Mini review of single cutter insert end mills

[BCRider]

A recent thread asked about tool options for cutting through the hard and abrasive outer skin on cast iron castings. And by extension this applies to mill scale. Big face mills were mentioned but the parts that were shown were smaller.

I went to have a look online with my new favorite home delivery supplier and found THIS THREE PIECE SET . Chuffed with my success with the 3 insert 1.25" face mill I bought about 6 months back and which has served well with prepping hot rolled stock a few times since I decided to order up this set to try out. The friendly Amazon guy dropped it off a couple of hours ago. It was a great excuse to put off some gardening.....

I used the 5/8 size to skim the bar shown. Yes there's swirl marks as one might expect. But my fingernail dragged over the surface in any direction feels nothing at all. Just a glass like smoothness.

I ran my first test at .015 DOC and 1400 RPM. Result was nice but a touch "cloudy" looking. Smooth to the finger nail though. I then ran at 1600 and now the finish had more of a shine to it. And needless to say I could traverse the cuts faster to keep a nice chip coming off the cut. For the 5/8 diameter 1600 worked out to 262 SFM. That's actually below the recommendation for mild steel by about 80SFM. So I might have to try the next speed up. But as it was I'm already pretty happy... but for one thing.

Note in picture 3 that I managed to chuck out part of the edge. This would be right where it was carving through the mill scale. I don't know if I did something wrong and caused a back drag or what. Or it might just be luck of the draw with the low cost import inserts. I'll get back to you all with that after some more testing. Sharp eyes might notice a deeper circle in the middle of the face on the test piece. I suspect that's where a piece of the carbide chunked out and got pulled around by the edge before being flipped away.

The close up of the insert face shows that the inserts are not simple triangle shapes. There's a small secondary skimming edge to aid with avoiding the usual wave like pattern that would occur with a simple round tip.

All in all I think I'm pretty happy with adding this trio of small flycutters, which is essentially what they are, to my milling ability. Especially if they avoid wear and tear on my other "proper" end mills for doing something as basic as skimming away the mill scale.

EDITED TO ADD- The vertical edge on the insert is not vertical. I made a set of three small vertical cuts along the one end with no X axis change. Just the table and traverse in and out on the Y. The result was a slight stair step. So these are not good for doing any vertical face skims. Very much small diameter fly cutters only for doing flat surfaces.

[BCRider]

Looking this over again I realize I've totally focused on the performance and any issues. Nothing about the quality of the tool bodies.

The machining is very smooth overall. I deliberately over exposed the picture below so you can see more detail in the black finish. Also note how the clamping screw on the one edge on cutter is angled so the edge of the head contacts near the middle of the insert for a really good hold. From what I can see they got the details right on these. Also that top edge on view shows that there's a slight negative rake to the face. I expect that this has something to do with the very smooth finish on the steel.



Measuring the shanks show that they are all right around 0.4996 to 0.4997 evenly along the length of the shank.

And since many of you work in aluminum a lot here's a shot of two passes on some scrap with the 9/16 again. RPM was 2500 and a new corner of the insert used for the test.



The first pass is the one on the right and the return pass the one up the middle and the band on the left is the raw stock. Touched off by probably a thou or two then added .01 more and ran the passes. The finish on the middle band is nicer than the start of the right band. But the right side pass was done dry. The return used water based fluid. My finger nail does catch a little on the finish of these. But it's very smooth in appearance. I tried to make it look as bad as I could with my small head LED light. So this picture is actually worse than it looks in regular shop light.

I also wonder if the slight negative back rake on the cutter is not great for aluminum? It may be that a similar size single cutter end mill with an aluminium specific APKT insert would do a better job? That might be next....

[MrWhoopee]

We used a lot of the larger version of those cutters you bought. The angle of the screw causes them to fatigue and eventually break. Both ends of the screws had hex sockets in them (to remove the broken stub) which made them thin and weak. Some were worse than others. Buy some extra screws.

I also wonder if the slight negative back rake on the cutter is not great for aluminum? It may be that a similar size single cutter end mill with an aluminium specific APKT insert would do a better job? That might be next....

I just ordered 3 of those. They come with metric shanks, so I ordered the ones I can turn to inch sizes, though the 19mm won't require it. Believe these cut to a square shoulder.

[BCRider]

Thanks for the warnings on the screws and shanks. I've been thinking of a set of R8 metric collets anyway since most of the solid carbide cutters (for Canada) are metric shanks. So if I opt for a set of these end mills with the APKT inserts for aluminium then that's how I'll go. Mind you I don't have to cut through mill scale on aluminum.... I might be overthinking the need.

[old mart]

Its always worth testing for square sides, many are not quite 90 degrees. I have a 50mm 4 insert APMT shell mill which leaves a slightly sloping shoulder, and the box is marked as such, the others I have are pretty good on shoulders. You should try the really cheap APKT or similar inserts for aluminium. I use these inserts in mills from 10mm to 80mm, 1 to 6 inserts each. The mills are 1 and 1.5 hp, so I have not been tempted to go larger.

[old mart]

BCR, I have a set of three very similar to yours, they have a 1/2" shank and are used in the boring head for the mills. I have never used them directly, having so many alternatives.
I also have several of the type recommended by Mr Whoopee, they are good, the only time I had to reduce a shank was with the 25mm one, R8 collets only go to 20mm, but the shank has been reduced to 19mm which gives a greater choice of lengths out from the collet. 20mm collets only allow about 1 1/4" holding length.

[Doozer]

They look like boring bars for sure.
Using one as an end mill makes me think
it is performing like a fly cutter, more than
anything else.

