Zero / Super Short gauge length toolholders CAT40

[zalectric]

I am considering purchasing more super short gauge length tool holders for my mills. I typically mill aluminium structural parts that are similar to aerospace parts. Lots of deep pockets and ribs in 6061 or 7075 aluminium. I have Fadal style 3 axis mills, nothing high-end.

A few years ago I got a Regofix zero gauge length er32 tool holder.

While this was used for a long insert mill. I am considering switching over to this type of tool holder for most of my tools. From my results, it seems on my mill that short gauge length is more important than everything else, runout, grip strength, ect. I do expect that these tool holders will have a larger run-out than a typical ER holder due to distortion in the CAT40 taper due to the thin wall in this area. Regardless of run-out the sound and surface finish seems better.

Please share any experience you have with gauge length vs other factors.

Super short toolholders:
Regofix: https://www.mscdirect.com/product/details/65369696
Shars: CAT40 ER32 1.1" Rigid ER Collet Chuck Tool Holder
Technics: CAT 40/50 ER Chucks - SuperRIGID | Techniks CNC Tooling Solutions

 

[Milland]

I have a few of the Techniks version of these holders. I like them and use them where convenient.

But I would suggest trying a few with tools tightened to "normal" levels, then bluing the shanks and seeing what fit you get to the spindle taper. If you're getting just a band where the collet is swelling the holder, you've got to revise your methods.

The other caution is risk of increased chip contamination of the spindle bearings. With closer proximity to chips and coolant splash, if there's not a good labyrinth seal design at the spindle nose you may have the bearings fail faster than you'd expect.

 

[mutiny]

Just to add to the mix, both YG1 and Schunk have some super short gauge length hydraulics:

YG-1: BEST VALUE IN THE WORLD OF CUTTING TOOLS

Clamping Technology

 

[mutiny]

I have a few of the Techniks version of these holders. I like them and use them where convenient.

But I would suggest trying a few with tools tightened to "normal" levels, then bluing the shanks and seeing what fit you get to the spindle taper. If you're getting just a band where the collet is swelling the holder, you've got to revise your methods.

The other caution is risk of increased chip contamination of the spindle bearings. With closer proximity to chips and coolant splash, if there's not a good labyrinth seal design at the spindle nose you may have the bearings fail faster than you'd expect.

I seem to remember that Frank Mari has explicitly said that he won't make these types of collet holders on this forum because they're bad for spindles. I do wonder if he feels the same about these stubby hydraulics. Since the pressures/forces are less variable, perhaps they can be designed not to suffer from the same issues?

 

[Milland]

I seem to remember that Frank Mari has explicitly said that he won't make these types of collet holders on this forum because they're bad for spindles. I do wonder if he feels the same about these stubby hydraulics. Since the pressures/forces are less variable, perhaps they can be designed not to suffer from the same issues?

You're saying his concern was more the risk of the holder taper being swelled? Interesting, I would have thought the contamination was a more important danger.

Maybe PM Frank and point him to this thread to get his direct input?

 

[Ianagos]

I have a few of the shars ones they are very well finished. I use one to holder my 3d indicator.

I never thought about the fact that it would swell the taper and cause damage to the spindle. But I also have not run any real cutting tools in these I bought 4 just for my 3d indicator and to have a couple spares for a special occasion where I may need it but so far 3 are still unopened.


If frank does chime in I have a question. Does the surface finish on the taper of the holder need to be more rough ground to not spin as easily? Or is it really just about how well the taper mates?

 

[Milland]

If frank does chime in I have a question. Does the surface finish on the taper of the holder need to be more rough ground to not spin as easily? Or is it really just about how well the taper mates?

I'll be Frank (or a facsimile) for the moment: No, you don't want a rough surface on the toolholder taper, that just makes torque drive capacity worse. It's the drive dogs that give you ultimate torque capability, although a properly mated holder and spindle can transmit a surprising amount of force just by the wedging action friction alone.

