Weldon Shank Tool Holding

[Clive FosterParticipant @clivefoster55965]

Paul

The Captain Obvious query when it comes to Weldon holders is how good does the fit of the tool shank in the holder bore have to be for satisfactory performance.

All my Weldon holders and Weldon shank tools are a sufficiently close fit that an at least firm push is needed to pump the air out from the bore behind the tool as it is inserted. Similarly a stiff pull is needed to get the cutters out. For one holder – tool pair I routinely remove the side screw before pulling the tool out to give a shorter air leak path. Turns removal from a right battle to merely hard work. That particular cutter is a carbide "Little Hogger" 1" diameter face mill from Chronos so it has to work for its living. Gives good finish and generates chips at an impressive rate. I imagine it would chatter badly if the fit of the tool shank in the holder were inadequate.

Fairly obviously if the fit is too slack the cutter is going to jump around so much that the whole thing becomes unusable. Presumably somewhere between impossibly slack and close enough to work properly there will be a a chatter prone region. How much and how often the chatter being the usual frustrating combination of circumstances.

Clive

[Neil LickfoldParticipant @neillickfold44316]

Another option is to make a MT2 shallow taper collet system. I have seen where there are collets that 1/2 the taper of the ER series, so is a 4 degree taper per side. As the standard MT2 has a small amount protruding the spindle /nose face, you could use this distance to make a retaining nut, or use an existing ER nut. Using an existing ER nut , then you could make collets that have a 4deg main taper with a 30 deg front taper. You can also make the collets as long as they need to be to have full engagement on the cutter. So they may only need to be like 20 or 25mm long. Collets do not like the holding part being shorter than the collet holding length. If you look inside the R8 collets for example, you will see it is only holding by a little more than the length of the front taper in the collet itself.

Another way is to make a set of collets that operate inside a MT2 holder like the Deckel FP1 collets for example.

Just another idea for you.

[JonParticipant @jon]

Ideally need to make a spindle lock up, one of the first things i did on current mill.

Cutters i will buy and use anything of repute whether threaded, weldon or just plain shanks all go in the MT collets i would not be without.
Have had a couple of MT collets bought from Chester the cutters drop or move upwards on them duly replaced from another reseller all hunk dory.

Previous at work we had 3 ER systems one from Wabeco, Chester worst of the lot and some where else, none we couldnt keep the cutters from dropping scrapping many hours of work. Collets were tightened a beefy bloke couldnt undo but still dropped.
Serious jobs used to take my MT collets and drawbar in, never a problem.

[Paul FallertParticipant @paulfallert28101]

Additional thank you's for more postings.

Jon:

My mill has a brake-band style spindle locking lever. I have older MT2 collets and a set of new imports. I don't recall which one slipped (other than it was 1/2" which I use frequently). The problem has only happened when side-milling with a high helix endmill when taking a deep cut in softer steel alloy (e.g. leaded) or aluminium. I have a bad reputation for overtightening everything, so maybe the problem is compensating too much, but more likely it is the Far Eastern manufacture, although others seem not to have that problem. I do have a torque wrench and this discussion is prompting me to use it. I wonder what the torque should be? I did have to make an extractor because the collets would not release (again duo to overtightening). At school all of the drawbars were ruined from overtightening the R8 collets and the day-school teacher gave one of them the task of making new drawbars, which did not last very long, either.

Paul

Edited By Paul Fallert on 06/05/2018 23:02:41

[David George 1Participant @davidgeorge1]

I used shrink fit cutters at my last job, for high speed milling and never saw a single one move even when crashed and smashed the solid carbide cutter. You heated the tool holder in a jig using a hot air gun or an induction heater slide the cutter in and allow to cool or blow with an airline to assist cooling. As there is no screw or any other fixing the there is no ballance problem and you can make the arbour as short or as long as you like and run as fast as you like.

David

[Ian S CParticipant @iansc]

David, that sounds an interesting tool holding system, how do you remove the tool once it,s in place?

Ian S C

[Neil LickfoldParticipant @neillickfold44316]

Ian, the ones at work use an induction coil to very quickly expand the body and not the tool. With carbide tooling it generally is not an issue. But sometimes we do see HSS tools getting stuck. It is like they have micro friction welded themselves into the holders. With the HSS tools, we put them in the freezer , and hit it on high with the induction heater, suspending the assembly by the tool to be removed. With carbide, we just heat it , and the tool just falls out. Generally the tool is only replaced because it has failed in some way or is damaged , or dull. Either way, in most cases, the tools that are removed , never get used again. Shrink holders are really awesome, but there is a new Hydraulic tool holder that holds just as well for concentricity, but with the added vibration dampening qualities. These new hydraulic chucks improve on surface finish obtained, and also extend the tool cutting life.

Neil

[not done it yetParticipant @notdoneityet]

Posted by Ian S C on 07/05/2018 12:36:38:

David, that sounds an interesting tool holding system, how do you remove the tool once it,s in place?

Ian S C

Unless the coefficient of expansion is much greater for the holder, it won’t loosen on heating. Cryogenic cooling might help, if appropriate. Otherwise the holder would need to be removed from the tool – in chips – I would imagine.

[Mark RandParticipant @markrand96270]

Posted by not done it yet on 07/05/2018 13:10:57:

Posted by Ian S C on 07/05/2018 12:36:38:

David, that sounds an interesting tool holding system, how do you remove the tool once it,s in place?

Ian S C

Unless the coefficient of expansion is much greater for the holder, it won’t loosen on heating. Cryogenic cooling might help, if appropriate. Otherwise the holder would need to be removed from the tool – in chips – I would imagine.

It does work . With the induction heater, you can put 10-20kW of heat into the outer 1/8" of a 1.5" diameter toolholder. The expansion of the outer layers opens the bore before the heat can transfer to the tool shank.

Marvelous things for the production shop.

[Paul FallertParticipant @paulfallert28101]

MT2 tightening the drawbar (short of heat shrinking the cutter into a dedicated holder)

How much to tighten a MT2 drawbar?

I found: "finger tight plus 1/4 turn"

Paul

[Another JohnSParticipant @anotherjohns]

One thing I've heard (from production toolsetters) about Weldon shanked tooling is that, on production environments, CNC weldon toolholders would wear quite quickly.

The reason went something like "if you can manually insert the tool, there's room for it to flex, and if there's flex in the toolholder it will wear".

It actually makes sense if you think about it – the set screw will act as a bit of a pivot, and the tool will bend; and once some wear gets in, it'll bend more, increasing wear…

Not something we'd need to be worried about in our workshops, I'd expect!

[JasonBModerator @jasonb]

One for the doubting Thomas types to watch while in their armchair, taking a tool out starts about 2.45

[Author]

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