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How useful is high 5000rpm spindle speed in a mill

This is yet another 'which mill' thread in disguise.

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jaCK Hobson02/02/2022 17:27:53
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I just can't make that final decision on 'which mill' but I do notice that of my short list (Warco 16/18, Sieg 2.7 - 3.5) that the Seig 3.5 has a 5000rpm spindle speed. I do fantasise that I might want to use 1mm mills and small drills for clock/watch work. Is that high speed really going to be any practical use.. and therefore could be a 'deciding factor', or is it a red-herring and I'm back to indecision?

ie. buy the sx3.5zp ... or not? Sorry, but some people never got bored of 'which mill'.

Peter Cook 602/02/2022 17:50:41
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Depends what you are planning to do with it.

I frequently use 4000rpm plus on my SX1LP when drilling tapping and clearance holes for M3 and M4 fastenings, particularly in aluminium. If M3 & M4 seem very small to you - it's probably of little value, and the odd hole at lower speed will work just as well.

I also use 1 & 2mm mills in aluminium to cut small 3-4mm wide slots. Again the high speed is useful.

I do feel pangs in the wallet when I look at the SX3.5ZP!!

Edited By Peter Cook 6 on 02/02/2022 17:52:22

jaCK Hobson02/02/2022 17:57:54
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M4 sounds medium size. I'm a little daunted about getting a bigger mill... workshop space is valuable.

Mike Poole02/02/2022 18:01:46
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A 3mm carbide end mill might need 30,000rpm to mill some aluminium at optimum speed, you are more likely to have not enough speed than too much to satisfy the calculated speed. Running slower than the theoretical speed will not do any harm but pay attention to whether the machine will have enough power at slow speeds to drive larger cutters, turning the speed down on an electronic control will also turn down the power available, mechanical speed reduction has the useful effect of multiplying torque and keeping the power up.

Mike

Edited By Mike Poole on 03/02/2022 00:22:41

JasonB02/02/2022 18:22:04
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As mike says if you want to run carbide cutters then they can use a lot more than 5000. ON the KX3 I use carbide all the time and a 6mm cutter at 4-5000rpm on steel depending on type of cut. If I had more I would use it when cutting aluminium and non ferrous.

It would certainly make a good basis for future CNC conversion or simply speed up any manual job as if you can run a cutter faster you can feed it faster so the cut does not take as long.

Slow speed should not be an issue with the h3.5 as it has two belt ratios so if you are swinging a big dia with a boring head or using a 199mm slitting saw it will be better than a single ratio machine.

Andrew Johnston02/02/2022 18:48:44
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Posted by jaCK Hobson on 02/02/2022 17:27:53:

..Is that high speed really going to be any practical use..

Depends what you want to do. I rarely run the Bridgeport beyond 3000rpm, as it gets quite noisy. But on the CNC mill I regularly run at the maximum of 5000rpm. For small cutters I have a separate high speed spindle. With a 1mm cutter I run at 24000rpm. High spindle speeds allow a higher feedrate and reduced machining time. But they also have the effect of minimising tool breakage due to small variations in the feedrate.

Andrew

Dave S02/02/2022 18:54:48
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Not directly comparable but my TOS has a top speed of 4500 and I often use it.
Dave

old mart02/02/2022 18:56:06
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Very useful if you are milling using cutters of 6mm and below for small projects.

JasonB02/02/2022 19:26:21
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And come Novenber 5th you can also run larger dia cutters at 5000rpm in stainless on it, climb cutting for good measure

sparks.jpg

Pete Rimmer02/02/2022 19:31:00
1233 forum posts
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Posted by Dave S on 02/02/2022 18:54:48:

Not directly comparable but my TOS has a top speed of 4500 and I often use it.
Dave

Which TOS do you have Dave? I am renovating a FN22 and it has a high-speed head for 3100-5000rpm.

Edited By Pete Rimmer on 02/02/2022 19:31:22

John Haine02/02/2022 20:41:32
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My little Novamill CNC has a maximum speed around 5K. Most of my work has been in aluminium or brass recently and I tend to run the spindle flat out with cutters up to 6mm. I've done some engraving and gear cutting with 1mm cutters and below and I wish I had a proper high speed spindle with at least double the speed.