 

[EmGo]

It's the drive dogs that give you ultimate torque capability,

I believe this is not correct. Have always read that the taper fit and friction are supposed to do all the work, the dogs are just for locating.

 

[Milland]

I believe this is not correct. Have always read that the taper fit and friction are supposed to do all the work, the dogs are just for locating.

Note that I said "ultimate". As in, at max capacity of a proper taper mate and draw load, if it still shifts to the point of contact with the drive dogs there will be a higher capacity to the point where they shear or the spindle stalls.

I think that's a fair statement.

 

[mutiny]

Okay, it was bugging me and I didn't want to be putting words in Frank's mouth, so I found the post I was referring to. Quoted here for convenience:

I've seen and purchased CAT40-ER32 super short collet chucks with the internal ER32 collet nut. The ER32 collet pocket sits so deep in the tool holder taper that just tightening the collet nut to 40 ft-lbs ( should be min 80) the outside taper bulges. Thats a serious no no and can damage the taper on your machine is used often enough. I plan on making these style but ER25 will be the max for 40 taper and probably ER20 will be the max for BT30. Min wall thicknesses must be observed to make sure your tool holder taper does not distort during tool clamping and while the tool is being used.

https://www.practicalmachinist.com/...-any-time-soon-356618/index2.html#post3260118

 

[Milland]

I sorta figured the smart move would be to have a solid arbor the shape of a ER32 collet, tighten that into the "almost done" toolholder, then do a final grind of the 40 taper to account for the swell. It would drive up costs a bit, but might be the ticket for getting good performance at the taper mate.

As long as the arbor was tight at the high end of allowable torque, being a bit lax means a small concave in the lenght of the taper, which hopefully is still located correctly at the top and bottom.

A man can dream, can't he??

 

[fmari --MariTool-]

Yep, I still have the same opinion. Laws of elastic deformation did not change. I would be concerned about the super short hydraulics as well. Unless it was ground with the bladder under full pressure so when you are clamping a tool the taper is straight and round.

Taper to taper contact is what drives the tool. The tool holder should never touch the drive keys. Never!

I wouldn't advise it, but you can remove the drive keys from your machine and you wouldn't even know it. The machine will run the same. Of coarse this is assuming you have a spindle taper in good condition and proper drawbar force.

Look at ISO tooling. No drive keys.

 

[metalmadness]

I have one extra short gauge length ER32 from Kennametal so it is not a true "zero gauge length" but it is very short. I would choose something like that over a zero gauge length tool holder any day.

I get the obsession with shortest gauge length possible. I get it. But is it really valuable enough to shave off every thousandth of gauge length if your spindle taper gets blown up? Hell naw. I would recommend just a standard shorty collet holder instead. You will get great performance without the risk to your spindle AND the risk as someone else mentioned of coolant/chip contamination with the spindle bearings. That is a very legit concern to have, especially if you have high pressure coolant.

Can you measure the time/performance benefit of a zero gauge length holder compared to a standard short length collet holder? My guess is that it is negligible.

 

[zalectric]

As always thanks for the great feedback, I will take a lookat the ER32 from Kennametal and also Mari.

 

[zalectric]

Yep, I still have the same opinion. Laws of elastic deformation did not change. I would be concerned about the super short hydraulics as well. Unless it was ground with the bladder under full pressure so when you are clamping a tool the taper is straight and round.

Taper to taper contact is what drives the tool. The tool holder should never touch the drive keys. Never!

I wouldn't advise it, but you can remove the drive keys from your machine and you wouldn't even know it. The machine will run the same. Of coarse this is assuming you have a spindle taper in good condition and proper drawbar force.

Look at ISO tooling. No drive keys.

Frank did you end up making the short ER25 Cat40 holders. I checked on the website and i dont think i saw them?

 

[fmari --MariTool-]

Frank did you end up making the short ER25 Cat40 holders. I checked on the website and i dont think i saw them?

No I did not. Probably in the future I will. But many other projects ahead of this one.