SK16 Pull out issue?

blkaplan · May 22, 2017

So I was very excited to see the Maritool now offers SK chucks and collets. I needed some more high quality low gauge height tool holders so i just ordered a set of 3.

On my first use I had my 5/8" endmill and 1/2" endmill pull out and ruin an expensive prototype I was working on.

The way Maritool describes them is
"
ER collets have an included angle of 16 degrees and most collets have a range of 1mm. Grip is strong and in most applications sufficient.

SK collets have an included angle of 8 degrees and most collets have a range of .5mm. Grip is very strong and is a step above ER collets. More of the collet sits in the taper pocket so concentricity is equal or better than ER collets.
"

I never have pullout issues with me ER-32 stuff, is this common with the SK setup? Was it just not tight enough? Am I missing something obvious?

eaglemike · May 22, 2017

Most likely not tight enough. I had a similar issue on my new Brother machine with the high torque spindle. Once I went to proper torque, no more issues. Ask Frank for proper torque, I don't want to tell you the wrong number......

blkaplan · May 22, 2017

I guess my main reason for posting to find out if the SK collet design is not good for roughing and will have pull out issues under those conditions.

Jeremy63 · May 22, 2017

5/8" is probably a bit too much for an SK16 when roughing. Call Maritool and see what they recommend. I've used them, but only with 3/16" or smaller tools in steel. Mainly use them for the low runout on small tools.

deadlykitten · May 23, 2017

Jeremy63 said:
5/8" is probably a bit too much for an SK16 when roughing.

hy

just like he said ...

an er32 would behave more elastic for that shank, because you are not near the upper limit

also, rego fix sells er32's with 0.5 increments

and an er40 would deliver a better grip for the 5/8

blkaplan said:
ER collets have an included angle of 16 degrees and most collets have a range of 1mm. Grip is strong and in most applications sufficient.

SK collets have an included angle of 8 degrees and most collets have a range of .5mm. Grip is very strong and is a step above ER collets. More of the collet sits in the taper pocket so concentricity is equal or better than ER collets

collets can clamp [ 0 ... - range ] ; near 0 is all ok, but as you get far from it, also collet frontal starts to deform

so "grip is very strong" only near 0

otherwise, thightening force is diminueshed, because an important fraction of it must deform the coollet body, and get beyond the point of normal plastic/elastic deformation chart ... this wont ireversebly damage the coollet, but will put the collet body to more stress

... if possible, try bearings nuts + h7 shanks

kindly !

wesg · May 23, 2017

Did you get the collets from him too? Check for burrs inside.

gregormarwick · May 23, 2017

Nominal size collets? 5/8" or 16mm? 1/2" or 13mm?

For roughing purposes with any collapsible collet nominal size shank is critical - forget about grip range.

riabma77 · May 23, 2017

blkaplan said:
So I was very excited to see the Maritool now offers SK chucks and collets. I needed some more high quality low gauge height tool holders so i just ordered a set of 3.

On my first use I had my 5/8" endmill and 1/2" endmill pull out and ruin an expensive prototype I was working on.

The way Maritool describes them is
"
ER collets have an included angle of 16 degrees and most collets have a range of 1mm. Grip is strong and in most applications sufficient.

SK collets have an included angle of 8 degrees and most collets have a range of .5mm. Grip is very strong and is a step above ER collets. More of the collet sits in the taper pocket so concentricity is equal or better than ER collets.
"

I never have pullout issues with me ER-32 stuff, is this common with the SK setup? Was it just not tight enough? Am I missing something obvious?

I think 5/8" is too big for SK16. I would go with SK25.

However, if you are roughing, and finish or tolerances are an issue, I would use ER40, or end mill holder if possible.

I use every day a 1/2" end mill with SK16 and never had a problem. 60 Ft-Lbs.

blkaplan · May 23, 2017

wesg said:
Did you get the collets from him too? Check for burrs inside.

