How important are odd-sized milling cutters? (Clarkson vs ER)

Good morning gents,

With the imminent arrival of a milling machine, I'm considering my tool holding position - up until now I have been building up my collection of Myford MT2 collets for use in my lathe and I'm only a couple short of a full set of 1/16" - 1/2".

They have been working GREAT for workholding and toolholding in the lathe. However, with no equivalent thread on my MT2 mill spindle they are about as much use there as a chocolate teapot.

While I am all up for vintage machines, tools, processes, etc. it seems that a Clarkson Autolock chuck is about the only collet chuck that's going to fit the bill i.e. imperial measurements and british made - and only comes with 1/4, 3/8, 1/2 and 5/8" divisions.

For the milling on my ML7 I've never used a more complex fractional cutter - 99% of work has been done with a 1/4" four flute endmill - but it does worry me a little that I wouldn't be able to use a 7/16" ball nosed cutter or 9/32" reamer if I went down the Clarkson route. I understand the Vertex Posilock is a similar design and principle.

On the other hand, I am strongly considering going against my principles and getting an ER32 collet holder and set for use both on the mill and the lathe - the Myford holders would pay for the entire thing just by themselves. If anyone has a recommended British/Euro-made set I would be very happy to hear it.

Screwed shank cutters have the standard shanks and for sizes that are different the flute is reduced, So your 7/16" cutter will have a 1/2" shank. You can also get metric collets for the autolock. Be aware that the choice of screwed shank cutter sis quite small, the majority now are made with plain shank possibly with a Weldon flat on some.

You seem to have ruled out MT2 finger collets they will fit and come in 1/64" increments.

There are several European options for ER tooling but often at the higher end of the price scale, Rego-fix for example

Edited By JasonB on 12/07/2021 09:23:35

As for the reamer, you can still get taper shank ones if you want a machine reamer or parallel shank machine reamer will go into a MT2 finger collet.

Or use a hand reamer driven by a tap wrench and using a homemade point to go in the Autolock, decent drill chuck will also work.

Edited By JasonB on 12/07/2021 09:44:56

I hadn't even considered MT2 finger collets - that's a great shout! I have ordered a set from Warco - time to fabricate up a drawbar I guess!

I thought you did not want far eastern products, Warco may be in teh UK but their stuff is Mostly from China with a bit from India?

The shank sizes on Clarkson cutters do not relate to the cutter diameter, so eg a 7/16 cutter will have a 1/2 inch shank to fit the Clarkson collet. so cutters from the minimum to 3/4 dia can be held in the 4 sizes of Clarkson collets.Previous to the Clarkson collet chuck there many different systems for holding cutters and depending a lot the milling machine manufacturer and most collets sytems had faults mainly with cutters pulling out and cutting deeper, the Clarkson system allowed their cutter to be used on the majority of machines as Clarkson holders were available for many different spindle types. My employer where I started work swore by the Clarkson system and said it solved most of the problems with holding cutters. I expect the demand for collet type systems was due to the development of cnc machines and automatic tool changers where a Clarkson holder would not be easy to grip in the tool changer,plus the increasing use of solid carbide cutters which only had plain shanks, I found the collets used on Bristol Erickson tooling would slip where as the ER collet maintains an execellent grip ,though if I have a job which is really tough steel I go back to Clarkson on my mill, Er collets also have the advantage of gripping any size twist of twist drill ,countersinks, centre drills ,where as on the Clarkson system a tool maker would thread a length of silver steel to suit the Clarkson collet and then drill a hole in the rod and solder in a centre drill,otherwise it meant that the Clarkson holder had to be removed and another type of holder ie drill chuck had to be put in the spindle,I was once given the contents of a deceased toolmakers kit and their were numerous fly cutters he had made to fit the Clarkson collets,Clarkson really excelled on production runs, The need to quickly change tooling for toolmaking was possibly why the Bridgeport and it R8 collet came so popular with toolmakers. For a Myford a ER collet system would be a good move either with 2mt fitting or a spindle nose fitting, I think that the expensive myford 2mt collets should only be used for work holding,they are precision collets and to maintain that precision should not be used for holding milling cutters,I only use my Myford collets for work holding, Though back in the sixties when I had my first Myford which was new and also had all new tooling I did all the milling on an Allchin TE with the cutters held in the 4 inch Burnerd 3 jaw chuck ,the work was very light so there was no slipping of cutters in the chuck .

While I'm at it - the mill is (obviously if you've helped in my other thread) a Centec 2B with a quill head. This is the drawing for the draw-bar that I have:

I'll thread 3/8" BSW to match the finger collets - but is this a design that'll work/not mash up the spindle bearings?

Cheers!

As Jason says Clarkson screwed shank is now primarily for the legacy folk (I have a lifetime supply).

The mill - lathe compatible thing is something of a chimera. You don't need many milling cutter holders so changing everything just to suit the mill is something of a waste.

