Weldon Shank Tool Holding

[Paul FallertParticipant @paulfallert28101]

MT2 collets minimize "stick out" from spindles etc and increase "daylight" between spindle and workpiece. However, under some conditions, a MT collet will allow a tool to be drawn out of the collet (also applies to R8 and certain other collets). The Clarkson threaded holder was the answer to holding tools, but the stick-out is greater.

Has anyone produced a (MT) collet modification that will retain a Weldon shank tool? Or, lacking that mod, a workable alternative?

Paul

Thought starter: Grind hole in side of collet and short T-headed-pin (pressed, epoxied, brazed into hole from inside the collet.)

[Paul FallertParticipant @paulfallert28101]

Weldon Shank FIX in MT2 Collet?

[John HaineParticipant @johnhaine32865]

Never had a tool drawn out of an R8 collet, obviously not trying hard enough.

[colin vercoeParticipant @colinvercoe57719]

TG and DA collets were made with a loose captive pin in the collet that when the collet chuck was tightened the pin went into weldon slot on the shank and stopped the cutter from pulling out and it worked fine,the only problem was when the collet was mistakenly used on straight shank cutters, chuck cutter etc could be damaged.

[John RuddParticipant @johnrudd16576]

Posted by John Haine on 29/04/2018 23:13:31:

Never had a tool drawn out of an R8 collet, obviously not trying hard enough.

I use ER32 collets, not had a cutter incident….( touch wood…)

[EmgeeParticipant @emgee]

Like others I have not experienced cutter work out with ER collet system but concede the Clarkson holder screw in cutters are more secure in use by design.

Emgee

[Thor 🇳🇴Participant @thor]

As others have mentioned I too have never had cutters move when using ER collets. It has happened to me when using MT collets. I have used Weldon end mill holders like these, and they have worked well for roughing.

Thor

[JasonBModerator @jasonb]

But ER chucks stick out more which is missing the point of the MT collet question.

I suppose there is nothing to stop you making your own MT "collet" that could be drilled and tapped for a grub screw. Probably would not even need slotting as the weldon holders do not close up on the tool. So just a solid MT taper with an accurately formed hole, grub screw thread and drawbar thread, could unharden a blank end arbor and cut the blank end off.

 

Edited By JasonB on 30/04/2018 07:06:07

[Michael GilliganParticipant @michaelgilligan61133]

 

Paul,

Useful table of refererence dimensions, here: **LINK**

http://www.armstrongmetalcrafts.com/Reference/TaperShankDimensions.aspx#weldon

Assuming that you only intend to use the smaller sizes; it should, as Jason suggests be a simple matter to modify a plain MT2 arbor.

MichaelG.

.

P.S. … I should mention my personal distaste for the simple 'Weldon' fixing: The design is theoretically flawed, because in order to insert the cutter, there must be some finite clearance, and therefore the cutter will run eccentrically. … The art is to render this flaw 'negligible'.

The likes of Kennametal have invented more accurate holders, but these are necessarily bulky and/or more complex.

This simple variant merits consideration:

https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=US&NR=2004253070A1&KC=A1&FT=D&ND=3&date=20041216&DB=EPODOC&locale=en_EP

Edited By Michael Gilligan on 30/04/2018 08:55:31

[Clive FosterParticipant @clivefoster55965]

Seems to be no reason why the retainer grub screw shouldn't be back up in the MT taper itself giving essentially zero extra stick out. Small flat with rounded edges so it doesn't interfere with or damage the machine taper.

Big disadvantage is that you need to pull the taper to change the tool.

In principle a set of shop made holders, one for each size of milling cutter you use, is not unaffordable compared to a new set of collets or collet chuck. If you went that way you could keep a cutter of each size permanently mounted with a note of the actual stick out. Works for the CNC boys. If I had an MT spindle mill I'd seriously consider this as making the holders is pretty trivial. But my lathe has a first class taper turning attachment so producing a batch of good tapers is basically shelling peas once set-up.

Although Michaels distaste is based on a valid point I think it is more theoretical than real. My Weldon holders are a sufficiently close fit on the shanks of good quality cutters that entrapped air can make it hard to insert the cutter so any shift when the screw is tightened will be miniscule. Contemplated drilling a relief hole more than once.

Theoretically they would be better made double bored with a smaller part bore intersecting the edge of the primary bore opposite the grub screw producing two line contacts about 20° or 30° apart. This would give true three point contact between holder and cutter. Two lines and screw. Standard set ups more two and a bit depending how well the cutter flat sits against grub screw. Worst case is simple single line on note bore immediately opposite the contacting "point" of the screw. In practice the screw point is of finite width so its more like one line and a narrow block. Although it generally works fine its somewhat unsatisfactorily indeterminate from a mechanical analysis point of view. Yet another issue to keep the Angles Dancing on the Head of a Pin debating society warm.

Clive.

[BazyleParticipant @bazyle]

Re eccentricity. The ones with a flat for the grub screw should be sharpened in a holder in which this flat governs the position – they would then be sharpened with an offset that allows for the error.

