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Milling cutter advise

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Daniel Chilvers23/09/2020 22:30:37
4 forum posts


I’m a complete beginner at milling and only had my machine two weeks so please be gentle.

I’m looking for advise for the best end mill for squaring up stock in one pass. I’ve got a selection of ends mills the biggest being 12mm which takes several passes to machine the top face.

I’ve heard people talk about fly cutters, face mills and shell mills for machine large surfaces. What are the advantages and disadvantages of each the cutters, ie which is fastest or gives the best surface finish?

BTW I’ll be using them on Aluminum

thanks for you help

JasonB24/09/2020 06:57:59
18884 forum posts
2080 photos
1 articles

Daniel, and Idea of what mill you have would help with suggested answers.

David George 124/09/2020 07:38:43
1339 forum posts
448 photos

Hi Daniel welcome to the forum.

It sounds like you need a fly cutter to cut the top of the material but like Jason says a bit more detail about mill size and type. Aluminium cutts well with a fly cutter with a small amount of paraffin to lubricate as you go brushed or squirted on with a squeeze bottle. 20181206_080315.jpg

This is my small one with a 12mm shank and 25mm body with a piece of HSS sharpened on a grinder. The small radius on cutting edge works well on aluminium.


Daniel Chilvers24/09/2020 07:48:31
4 forum posts

It’s a Sieg sx2p mill, it’s end milling capacity is 20mm and face mill is 35mm. I’ll only be milling Aluminum about 20mm wide for now

HOWARDT24/09/2020 07:57:50
595 forum posts
15 photos

I have a the same machine but use steel, until recently I stuck with a fly cutter for larger surface widths but now use a 40mm dia face mill. Both are good but the 4 inserts on the face mill allow deeper cuts where required.

not done it yet24/09/2020 08:10:49
5016 forum posts
20 photos

Firstly tramming is important. Tighten unused axes for every cut once the head is trammed (with the axes clamped).

Larger cutters are better but any out-of-tram in either axis would leave fewer but larger ‘bumps’ between passes.

Fly cutters will leave ‘undulations’ as they will cut a wide shallow arc if not trammed perfectly. This may affect squaring-up more than several ridges on the workpiece when tightening against the fixed jaw.

Fly cutters are slower due to one cutting edge and speed limited due to high surface cutting speed and possible out-of-balance issues.

End mills can cut top and ends of workpieces.

Fly cutters are easily re-sharpened and are much cheaper to run, after the initial purchase (if not made in the workshop).

End mils are expensive and not easily sharpened. Generally have to be bought in, not home made.

For one-pass cutting, the cutter will clearly need to be bigger than ‘about 20mm’. The 20mm capacity is likely for steel - it will be larger for softer materials.

JasonB24/09/2020 08:14:34
18884 forum posts
2080 photos
1 articles

As the others have said a flycutter would have been the traditional choice and one that I would have used, with a plain shank one the same size as David's being my usual weapon of choice. These are not expensive and provided you are happy sharpening the tool bit will get many "sharp" edges for the initial outlay.

But lately I'm more likely to reach for an insert shell/face mill particularly on aluminium with suitable inserts. These tend to be more balanced that flycutters as the speed goes up which is what you want for aluminium and if using as 40mm dia 4 insert body you can feed a lot faster for the same given chip load. You can run one of these at full speed of teh SX2P and wind as fast as you can roughing at 1mm deep per pass and finish with that depth or less with half the feed rate.

From personal experience I would say avoid the very cheap facemills as there are issues with them but mid range from a known source with mid range Aluminium specific inserts will work well, this is what I'm currently using.

In both cases a small amount of Paraffin or WD40 will improve finish and stop metal sticking to the cutter

Edited By JasonB on 24/09/2020 08:26:14

Vic24/09/2020 10:43:33
2612 forum posts
20 photos

I use fly cutting a lot to square up stock etc. both steel and aluminium alloy. You can use a fly cutter on even a small mill provided the cutter isn’t too big.

I managed to buy a quantity of polished 6mm round carbide inserts so I made a holder for them and they work very well on aluminium alloy.

