Choice of collets

Hello,

I’m in the process of buying a collet holder and collets for my EMCO FB2 mill. Looking around the web I’ve narrowed it down to either ER25 or Clarkson autolock.
I have heard that when using ER type collets the cutter could move in the collet if too large a z load were applied, where as with the Clarkson system the cutters I believe lock into the collet.

Your thoughts as ever would be very welcome

Thanks in advance

The ER 25 requires a lot more ft/lbs torque to operate. The Clarkson or the Osborn version require a lot less.

The ER25 will take most modern cutters. The Clarkson only works for threaded cutters.

At 68 I use an Osborn as arm power can only go one way, down hill.

Done up properly they all hold cutters equally as well as each other.

Edited By Dave Halford on 29/10/2021 18:53:25

I have used ER collets for more than 20 years and have never had any problems with cutters moving in collets. I have also used the Clarkson system, and it works fine but the disadvantage is that you must use special endmills that have a threaded shank.

Jan

I can't say I have found it to be a problem, cutters seem to stay put in all my ER16, 25 and 32 collets. I do try to use the correct size collet for the shank for example I don't hold 1/4" shank (6.35mm) cutter is a 7-6mm collet but use an imperial 1/4" collet for best contact.

ER also have the advantage of being able to hold screwed, plain or Weaden9side lock) cutters which opens up the range of cutter styles and materials you can use as screwed shank ones are being made is less quantities now.

The Clarkson, Acramil, Osborn Titanic and similar will only work with threaded shank cutters. Solid carbide endmills or any plain shank types plus the threaded shank cutters will work in the er type system. It is easy to extend the er spanners, I made 12" long ones for the er25, so the tightness need not be a problem.

Cutter pull-out from ER collets is more an issue for CNC machines with much more power running cutters far harder in a coolant soaked atmosphere. We generally don't have machines powerful enough to pull a cutter out of a half decently tightened collet. Even if we did dealing with the chip blizzard and breathing coolant mix spoils the fun.

Although I have an ER set it pretty much never gets used. My go to is the Clarkson system. Worst thing about an ER set is that you loose all cutter length registration every time you change sizes. At least with Clarkson any changes are predictable as the cutter always goes back to the same place. Over the years I have "obtained" (nice elastic word) a "lifetime" supply of screwed shank end mills which helps. Imperial only tho' so I have to buy metric.

The native R8 collets get used more than the ER set. Generally when I need to hold carbide or when I don't want to pull the cutter out of the Clarkson for part of a job.

Also have sets of Metric and Imperial sidelock holders for Weldon flat end-mills. These days the only cutters I buy are metric, usually special at that, with sidelock flats. If I were starting over I'd standardise on sidelock holders and splash out on a couple or three of each of the sizes I use so I could keep my commonly used end-mills permanently mounted like the CNC boys do.

Its very easy to overspend on getting things you turn out not to actually use. Especially when starting out. A habit I've mostly outgrown over the last 5 out (of 45) years metal mangling. Back in the day affordable or "obtainable" stuff had to be grabbed when the grabbing was good. Hence Magpie syndrome. These days imports of at least acceptable are widely available in Home Shop price ranges and E-Bay turns up enough bargains to be worth watching. So no need to be a Magpie as buying what you need when you need has become financially acceptable.

Clive

Threaded shank cutters are a dying breed so go the ER or R8 collet route.

Tony

Never had a cutter shift in a properly done up ER collet. I have forgot to do them up but that’s a different problem.

I use ER16 on my Unimat, which predates me getting a mill, so I bought an ER16 chuck for the mill when I got it.
It’s an INT40 machine - TOS FNK25 so a bit larger than the typical hobby machine.

The other size i use is ER32 in the TOS, and in various fixtures like the Stevenson Spindexer for instance.

The tightening torque spec is quite large iirc, the ER32 hook spanner I use is about 18” long.
Do em up properly and I don’t think you’ll see a cutter shift

Dave

Consider the headroom you have between spindle nose and table. A small Clarkson chuck on whatever taper will have a certain length (height). An ER25 chuck and its nut is likely to have a shorter length, which may prove an advantage. The projection of a given cutter from a Clarkson chuck is fixed. You can, within reasonable limits, vary the projection of the same cutter from an ER chuck (choke it up or hang it out).

Here are a few things to consider.

If you use a collet directly in the spindle you need some way to lock the spindle to be able to tighten and then loosen the collet otherwise you may be on here at some point in the future asking about spindle locks.

If you get an ER collet system be aware that some collet holders do not have spanner flats on them. Same issue as above. It is easier to make sure you buy them with suitable spanner flats as otherwise you may have to add some by grinding or machining.

It takes a reasonable amount of torque to close down an ER collet so that it doesn't slip but you can buy replacement nuts with built in bearings that make it a lot easier to close down the collet and they don't try to twist the collet as you do so.

With ER collets don't use hook wrenches on the nuts, apart from wear and tear you are likely to skin some knuckles at some point. A properly designed wrench to suit the nut is much better and allows better application of torque. It should be noted that sizes such as ER16 can be supplied with different types of closing nut, some are simple hex nuts but others are slimmer with finger slots and are usually supplied with a matching wrench.

According to some professional machinists on YouTube ER collets are a consumable item. I have not destroyed one yet but then I don't apply the torques they use in CNC for machining to machine parts with huge value that I don't dare scrap off.

