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

[duncan webster 1Participant @duncanwebster1]

If you have a captive drawbar, which is what centec is designed for, you can't get a mt2 with tang in. If you cut off the tang you then can't get the mt2 out, no slot in mandrel. You could have a non captive drawbar and use a rod down the hole to bump the mt2 out, but far and away the best is mt2 with tapped hole for drawbar and a captive drawbar

[JourneymanParticipant @journeyman]

If you go the ER route you can happily hold drills, reamers, countersinks etc. without changing the chuck. As ER collets have a 1mm range (or imperial equivalent) all sizes of shank may be held.

John

[peak4Participant @peak4]

Posted by duncan webster on 12/07/2021 15:21:58:

If you have a captive drawbar, which is what centec is designed for, you can't get a mt2 with tang in. If you cut off the tang you then can't get the mt2 out, no slot in mandrel. You could have a non captive drawbar and use a rod down the hole to bump the mt2 out, but far and away the best is mt2 with tapped hole for drawbar and a captive drawbar

I'd go along with that; there's a couple of photos of my own drawbar in This Album, which I uploaded for someone previously.
https://www.model-engineer.co.uk/albums/member_album.asp?a=49998

See also This Album for a variety of threaded shank collet chucks
https://www.model-engineer.co.uk/albums/member_album.asp?a=53353

N.B. most of the MT2 ER25/32 collect chucks these days seem to come with an M10 thread, rather than 3/8 BSW (I suspect the thread designation of 1/2"BSW in your diagram may be wrong)

I use a Clarkson in the Centec, which came threaded 3/8" as standard, so no problem for me.
In the Dore Westbury, I use various different MT2 cutters and chucks, but this only has a small through hole for the drawbar. As such, I've got several small collar converters to fit the shanks of my various MT2 tooling, all are tapped 1/4 BSW for the drawbar, but have ODs of either 3/8"BSW or M10 so I can use any combination.

If you're going to make a new drawbar for the Centec, one idea might be to terminate in in an M6 high tensile stud, and then use adaptors, so that both 3/8"BSW and M10 MT" shanks can be accommodated.

Maybe put a screwdriver slot in the bottom end of the thread adaptor, just in case you leave it behind on the end of the captive drawbar, to save having to remove the top collar and spring etc.

Re. the tang situation, for the DW mill I do have a couple of tanged MT2 tapers, which I have drilled and tapped M6 for its drawbar, so if you're careful with the length of your Centec drawbar, you might be able to do something similar with that as well.

Bill

[William AyerstParticipant @williamayerst55662]

I think the crucial point is that if the holder is threaded M10 that it won't fit into the spindle bore of the Centec Quill head – then I need to ensure I get 3/8" or maybe the Clarkson chuck is back on the menu. JasonB – the holder you specified does have an M10 thread on the 2MT version It looks like Vertex do one with a 3/8" drawbar at one end of the spectrum, and Amadeal at the other.

I do have a Jacobs chuck at 2MT but no drawbar and it does have a tang. I use it on the tailstock of my lathe.

Peak4 your setup looks very impressive for the head there – how is the spring/plate arrangement fitted around the drawbar? Is it something you fabricated or bought?

Edited By William Ayerst on 12/07/2021 18:24:36

[not done it yetParticipant @notdoneityet]

Posted by duncan webster on 12/07/2021 15:21:58:

If you have a captive drawbar, which is what centec is designed for, you can't get a mt2 with tang in. If you cut off the tang you then can't get the mt2 out, no slot in mandrel. You could have a non captive drawbar and use a rod down the hole to bump the mt2 out, but far and away the best is mt2 with tapped hole for drawbar and a captive drawbar

Duncan,

I don’t think tangs will fit in most spindles not designed for them. The tang is only useful for quills with a cross slot – to use a wedge to remove the drill.

I rarely bump mine out. A couple of wedges between the quill and tool is so much kinder on the machine. (Some) Clarkson have a ring for jacking out the tool from the quill?

Wedges are easily made on the mill, in different thicknesses, for that purpose. I have two sets )and a couple of ‘parallels’ for occasional use when the gap is too large).

[Martin BryarsParticipant @martinbryars38535]

Posted by Journeyman on 12/07/2021 16:10:25:

If you go the ER route you can happily hold drills, reamers, countersinks etc. without changing the chuck. As ER collets have a 1mm range (or imperial equivalent) all sizes of shank may be held.