--D

[BCRider]

They look like boring bars for sure.
Using one as an end mill makes me think
it is performing like a fly cutter, more than
anything else.

--D

Yer right, I mentioned it when I tried to do a facing on an end of the test piece. They really are mini flycutters. Here's a shot of the results from three downward steps. The cut surfaces are on the lower part of the picture. As you can see the finish wasn't all that great anyway. No where near as smooth as the surfaces made when used as directed.... The steps are only a couple of thous but as you can imagine this is not their strong point.

[JRouche]

They look like boring bars for sure.
Using one as an end mill makes me think
it is performing like a fly cutter, more than
anything else.

--D

Yes Sir, you are correct. They are just boring bars listed as end mills, Y


You have to blame the marketing Manager? Call a drill bit an end mill, They will buy it, JR
To expound..

[BCRider]

The shape of the "wiper" tip with the flat on it which puts some focus on it as a "mini fly cutter" would make it not that great as a boring bar to be used with a boring head. But the same plane tips are available with simple rounded corners. HERE IS THE WIPER TIP INSERTS.

I wonder if the slight negative back rake on the inserts might make them a bit less than ideal though. Or perhaps it would result in even better finish? It would cost me $32 to buy a 10 pack of the fairly LARGE NOSE RADIUS TPG222 INSERTS to find out.

As boring bars go though they are pretty darn short.

[Doozer]

Yes Sir, you are correct. They are just boring bars listed as end mills, Y


You have to blame the marketing Manager? Call a drill bit an end mill, They will buy it, JR
To expound..

Why not call them, drill mills ? ? ? ? ? ? ? ? ? ! ! ! ! ! ! ! ! ! ! ! !
Why not call them, mill drills ? ? ? ? ? ? ? ? ? ! ! ! ! ! ! ! ! ! ! ! !
Or better yet,
call them DMs
or
MD?
Maryland and Medical Doctors will surely not mind !
No one uses Digital Meters here. No biggie there.

-D

[Glug]

Don't single insert 'end mills' hammer the spindle due to the interrupted cut?

[Fasturn]

Don't single insert 'end mills' hammer the spindle due to the interrupted cut?

It can ? When there is no shearing on a cutter, they wont cut well. Old 2 flute carbide end mill with one side cut short would work better. When it looks like a tool for a hammer drill, it ain't going to work. BC has the same mill as I do. NO insert tools, just roughing mills and light fly cutting on a lite duty mill spindel.

5 inserts on a CAT 40 / 50 spindel is a money maker, but 1/3 on a Chi- com mill is a disaster $$ Retired, I have more time......than money. 🌝

You want to cut steel on that small mill, here you go ! Your insert mill / fly cutter for a finish tool.

[BCRider]

Don't single insert 'end mills' hammer the spindle due to the interrupted cut?

To add to Fasturn's answer.....

Yes it does. But then when doing light surfacing cuts so does a two flute. And if a thin edge is done with the wrong approach so can even a four flute.

How the pass is done can make a big difference. This sketch to shows some choices.....



"A" shows a conventional milling pass to take away much of the stock. The fine entry at the engagement point at the top of the circle reduces the banging and slamming.

"B" shows what might be an "obvious" way to make the second pass. But now the cutter is slamming into the metal harshly. And yeah, that gets noisy in a hurry. So I do the second cut as per "C" which greatly reduces the entry slam.

And if the truth be told I actually make my first pass as per "D". Technically this is climb milling. But by keeping almost all of the cutter engaged there is almost no tendency to self feed into the part. And this way since I'm cutting into the edge I don't get any significant burr like I would with the pass in "A". It's not quite as smooth on the cutter but it's smooth enough.

I used these methods even with the HSS cutters since it did seem to make them smoother cutting and last a touch longer.

I hope that helps?

I'd like to also add something new that wasn't mentioned in the review.

I did mentione that I didn't buy these to use for just regular milling. The sole function of these insert tools is to prep hot rolled stock or cast parts to clean through the hard skins and mill scale.

Up to now I've been buying cheap 1/2" end mills to do just this. But those prep mills are currently $13 each. I've been buying these dedicated prep tools for a while now and keeping them separate from the other shapes. I've found that they dull to non useable about four times faster than the tooling that only sees prepared metal since I started this a couple of years back.

The insert in these new cutters are $3.20 each and there's three tips. So even if each corner only lasts half as long as the HSS mills that's still about 6 times cheaper. And if I get the much higher life that most of us expect then my costs for just removing surface scale will drop hugely. So buying these and the three flute 1.25 cutter all stand to save me a heap of money.

Generally we expect a single fly cutter style to result in extra time per pass. But in this case with being able to run at 1600RPM or 5 times more than I found I got the best results with by using the 1/2" HSS mills I'm actually able to crank the handwheels at roughly 2 to 2.5 times as fast. And even that is resulting in very small delicate curly chips. If I slowed down at all I get dust. The passes on the test bar in the pictures were done at around 0.1" in 1.5'ish seconds So about 4 inches per minute. That's easily twice as fast as with the HSS end mills. So despite the single tooth I'm actually going to be able to clean up the surfaces in about half the time.

[Cenedd]

I tend to run an aluminium profile CCGT insert in a left-hand lathe tool mounted in a modified fly cutter(slot widened but still on centre). The one time I've had to deal with mill scale I ended up buying a cheap import CBN CCMT/CCGT insert and got a lovely finish from it. Not sure if the wider swath but lower feed/speed would help your productivity or harm it...but thought I'd throw it in on the off-chance it was interesting.