ER25 Collet holder @ 2MT w/ 3/8″ BSW drawbar?

[William AyerstParticipant @williamayerst55662]

Hi all,

I’ve availed myself of the ER25 collet block sets from ArcEuroTrade and a set of imperial ER25 collets, and realised that I could use those selfsame collets to hold non-Clarkson Autolock milling cutters in my mill. The only problem is that my mill is 2MT/MT2 and has a 3/8″ BSW drawbar – with absolutely no clearance down the spindle to fit an M10 – and I cannot find the combination of an ER25 collet holder in 2MT/MT2 with a 3/8″ BSW drawbar ANYWHERE.

Is there one available somewhere on the corner of the internet I haven’t managed to winkle out?

Many thanks,

[NealebParticipant @nealeb]

I seem to remember a similar problem back when I was using my Dore-Westbury years ago. I made up a little plug for the morse taper, male M10 to screw into the taper and extended, drilled and tapped to take the 3/8 male drawbar. This pushed the drawbar a little higher so I made a simple spacer to go under the head of the drawbar – plenty of room above on a mill with no top cover! Those does depend on space available inside the spindle but given that it will probably have room to take a taper with tang, it might work for you. I suggest well-fixing the plug into the taper as if that thread unscrews you might find yourself in an embarrassing position. Don’t ask…

[bernard towersParticipant @bernardtowers37738]

The one I bought years ago was M8 so just made another draw bar.

[JasonBModerator @jasonb]

As you don’t need to put silly tightening loads into a drawbar just cut a M10 thread on a bit of 3/8″ bar, should be enough engagement

[Thor 🇳🇴Participant @thor]

I assume you are based in the UK, it seems Amadeal will be able to supply you soon (if you can wait).

Thor

[Ian PParticipant @ianp]

Why not open up the hole in the spindle to take M10

What I did on my Emco mill was hold a longish 10.2 drill vertically in a machine vice (very loosely fastened to the table so it self aligned) and bored out the milling machine spindle. I dont recall it being tough but it drilled easily enough.

IanP

[William AyerstParticipant @williamayerst55662]

Thanks, Amadeal have confirmed they are sold out rather than coming soon with no ETA on a re-order, let alone arrival back on shore. I’d have thought the chinese/indian suppliers might have some available but I’m coming up short again 🙁

With regard to a new drawbar – thank you for the suggestions – I like the idea of a 10mm thread on a piece of 3/8″ bar if I can get it to work that way. It looks like my current drawbar has been fabricated rather than being stock:  someone has welded the retaining ring at the top, and welded the 3/8 BSW threaded portion to the bottom of the same rod.

In terms of fabricating my own replacements (one 10mm @ 3/8″ dia and one a standard 3/8 BSW thread)  am I going to be OK with a cross-pin + loctite the end cap/retaining ring section on top, or is it going to require silver brazing?

I found a drawing online a while ago of what I’ll need – but obviously in this drawing the thread is oversized:

Many thanks,

William

[William AyerstParticipant @williamayerst55662]

The kind gent at Amadeal advised they DO have M10 drawbar chucks – but I have found that Rotagrip have them with a 3/8 Drawbar thread: https://rotagrip.co.uk/amp/2mt-er25-collet-chuck-3-8-whit-vertex.html

[Paul LousickParticipant @paullousick59116]

Make a 3/8″ drawbar to suit the collet.
My mill came with a 1/2″ drawbar and I also have collets and tool holders with 3/8″ and M12 threads. The drawbars are just a piece of threaded rod with a hex nut on top. Screw the rod down into the collet, then tighten the nut.

[noel shelleyParticipant @noelshelley55608]

Take a length of 10mm threaded rod and reduce dia to suit by lathe or file, it only needs a few thou off.  Noel

[William AyerstParticipant @williamayerst55662]

Thanks Noel/Paul – I’d need to buy a collet holder even if I used M10, so I decided to just buy one with a 3/8″ drawbar!

Time will tell if the Arc collets are a good match for the Vertex/Rotagrip holder, I guess!

 

[peak4Participant @peak4]

William, as you’ve shown, the Centec drawbar is good in that it’s captive and also self ejects the MT2 arbor.
When I pulled my own drawbar out, the thread was well chewed, so i made a new pair, one 3/8″BSW and the other M10.
It’s not just about the ER25 chuck, but it also allows me to use other imported stuff, such as shell mill arbors etc.

As well as the extra draw bar, for the vertical head anyway, I knocked up a quick peg socket for easy removal of the top hat nut/drawbar retainer.
The gas bottle spanner fits the drawbar, and the hex on the peg socket is 17mm, as that’s the size of my clamping set nuts

Bill

[old martParticipant @oldmart]

I had a problem even greater when I converted the Tom Senior light vertical from MT2 with a 3/8W drawbar to R8 which usesa 7/16 UNF drawbar. I wished to keep the top section and marry it up to a new R8 bottom from ARC. The top half was splined for the sliding drive. I managed to get a hand reamer with its longer lead in to start and when it reached its full length from both ends, silver soldered on an extension to reach the middle. The hole in the bottom part was already the correct size.

 

 

 

 

 

[Martin ConnellyParticipant @martinconnelly55370]

You can buy a parallel shank ER25 collet holder, cut to length, plug the end if required (I tapped it and screwed in a bit off a bolt with Loctite), centre drill it and thread the outside diameter to fit in an AutoLock chuck. This is a 16mm shank ER16

Martin C

[old martParticipant @oldmart]

A hand 10mm reamer would easily increase the bore of the 3/8W leadscrew hole, andnot prevent the 3/8 from being used with compatible tooling. I turned the reamer handle end down in steps and drilled matching holes in the extension which had the end squared for a tap wrench after silver soldering. This could be done without removing the spindle from the mill. A normal 10 mm piece of studding will be under 10 mm diameter, they always are.

[not done it yetParticipant @notdoneityet]

A storm in a teacup or a mountain out of a molehill?

3/8” drawbar will have some clearance in the spindle.  That means the spindle will have a bore greater than 9.52mm – only a mere 20thou (in old money) as maximum difference.  It may well be very close to 10mm.  A 10mm drawbar reduced by less than 0.5mm does not exactly present a huge problem – only the 10mm thread needs to be reduced to pass through the 3/8” + clearance.  The rest of the drawbar could be reduced by some arbitrary amount.  So I basically agree with JB, but with the absolute minimum 10mm thread diameter reduction.  TBH, IIRC, I didn’t have any great problem with 10mm drawbars in my Centec.

Thus, like I said, a mountain out of a molehill.  Theory over practicality.

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