John

I have 0.5mm steps for the, I think, two smallest sizes, 3.5 etc. I find it hard to get the smallest ER32 collets to hold a size over.5 mm under nominal satisfactorily.

With my old mill, I had a Clarkson chuck with metric and imperial collets. I now have a Bridgeport and use ER32 collets and have had no trouble with slippage. The same system I also use in the tailstock of my lathe and in Stevenson blocks from Arc Euro, which are very useful pieces of kit. I was worried about leaving the Clarkson system, which really is excellent, but have not found any problems in practice.

Some of my ER32 collets are from Arc, and they are OK, but most are from Cutwel, which I think are that bit better.

[peak4Participant @peak4]

Posted by William Ayerst on 12/07/2021 18:07:57:

………….

Peak4 your setup looks very impressive for the head there – how is the spring/plate arrangement fitted around the drawbar? Is it something you fabricated or bought?

Edited By William Ayerst on 12/07/2021 18:24:36

No it's standard as far as I know.
If you have a look at the top of your V head, assuming it's the Mk3 with the quill, there should be the nut with the two holes; that's why I have the angle grinder spanner in the photo, for removing it.
The nut I'm referring to traps the collar on the drawbar twixt itself and the top of the quill, meaning that when you turn the square headed drawbar anti-clockwise, it bears on the bottom of the nut and pushes the MT2 tooling out of the head.

If you need further photos, shout up, though you might need to message me to remind me to look at this thread.
I have an engineering diagram of the mill itself, but I've never been able to find (a free) one for the vertical head.

My drawbar on the Centec is threaded 3/8" BSW, and a 10mm one may not fit through the quill hole (I've not tried it), hence my comment about terminating your new drawbar M6, as a high tensile stud insert could be made from an Allen bolt, screwed and glued in the end.
You can then add an M6 threaded hollow slug in the end of your proposed M10 threaded MT2 shanked ER collet chuck.
If you then get a Clarkson collet chuck or similar, just add a similar slug to the end of that, but with an external 3/8"BSW thread.
This gives you the best of both worlds.

p.s. there's nothing to stop you changing the arbor on your drill chuck to one with a threaded hole.
I've even seen tangs available to screw into the hole in the end of an arbor, to convert it to a type suitable for wedge extraction when required.
I accept that this is the wrong item to convert an MT2, but you get the idea
https://www.ebay.co.uk/itm/361412785151

Bill

 

Edited By peak4 on 12/07/2021 19:54:47

[Dave HalfordParticipant @davehalford22513]

The Centec horizontal shaft is smaller than 3/8, just to be awkward.

[duncan webster 1Participant @duncanwebster1]

?? my 3/8 BSW stuff fits in the horizontal as well, and it has a captive drawbar

[Dave HalfordParticipant @davehalford22513]

Posted by duncan webster on 12/07/2021 20:12:39:

?? my 3/8 BSW stuff fits in the horizontal as well, and it has a captive drawbar

Mines a 2A so might be older than yours, but but the 2 that I had and the 2A will not pass the VH drawbar through the shaft. I have to put the draw bar in from the front, M6 studding fits and a loose M6 nut at the rear.

[William AyerstParticipant @williamayerst55662]

Drawbar

I have asked the kind gent who has sold me the mill to see if the drawbar or components are with it or not – it may be that I need to fabricate the whole shooting match, presumably I'll be OK to use some BSW studding in the interim? Peak4 if it's OK may I trouble you for some measurements when you have some time?

Collets & Holders

Vertex and Amadeal both do 2MT ER25 collet holders with a 3/8" drawbar, but the former won't have any in stock until around October and I've heard bad things about the latter.

I have done a small inventory of my cutters and only three are not clarkson compatible (a 1/2" slot drill with no thread, a 5/16" cutter and a 1/4" cutter with no thread). I have found a 2MT Clarkson Autolock chuck with imperial collets available within walking distance, so it seems as though fortune is directing me that way for now.

Drilling in the Mill

The ML7 doesn't have anything to engage the tang on my current Jacobs chuck arbor anyway, so replacing with one with a 3/8" drawbar thread is probably a smart choice! Are jacobs chucks considered accurate enough for reamer work if I end up needing a reamer that is non-Clarkson compatible?