If I were starting out now I'd choose side lock holders and Weldon flat cutters. Weldon flat cutters are now readily available at homeworker friendly prices. If you luck into a stash of plain shanks the flat is easily fitted. Big advantage of side locks over ER is that they are shorter, essentially immune from pull out issues and don't need a hefty heave on the spanner to tighten them up. All good things when using on smaller machines where space and stiffness is limited.

There seems to be considerable legitimate debate on how tight an ER collet needs to be to hold well enough for our purposes. I suspect that very small differences in quality, accuracy and finish of both collet and cutter make a big difference to how tight they need to be for our use.

Buy the holders as you need them, you may be surprised how few you actually use. For my Bridgeport I have full sets of ER32 along with native R8 finger collets in both metric and imperial as well as the Clarkson that I use for most jobs. I also have the full range of side lock holders. Most of the collets I have never used in 20 years.

Frankly, with 20/20 hindsight, the money tied up in them would be better invested in extra side lock holders so I could leave some of my favourite cutters ready mounted CNC style. But I got nearly everything at very attractive prices so not too bad really.

Clive

re: import JasonB - you're quite right but this at least gets me in the door. I may pivot to Clarkson tbh but if I can double-up these finger collets on the ML7 then that would free up some capital for that slightly later?

Well if I'd known you were not really fussed then I'd have said an imported ER chuck and say six collets would have got you in the door and been the better option

You can double up the ER in the Myford too both in the spindle and the tailstock which you can't with finger collets.

Ah, well luckily Warco don't have the 1/4" in stock and I have cancelled that order because that's basically what I think I'd be using - what a roller coaster lol. I'll reconsider Clarkson but if you could recommend me an ER set in the meantime to review that would be wonderful? I'll report back before applying card to internet.

I use ER32 collets for general work and larger shank cutters, however:

I have a Vertex Posilock, similar action to the Clarkson Autolock, with inch size collets and metric size collets. They all use a 16tpi thread. I have a Ø16 2 insert carbide milling cutter that I have added the 16tpi thread to and can hold it in the Vertex chuck, I have also done the same with a Ø16 shank ER chuck so I can hold anything up to Ø10mm in it as well (I tapped the bore M12 and plugged it to put a centre in it). I have made some Ø16 electrically isolated probes for edge and centre location. I also turned down the shank and added the thread to a set of Mini Hoggers (as available from plenty of sources). I did start off having a quantity of threaded cutters though and wanted to be able to make best use of them.

For CNC work they can be used for simple manual tool change without having to find the Z axis zero as they always seat back in the same position against the pointed stop, you just need the tool stored with a number and know its effective length.

The idea that these type of tool holders are legacy only may be a bit premature.

Martin C

Martin,

So the Vertex Posilock needs special 16 tpi "Clarkson" type cutters as opposed to the ordinary ones which are 20 tpi ?

Chris

News of my death may have been overstated?

I have realised that if I use Clarkson, I won't be able to drill with my existing drill bits, or ream with my existing reamers (unless they fall into those precise measurements) - so I think (!) I'm going to go with a 2MT ER set despite my reservations. I don't suppose there's a set knocking around which has imperial designations (yes I know it's a metric standard).

ER25 or ER32? Mill is a Centec 2B so probably not up to hogging out huge cuts so...

Edited By William Ayerst on 12/07/2021 11:16:15

Imported ER 32 such as this and a set * of imperial collets, Can't think of any sets of holders and imperial collets unless you buy sets for the US market.

* will be supplied as separates so make your own storage.

I don't know the details of the Centec vertical head, but the square on that drawbar looks as if it's intended for self-ejection of the MT, in which case you'll need also to make a cap to attach onto the end of the spindle, assuming there's provision for it. A good idea as it avoids impact on the bearings when the arbour.

If not, then a plain hexagon of convenient spanner size is probably better.

Thanks Jason - I've heard nothing but good things from Arc so may as well give it a bash. Any opinion on ER32 vs ER25?

I appreciate the comments above that the Myford collets are more accurate - but having ten or twelve of them, I think I would prefer to move them on and use that to pay for setting up the mill. I'm not sure the work I do needs to be that accurate!

Edited By William Ayerst on 12/07/2021 11:29:27

Clive - presumably a cap which keeps the plate on the drawbar captive? I'll have to investigate...

I don't know where that drawing came from, but 1/2" BSW won't go down the spindle on a Centec VH, at least not mine. 3/8" is the biggest, it won't even accept M10. If I were starting again I'd look into getting the hole opened up, as 3/8" BSW stuff is getting increasingly rare. Don't panic, you can still get it.

ER25 is big enough for a Centec, will hold 16mm cutter. The only drawback with ER vs Clarkson is if you are doing a big cut with the side of the cutter they can tend to draw out with ER, but Centec isn't that sort of machine.

32 vs 25. If you are going to do away with the Myford lathe collets and make use of the ER ones for workholding then 32 is a better size allowing work upto 20mm to be held. If only for use on the mill to hold tools then 25 would do on that size mill