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[4]

How to measure drill chuck runout?

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5ubtle

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#1
I would like to reduce the runout of my drill press. I've made about 50 measurements, and have determined that most of my runout is in the chuck, and that most of my problem is with repeatability of chucking the drill rod. See attached sketch which depicts the problem (exaggerated). I measured TIR on the drill rod at a location just below the chuck and again 4 inches below the chuck. The TIR measurement was repeatedly made at these 2 locations while I re-indexed 1) the arbor in the spindle, 2) the chuck on the arbor, or 3) the drill rod in the chuck. The high spot always follows the chuck. TIR near the chuck ranged from 0.0005-0.0045" with 0.0025" being typical. TIR '4 inches down' ranged from 0.003-0.014" with 0.009" being typical. I don't think this is really all that bad, and I can get acceptable results by just matching high spots to low spots. I am however considering purchasing a new chuck with less runout and hopefully more repeatability. All of this is just background to frame my question. It's not really important to my question, but I figure that someone will ask for more info.

Drill press spindle arbor chuck.jpg

My question:
The makers and sellers of chucks will advertise maximum TIR. What exactly are they claiming to be within the spec? For example: Shar's model 202-4968, "High Precision Heavy Duty Keyless Drill Chuck" claims TIR of 0.002". If I bought one and measured a repeatable TIR of 0.002" near the drill chuck, and TIR of 0.010" at '4 inches down', I would be disappointed, but would it be 'Out of Spec'? In other words, is the maximum TIR (for the purpose of comparing it to the spec) to be measured on the drill rod, near the chuck or somewhere else?
 

RJSakowski

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#2
If TIR is not specified at a distance, it is most likely in close proximity to the chuck jaws.
 

kd4gij

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#3
And drill rod isn't the best thing to use for that. It isn't always round and straight.
 

benmychree

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#4
Another thing to consider is the condition of your spindle bearings and the fit of the quill in its housing.
 

kd4gij

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#7
I use a 1/2" dowel pin 3" long
 

RJSakowski

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#8
If you want to use drill rod, roll it on a flat surface to see if it has any serious bend. If not, chuck it up. Make a mark on the drill rod next to a reference mark on one of the chuck jaws. Measure runout. Make a mark on the drill rod at the point of maximum runout. Also mark the chuck position next to a stationary reference mark on the spindle housing.

Now rotate the drill rod 180º in the chuck. Repeat the runout measurement. If the high spot is still at the same place on the drill rod, the drill rod is bent. If it rotates 180º to the opposite side of the drill rod, the spindle/drill chuck is responsible. As a check, the witness marks between the chuck and the spindle housing will still coincide.

Most likely, both will be contributing.

For straight rods, I use old shafting from printers. In my experience, it is about as close as I can get. Shafting is available from McMaster Carr and has specified straightness tolerances. Dowel pins are use by some but I don't recall ever seeing a straightness spec.
 

markba633csi

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#10
Collet chuck vendors play this game too- they give a great spec near the face of the tool but at some distance away- anybody's guess
Mark
 

epanzella

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#11
Desktop printers have a ground rod that's round and straight. If you see one at the dump grab it and take the rod out. I keep one on the shelf. It comes in handy.
 

Bob Korves

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#14
The import chuck seller takes a number out of thin air, puts the number on the advertising, sometimes includes a "test document" that has been copied so many times it cannot be read, and sends it to you. He is hoping you will not be willing or able to check it, and even if you do find an error, unlikely to send it back. He wins at that game...
 

P. Waller

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#15
Are you looking for a method of measuring drill chuck run out or a way to quantify it?
 
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