Using a face mill & choosing the right inserts.

[diamond]

I own one 2" face mill with triangular HSS inserts. I have a fly cutter as well. I don't get the kind of finish out of it that I'd like on either. Best I seem to do is with really light cuts.

I've mostly used them on aluminum so far but have a project coming up in mild steel. Thinking about getting a face mill with circular inserts. Something along the lines of this https://www.ebay.com/i/183515058263.

On this project will need to face off mill scale on 2" A36 and (hopefully) get a good parallel surface.

I'm also wondering if I'd do better by replacing those triangular HSS inserts with carbide but I'm concerned about chipping on something like a face mill where it's going to be interrupted cuts quite often. That plus the better surface finish I "think" I'll get from the circular inserts is what's making me think to try that.

I'm sure some of what I'm doing wrong with both tools is about speeds and feeds and with the fly cutter I am sure my tool geometry is not optimal. Thing is I am not set up to grind tools. I know I'll be told it learn to do it but I use inserts a lot on my lathe work and just prefer the convenience of inserts. I know, sacralige right? I've invested quite a lot in insert tooling.

That said if anyone has any advice on how to run that face mill better and selecting insert geometry I'll take anything. This is on a 1-1/2 HP Bridgeport.

 

[Lo-Fi]

I run a 3" face mill with 6 square SPMN carbide inserts on my 2hp bridgeport and get spectacular surface finishes on steel. High speed and a feed that gives coloured chips is the sweet spot and I've never chipped an insert. You can really hog with it, but I don't tend to go beyond 0.5mm cuts as its a bit much for a Bridgeport quill. I'm running a VFD, so play with fine tuning the speed and feed, listening to the machine for the best result. It's one of my favourite milling tools. I'm sure inserts the triangular inserts will work just as well.
Something to note with carbide is it needs to bite for the best finish. It really doesn't like to rub, either in depth of cut or feed. It wants to get loaded up and cut! This may mean the circular inserts need quite a bit of power as they'll have a large contact area.
The finish in the pic is straight off the mill, 0.25mm depth of cut:



Its very hard to photograph!

 

[benmychree]

For a low power mill, I'd stick with the positive rake triangular carbide inserts, I had two of them in my shop, a 1.5" and a 3", used on a Italian Bridgeport type mill (Induma), and they worked fine on steel, with no chipping problems, also used them frequently on 303 stainless with good results.

 

[pontiac428]

I have a few 2" 5-insert face mills that accept WHOGAF inserts. I carefully center the cutters on Shars R8 arbors, turning 800 RPM on my 2 HP RF. I treat it just like an end mill, with up to .040 DOC (bet they could do more) and x-feed. Even on my questionable equipment I get a spectacular finish. I suggest you try the tooling out, it's well within your machine's range to run it. Face mills are very useful tools.

 

[DavidR8]

Can you post a picture of your face mills @pontiac428?


Sent from my iPhone using Tapatalk

 

[pontiac428]

Here you go. I paid about $30 for the lot (less arbor) and am really happy with the results.

 

[mikey]

I don't own a face mill so have no dog in the fight here but I wanted to say that for a low horsepower mill, fly cutters actually are a good option. I know you said they don't work well for you but they should. The advantage of a fly cutter is that they put all the available power into a single cutting tip so they can usually hog a lot of material while providing a decent finish. The trick, it seems, is to have the right insert. I don't use HSS tools in my flycutters anymore. They don't last nearly as well as carbide, although they do finish better if the tool is properly ground.

In my Sherline mill, I use their proprietary carbide insert fly cutter and I have not seen a flycutter that will put a better finish on a work piece. It uses a single CPMW insert that will produce a really nice finish in most materials. I used this to surface the steel plates for my knurler.

I use a Tormach Superfly on my RF mill and it works well. Although it can't finish as well as my Sherline tool, it does a very acceptable job of it while also being able to hog an amazing amount of material off. The big advantage is that it will surface up a 6" piece of work.

You might want to look at the Tormach Superfly. I could have gone with a small face mill but having a single insert gets around a lot of issues - cost, aligning all the inserts, etc.

 

[diamond]

@mikey I appreciate the input on using a fly cutter with inserts as well. In fact I've looked at that Tormach superfly and it's on my list of options.

Thanks for the inputs on the face cutters. I suspect insert alignment on my 2" may be some of my problem with it. It seems to make a lot of noise no matter what speed/feed/DoC I run it at. Not sure about how to go about adjusting that. Might be another whole topic.

@Lo-Fi good thought on the extra power a circular insert would require.

 

[diamond]

Flipped the face mill inserts to a fresh point. Still got a crappy finish so watching for chip color I kept DoC same and increased both speed and feed until I saw chips starting to come off golden brown. At that point I was at 1200 rpm and ~6-7 ipm the finish cleaned up decently. I wouldn't call it spectacular but definitely serviceable. This is faster than I usually would run this tool so thanks for the tip.