FARO Concentricity vs Lathe Runout  - Page 1
Forum section: electronics / general

author: Jack4242
author_rank: Newbie
timestamp: April 14, 2022, 10:25:10 am
content: Hello all,I am part of a quality department which sometimes deals with issues like bent/worn shafts. We have measured one of these and our FARO arm and our creaform C-track and Metra-scanner both showed us a concentricity reading of 3.5mm across the entire length. We reported this and the customer who owned the Shaft checked this by using runout on a lathe. I don't know the specifica of this (whether it was total run out or just runout) and they got a reading of appropriately 0.05mm runout. Could anyone explain why we could have got 3.5mm concentricity with runout that good. For reference, the Shaft was around 4m long and all the physical equipment is Calibrated.

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: April 14, 2022, 11:38:53 am
content: Hello, discussing about measurements results without going to the deepest level of explanation of the procedures is pointless. A perfectly concentic 4m shaft can bend itself from several meters under its own weight, depending on the diameter.

author: Ian.M
author_rank: Super Contributor
timestamp: April 14, 2022, 12:13:19 pm
content: Workpiece runout measured on the OD between a properly adjusted four jaw chuck and steady rest, both gripping the OD of the shaft can only tell you if the shaft is bent or oval. OTOH if they'd set up the shaft between centers with a drive dog (or manually rotated it), the runout measurement would set an upper limit for the concentricity, with respect to a line between the two center holes in the shaft ends.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: April 14, 2022, 04:55:17 pm
content: Not enough info but if you grab it in a 4-jaw and try to locate the free end, say with a center, the part is over constrained and the measurements are invalid. There are very good mechanical people here but you might try a post in the Practicalmachinist forum where they do this for a living-https://www.practicalmachinist.com/vb/CH

author: mendip_discovery
author_rank: Super Contributor
timestamp: April 14, 2022, 04:56:14 pm
content: Quote from: Coordonnée_chromatique on April 14, 2022, 11:38:53 amThat would be it.I have the maths somewhere for this as I had a play with it regarding measuring setting rods in a horizontal measuring machine, but my assor didn't like the way it was mounted so I had to go for another option.Another thing is they may well be measuring runout on the lathe which is different,https://www.gdandtbasics.com/concentricity

author: Coordonnée_chromatique
author_rank: Frequent Contributor
timestamp: April 14, 2022, 06:44:08 pm
content: Quote from: mendip_discovery on April 14, 2022, 04:56:14 pmI remember that the ISO norms and procedures has changed a few weeks after my graduation, the same time that the academy rector was signing my diploma, i was not anymore able to read a basic standard steel grade codification in a company.Because i was not at school anymore and neither employed in a enterprise and the ISO documents were not free

author: MK
author_rank: Regular Contributor
timestamp: April 14, 2022, 07:10:20 pm
content: On a Lathe they have to find the center for both ends, then spin it, presumably you found the center at one end and then worked along the item?