[steamdaveParticipant @steamdave]

Posted by JasonB on 30/04/2018 07:02:24:

But ER chucks stick out more which is missing the point of the MT collet question.

I suppose there is nothing to stop you making your own MT "collet" that could be drilled and tapped for a grub screw. Probably would not even need slotting as the weldon holders do not close up on the tool. So just a solid MT taper with an accurately formed hole, grub screw thread and drawbar thread, could unharden a blank end arbor and cut the blank end off.

Isn't this similar to the cheap endmill holders readily available, particularly 'Over There'. The only possible difference is that with them, the grub screw is not in the taper but on a collar below the taper (I think). If there is a daylight issue, the collar could be trimmed back somewhat.

Dave
The Emerald Isle

[JasonBModerator @jasonb]

Yes Dave, exactly the same principal except the hole and grub screw go into the actual taper rather than having a bit sticking out the end which would save 20-30mm. We can get them over here.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Clive Foster on 30/04/2018 11:01:18:

[ … ] Theoretically they would be better made double bored with a smaller part bore intersecting the edge of the primary bore opposite the grub screw producing two line contacts about 20° or 30° apart. This would give true three point contact between holder and cutter. Two lines and screw. [ … ]

.

Rather like the patent that I linked, Clive

MichaelG.

[MuzzerParticipant @muzzer]

As Clive said, this is angels and pinheads territory, strictly for the armchair experts. You may not have noted that Weldon / sidelock shank holders are commonly available in G2.5 balance ie fit for 25,000rpm with runout better than 3um. They are hardly going to sell stuff like that if the very principle is so deeply flawed. Certainly not an issue for some guy in a shed / armchair to worry about.

I prefer end mill holders like that. Unless you want to spend a few hundred quid on a really fancy set of collets, it's a more rigid, accurate and consistent way to hold cutters. And that's before you look at the runout on your spindle and the cutters themselves…..

Murray

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Muzzer on 30/04/2018 16:10:11:

As Clive said, this is angels and pinheads territory, strictly for the armchair experts. You may not have noted that Weldon / sidelock shank holders are commonly available in G2.5 balance ie fit for 25,000rpm with runout better than 3um. They are hardly going to sell stuff like that if the very principle is so deeply flawed …

.

… and YOU may not have noted that I wrote: " The art is to render this flaw 'negligible' "

If I understand correctly; the discussion at that time was about DIY options.

MichaelG.

[Trevor Crossman 1Participant @trevorcrossman1]

Paul​ in answer to the original question, from my own experience I'd say that it is quite practical to carefully bore a blank MT2 arbor to accept a Weldon shank and drill/tap for a retaining grubscrew, then I case harden the holes. I've made them in this manner to hold and drive Rotobor type cutters up to 48mm diameter to cut holes in thick plate and I do not see an issue with runout, though I must admit that I tend to be more interested in achieving a practical working result rather than fretting over theoretical perfection. Give it a try, the blanks are cheap enough and the result will be down to the accuracy of your boring.

Trevor.

[Mark RandParticipant @markrand96270]

I suspect that you might have been using MT3 shanks though. An MT2 one would have a negative amount of metal left is you stuffed a Rotabroach 3/4" Weldon shank up it.

 

Added:- or was that in the 'sticking out' bit of the arbor?

Edited By Mark Rand on 30/04/2018 22:02:21

[Trevor Crossman 1Participant @trevorcrossman1]

yes Mark​ , you're quite correct, I was referring to my use of MT2 arbors with a soft stub that 'sticks out' Trevor

[VicParticipant @vic]

Posted by Paul Fallert on 29/04/2018 22:38:43:

MT2 collets minimize "stick out" from spindles etc and increase "daylight" between spindle and workpiece.

Paul

This is true Paul but are you that short of Z height? Or is it a large workpiece. Just interested.

The lack of “stick out” as you put it also makes things more rigid. Sometimes though I choose to use an ER chuck with small cutters because it’s easier to see the cutter simply because it’s not so much in shadow from the quill.

[Mark RandParticipant @markrand96270]

Posted by Trevor Crossman 1 on 30/04/2018 22:29:28:

yes Mark​ , you're quite correct, I was referring to my use of MT2 arbors with a soft stub that 'sticks out' Trevor

Sorry, I'd got my head stuck on Clive Foster's idea of having the grub screw back in the tapered part of the holder.

Got a trivial bit of milling to do on a too high item. Haven't got enough headroom even with zero stickout, so I've got to make a raising block.

[Paul FallertParticipant @paulfallert28101]

I want to thank everyone for your thoughtful and creative suggestions, questions and implied questions.

Encouraging news: Collets with pins to engage and retain Weldon-flat-shank tools have been made and used before by MEW members.

Question: Why don’t I use a setscrew or ER collet holder?

Answer: They have excess stick out compared to a MT collet (see later tests). Stick out leads to chatter, vibration, tool wear and small tool breakage. My ER32 collet adapter sticks out even further than my setscrew (sidelock) tool holder. Of secondary importance is increasing headroom.

