Holding screw-end end-mills/slot-drills

Until now, I have held end-mill/ slot-drill cutters in ER25 collets. And am aware of the hazard of these being drawn out.

Hence considering toolholder alternatives? I have seen specific-diameter toolholders that work with a grubscrew on the flat of throwaway cutters. But are these commonly threaded internally to be able to accept screw-end cutters too? Or is there another type of holder for these that I have not seen?

Cheers, Colin

If you haven't got a ball bearing nut for your ER25 get one and increase the clamping effect with the same torque you are using now. Put on the recommended torque and keep the tooling and collet oil free before fitting and tooling doesn't pull out.

Martin C

Cutters with flat are designed to fit a 1 size toolholder, the screw is the only security.

Using this type of cutter should be possible in your ER25 chuck as long as the cutter is long enough to provide full contact with the collet length.

Emgee

Posilock?

But I find ER32 OK even though I don't tighten them fully to the recommended torque. Not had a cutter slip yet.

+1 for ball bearing nuts.

Yes, same here.

I don't remember a cutter ever getting pulled out of my ER holders be it plain shank, screwed or with a Weldon flat.

You will also be limiting the range of available cutters if you go to screwed shank

In our machine shop at work they have an ISO 40 female holder screwed to the bench. Tooling is popped in there, tightened up with the appropriate ER spanner (the bloke goes "NNNNINNNG!" like they used to do in the Beano) and the cutters simply do not come out. If you're trying to tighten the collet chuck in the machine, you may not get them tight enuff. I have a similar bench-mounted fixture at home for my ISO 30 tooling - and I've not had a problem with cutters coming out.

I have a Vertex version of the Posilock, mine gets tightened with my index finger and released by a thump with the flat of my hand, the cutters don't move in that either.

I put them in my R8 collets. Never had one so much as move.

Thanks for all this input.

No. I have not actually had a cutter 'drawn' on an ER collet either, but aware of the hazard. Understanding that, and looking at my collection of fleabay cutters I wanted to explore what the alternatives are.

Assessing all of this (and another thread or two) I reckon I'll be saving those beer coupons for something else....

Cheers, Colin

Just get the ball bearing nut if you haven't got one.

Steve

ER collets have a wide clamping range for each nominal size but you should use one that is the correct size for strongest grip. Colin

My most used milling chuck in an ER40. Not that good at holding the small sizes, <7mm diameter will move with a big cut/quick feed. I use an ER16 chuck for small cutters and have the opposite problem, cutters >8mm will move in the chuck.

I still use an Autolock chuck as well, no risk of a cutter moving with those.

From my time in industry I remember R8's being a pain. Not a particularly tight grip so an Autolock with an R8 shank would be used. With a lot of use accuracy was suspect, the parallel section would wear and cause a slight run out. As for the key, a b****y nuisance!

John

I was about to post that ER collets sell like hot cakes because they provide a strong grip with less fuss than belt-and-braces alternatives. The hazard is low.

But Colin makes a really good point: an ER collet is noticeably harder to tighten fully at the small diameter end of its grip range. For example a 1/8" diameter twist drill is better held by a 1/8" Imperial Collet than a 3-4mm Metric Collet crunched down to 3.2mm

Despite a deep rooted instinct to hang on to my cash I reluctantly found it worth buying every collet needed to hold all the common diameters used in my workshop.

Dave

Clarkson Autolock Osborn Titanic II / Posilock Acramil Small versions of these work with 1/4", 3/8", 1/2" and 5/8" shank threaded hss cutters, with the appropriate size collets and with the metric collets in 6mm, 10mm, 12mm and 16mm. The three types of collet are not interchangeable. Solid carbide cutters are not made owing to the weakness of the threads, but steel shank with inlaid carbide are available, and I have seen some indexable cutters with inserts in the large sizes. Larger versions are not really compatible with smaller milling machines. These types of cutter holder will only work with threaded shank tools.

Edited By old mart on 19/11/2019 17:21:29

This is a hazard only observed by those not using correct assembly techniques and tightening torques for ER collets.
The tool and collet bore must be clean and dry.
The outer faces of the collet, the holder taper and the nut must be clean, they can be dry or very lightly lubricated.
The correct torque for the nut size and nut style must be applied, look it up, it's more than you think!

Agree with Nick. Torque required for an ER32 is likely more than one tightens the car wheel nuts to! Wimpy ‘C’ spanners need a lot of force to tighten them sufficiently. The

But, of course, there may be some collets and/or holders that are below spec items.... and there are the ball bearing nuts which secure the cutter with less torque than the plain nuts.

I use er25 as well as threaded shank with the Osborn Titanic II. I never try to tighten the er collets on the machine, but use the standard length spanners by leaning on them using a worktop. I keep promising to extent the spanners to at least a foot to tighten them on the machine, that being the minimum length I believe would be acceptable for 12 and 16mm cutters. If the shank of threaded cutters is long enough to fit in an er collet beyond the threads, then it is safe to use. The threaded system is easier to use and being self tightening, possibly safer. They are not absolutely guaranteed perfect as the threaded part can snap off in extreme conditions.

I can only remember one instance where an cutter got drawn out from an ER collet, and that was because I had messed up in the first place and left a piece of swarf in there during assembling.

When done correctly ER collets have always been reliable for me. Unlike many other collets ER collets closes and grips in a parallel fashion along the entire length. (As opposed to just closing in on one end). That makes for a better and more flexible grip.

Joe Pieczynski made a nice video about different collets some way back. I'll find found and linked to it here:

Collets ---- Types, Pros, Cons and General info.

(That said, with some collets being sold for far less than others I guess some of them might have issues. Then it is more about the price and quality than the system itself though).

Having both an ER25 collet and a Osborn Titanic II, I can say that the latter barely gets used and would have been a waste of money if it hadn't been so cheap.

The main issue is that it takes up so much headroom compared to ER25, but also cutters are more expensive unless you go for 2nd hand ones.

Best investment is not just the ball-nut but also a pair of good matching spanners to make locking the ER collet easy. Correct torque is as much as you can manage.

Neil