My advice would be to go for the high speed.

Dave S02/02/2022 22:16:50
370 forum posts
90 photos

A FNK25. Bought it on eBay for £600 a good few years ago. It was somewhat larger that I intended, but I’m very attached to it now.

FNK25.jpeg

The size is really useful sometimes, but it’s also sensitive enough to drill sub 1mm holes and use 2mm carbide cutters. It makes an excellent tapping stand - done a fair number of M1.6 threads with it.

caac810b-4ddb-4002-ae84-8d28c1ab08e9.jpeg

This was during the making of a stainless steel watch case for my daughter. If you look closely you can see the tiny cutter.
I can’t figure out how to make the pictures the right way up.

Dave

Emgee02/02/2022 23:13:38
2426 forum posts
290 photos

Jack

My mill has a top speed of 2k so when using small cutters feedrates have to be very low to preserve the tool, I would love to have 5k available on the spindle but not at the expense of low power at low rpm, I believe the Sieg machine you stated would not have this problem but other makes may.

Emgee

Edited By Emgee on 02/02/2022 23:14:22

jaCK Hobson03/02/2022 08:51:32
262 forum posts
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Hurrah! I think I have found a decision point! I really expect that I'd be happy with any of the mills on the shortlist, small or large, and that I can't really go wrong, but it is sometime useful to have something simple to remind you of 'why' you made the decision... which was 'right at the time' even if you want to change it later.

jaCK Hobson04/02/2022 15:37:10
262 forum posts
92 photos

The next procrastination is whether to get the cabinet stand. Looks pricey for not much storage. Does anyone get excited about the stand for their machine and are really pleased they bought it? I'm thinking just putting a back panel and decent top on an old kitchen cabinet...

Andrew Johnston04/02/2022 15:54:32
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Posted by jaCK Hobson on 04/02/2022 15:37:10:

....anyone get excited about the stand for their machine....

Not really; two of my mills are floor standing. For the third (CNC) I made my own stand and coolant tank:

tormach stand me.jpg

Andrew

John Haine04/02/2022 17:21:56
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pxl_20220204_161219651.jpg

I think you need something a bit stouter than an old kitchen cabinet.

John Haine04/02/2022 18:03:01
4679 forum posts
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My VMB sits on a stand with 3x3 uprights, a top frame of 2x2 with 2 cross braces under the worktop, 2x2 braces half way up side and back legs, double thickness of high quality 3/4 ply for the top. Sides and back further braced with veneered chipboard glued and screwed. The side braces provide convenient ledges for a shelf, and there's a lot of storage underneath as well.

JasonB04/02/2022 18:27:10
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If you put legs down each corner of the kitchen cabinet and a solid back panel over the lot that should stiffen things up.

My X3 and SX2.7 sit on not much more than carcases with a solid bench over the to that is fixed to a batten along the wall. The KX3 is on a pair of legs fixed to the cabinet at the side with a tick ply top also tied to the wall

jaCK Hobson05/02/2022 14:24:38
262 forum posts
92 photos

I'm starting to get excited! I have a part-full shopping cart at Arc. sx3.5, no stand.

I think I'm going to buy just a vice and what I need for the first job (fit a DRO to my Myford with the scale under the slide) which means I won't get one of those package deals on cutter and clamp set... but then I miss out on 10% saving!!

I have a 10mm Myford size clamp set, and a 15mm already... but the sx 3.5 needs the one I haven't got - 12mm. I'm thinking I don't need that - just something to hold the vice on?

I get one half-decent HSS 10mm 3 flute cutter and one r8 10mm collet

And the 100mm, not the 125mm vice... which seems to be Jason and Ketan's recommended size for these machines. Cost different is insignificant to me.

And I imagine I need at least a cheap set of parallels to make good use of vice.

Then, if I can bring myself to push the button, I have to find and read those threads about how to move the crate from the road to the end of the garden...

Mind you , I worry that once I commit I will lose one of my favourite past-times - checking specs of different mills on the internet - I've been reading about mills for many years.

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