Thread: replacing ER collet 'M' series (castle nut) with 'UM' series?

Just use a C spanner?

EDIT: Or leave enough space under the bit to fit the spanner you have around the shank

C - spanner ? Nope. an "M" series nut has tapered slots for the castle spanner to sit in. - A C spanner will just slip in those grooves. If the nut was a 'UM' series (with straight slots) then you could use a C-spanner. but it's the tapered slots in the 'M' series that are giving me the headache. I'd love to replace the 'M' series nut with a 'UM' series, which has straight grooves, and then yes, a C-spanner would work a treat, but as mentioned above the 'UM' series are totally different threads so won't go.

As for leaving enough clearance for the castle spanner - no can do. The tapered lands on the castle spanner, plus thickness of the spanner body would mean you'd need to leave the shank of the router bit with less than 1/3rd still in the collet - that's a recipe for a flying router bit as soon as the spindle spins up. I've already had 1 bit come loose during operation and nearly soiled myself.

If I'm using straight bits, then I can just use the correct castle spanner, but when I need to use wide bits, then a flat spanner like 'UM' series will slip between the nut and wings of the bit, BUT the grooves in the nut are tapered, and the 'UM' spanner isn't, so we've got a square peg-round hole problem.

If felder had just made the spindle to accept a ER25UM nut then it'd be no issue at all, but for whatever reason have threaded the spindle to ONLY accept an 'M' series thread, and then supplied a 'UM' series spanner.
I'm ordering a replacement spanner (as mine is worn), but ultimately that's just recreating the problem that should never have existed in the first place - they've designed the machine to have a collet nut, and collet spanner that ultimately are incompatible but supplied them that way anyway.

Hence if any engineers have a better solution to get around the problem I'm all ears.

EDIT: I've just found these - CON-ER25M 35mm CNC Collet Nut for Standard ER25M

which is the 'GM' series that seems to take the correct collet (ER25), and has correct thread (M30x1.0) but I can't locate any sellers outside of US, and no one else listing 'GM' series collet nuts.
That has straight gRooves, but they come from the bottom of the nut, not the top, and my spindle doesn't raise out of the machine by a whole lot, so is less than perfect. I'd need to buy a c-spanner and bend the shaft by about 30 degrees to get it up and clear of the machine body, but I reckon that'd still slip far less than the whole debacle outlined above...
Ideas?

If the nut isn't hardened, someone with a metal mill could mill out the slots to be not tapered. Wouldn't take long to do

I thought the same thing, but close inspection of the nut shows there's only enough meat for the tapered slots. The (incorrect) UM nut I bought has much more material around it's straight slots (hence it's overall diameter is much larger), but the 'M' series nut is tapered to match the grooves, hence if you were to try to mill straight slots you'd go right through the nut.

I haven't done a search, but Bolt & Nut Australia have a pretty comprehensive catalogue.

I’m struggling to visualise the issue, so maybe I’m misunderstanding, but is it possible Felder didn’t want you using router bits with wings wider than the spanner?

Originally Posted by TimberNut

I bought an ER25UM collet nut and ER25UM spanner, thinking that'd be a solution, but it turns out the UM series has totally different thread (M32x1.5) as opposed to the 'M' series which is M30x1.0 - and this is what the spindle is - M30x1.0 so I can't use the 'UM' series nut on the 'M' series spindle.

Yes, I learned that the hard way too. Great having multiple "universal" ER25 manufacturing "standards."

Ah cr@p. I was planning on using my Felder router spindle for the first time, spinning a large bit. Your post had me looking for a hex nut. They seem to be available for every size except ER25M.

I may have to resort to more hobbyist type measures, like making a small router extension to live outboard of the spindle moulder. My application is a through cut about 50mm wide, so it has to be mounted in some kind of router.

Beats me why Felder do some of the goofy things they do. Using an obscure ER standard made for endmills is just one more example. Especially considering that they were designing the router spindles unique to their machines.

Originally Posted by Greg Q

Ah cr@p. I was planning on using my Felder router spindle for the first time, spinning a large bit. Your post had me looking for a hex nut. They seem to be available for every size except ER25M.

I may have to resort to more hobbyist type measures, like making a small router extension to live outboard of the spindle moulder. My application is a through cut about 50mm wide, so it has to be mounted in some kind of router.

