This comment is based on ER collets for use in a milling machine. Not the same thing but hopefully some of the methodology is applicable.
I've purchased a number of import collet chucks and collets over the years. I've standardized on ER20 collets for my CNC and have 20-30 toolholders at this point.
My CNC spindle has a TIR on the spindle taper (checked in multiple places using a calibrated Interapid .0001 DTI) of .0002". This isn't particularly good but it is what I have to work with.
The collet chucks are held in a 3/4" precision R8 collet (Tormach TTS) which contributes to the TIR giving me about .0003" when measured on a 3/4" test bar roughly 1" from the spindle. Again not great but it is what it is.
The import chucks are guaranteed to have a TIR <0.0004". Of the 20-30 I've purchased, 6 have been out of spec by as much as 0.0025". These were replaced, but I could have been using garbage if I did not inspect them. Most of the chucks read about .0001-.0002" when spun on a Vee block with a test indicator in the bore.
Depending on how I clock the toolholder in the spindle I can consistently get runout in the spindle of .0002-.0008" or so.
Then it gets bad. The import ER20 collets I've bought are absolute garbage. They are very rough finished and have TIR from 0.001-0.012" (yes, those are thousandths). I've given up on those and only buy Techniks collets at $10 each. I trust them to their 0.0002" TIR.
Finally, the collet nuts. I took my best collet chuck and collet and got them running as true as possible in the spindle. I then tried assembling a test bar with each nut that I owned. The measured runout was highly variable based on the nut used. All were torqued evenly. I have numbered each chuck and nut, and created assemblies which mate the highest precision nut to the highest precision collet chuck.
After all this effort, I have 8 chucks which have excellent assembled TIR (<0.0003") and are good for small tools or anything where the runout really matters. I have roughly 10 chucks which have acceptable (<0.001") TIR and are ok for general purpose use. Finally I have 6-8 chucks with 0.001-0.002" assembled TIR that are only good for roughing tools or drilling.
All this saved me from paying ~$100 per tool assembly ($2-3000 in total) to have guaranteed precision out of the box, but it was a lot of work.
Just sharing my experience,
Mike
I've purchased a number of import collet chucks and collets over the years. I've standardized on ER20 collets for my CNC and have 20-30 toolholders at this point.
My CNC spindle has a TIR on the spindle taper (checked in multiple places using a calibrated Interapid .0001 DTI) of .0002". This isn't particularly good but it is what I have to work with.
The collet chucks are held in a 3/4" precision R8 collet (Tormach TTS) which contributes to the TIR giving me about .0003" when measured on a 3/4" test bar roughly 1" from the spindle. Again not great but it is what it is.
The import chucks are guaranteed to have a TIR <0.0004". Of the 20-30 I've purchased, 6 have been out of spec by as much as 0.0025". These were replaced, but I could have been using garbage if I did not inspect them. Most of the chucks read about .0001-.0002" when spun on a Vee block with a test indicator in the bore.
Depending on how I clock the toolholder in the spindle I can consistently get runout in the spindle of .0002-.0008" or so.
Then it gets bad. The import ER20 collets I've bought are absolute garbage. They are very rough finished and have TIR from 0.001-0.012" (yes, those are thousandths). I've given up on those and only buy Techniks collets at $10 each. I trust them to their 0.0002" TIR.
Finally, the collet nuts. I took my best collet chuck and collet and got them running as true as possible in the spindle. I then tried assembling a test bar with each nut that I owned. The measured runout was highly variable based on the nut used. All were torqued evenly. I have numbered each chuck and nut, and created assemblies which mate the highest precision nut to the highest precision collet chuck.
After all this effort, I have 8 chucks which have excellent assembled TIR (<0.0003") and are good for small tools or anything where the runout really matters. I have roughly 10 chucks which have acceptable (<0.001") TIR and are ok for general purpose use. Finally I have 6-8 chucks with 0.001-0.002" assembled TIR that are only good for roughing tools or drilling.
All this saved me from paying ~$100 per tool assembly ($2-3000 in total) to have guaranteed precision out of the box, but it was a lot of work.
Just sharing my experience,
Mike
