Understanding chuck test certificates

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Not sure if that “… well” was intended for me

… but, if so, it completely misses my point.

MichaelG.

On rereading the OP it seems Long V and Short V is an assumption by the OP. The chart itself only says LV and SV, which could be anything, even just randomly assigned model letters to identify different jaws. The OP should call Pratt Burnerd's UK HQ and enquire. But he has made his first and only post here and no return since so can't be too worried about it.

I know this is a bit off topic, but SOD, if you want to take parts out of the chuck and put them back later with precision, get yourself some soft jaws, very cheap and easy solution.

Chris Gunn

Or practice using the quick method of setting up the four jaw chuck. IE set the dial indicator on the back of the job in the horizontal plane. Rotate the job once and set the dial's zero to halfway between the highest and lowest reading on the indicator. Then go around and adjust each pair of jaws until each reads zero. A pair of "twiddlers",short chuck keys, makes this easier. Then go around again and final tighten and adjust that last thou or so. Two to maybe four revolutions of the chuck. It takes about a minute or two with a very little bit of practice.

If you just use the trial and error and hope for the best method, it can take all day.

I may be missing your point but what about the asterisked footnote to the certificate?

SV and LV are defined in the footnote to the certificate.

I note that the serial numbers are missing for the SV & LV lines at the top.
I've no idea what the 511/358 refers to, but maybe the SP is short for Super Precision, as per the catalogue on P8
https://prattburnerd.com/wp-content/uploads/2021/08/PBA-Atlas-Catalog-2021-web.pdf

That being the case, then the chuck is of the type with reversible jaw fronts for inside/outside use, hence not having two different sets of serial numbers on the certificate.

The SV & LV would likely denote in which orientation the jaws were set, in this case, or which set of jaws were selected in the case of a different style of chuck, thus allowing the ticket to be used for more than one application.

Bill

Good point - never used soft jaws, even though I should!

Dave,

haha. I thnk you didnt miss the point, I did. Didn't read the fine print. Story of my life.

Hopper:

You have the consolation that your original answer to the OP's query apparently stands!

In reading round the subject I noted Sparey's comment (page 96 in my copy):

"Most self-centring chucks are provided with two sets of steel jaws, one set of which allows larger work to be held."

The "small" jaws are also sometimes referred to as "drill" jaws, of course.

It's a shame that soft jaws are not more readily available. Including them with the purchase would be a big selling point.

Edited By ega on 22/06/2022 09:26:44

I got a set of soft jaws for a worn P and B chuck from Rotagrip for not very much money.

regrds Martin