I did and I did see some burrs. Maybe i should go back and check them more carefully.

gregormarwick said:
Nominal size collets? 5/8" or 16mm? 1/2" or 13mm?

For roughing purposes with any collapsible collet nominal size shank is critical - forget about grip range.

I was using brand new 1/2" Carbide endmills in a new 1/2" SK collet and the same with the 5/8.

riabma77 said:
I think 5/8" is too big for SK16. I would go with SK25.

However, if you are roughing, and finish or tolerances are an issue, I would use ER40, or end mill holder if possible.

I use every day a 1/2" end mill with SK16 and never had a problem. 60 Ft-Lbs.

I would of opted for a SK25 if it were available through Mari, maybe hes working on them.

I had issues with my 1/2" endmill pulling out too. With the 1/2" I was doing a 70% step over with a .45 DOC in 6061 T6 Aluminum @ .006 FPT Didn't really seem like anything too crazy to me. When I did pull it out of the mill the collet nut was loose!!! :nutter:

I re-tightened and checked my tools that I had just setup and the nuts don't really tighten smoothly. Maybe its because they are new? They get pretty tight and if you really yank and then get passed a point and have some extra movement on them you can get another 30 degrees.

With the 5/8 endmill its a 3.75 LOC 3 fl endmill that was HSM 6061 with a .08" step over and 3" DOC at .0076 FPT. Didn't really seem like i was pushing it. Its not like I was slotting in 4140.

riabma77 · May 23, 2017

blkaplan said:
I did and I did see some burrs. Maybe i should go back and check them more carefully.

I was using brand new 1/2" Carbide endmills in a new 1/2" SK collet and the same with the 5/8.

I would of opted for a SK25 if it were available through Mari, maybe hes working on them.

I had issues with my 1/2" endmill pulling out too. With the 1/2" I was doing a 70% step over with a .45 DOC in 6061 T6 Aluminum @ .006 FPT Didn't really seem like anything too crazy to me. When I did pull it out of the mill the collet nut was loose!!! I re-tightened and checked my tools that I had just setup and the nuts don't really tighten smoothly. Maybe its because they are new? They get pretty tight and if you really yank and then get passed a point and have some extra movement on them you can get another 30 degrees.

With the 5/8 endmill its a 3.75 LOC 3 fl endmill that was HSM 6061 with a .08" step over and 3" DOC at .0076 FPT. Didn't really seem like i was pushing it. Its not like I was slotting in 4140.

You have more options for SK25: Nikken, HPI, etc...

Not sure what you mean with this:

"They get pretty tight and if you really yank and then get passed a point and have some extra movement on them you can get another 30 degrees"

Are you tightening them by hand, or with a torque wrench?

Are the tool holder and collet perfectly clean and dry before assembly?

IMHO, SK is great for drilling and reaming. For heavy milling there are better options.

blkaplan · May 23, 2017

riabma77 said:
You have more options for SK25: Nikken, HPI, etc...

Not sure what you mean with this:

"They get pretty tight and if you really yank and then get passed a point and have some extra movement on them you can get another 30 degrees"

Are you tightening them by hand, or with a torque wrench?

Are the tool holder and collet perfectly clean and dry before assembly?

IMHO, SK is great for drilling and reaming. For heavy milling there are better options.

Yes, they were perfectly clean.

I dont have a torque wrench for these style collets yet unfortunately but I use torque wrenches frequently and have a good feeling for how much torque I am applying. But to answer your question directly, by hand. I need to put a torque wrench compatible with collet chucks on my short list of things to buy.

What I mean is it felt like when I was tightening the collets to around 60 ft/lb, it got very tight and nut stopped moving. When I gave it a quick pull around 75 ft-lbs it loosened up and moved again by 30 degrees until it got tight.

riabma77 · May 23, 2017

blkaplan said:
What I mean is it felt like when I was tightening the collets to around 60 ft/lb, it got very tight and nut stopped moving. When I gave it a quick pull around 75 ft-lbs it loosened up and moved again by 30 degrees until it got tight.

