. It is a 90 degree carbide bit made by Melin that has an AlTIN (Aluminum Titanium Nitride) coating. I told him to just make it thicker and out of aluminum but he is set on stainless. I just did a big order from Enco and added his mill bit to get the free shipping. If need be I can pass on the favor and just keep the end mill for something else. Or I can just try and if the bit breaks then....we tried!

[pippin88]

So the requested slot in 1/8" wide, 1 inch long, through 1/8" thick material?

[Potatohead908]

Yes. Sorry if I haven't made that clear.

[bjones]

that makes one heck of a difference in what we thought you were attempting, 1/8 thick stock should be easy enough but you need to be clearer in what you are saying. "1/8th slot less than an inch thick" still sounds like you want to go nearly an inch deep. do you mean nearly an inch long?

[Potatohead908]

Ok sorry I wasn't clearer. This is for a finger guard on a knife my friend is making. It's a piece that is sandwiched between the blade and the handle. The material is less than 1/4" thick and I hope closer to 1/8th". The slot needs to be close to 1/8" wide. I don't know the length yet but it has to be under an inch.

I changed my previous post. Totally screwed up what I was trying to say.

[Fastest1]

That should be much easier.

Since you are green, try using the wizards. They are built in to Mach if you are not familiar with them. The wizards are designed for simple tasks. Multiple operations can be linked together if so desired. Those gcodes can also be saved if you were doing a process repeatedly.

[RCaffin]

1/8" slot in SS? I would be tempted to buy a 3/16" 3/32"carbide drill and drill most of the slot out first. Slow revs and aggressive feed and air blast to clear the chips out fast. Then mill the slot to size with medium revs, medium feed (ie avoid work-hardening!) and lots of shallow cuts. Put some oil in the air blast to keep the cutter wet and avoid metal sticking to the cutter.

Cheers

[fizzissist]

Use a 3/32" endmill. Run it down the middle, then climb cut up one side, then move over and climb cut down the other side...... .125 - .094 = .031
.031 / 2 = .0155/side stepover. I'd do a rough pass and a .003" finish pass on each side.

You can use a good quality 3fl solid carbide endmill at around 350SFM, dry w/air blast, around .0018"/rev feed rate. DOC no more than 1/2 Dia of cutter.

I use this approach all the time for O-ring grooves in 304. Like RCaffin says, don't baby it, it will work harden, but it's not all that bad. 304 has a reputation far worse than it deserves.

[bjones]

1/8" slot in SS? I would be tempted to buy a 3/16" carbide drill and drill most of the slot out first. Slow revs and aggressive feed and air blast to clear the chips out fast. Then mill the slot to size with medium revs, medium feed (ie avoid work-hardening!) and lots of shallow cuts. Put some oil in the air blast to keep the cutter wet and avoid metal sticking to the cutter.

Cheers

uh, 3/16" is bigger than 1/8" mate.

[RCaffin]

Errr ... yeah ... oops!
Corrected.
Damn imperial measurements - give me metric any day.
Cheers

[Potatohead908]

So I pretty much hosed the first part of this thread up.....BUT that doesn't matter so much. I talked to my friend and he found the receipt that says it's 303 Stainless. I asked him what the height of the material was that I need to slot all the way through. He said 1/2". So to recap....1/8" wide slot (doesn't need to be right on the gnat's ass), less than 1" in length all the way through a 1/2" tall piece of 303 stainless. I think I read that 303 is not as hard to machine as 304. Is this correct or am I still pretty much going to break some end mills? I have a 60 gallon air compressor to keep the chips at bay. I understand some of the wizards in Mach3 and I can practice on some softer material before I make the cut....ie wood or plastic or aluminum.