Weldon arbor?

[Bo’sunParticipant @bosun58570]

I’m trying to source a 19mm Weldon shank arbor with a No.3 MT and M12 drawbar thread.  I can only seem to find ones with MT3 tanged arbors.  Does such an arbor exist?

Alternatively, would making one from a “soft arbor” be feasible, boring the 19mm hole?

Just in case anyone’s wondering why.  I’ve been given a set of annular cutters, and just curious if they might be of use.

 

[Mark RandParticipant @markrand96270]

They won’t be 19mm shank, they’ll be 3/4″ shank. This is the standard for Rotabroach type cutters.

Not MT3, but I use an INT30 ER32 collet holder with a small 3/4 rim and 1/2″ hat top-hat spacer behind the cutter shank to ensure that the collet closes evenly. Haven’t had one slip yet.

ArcEuro list them, but are currently out of stock.

 

And, yes they are brilliant for cutting clean holes quickly with relatively little motor load.

[Bo’sunParticipant @bosun58570]

Thanks Mark,

I have an ER32 collet holder and suitable collet, but was concerned about slippage.

[DiogenesParticipant @diogenes]

If your mill spindle has slots for ejecting an untapped arbor you’re probably good to go – if it has slots, it’ll probably have flats too..

I use a ‘standard’ MT3 mag-drill arbor in a Warco Major, never had any problems with it pulling out – last job was 26mm holes through 40mm steel for a farm implement. Arbor from Ebay.

I have used them in a collet, but the shank is short and as noted above you need to pack the back-end.

As Mark says, the cutting action is efficient so cutting forces are low, and – for an aggressive-looking process – very mild-mannered / well-behaved.

I really like them, far and away the easiest & quickest method for large, neat holes in thick, tough material.

[DC31kParticipant @dc31k]

What is the reason for requiring a drawbar thread?

If every one that is commercially available has a tang, that would indicate a tanged version works.

If your own machine cannot accommodate a tang, there is lots of parallel area on the tanged version enabling it to be gripped to cut off the tang, drill and tap to suit.

The advantage of one made from a soft arbor is you can make it quite short – the standard ones take up a lot of headroom, and added to that is the cutter projection from the arbor.

A good way to locate any spacer could be a pin concentric with the ejection pin hole in the cutter with an O ring on it for grip.

[noel shelleyParticipant @noelshelley55608]

Rotabroaches are wonderful for making holes from 11mm up to 50mm + and in a mag drill great  The shank is 3/4″ NOT 19mm. As the size goes up so does the number of cutting teeth and load, how well a lathe or mill would drive say a 25mm or bigger I have not tried, my mag drill is rated for 30mm on 1200Watts. I would be interested to hear how well they work on a small lathe or mill. Noel.

[Bo’sunParticipant @bosun58570]

DC31k,

I need a drawbar thread because my mill has an M12 drawbar.  Cutting off the tang and tapping M12 sounds like a solution.  Presumably that means they’re soft enough.  I’d always assumed they were toughened.

[Bo’sun]

On Bo’sun Said:

I’d always assumed they were toughened.

Toughened is different to hardened. A12.9 grade Unbrako capscrew is tough.

When you cut off the tang, you would expose the softer inner core of the item so any surface hardness should not interfere with the modification.

As above, perhaps do a mock up with the largest cutter you have on the largest item you are likely to want to make a hole in and see what headroom remains for the cutter holder. That will dictate which route is best for you.

[Bo’sunParticipant @bosun58570]

Thanks DC31k,

Yes, I guessed they wouldn’t be hardened, as an inadvertent attempt to drive through the tang would be unlikely to end well.

[Martin ConnellyParticipant @martinconnelly55370]

I use Rotabroach cutters in a Ø19 ER collet and have never had one slip. You are more likely to have the morse taper slip than an ER collet. I also use them in the MT2 tailstock on my lathe with back gear engaged for high torque on larger sizes.

Martin C

[Bo’sunParticipant @bosun58570]

Thanks for the suggestions all.

I’m going to try the ER32 collet route first, as I have them both for my Mill and my Lathe.  Reworking an MT3 tanged holder will be a good second choice for the Mill, but would limit use of the cutters on the Lathe with an MT2 taper.  Having said that, I can see them being of more use on the mill.

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