[kstrauss]

The September 2015 issue of Model Engineers' Workshop Magazine (a UK publication) has an interesting tip to reduce ER collet runout. The author claims that lightly tapping the ER nut (not the cutter) will allow dramatic reductions in runout. Has anyone tried this?

[popspipes]

It does make sense as the threads arent a precision fit and any pressure to tighten from one side could cause them to be off center a bit.

I have had a centering problem with small diameter drills, cleaning the bore of the collets thoroughly and retightening put it within specs. I have also noticed this on collets that are almost at the bottom of their range.
Tightening in an axial plane may help to eliminate side load, but I havent tried it.

[kstrauss]

See YUKIWA SEIKO INC. | Tooling System | Super G1 Chucks for a design that appears to use a screw instead of a hammer to reduce TIR.

[mactec54]

See YUKIWA SEIKO INC.Â*|Â*Tooling SystemÂ*|Â*Super G1 Chucks for a design that appears to use a screw instead of a hammer to reduce TIR.

That is a lot better than beating on the ER Collet Nut with a hammer, if you have quality ER tool holders and Collets you don't have TIR problem

[popspipes]

See YUKIWA SEIKO INC.Â*|Â*Tooling SystemÂ*|Â*Super G1 Chucks for a design that appears to use a screw instead of a hammer to reduce TIR.

I would try it with a piece of aluminum or brass as a drift and tap very lightly.

I just made a slitting saw arbor and its off a touch too, not as bad as the one I was using but still not perfect, could be the used saw blade I am using ha!

[A_Camera]

Not an expert, but it sounds crazy to my ears to hit the collet nut, even it is a light hit, every time a tool change takes place. I never hit it and would never do that to any machine with a rotating axis because eventually, not only the collet thread which could be damaged but also the axis might get off centered. OK, I am using ER11, which is very small, so that may be the reason why I have actually not felt this to be a problem at all. If it would be a problem I am pretty sure I would have noticed it.

[popspipes]

Im not going to be tapping, beating, or drilling holes in the nut on mine thats for sure.

I would think if one is that concerned, maybe try moving the wrench to a different side of the nut to tighten, or swap flats as you tighten it, similar to using all three holes to tighten a drill chuck etc, maybe try another collet / collet chuck, maybe rotate the collet chuck in the drawbar collet, as everything has some amount of runout.

I havent found that I needed to do anything other than make sure everything is clean and oiled and tighten, but then I dont build aerospace parts ..........

[TurboStep]

The September 2015 issue of Model Engineers' Workshop Magazine (a UK publication) has an interesting tip to reduce ER collet runout. The author claims that lightly tapping the ER nut (not the cutter) will allow dramatic reductions in runout. Has anyone tried this?

Do you actually have a runout issue or are you just interested in the idea?
Step

[kstrauss]

I'm using Tormach ER16 TTS holders and mainly Techniks precision collets so things work reasonably well. That said, I sometimes use cutters of 0.5mm or smaller so minimizing TIR is critical. I thought that the nut suggestion was interesting and wondered if it was an old idea that didn't really work or perhaps something new and useful.

[TurboStep]

I'm using Tormach ER16 TTS holders and mainly Techniks precision collets so things work reasonably well. That said, I sometimes use cutters of 0.5mm or smaller so minimizing TIR is critical. I thought that the nut suggestion was interesting and wondered if it was an old idea that didn't really work or perhaps something new and useful.

Tormach ER holders have very low runout and combining them with Techniks or Maritool precision collets is definitely the way to go. Even with this approach I had some unexpectedly high runout when using smaller end mills with 1/8" shanks. I found that if I only lightly mounted the ER nut the runout was very good. As I gradually increased the torque, still just lightly tightening by hand, the runout suddenly began to increase. I believe the collet segments begin to twist and the assembly looses concentricity. This isn't such an issue for larger diameter end mills because the segments become flatter. With smaller end mills I now only tighten very lightly by hand (a 0.5mm end mill isn't going to budge due to milling forces) or use bearing collet nuts to be able to apply a little more pressure but without applying a twisting force to the segments. I have also successfully tried adding a small amount of grease to the inside of the standard nut (not in the taper) to simulate the effect of the bearing nut. In the case of the rotating bearing nut the restraining force is provided by the ER taper and not the nut so the grease should have no negative effects.
Step

[prototype3a]

Making sure the collet is properly sized for the tool, the tool is inserted to an appropriate depth and actually tightening them to the design torque goes a long way on ERs. Honestly, I don't think most people tighten them enough. I forget where I saw the torque specs but they were tighter than I expected.

