Er collet accuracy trick?

[Batmanacw]

I have both er40 and er16 collets. I noticed a while ago that the er40 do not always seem to grip really straight. On my er40 lathe chuck i could lightly tap the work piece and get it really straight and very low run-out. It would stay when turning so it wasn't a fluke.

I just bought a very nice Iscar r8 to er16 collet chuck. I checked the run-out without a collet and it ran out 0.00015". Really nice. I chucked up a 1/4" gauge pin and I had 0.0005" with a collet guaranteed to give 0.0002" tir. I tapped the pin in just like before and i ended up under 0.0002" and 0.0003" at 4 times diameter. I did the same with an endmill. Nyc cnc did similar on his YouTube channel.

If the accuracy is available, then why doesn't the collet seat well enough to access that accuracy without the messing around? I must be ignorant to a trick of some sort...

 

[Ken226]

What brand of collets are they? I've bought and then discarded some pretty horrible imports. I got a set of technik collets that are great.

I get the best, most repeatable results with a ball bearing type collet nut.

 

[Batmanacw]

What brand of collets are they? I've bought and then discarded some pretty horrible imports. I got a set of technik collets that are great.

I get the best, most repeatable results with a ball bearing type collet nut.

I bought I-carbide ultra precision guaranteed to 0.0002". The Iscar has a bearing nut.

I might try the Technik collets sometime.

 

[Batmanacw]

I did a test today with the Iscar er16 collet chuck.

I chucked up a 1/4" endmill. It was running out 0.0006" tir. I took a cut 3/8" deep and 0.06" width at 6 ipm.

Then i checked the run-out which had not changed.

Then I tapped it in to 0.0001" tir and took a couple more cuts. Then I checked the run-out and it was the same.

It appears that the extra force on one side of the endmill will not force the cutter to center itself.

 

[Batmanacw]

I just received a Sowa r8 er16 collet chuck from Suncoast tools. It's made in Taiwan. It is right at 0.0001" tir without a collet. Chucking a dowel pin and end mill it was right at 0.0005" at the chuck. It was easy to give it a couple light taps to get to 0.0002" at the chuck and at 3xD. I think its every bit as nice as the Iscar except no bearing nut. $80 instead of $180.

I will definitely buy a Sowa r8 er16 collet chuck next pay. Definitely a quality tool.

I may try a better brand of collets as well. I'm not sure which brand though.

 

[llamatrails]

Are you aware of the high tightening torque specs for ER collets?
One Google example.

 

[Batmanacw]

Are you aware of the high tightening torque specs for ER collets?
One Google example.

Yes. I am. I have not set up a torque wrench yet but I do have a reasonable idea of how tight to make them. The ER16 are rated to 30 to 45 ft lbs and the ER20 are rated to 59 to 67 ft lbs.

I do not have exact specs for the Iscar er16 because it had a bearing nut.

The numbers are not consistent through all manufacturers

 

[Batmanacw]

I know many folks think I'm crazy asking stupid questions about accuracy i don't actually need, but bear with me.

I mounted a generic tialn coated 4 flute carbide endmill in the I-carbide er20 collet chuck. I tapped it in so the flutes were running out 0.0002" tir. I used a crows foot at 90⁰ in my torque wrench to hit 60 ft lbs.

The following picture is mystery steel somewhat similar to 1018. I took two hogging passes @ 1/2" deep and 0.060" wide. Then a finishing pass at 0.010" width. 2720 rpm at 13 ipm.



The er20 and er16 collet chucks are definitely not as rigid as using a collet in the spindle. I do like the ability to run drills and such in the collet chucks so I'm positive these collet chucks are going to get lots of love.

 

[Batmanacw]

Same mill. 3/4" 2 flute hand cranked in aluminum. I'm not displeased with this but it is striking how smooth the other endmill cut.

 

[Batmanacw]

I made this today to make it easier to torque my er collet nuts. It's for an r8 taper.



So much easier.