The self locking collet systems such as Clarkson, Vertex etc. require a threaded shank tool but there is nothing to stop someone with a lathe from threading a Ø16 ER collet chuck shank to suit and so adding the option of a small ER chuck for use with them. It is also something that can easily be done with the shank of insert milling tooling to allow their use with these systems. I have also made a Ø16 hollow shank for one of these that holds a Ø10 edge finder (with a bit of Loctite for extra security). If an edge finder is not sufficiently accurate for your needs a holder for a DTI is an easy project.

Martin C

This does come up from time to time. I have both Clarkson and ER (11,16,32) chucks,

I have had a cutter move in a collet when pushing a large cut (in a Bridgeport) at evening school. Everything was tight. It ruined a large part that I'd spent money and time on. So I always use the Clarkson where possible and when I have the right cutter available.

Having said that, I've never had a cutter move in an ER. As Jason has already suggested, I also always use the right sized collet, be that imperial or metric to match the cutter I'm using.

If I could have only one milling chuck, it would have to be an ER32, with collets to match the cutters.

Regards,

IanT

I am surprised that no one has mentioned the ball bearing style collet nuts available for ER series collet chucks from the likes of ArcEurotrade. I have bought these as replacements for both ER25 and 32 versions of mine and they greatly reduce the torque required to adequately grip the cutter or work piece. I have never had a cutter "walk" out of a chuck, but perhaps I don't push my machines as hard as others do.

John

Ahem, see post at 09:45

Martin C

Lots of nice things said about the FB2 but as milling machines go it's a tiddler. ER Collets are designed for much more powerful machines, perhaps 10kW at 20000rpm. In principle, ER collets have no chance of slipping on a small mill.

In practice, operator error causes trouble:

• Newbies may not realise at first that ER collets click into the nut in a particular way. Vital to get this right - see ArcEuroTrade's Advice
• The tool (or work) must be inserted deep so the entire length of the collet grips it. Apart from reducing grip if this isn't done, there's a high risk of permanently damaging the collet so it never grips properly again.
• Forgetting to tighten the collet, or not tightening it enough, allow the tool to spin in the collet. Again with high risk of permanent damage.
• Although ER collets have a wide clamp range, it pays to avoid squeezing them down fully. In other words use 7-8mm collets to grip 8mm, rather than 8 to 9mm. Forcing a slightly oversized tool into a collet is liable to damage the collet. (Don't put 10mm drills into 3/8" collets!)
• Industry get rid of collets at the first sign of trouble and after a certain number of hours. To them ER collets are consumables. Although it's unlikely I would ever wear out a collet, the amateur operator can still get into trouble by buying them unwisely. Some believe that older brand-name tools are automatically of better quality than modern tooling. Even if true, they forget second-hand tools may be worn, damaged or bodged. Others buy the cheapest possible they can find on the web, and it should be no surprise if they sometimes get manufacturing rejects or cheap and nasty. I buy new from UK hobby distributors, not because they are the best, but because the supplier will replace or refund if I happen to get a dud. I'm not keen to buy expensive collets because it costs quite a lot of money to balance collets to run at 30000rpm, and my mill only does 2500rpm! Opinions differ, but in my book paying for unecessary qualities is bad engineering.

ER collets are great. Just keep an eye on the operator. He might buy rubbish, or wreck good ones!

Dave

You don't say what spindle taper you have. If it's R8 I would strongly recommend R8 collets, they grip well and don't get stuck in the internal taper, just need a light tap on the top of the drawbar to release. In my experience over many years using them in my VMB they don't need any way to lock the spindle either - I just hold the nose of the quill tight in one hand while tightening the drawbar with a spanner. I have not had a cutter move unless I forgot to tighten it. R8 collets are quite cheap too. MT collets are another possibility but more prone to get stuck. Direct-in-spindle collets give you at least 40mm and possibly more headroom and are more rigid.

I also use ER16 collets in my little Novamill and have never had a cutter shift. I now use ball-bearing closer nuts which makes it easier to tighten them. In the Novamill headroom is in short supply so I also have a small number of BT30 collets which are obtainable on Aliexpress.

I think the FB2 has a MT2 taper

Missed that, Martin. As it happens, I've just booked an appointment with the optician's for next month! Yes, it is at Specsavers!

John

One point that seems not to be mentioned, unless i missed it.

Clarkson collets will be fixed size, where ER (Extended Range) other than in the smaller sizes, have a range of 1 mm. So they can be used with Metric or Imperial tooling / workpieces, or even non standard sizes.

Yes, I have had a cutter move, when the clamp nut has not been sufficiently tight, but overall, I have used ER collets in commercial and shop made holders for over 20 years without major problems. (ER 20, 25 and 32 including home made ones to take Morse taper Reamers! )

Howard

I bought a set of "0.005mm run-out" ER32 collets from shop-apt that "should only be used to grip the nominal diameter. If used for smaller diameters, runout will increase and collet life will be shortened."

There is only one number stamped on each collet and that is the diameter you should be putting in it, not something smaller.

Edited By Bill Phinn on 30/10/2021 18:51:36

Bill

Using anything but the correct size material for a single size collet will strain the collet and hence damage it.

When you examine ER collets,  most have two numbers engraved on them such "10 - 9"

Only when you get down to 3 mm or so does the range decreases to 0.5 mm

At least those are the markings on my ER32, 25 and 20 collets.

The Arc Eurotrade catalogue No 11 says

"This provides a good grip and some variation in the sizes that may be used in a single collet.(Upto 1mm ) Smaller sizes are best used to grip cutters (or work ) with shanks up to 0.5 mm below the nominal size"below the nominal size" 

Howard

Edited By Howard Lewis on 30/10/2021 21:06:31