Speed is about right at 900-1000rpm

I would feed a little slower something like 75-100mm/min which would give a chip load of 0.015 -0.02mm per tooth.

You don’t say which inserts you are using but if you go with the more polished inserts meant for aluminium and non ferrous metals you should get a slightly better finish and the machine will thank you for it as these inserts are sharper and put less load onto the light machine. Keep one corner for the ali and non ferrous and the other for steel & iron as they will blunt a little bit faster but worth it.

This is a 2.7 using the 80mm 6 insert at the same sort of speeds and feeds I mentioned, full details in the comments

Difficult to tell but the  finish doesn’t look great; seems quite rough? I used a 50mm diameter insert mill from ARC a few days ago to clean up some hot rolled steel plate. It has five inserts and I used ordinary inserts. I find the inserts intended for aluminium are a bit delicate for general purpose work. Parameters were 800rpm, depth of cut 1mm and feedrate 400mm/min. Feed is based on a chip load of 0.1mm per insert, times 5 and then times 800. Swarf came off as short chips and straw colour. The finish feels quite smooth to the touch. Just done a fingernail test compared to a Rubert scale and I estimate the finish to be about 2 microns Ra.

Andrew

ARC don’t do a 5 insert 50mm one.

The much lighter SX2.7 would struggle and probably stall with the Chipload Andrew mentions but fine if you have a decent size solid machine with belt/gear drive rather than electronic variable speed they can also make the most of the ordinary inserts

Aluminium you can run faster, feed faster and take a deeper cut, there are some here using the SX2.7. Without powerfeed it is hard to feed faster, particularly with the 2mm pitch screw. Earlier the X3 is feeding at 300mm/min. Add a bit of paraffin to prevent metal from sticking to the inserts

Sorry Andrew, My mistake I was forgetting there were two heads with 5T

I suppose without an optimum machine you can’t really expect the inserts to be able to operate at optimum either. The benchtop ones just can’t hack it.

I have found with the electronic variable speed lightweigh hobby machines the Cutting speed from makes tables can be used if you pick the top of the speed ranges but feed rate (chipload) and DOC have to be adjusted downwards. I’m sure with bigger machines you can run closer to makers suggestions but I’ve no experience using those so can’t offer an opinion based on actually using that type of machine but I do have the same machine as the OP and know what it can and can’t do.

Chip loads also seem to vary between makes, take this chart which is handily divided up into facemill diameters and quite a few are 0.05mm, amount of cutter engagemet is what the fig 1, 2, 3 is related to. The chip thinning when less of a stepover is used allows an effective higher chip load.

If I get a chance in the next day or two I will give it a go on the SX2.7 using Andrews 125m/min cutting speed, 0.5mm DOC and 0.1mm chip load provided I can turn the handle at 200revs per min. I don’t have a 5T 50mm dia but as the OP has a 5T 63mm dia facemill will use that. Keep an eye out for the video and smoke.

Since we’re talking metric on this thread:- 63mm at 950rpm is 188m/min.

I’d suggest that this is too fast without serious coolant. Try going down to 500 rpm

­Out of idle curiosity I’ve just measured the surface finish on my steel block and got results ranging from 1.26µm to 2.06µm, both Ra. That’s a fairly good finish, and way better than the block needed as it was a former for hot forming 3/8″ and 1/2″ internal radius flanges in 3mm and 5mm steel sheet.

Andrew

I’ve got the 50mm 5 insert one (presumably the same as Andrew’s), used in a Warco WM16B. The machine doesn’t sound too happy at around 1000 rpm or less, and the surface finish isn’t great, but crank the speed up, right up!, 2000 rpm+, and it starts working properly – the machine cuts smoothly and the surface finish is like a mirror (n.b. not rubbed but cut cleanly, and to desired dimension).

It is very messy though, producing a Catherine wheel-like spray of incandescent chips, so it only gets occasional use, which is why I can’t remember what depth of cut seems to work best, probably about 0.25 to 0.5. Feed was just what seemed to feel best.

This is with the supplied coated cutters on mild steel. I have also used it on some hardened steel jaws from a pipe vice – again it needed high speed, and inspection with a magnifier shows some erosion of the inserts, though they still cut well.

There isn’t a max rpm marked on it, which is a bit off-putting, but I can’t imagine it doing an unplanned disassembly at what is, in the general scheme of things, a fairly moderate speed for a well-balanced steel item. Best to use the variable speed control to wind it up from low speed and beware of any untoward vibration (the WM16B won’t start unless the speed is set to minimum anyway).

5000rpm sounds pretty plausible, the Warco goes up to 3000 and that worked fine, but I’d need to rig up some swarf shields to avoid playing too personal a role in the firework display.

edit: What’s it cutting in the photo?

On 31 October 2023 at 20:09 JasonB Said:

I seem to recall that Ketan has had the shell mills upto 5000rpm cutting stainless on the 3.5 machine, he may be doing it again in a few days when it’s Fireworks night.

As Jason YT link says: ‘Don’t try this at home’

The video was taken back in 2018 when I was testing the limitations of the SX3.5. It was one of many tests conducted with shell mills on the SX3.5 at the time. If one was to use it at high speeds, appropriate guarding should be considered, as the the swaft/bits which come flying towards you are hot and if they imbed into any exposed skin, you will remember it. For the purpose of the tests, machine fitted with a power feed was used.

The shell mills with inserts are designed to be run at high speeds.. usually for CNC applications which run at much higher speeds.. This is a positive attribute, especially for finishing cuts.

When used with a BRUSHLESS motor SIEG SX2.7 or similar range, one has to consider rigidity of the machine, along with delivery of toque.

The SX2.7 is a hobby machine with lighter weight casting than an industrial or CNC machine. If you try to run it too hard with a shell mill – higher dept of cut + low speed : greater diameter of cut, there will be greater vibration/stall event, followed by everything becoming loose/slack…. especially the table/head which could need re-adjusting of the gibs.

The toque on the SIEG range of BRUSHLESS motor machines is delivered by the programming on the control board. The programming on the control board is based on the maximum speed the machine is expected to deliver. The SX2.7 has a 750w output brushless motor with maximum speed of 2000rpm. The torque delivered at higher speeds will be greater than that at low speed.

So, based on the experience I have hand with these machines, it is better to run them at high speeds with low dept of cut when running full diameter … at a particular comfortable feed rate… based on the material being cut. Similarly adjusting the feed rate (reduce) for half or quarter diameter of shell mill being used for increased DOC.

Feed rate: to get a consistent feed rate, as well as to protect one self from flying swarf (even after shielding), I found it useful to use a power feed. This helped me to get the right combination for consistency and finish, for the material being cut.

I have spoken with Jason about this, and I understand that he will be putting up some photos/videos of his SX2.7 performing the above tests, in the coming weeks.

Ketan at ARC.

On the lines of ‘don’t try this at home’ (why not, I did 🙂 ) :-

Skimming a 10″ dia cast iron lapping plate with a diamond insert

That looks great Jason 😎

The feed rate looked a little fast. It looked as if you were working on a hobby CNC machine.

Hopefully this visual demonstration helps answer the OPs question better, using the coated inserts he has, for the ferrous material.

Ketan at ARC