Opinions on tool holding runout and rigidity

I’m a noob( I didn’t know what and endmill was 10 months ago) with a 440. I have seen online where multiple people think that set screw holders are usually better than ER collets(and other types) as far as runout and rigidity. I’m interested in what everyone here thinks?? The closest thing I have to experience on this is I had a 1/2" carbide endmill pull out of a setscrew holder last night, but I don’t know if that’s “typical” or what. It would be nice to have shrink fit for TTS, but I haven’t seen it anywhere. Measuring runout on the stuff I have, it’s all between 0.0005 and 0.001. So what are your opinions on the best tool holders based on years of experience??

@Joseph_Arledge welcome to the forums.

One thing I always did to my endmills I planned to rough with in a set screw holder, was grind a flat on the endmill shank. This gives a nice location for the set screw to tighten.

@Joseph_Arledge the general rule, as I understand it, is that an ER tool holder will have less runout than a set screw style due to the self centering nature of the collet system. A while back NYC CNC did a good video on set screw style holder run out. Do Set Screw Holders Push End Mill Tools off Center? WW122 - YouTube

Yeah, I saw both parts of his testing. His conclusions were that set screw holders are equal to or better than ER collets in runout and rigidity. Part of the proposed hypotheses as to why are: ER holders are longer thus less rigid, asymmetrical closing of the collet around the shank causes it to be “off center”, more parts and pieces involved equals more chance for tolerance stacking leading to more runout. I’ve also seen him “adjust” small endmills in ER collets to reduce the runout, which I was surprised actually worked and held through cutting. I’ve seen other videos of guys “indexing” the collets in the holders and the holders in the spindles to fight runout. I try not to base my knowledge on 1 guy doing 1 test at 1 time, so that’s why I’m here, to see what y’all think based on experience?

My “intuition” tells me that ER collets are more better, but evidence would seem to call that into question.

Weldon shanks are actually the industry standard. ER collets are more of a convenience because they can hold just about any size. They do however have issues with endmills walking in and out. They also do not hold well if the minimum or maximum size tool that will fit in the collet is used. Your milling machine is limited by power so you should never have an issue using collets. Any holder of any type will have issues if it is crashed. Shrink fit holders are the absolute best but have a limited number of heating cycles and one day you will just not be able to remove the tool from it no matter how much you heat it. You cannot go wrong with the convenience of collets on a tormach machine.

sweet! I didn’t know that about shrink fit holders. Seems like if the you intend for the tool and holder to be permanently married together, it’s a good idea, but not so much if you intend to switch it out relatively regularly… I guess my follow up question is, if Weldon Shanks are the standard, why is it not more commonly offered as an option from popular tooling companies? Seems like putting one on a smooth carbide shank would be a pain in the home shop(I’m sure it’s not an issue for pro shops), unless I’m overestimating the difficulty of milling a flat on carbide with a home mill.
Thanks for the input, I sincerely appreciate everyone’s help and opinions!

Inserted carbide tooling is becoming more prevalent so you order the tools with Weldon shanks. Flats are put on carbide shanks with either a green grinding wheel or a diamond wheel. You can’t cut carbide with carbide.

The weaker point in the TTS system is the r8 collet hold, the r8 will slip on the er adapter stud before the tool slips. When I have to push it at work I use a solid holder with an integral r8 shank.

I can’t cite where I saw it but a higher quality end mill holder advertised it had the bore offset a tenth or two, too compensate for the set screw push.


Thanks for the input!