Milling flats on an ER Chuck?

[andy198712Participant @andy198712]

Hi,

 

im new to milling and still learning what you can and can’t do.

 

i have an Arc ER40 collet Chuck but it’s a bit of a pain to change the collect as there’s no flats on it.

New sieg 2.7l mill too. As the ER40 is big getting the spindle holding tool up there is a pain (had to grind the tool to get it to fit with the collet Chuck)

 

so my question is, can I go at the collet Chuck with coated HSS end mills or will it have to be carbide?

or will the Chuck simply laugh at me and it’ll need some sort of grinding arrangement ?

 

thanks

Andy

[SillyOldDufferModerator @sillyoldduffer]

Test it with a file.   If the file cuts easily, it should mill OK with HSS.  If the it cuts reluctantly, go carbide.  If the file bounces off grind it.

Also useful sometimes is to rough cut with a grinder and only use the mill to tidy up.

Dave

[andy198712Participant @andy198712]

Thanks.

 

that tells me if it’s case hardened right?

[SillyOldDufferModerator @sillyoldduffer]

Maybe – if it’s case hardened, grind some off and try the file again.  If it cuts more easily, you’ve got through the hard later and can mill it.  Don’t be afraid to attack aggressively with the file.

Best way to find out is to try it – with a little practice on various metals you get a feel for how soft, or hard a metal is, and whether or not the hardness is only a surface layer.

My guess is an ER chuck will either be hardened or not – but it might be case hardened.

Dave

[Howard LewisParticipant @howardlewis46836]

Very often the inertia of the motor and the drive train will be sufficient for a sharp blow, or two, on the clamp nut spanner, to tighten it enough to hold the cutter securely.

This method will be more effective, if a low  spindle speed is selected (So that the spindle is trying to drive the motor at a higher speed) Then, when the clamp nut is tight, select the actual speed that you want to use.

Howard

[Dave SParticipant @daves59043]

Carbide endmill will do it.
Though they are hardened it’s not for hardness as such, more for toughness. I turned an er16 one to fit into my Deckel S0, and milled flats on a different one in the construction of a work head for grinding.

Be sure to check your feeds and speeds for the mill you are using, even carbide isn’t indestructible

Dave

[peak4Participant @peak4]

If all else fails, sharpen a carbide tipped masonry bit and drill a shallow hole, using another piece of metal with a hole in it as a guide to save the bit skating around on the curved surface of the chuck.
You can then use a C/peg spanner, similar to the one for tightening the ER nut

Bill

[DC31kParticipant @dc31k]

A holding device that works on a cylindrical surface could be an option to bypass the need to touch the chuck at all.

Something that looks like a pair of nut crackers, with rubber or abrasive paper glued inside the jaws, providing maximal circumferential contact, might work.

The chicken and egg question is what chuck do you use to hold the cutter to mill the flats in the chuck?

[VicParticipant @vic]

Do you have a full set of ER40 collets? I ask as it might be easier in the end to just buy an ER32 collet Chuck with flats on it. ER32 collets are cheaper and go up to a size more than big enough for your mill. I actually have oversize collets going up to 1” for my ER32 chuck. Just a thought.

[andy198712Participant @andy198712]

Some very good points raised.

and yes the irony of needing another collet or Chuck to machine my Chuck!

 

I only have 4 collets in ER40 (or any for that matter, early days!)

 

I went with ER40 as I assumed bigger ment more ridged and allows for bigger tools or work holding if I got those square and hex holders

 

but as I found this week the width of the head limits you at times which made me think about getting an ER16 Chuck with a straight shank for fine work 3mm end mill kind of stuff on the odd occasion the ER40 wouldn’t get in.

thoughts?

im quite happy to have 2 chucks

[andy198712Participant @andy198712]

I should mention too I was also thinking er40 as I could get a mount for my lathe too and it’ll work for work holding in that too

[JasonBModerator @jasonb]

I’d get the ER16 on an R8, less stick out which makes it more rigid and you get more head room.

I’ve only used upto ER25 on the SX2.7 but for larger dia tooling like the face mills and big flycutter have just held the tool and tightened the drawbar as the pin spanner does not fit.

Drilling the chuck for a tommy bar would be another option

[Bill PhinnParticipant @billphinn90025]

I had an ER25 chuck from Arc with no flats. I tried a strap wrench initially and then a pin wrench. These worked, but the first wasn’t very convenient and neither allowed adequate torque to be applied in some cases.

So I milled flats using a carbide end mill held in a direct collet. I seem to remember I tried with HSS first but it didn’t sound good so I moved to carbide.

[old martParticipant @oldmart]

I have added flats to two er25 R8 arbors using a solid carbide endmill. More by luck than anything else the spanner size is the same as newer ones that have them from new. I have not seen any size er arbors on sale recently which don’t have flats as standard.