Its worth mentioning that on a correctly set up mill, if you traverse the fly cutter completely over the work piece you will get a “hatched” finish as the cutter cuts in both directions as it goes over the workpiece. This is normal. If however the part is small enough and/or the swing of the fly cutter is large enough you can get a superior finish by only letting the cutter work from its maximum swing up to the fulcrum. This is difficult for some to understand and incorrectly assume that if you don’t get a hatched pattern the mill isn’t set up properly or “trammed”.

Vic24/09/2020 12:03:55
2612 forum posts
20 photos

This is my 3 Morse taper Fly Cutter. I use a variety of cutters in it, I just swap the bar over. I also use a piece of HSS in it at times. Pictured is the 6mm round carbide insert for Aluminium. It’s actually a turning insert that I managed to get a box full very cheap. It works really well though on aluminium even with the interrupted cut of a fly cutter. You can also rotate the cutter several times to get a fresh cutting edge so cheap to run. I use it on a VMC but I’m sure you could run it on a smaller mill.

I always wear eye protection but this is particularly important when using any type of fly cutter as it throws chips everywhere! smiley


BOB BLACKSHAW24/09/2020 15:02:20
339 forum posts
68 photos

As stated don't bother with the cheap face mills, they look the business but the inserts on mine when fitted are all over the place.


Daniel Chilvers27/09/2020 14:46:09
4 forum posts

Thanks for all the replies. I’m leaning toward the shell mill at the moment as I’m not confident about shaping/sharpening the fly cutter blade. How easy is it to set all the inserts the same height on the shell Mill?

Daniel Chilvers27/09/2020 14:56:56
4 forum posts

Also is bigger better for end mills? If I can make the same cut with either the 6mm or 12mm cutter which one should I use? I’ve been using the 12mm cutter unless it’s to big to help get the SFM closer to the sweet spot

JasonB27/09/2020 15:52:29
18884 forum posts
2080 photos
1 articles

With a reasonable quality facemill the inserts will not be a problem to fit, just screw em in. very cheap ones can have loose fitting pockets.

Provided you are cutting around the right speed size won't make much difference and unless you have a means to sharpen then its more economic t wear and replace a 6mm one than a 12mm one

HOWARDT27/09/2020 17:38:29
595 forum posts
15 photos

No matter what diameter the cutter when face cutting you are only cutting on a small length of each tip. The larger the diameter the larger the torque required for the same cutting details. I find an 8mm diameter cutter ideal on my SX2P when cutting features in steel generally. Larger diameter may have to be used for side milling to cover a larger depth.

old mart28/09/2020 14:09:07
1991 forum posts
151 photos

If you want a shell mill, there are plenty of 40mm ones whick use 4 off APKT 11, or APMT 11 inserts. You will also need an arbor with a 22mm end which fits your spindle. You can use them with 2 or 4 inserts in them, or even 1 if you reduce the speed to allow for the out of balance forces. Inserts for steel and aluminium are freely available. I am not allowed to post a link on this forum.

Martin Connelly28/09/2020 20:10:13
1463 forum posts
168 photos

You could see what Arc Eurotrade have o start with, they advertise on this site and have plenty of people on this forum who have praised their service.

Martin C

J BENNETT 101/10/2020 13:47:08
46 forum posts

Just a small correction APKT inserts are size 10 or 16. APMT inserts are size 11 or 16.

The 40mm shell mills from ARC take an arbor with a 16mm spigot, 50mm and 63mm use a 22mm spigot and the 80mm uses a 27mm spigot. Also, from the web site it would appear that all of the ARC shell mills take size 16 inserts i.e. APKT 16 or APMT 16.

As you have a SX2P mill I assume it has an R8 spindle, it was the only option when I bought mine.

Now the bad news, ARC are out of stock of of R8 shell mill arbours in all sizes. When I spoke to them they said it would be around Christmas time before they expected to receive any more. I was on the email notification list for the last batch which came in a couple of months back but delayed a couple of days before trying to order and the 16mm arbors were already sold out. They seem to sell out very quickly.

R8 16mm shell mill arbors are available from other sources but are at least two and a half times dearer than ARC's. R8 shell mill arbors in 22mm and above are much more widely available.

I have been very pleased with my SX2P and try to support ARC as much as possible as I have found they provide acceptable quality at a fair price. (Usual disclaimer, I have no association with ARC whatsoever)

John B

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