I never experienced this before. Maybe you are over tightening? I will start acquiring a torque wrench, with the appropriate head adapter.

Also the torque doesn't depend of the tool holder. It depends the tool you are using. For example, If you are using SK16 for 1/4" and 1/2", they should be tightened with different torques.

Again, 5/8" I think is too big for SK16.

blkaplan · May 23, 2017

riabma77 said:
I never experienced this before. Maybe you are over tightening? I will start acquiring a torque wrench, with the appropriate head adapter.

Also the torque doesn't depend of the tool holder. It depends the tool you are using. For example, If you are using SK16 for 1/4" and 1/2", they should be tightened with different torques.

Again, 5/8" I think is too big for SK16.

I'm guessing its because it was all brand new and maybe there were some burrs on the collet? Just talked to Maritool and they recommended using heavy machine oil on the threads and collet driving surface.

I agree with you that 5/8" seems to be big for a sk16, unless its just finishing ops. Hopefully it will be ok with the 1/2"

blkaplan · May 23, 2017

Based on this seems like it should be, unless I'm not considering something important

Lyndex-Nikken - ER32 vs. SK16 Torque Test - YouTube

deadlykitten · May 23, 2017

hy

it is interesting that www is full with videos showing how sk16 is better than er32, but in your case things are not like that

i also was tented once to buy sk collets, but how nikken dealer was pretty far, i give up

this is what i do now :
... er32 : max endmill diameter 10 .. 12 .. 14 maybe
... hydra holder : 16 and up

dstryr · May 23, 2017

blkaplan said:
I would of opted for a SK25 if it were available through Mari, maybe hes working on them.

I had issues with my 1/2" endmill pulling out too. With the 1/2" I was doing a 70% step over with a .45 DOC in 6061 T6 Aluminum @ .006 FPT Didn't really seem like anything too crazy to me. When I did pull it out of the mill the collet nut was loose!!! I re-tightened and checked my tools that I had just setup and the nuts don't really tighten smoothly. Maybe its because they are new? They get pretty tight and if you really yank and then get passed a point and have some extra movement on them you can get another 30 degrees.

With the 5/8 endmill its a 3.75 LOC 3 fl endmill that was HSM 6061 with a .08" step over and 3" DOC at .0076 FPT. Didn't really seem like i was pushing it. Its not like I was slotting in 4140.

That 5/8 is a ton of force in a 3" LOC on a collet like that....

Job Shopper TN · May 24, 2017

I have not used SK chucks. Howver, 3 inches cutting lwngth is going to provide a LOT of pull on that end mill. Especially if you have a high helix end mill but regardless, whether you are "pushing" it or not, that is a lot of cutting length at one time.

I would not use a collet chuck for such an application. Weldon holder or milling chuck.

blkaplan · May 30, 2017

Does anyone have any recommendations for a low gauge height milling chuck that wont break the bank?

steve_p · May 30, 2017

Not sure if you mentioned what machine taper? Cat40?
Define "low cost" chuck?

Last time I purchased a milling chuck, I bought two Nikken 3/4" x 70mm gage length chucks. I think price was about 385, plus about 40 for the collets.

I've also used the HPI pioneer SX25 x 1.85" gage length collet chucks. Those are quite short and should give an very high grip as well. I want to say those are around 2 bills each, plus collets.

Good luck,
Steve

blkaplan · May 30, 2017

steve_p said:
Not sure if you mentioned what machine taper? Cat40?
Define "low cost" chuck?

Last time I purchased a milling chuck, I bought two Nikken 3/4" x 70mm gage length chucks. I think price was about 385, plus about 40 for the collets.

I've also used the HPI pioneer SX25 x 1.85" gage length collet chucks. Those are quite short and should give an very high grip as well. I want to say those are around 2 bills each, plus collets.

Good luck,
Steve

Its a CT40 machine, older mori seiki MV

It would be nice to be sub 300.

385 for each nikken chuck, right?

SK16 Pull out issue?

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