[Dave HalfordParticipant @davehalford22513]

William,

Milling cutter collets are size specific imperial collets will not take metric and vice-aversa.

Removing the tang on your Myford tailstock chuck may also remove a self eject function on the tailstock.

[William AyerstParticipant @williamayerst55662]

Thank you for the thought Dave, there is no self eject on the tailstock – it is effected by putting a piece of square bar between the back of the jacobs chuck and the front of the tialstock casting and winding in!

re: the tip on metric vs imperial – I've found a supplier on fleabay (cncpoorboy) who supplies new Clarkson/Europa brand milling cutters with Autolock threads so happy with that…

[peak4Participant @peak4]

William, happy enough to do some measurements, but first we need to confirm which vertical head you have if it's to be meaningful.
There were 3 genuine Centec ones, plus at least one after market.
Mine is a Mk3, with the quill
http://www.lathes.co.uk/centec/index.html

Bill

[JasonBModerator @jasonb]

If you do go for a Clarkson with set of imperial collets than you can buy or even make a sidelock adaptor. One ith 1/4" hole and another with 6mm hole would allow the use of the cheaper FC-3 type cutters as well as anything with a flat on the side with those size shanks or even add your own flat. A 10mm and 3/8" would also be possible without it getting too weak.

Now who's up for making an ER16 chuck with 5/8 or 16mm screwed shank?

[not done it yetParticipant @notdoneityet]

Drawbars: I’ve got umpteen drawbars (well, at least eight). Both metric and imperial for each of the Centec spindles, a pair for the Raglan a 5/16th one and one ( metric, I think) for the lathe.. All home made from threaded rod, but not all painted yet, for easier recognition.

My 2B accepts 10mm studding without any problem.

Reaming on the lathe: Ideally one should consider (and likely make) a floating holder for machine reamers.

Some of my 2MTs need an extension to allow ejection from my lathe tailstock. It is usually a rounded-off setscrew. Some others eject while the tailstock quill is extended by an inch.

I’ve made some extra arbors for the horizontal starting with soft blank MT arbors. Maybe, one day, I might thread the blanks and fit an ejection collar for easier removal (at least one wedge is usually dropped when the arbors come loose from the spindle). Will I ever get roundtuit? I don’t know…..

[Martin ConnellyParticipant @martinconnelly55370]

Like this Jason? As mentioned earlier.

Martin C

[JasonBModerator @jasonb]

That's the one.

Do you have one with a small drill chuck on it too? I recently got a 1/2" plain shank with M14x1 thread that has come in useful when I just want a drill or lathe chuck and don't want to change what's in the spindle such as wanting a 4-jaw for a small job while 5C chuck is mounted or small drill on mill when ER chuck mounted. It takes my old Unimat3 stuff.

[William AyerstParticipant @williamayerst55662]

Oh I'm overwhelmed – thank you all for the help. My mill is now en route via Landylift so I'm all on tenter hooks.

JasonB/Martin – thank you for the tip on using 5/8" shanks for other things – what a good idea!

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 13/07/2021 14:59:31:

That's the one.

Do you have one with a small drill chuck on it too? […]

.

I made a 3/8” Clarkson-threaded shank for a small Rohm drill chuck … works nicely in the ‘special’ threaded collet for the BCA.

MichaelG.

[Frances IoMParticipant @francesiom58905]

Martin C is that 5/8 shanked ER16 a home brew or can it be bought?

[Martin ConnellyParticipant @martinconnelly55370]

It is an off the shelf ER collet chuck with a Ø16 parallel shank. The Shank was cut down in length to minimise stick out from the Vertex chuck. The end was tapped M12 for about 12mm so that the thread tapered and left a reasonable recess for drills to fit up the bore. A piece of M12 bolt was screwed in tight with some Loctite. Then it was put in a collet in the lathe spindle and faced off and runout checked before drilling the centre in the end. A centre was used to support it for thread cutting and it is a 20tpi thread with (if I remember correctly) a 55° Whitworth form. Threading progress was checked with a Posilock collet to ensure the collet went on without resistance as this is important for proper functioning of these auto locking chucks. The thread was also polished with some worn Scotchbrite before it was removed from the lathe.

Martin C

Edited By Martin Connelly on 13/07/2021 16:07:41

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