Re: Further testing needed ...

On 9/21/2024 12:06 PM, Snag wrote:

On 9/20/2024 5:51 PM, Snag wrote:

   I got the back plate finished for the 3 inch chuck and I'm a bit disappointed at my initial testing results . I've measured .015 runout on a piece of 1/2 inch stock that I'm pretty sure is straight . Might be the jaws since the chuck body indicates about .004 near the face . These are the inside step jaws and the clamping surface is not very long so that may be part of it . I'll be installing the outside step jaws tomorrow and checking them - it came with 2 sets of those , one which matches the chuck s/n and one that doesn't . The inside step set I have installed do not match numbers ... aaahhh , what should I expect for a $10 yard sale purchase !
   Actually , it may be as simple as regrinding the mismatched jaw sets to match this chuck . I have a little time to play with it , got no "other people's projects" in the shop right now .

    Further testing having been completed the chuck has runout with all 3 sets of jaws of around .007" . Chuck body is more like .002-.003 . A known straight 1/2" rod is not pointing  straight with the ways ... looks like it's time to set up the toolpost grinder .
   So it looks like maybe a cheap chuck , though well made . Fit and finish are good , everything fits as it should and the scroll moves smoothly with all 3 pinions . Which brings me to a question - since there's more than one pinion is it going to make any difference which one I use ? Do I need to give 'em all 3 a twist when I mount a piece of stock ?

Does a known straight rod point straight and parallel if is directly in a collet that fits in the native spindle bore?  If not then level (untwist) your lathe before doing anything else.
Which pinion to use?  I have no idea.  Whenever I use a scroll chuck I try to do all operations that are important to be concentric in a single setup so runout is not a big deal.  If I can't and close is good enough sometimes I wing it or carefully clock the part, but if it must be dead nuts I either dial in the set tru for that size or use the 4 jaw.
I expect when I get the turret/collet lathe finished I'll do most of the close enough repetitive work in it.
--
Bob La Londe
CNC Molds N Stuff
--
This email has been checked for viruses by AVG antivirus software.
www.avg.com