Found out my tool holder runout was way worse than I thought from a video I saw

I was watching a YouTube video from some old timer machinist last Tuesday and he showed how to check runout with a dial indicator on a CAT40 holder. I tested mine and found one had 0.003 inches of runout, which explained my crappy surface finishes on a job I ran last month. Anyone else ever run a test like that and get numbers that surprised you?

3 comments

3 Comments

blair_chen815d agoMost Upvoted

Check the drawbar force too @brooke_jones, weak pullback can let even a good holder wobble and the holders look fine until you measure the force with a gage.

charles7205d ago

Had a buddy run into something similar last year. He chased chatter for THREE weeks before checking his drawbar force and found it was barely half what it should be. Brand new machine too, came from the factory with the tension set wrong.

brooke_jones6d ago

Wait you had 0.003 inches of runout??? That's wild. I honestly would have thought a CAT40 holder would be way tighter than that out of the box. I've seen guys get that kind of slop from cheap Chinese holders but if yours was supposed to be decent quality that's just crazy disappointing. Surface finish issues make so much sense now though, that much wobble would mess up any finish pass. Did you check the holder taper itself for wear or was it just the collet or nut being loose? I've had holders that looked fine but were actually worn in the taper from not being cleaned properly before running them.

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