Endmill Bits

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Taximanny

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Jul 27, 2015
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Ok I have been trying everyway under the sun to relieve brass liners without a mill.
Now it can be done but does not look very clean.

So the idea now is to use an end mill bit in the drill press.
I know sideways movement is not the way to go, so I am thinking of just plunges into the liner.
I'm sure it will take some time but it my last hope for a cleaner look.

I'm going to pick up a cheap HSS mill but this evening and just give it a try before spending bigger money on real good end mill bits.

Question is two flute vs three flute
What do you recommend?
I've never machined anything
And has anyone tried this already ?
 
I'm sure it will but got a jig to hold it.
I do understand the danger, I plan on taking very very little off at a time.
 
For soft materials with large chip loads you typically want to use a two flute endmill. If you are going to be plunging make sure to get a center cutting endmill. Feed the endmill down very, very slowly. Raise often, peck and clear chips with a brush or air. Make sure the piece is held firmly with mechanical means.
 
For brass I would want to go with 2 flutes for chip loading, but you are looking for a better finish so more flutes the better. The problem will be using HSS on your drill press, you are going to have to go reduce the rpm based on the sfpm of brass.
 
Thanks for the info...
I tried etching but only got about .001 depth
I would think I need at least .005
 
I use a .005'' bronze washer on either side of the blade. So, for me there's no need to relieve liners.
 
It's an "end mill", not an endmill "bit".

.005" is such a shallow cut that a lot of conventional wisdom and concerns don't apply, so long as you're careful to constrain your work so you don't run into trouble. If your work can lift or move you can run into trouble with a grabby material like this. I've seen it auger a drill in and pull a chuck off its taper. But keep it to .005" with a good setup and you can get away with a drill press.

Don't plunge, that will give you a large amount of edge in the cut all at once that's going to wobble around and lead to some uncontrolled cutting, it takes a rigid setup to get good results with that. And the bottom of a square end endmill isn't flat, you'll get a shallow cone. For all the more you're dusting off you can side mill.

In theory a three flute is better for this, but not the reason people think. Chip control is not an issue in such a shallow cut, but cutting forces could cause some problems. By their nature a two flue endmill is often more flexible in a direction perpendicular to the cut leading to wobble. Worse, a four flute endmill has a cutting edge 90 degrees to the flute in the deepest part of the cut, leading to gouging. This is why cutters steer to the left. Three flutes have the best combination of chip clearance, rigidity and cutting dynamics for certain materials and cuts and would be ideal for a less than rigid setup in a material like brass. <- but that's just theory, and in reality you're making such a shallow cut I'd just use a 4 flute, they're more common and you get a free cutting edge. Also, HSS is a good idea in a non-rigid setup, but you're cutting so shallow I'd use carbide anyways for a better finish.

Be aware that 360 brass is leaded and making dust releases some of that lead. Not a big deal, but I wouldn't put it in my sandwich.
 
Thanks Nathan for the lessons...
So you think taking .005 wouldn't be a strain on the drill press?
If I try that I'm going to try to get that in like three passes.

I have a 4" cross slide vise I'm going to bolt to my press table so I can controll the feed.
Would be nice to not have to plunge it all out.

I'll try and report back.
I'm sure we have all heard a thousand times a drill press can't take side to side.
But I did do it with G10 with no issues.
 
Taximanny said:
So you think taking .005 wouldn't be a strain on the drill press?
If I try that I'm going to try to get that in like three passes.
Click to expand...

Yeah. If I'm wrong and it kills you, I owe you a Coke.

To be sure we're on the same page here, .005" isn't much more than the thickness of a sheet of paper. You could just about scrape that much material off without even turning on the spindle.
 
I thought about this post a good bit today. I really don't understand why you accept the risks of this (machining thin brass stock in a questionable machine), for what I see as little gain. There are many good folders out there with no relief cuts.

¢.02
 
Well it worked!
Just got to learn to use the knobby thingies at the same time to make a nice radius.
It was only one pass, trying to get my machine set up to take .0025 was impossible.
I fed it super super slow had everything bolted down solid.
Glued two pieces of 3/4" MDF together at work today and set up the jig to hold liners.
Probably took two hours.
I might have been able to go faster but was not going to ruin my drill press or bit.


 
Got the second one done in half the time...
Getting the radius a little better.

Nathan I'm running at 220 rpm and feeding very slowly using a 1/4" HSS spiral cut bit.

To improve performance and less wobble what type end mill would you recommend ?
 
Nathan the Machinist said:
Yeah. If I'm wrong and it kills you, I owe you a Coke.
Click to expand...

For some reason, I started laughing hysterically at this... my wife looked at me like I was nuts. I tried to explain, but her look of confusion/concern only grew from there...

As for milling out the brass, I agree that with such light cuts it shouldn't be a big deal. Personally, I'd make a little "pivot block" like Tony Bose uses, and step up to the biggest mill my drill press could handle.
Lock the quill all the way up, move the table where you'll need it, lock it securely, and if you need a little extra depth, just use some shim stock (paper would even work) under your block.

http://boseknives.com/liner-milling/index.htm
 
That finish is appalling, I suspect that cutter is beat up. A sharp new cutter that isn't so much longer than it needs to be would help. I'd use a 3/8" 4 flute carbide, and spin it faster, but the specific cutter you use isn't all at important.

Remember not to climb mill in this setup.
 
I do agree the finish should and can be better with the right end mill.

Just knowing now that this can be done, I can now buy a good end mill with no worries of it just setting.
I had to google climb milling to understand what your talking about.
And I'm sure I did, so will now try not to.

Thanks for the help!
And encouragement with the Coke !
 
I was wondering if that was more than 5 thousandths myself....When I cut the relief I just do a straight cut on the shoulders so much easier than trying to round the relief and serves the same purpose. I also use a 3/8" carbide endmill in fact I don't think I have ever replaced that particular endmill.
 
It's not much more than .005
Next time During set up I'm going to put s piece of Mylar under the jig.

I did order the 3/8" 4 flute carbide end mill.
Im sure with the more I do they will get better.

Understanding how to NOT climb mill is going to be the trick now.
I really don't believe this to be dangerous at all.
As long as everything is secure and bolted down.
 
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