Note: According to G-Wizard and others, excess stick out (defined as a multiple of cutting tool diameter) must be taken into consideration when establishing milling parameters. (usually by slowing the feed rate)

Several respondents suggested (and pictured) setscrew tool holders designed with less stick out than mine and even suggested making one from a blank arbor. Still, with setscrew holders a solid bore with the necessary clearance, adds to the TIR. See spring collets, next.

Don’t spring collets (such as MT, DA, Myford and ER) automatically center the tool inside their taper? And if the answer is Yes, then quality spring collets might center the tool to at least the TIR of the spindle thus eliminating some of the vibration/chatter? Observation: Limit pin protrusion into the Weldon flat area so as not to apply unwanted radial pressures that force tool eccentricity.

Question: What was the problem I was trying to solve?

Facemill chatter was exacerbated when milling hardened steel workpieces. Chatter problems traced to excess vibration and deflection which can be caused by any of the following:

· Weak or low-mass lightweight machines

· Spindle stick out (flexing) and/or excess quill extension (unavoidable on many mill drills)

· Non-concentricity of cutting tools

o Manufacturing tolerances

o Bent or worn tools

o Excessive tool length [or “long-series-cutters”] causing tool flexing

· Machine vibrations induced by the following:

o Workpiece “material conditions”

o Unbalanced rotating mass

o Climb cutting vs conventional cutting due to force vectors

o Unbalanced step-overs/lack of tool overhang, see next

o Cutter width not appropriate for workpiece width (aka improper step over/overhang)

o Improper feed rate, given certain “cutting conditions”

o Excess cutting edge radius and/or a chip load which is less than the cutting edge

My facemill chatter problem was traced to excessive stick out. Thus, my search for a reduction of stick out. Changing feeds and speeds helped, but not appreciably.

Theory: Why would spindle runout reduce tool life? Because “runout=uneven chiploads” source: **LINK** This author also refers to Weldon holders as “sidelock” toolholders. He describes techniques to reduce runout and one I have tried with much success he calls “clocking”.

Cutters don’t pull-out for a majority of the respondents. But, it has occasionally occurred to me and the other students, particularly when side-milling in aluminium using an endmill with a strong helix. At school we used R8 collets and “sidelock” tool holders. Only the R8 collets allowed tools to pull out. This was my reason for restricting the Weldon flat from axial movement on my home-based MT2 mill.

​Tentative conclusion: Since no one else has this problem of cutter pull-out, am I looking for a solution to a non-problem or is there another solution, maybe more knowledge of how to use high-helix endmills?

[JasonBModerator @jasonb]

Paul, out of interest what mill are you using?

Murray posted earlier, why not have a look at a few of his videos which mostly show the cutters held by weldon type holders, he does not have much of aproblem with chatter and still takes a sizeable cut, does have a half decent machine behind the cutter though!

I've not had problems using 45degree helix aluminium cutters in a ER32 collet chuck

[richardandtracyParticipant @richardandtracy]

I will be the first to admit I've not had a lot of experience milling, but I have used Weldon, Clarkson, MT and ER 32 collets. I now use ER32 almost exclusively. I had tool edge out in MT tapers – I wasn't really willing or able to tighten it enough. Weldon worked well, but the expense to cover each and every size I was likely to use was excessive. I already have ER 32 collets to hold pen making materials from 6-20 mm, so the choice was a no-brainer. The results I get are acceptable commercial quality, meeting Ra1.6 standards without trouble. This with mills bought direct from China, in a collet holder also bought direct from China, using collets bought one at a time from Axminster. All using the milling head of a Warco WMT300, a Clarke CL500 clone. According to some of the more opinionated authorities here, everything about the equipment I use should make the achievement impossible. As it isn't, I'd suggest you don't get too hung up about perfection and think more about what is acceptable to you in your situation.

At work, until he retired in March, our machinist used ER50 collets on the works mill and never had a mill edge out. If he had, the whole factory would have known. He was not one to hide his feelings.

Regards

Richard.

[Paul FallertParticipant @paulfallert28101]

To JasonB:

At school we had six variable-speed Bridgeport mills with the larger tables. I use a Clausing 6"x24" Model 8520, pulley driven at 180-3,500 rpm with a 1/2hp motor. Ironically, this mill came from a school shop and had seen very little use and the only abuse was one shallow drilling mark on the table.

At Vo-Tech we were told to not use climb milling. Our training was in speeds and feeds, but not about where to position the milling cutter with respect to the workpiece. I am now seeing that speeds and feeds is but 20% of what you need to know and the other 80% was neither in the classes nor in most of the textbooks I have found, so far. On the web, I finding videos from major tool suppliers (CNC oriented, of course) and that's where I began to realize that there is so much more to "balancing" the cut, step over, overhang, when to use climb and when to use conventional milling. Most of the people I have talked to tell me, "just do it". But, I now see that there are some fundamental "do's and don't do's" that could be shared. A recent MEW "Milling for Beginners" article mentioned a 66% width of cut. Harold Hall mentioned something similar in his book on milling.

Thank you for pointing out Murray's videos.

Paul

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