[andy198712]

On andy198712 Said:

Some very good points raised.

and yes the irony of needing another collet or Chuck to machine my Chuck!

 

I only have 4 collets in ER40 (or any for that matter, early days!)

 

I went with ER40 as I assumed bigger ment more ridged and allows for bigger tools or work holding if I got those square and hex holders

 

but as I found this week the width of the head limits you at times which made me think about getting an ER16 Chuck with a straight shank for fine work 3mm end mill kind of stuff on the odd occasion the ER40 wouldn’t get in.

thoughts?

im quite happy to have 2 chucks

From my own experience there always seemed to be more equipment and fixtures available for ER32 than any other size. One example being the Spin Indexer that Arc used to sell.

You can’t have too many collet chucks though provided you’re prepared to buy some more collets! 😉

 

[old mart]

On old mart Said:

I have not seen any size er arbors on sale recently which don’t have flats as standard.

Well OM – these ones fom Warco (one of which I’ve just purchased) don’t have any flats.

The subject was debated here quite recently. I was assured it was normal!  🙂

Warco R8/ER32 Chuck

Regards,

 

IanT

[IanT]

On IanT Said:

On old mart Said:

I have not seen any size er arbors on sale recently which don’t have flats as standard.

 

The subject was debated here quite recently. I was assured it was normal!  🙂

Warco R8/ER32 Chuck

Regards,

 

IanT

Please could you provide a link, Ian? The last time I remember it being debated was over five years ago, and although Arc aren’t/weren’t the only suppliers selling flatless ER collet chucks my experience is that flatted versions are commoner than flatless ones.

Why you’d want one without flats I’ve yet to find out.

[Dave SParticipant @daves59043]

I mostly use ER32 on my main mill – which is a 40 taper 1700 kg TOS FNK25… Tooling larger than that is direct in the taper.

I also have ER16 which is handy when the ER32 is in the dividing head.

 

[Bill Phinn]

On Bill Phinn Said:

[…[ Please could you provide a link, Ian? The last time I remember it being debated was over five years ago, and although Arc aren’t/weren’t the only suppliers selling flatless ER collet chucks my experience is that flatted versions are commoner than flatless ones.

Why you’d want one without flats I’ve yet to find out.

Not wishing to steal Ian’s thunder, Bill … I think this is the link you want:

https://www.model-engineer.co.uk/forums/topic/easiest-cheapest-source-of-r8-socket/#post-806492

MichaelG.

[Bill PhinnParticipant @billphinn90025]

Thanks, Michael. I may post in that other thread.

[andy198712Participant @andy198712]

This one came from Warco just recently but in the ArcEuro packing, they must have brought there stock I think. Same with the collets. Wish I brought more when they were on sale but gotta draw a line in the credit card somewhere!

good info on the milling, carbide and away I go! After I buy a ER16 collet setup!

yeah the pin spanner got modified to fit, first thing I did shaved the edges and shortened the pins a tad. Not ideal but needs must an it would be cheap to replace.

[andy198712Participant @andy198712]

Just to follow this up.

 

10mm arc carbide endmill cut it fine!
it was 50mm dia so made the flats 42mm which means I can use the pin/open wrench that came with the mill.

probably make a 42mm tool at some point

[andy198712]

On andy198712 Said:

Some very good points raised

(——-)

think about getting an ER16 Chuck with a straight shank for fine work 3mm end mill kind of stuff on the odd occasion the ER40 wouldn’t get in.

You would still need a collet holder to hold the straight shank. Do NOT use a drill chuck for that.

[andy198712]

On 12 September 2025 at 20:40 andy198712 Said:

…

i have an Arc ER40 collet Chuck but it’s a bit of a pain to change the collect as there’s no flats on it.

…Andy

This came up in another recent thread, in which I posited that flats aren’t necessary.  Well I tried it, and not using flats works, but it made life difficult. A timewaster.  So I’d mill flats on holder if they weren’t already there.

Not difficult because I have an MT milling cutter holder, assuming that is that the holder isn’t rock hard.  Mine isn’t.

Could be done manually – start with an angle-grinder and then file to size neatly.  Size not critical: my flats are gripped with a home-made spanner because I was too mean to buy a real one.  Home-made spanners can be fitted to home-made flats, no need for replicate a standard Across Flats dimension.

[HollowpointParticipant @hollowpoint]

It looks like you’re sorted now, but I had a similar problem, I needed a collet chuck for my new VMC. It needed to have fats as it doesn’t have a spindle lock. I already had a comprehensive set of ER40 collets.

In the end I bought an R8 ER40 collet chuck from shop-apt for the princely sum of £20, it has flats and I was very pleasantly surprised with the quality.

Since then I also bought a good set of R8 collets, I use these far more often now as they leave more room under the quill and are slightly more rigid.

[Author]

Posts