[kstrauss]

Making sure the collet is properly sized for the tool, the tool is inserted to an appropriate depth and actually tightening them to the design torque goes a long way on ERs. Honestly, I don't think most people tighten them enough. I forget where I saw the torque specs but they were tighter than I expected.

Using an imperial collet is particularly appropriate for 1/8-inch shank cutters since 3.175mm requires considerable squeeze.

See Torque Specifications Chart for Collet Nuts and Tool Holders for torque recommendations. That seems a lot more torque than I normally apply!

Thanks to Step for his comments. I'll have to do some serious testing when I'm less busy.

[A_Camera]

I'm using Tormach ER16 TTS holders and mainly Techniks precision collets so things work reasonably well. That said, I sometimes use cutters of 0.5mm or smaller so minimizing TIR is critical. I thought that the nut suggestion was interesting and wondered if it was an old idea that didn't really work or perhaps something new and useful.

That's exactly why I would NOT hit the collet nut... I am not only some times, but often use 0.5mm or smaller cutters and if I'd hit the collet then I think eventually I'd get problems with accuracy. ER16 is larger than ER11, which I am using, but I am pretty sure that if runout is a problem it should not be solved by hitting the nut. I think that can only make things worse or just solve things temporarily.

[philbur]

When a machine set up should naturally align but doesn't it is common practice to "bump" it in order to encourage it to align correctly. This technique has been around for as long as machine tools have. The skill (that you can acquire) is knowing at what point and how hard to "bump" it..

Phil

PS: It's about friction forces versus alignment forces. Appropriate bumping can briefly relax the friction forces allowing the alignment forces to complete their job.

[CNCDevil]

I´ve just made a fly cutter (shank and body cut in one operation) and the initial runout was 0.1mm / 0.004". I then turned it by 1/4 rev. in the collet and the runout decreased to 0.05mm / 0.002". By tapping it "gently" with a rubber hammer the runout settled to 0.01mm / 0.0004". Tapping it more neither de- or increased the runout. ER40 ø26 import collet. Method approved!

Brian

[philbur]

I´ve just made a fly cutter (shank and body cut in one operation) and the initial runout was 0.1mm / 0.004". I then turned it by 1/4 rev. in the collet and the runout decreased to 0.05mm / 0.002". By tapping it "gently" with a rubber hammer the runout settled to 0.01mm / 0.0004". Tapping it more neither de- or increased the runout. ER40 ø26 import collet. Method approved!

Brian

How can a fly cutter have run-out?

Phil

[MichaelHenry]

How can a fly cutter have run-out?

Phil

Wobble in the X-Y plane?

[philbur]

Wobble in the X-Y plane?

Hi Michael, it's not clear what you mean by wobble. The tip of the cutter will describe a circle, the plane of which will be at 90 degrees to the spindles' axis of rotation!

Phil

[popspipes]

Its machined in one piece, my guess is its being indicated on the head near the shank, above the cutter slot.


I would try to tighten the collet axially if possible, all threads have some clearance in them and tightening from one side could conceivably cause a small bit of error.
I would just try it and see if it works or makes any difference, (just my seat of the pants engineering).

[philbur]

Its machined in one piece, my guess is its being indicated on the head near the shank, above the cutter slot.


I would try to tighten the collet axially if possible, all threads have some clearance in them and tightening from one side could conceivably cause a small bit of error.
I would just try it and see if it works or makes any difference, (just my seat of the pants engineering).

The head/body/shank of the fly cutter can have a run-out of 1/2" or any other value, the cutter tip will still run in a perfect circle with no run-out whatsoever.

Phil