Beats me why Felder do some of the goofy things they do. Using an obscure ER standard made for endmills is just one more example. Especially considering that they were designing the router spindles unique to their machines.

Hi Greg,
I've emailed Amana tools (US) to see what the detail is about this nut - CON-ER25M 35mm CNC Collet Nut for Standard ER25M

From the specs online it looks like it will work as a replacement for the ER25M nut that comes with the router spindle for the Felder, using the same ER25 collets that you currently use with it. Having straight slots it will allow for more torque to be applied, but the only problem I can foresee is the slots come from under the nut, so I will probably end up buying a C-spanner (not sure what the correct size will be - I've asked Amana for that info too), and then heating and bending the handle up to clear the bed of the Felder when tightening. That should work for you too (presuming the detail re this nut is correct). I'll post an update when I hear back from Amana Tools.

Thanks for that. Please keep me in mind when ordering …perhaps we can share the freight by ordering two. Is there any reason we couldn’t use our ER 25m spanners upside down? I understand that the handle will have to be cranked, but that shouldn’t be a problem.

Greg

C7BE10B7-01FA-49EF-8775-874C9EA1EC2C.jpegI was looking at a related thread on the Felder user’s group. Apparently Felder used to sell a flat E type spanner for these nuts. I cannot see it in the catalogue, nor on the Felder E-Shop (which is as crap an online shopping site as you will ever find).

If we can get those flat spanners then we could probably have something that only needs 6mm clearance, not 14 as on the typical ER 25M castellated spanners.

I just searched through my massive pile of accessories that came with my machine, and of course, no spanner.

Greg

Timbernut, could you please put up some photos of the problem as some of us are metal machinists as well and may look at your problem differently.
Rgds,
Crocy.

Pardon me jumping in here, but these two photos should give you the gist:

With a big router bit we can only give up a few mm of shaft projection. About a 5mm thick spanner would be ideal, since you have to come down on the nut to engage the spanner, and 5mm is what I am showing in the picture. As you can see, the slots themselves are tapered, so there’s no purchase for a c spanner.

If we could find a cranked or bent handle version of the silver spanner I showed above that should solve the problem.

8C4371C6-F4EB-4D28-92E2-99146B1958DE.jpg
CAFC4927-6FFC-45AB-939A-A81354A6634A.jpeg

ER 25 Mini seems to be the only ER standard that doesn’t have an E type flat spanner, nor a hex collet nut option.

On edit…I looked at the charts of the nut dimensions to discover that the ER 25M is 35mm dia, while the ER 20 UM is 34mm.
I am going to try a ER20 UM flat spanner to see if that might end our woes.

Originally Posted by Greg Q

Pardon me jumping in here, but these two photos should give you the gist:

With a big router bit we can only give up a few mm of shaft projection. About a 5mm thick spanner would be ideal, since you have to come down on the nut to engage the spanner, and 5mm is what I am showing in the picture. As you can see, the slots themselves are tapered, so there’s no purchase for a c spanner.

If we could find a cranked or bent handle version of the silver spanner I showed above that should solve the problem.

8C4371C6-F4EB-4D28-92E2-99146B1958DE.jpg
CAFC4927-6FFC-45AB-939A-A81354A6634A.jpeg

ER 25 Mini seems to be the only ER standard that doesn’t have an E type flat spanner, nor a hex collet nut option.

On edit…I looked at the charts of the nut dimensions to discover that the ER 25M is 35mm dia, while the ER 20 UM is 34mm.
I am going to try a ER20 UM flat spanner to see if that might end our woes.

Hi Greg, yes I've reached the same conclusion - I was trying to figure out what that silver spanner is that Felder supplied - my best guess it is ER20UM.
Whilst I could go and buy one of those we're back to the same problem (albeit with a spanner that is no longer burred over) - trying to tighten a nut that has tapered slots, using a spanner designed for straight slots.
I may well do the same - buy an ER20UM spanner in addition, but that Amana collet nut looks like a better end result - I could apply more tightening force to it (with the correct spanner) as it has straight slots, not tapered.

So far I haven't heard back from Amana tools, but when I do I'll update this thread and keep you in mind to share postage if you want one too.