Clocking square or rectangular stock accurately to run concentric in a 4 jaw chuck

[thehomeengineer]

Hi All
I hope some will find this short video useful when setting up square or rectangular stock in a 4 jaw chuck and need it to run concentric.
Thank you for taking the time to view and if this is of interest I have other videos on my youtube channel on other engineering machining topics.

The Home Engineer

[greenie]

You can do exactly the same thing using the tooltip, just bring the tooltip up close to the square section and rotate the chuck and you'll soon see where you have to adjust the jaws to get it concentric.
You can not damage the dial indicator by using the tooltip, now can you ?

[thehomeengineer]

Hi Greenie
I would use the tooltip or a scribing block to get it close to centre but using the clock ensures the work piece is definitely running concentric and leaves nothing to chance by eye. It is amazing how close you can get things by eye as proof in the video. The first side was a total of 0.008” and the other was spot on. But if I hadn’t used this method one set of the flats would have had this error. Check twice cut once

[mklotz]

For polygonal stock you can avoid having to withdraw the DI/DTI by making a "flapper" to protect the instrument as the stock is rotated. A full description of my method is available here...

Centering aid for polygonal stock

[Canyonman44]

I'm gonna ask a really stupid question. How did you determine the length[height] of your bar {round stock}?

[thehomeengineer]

Hi canyonman44
Thank you for your interest.
the length of bar that fits under the chuck jaws does not matter as the clock will be at the same height therefore the angle of the stock relative to the bed will be the same for both sides of the stock being clocked. I have always used that bit of stock as it is a nice diameter so sits on the bed and under the jaws nicely and it is roughly the right length when sat on a jaw to place the workpiece at a right angle to bed. But the length does not matter.
Hope this has helped
The Home Engineer

[thehomeengineer]

posted this a couple of years back

https://www.homemadetools.net/forum/method-clocking-rectangular-square-four-jaw-known-reference-point-66041?highlight=Clocking+chuck

[DIYer]

Thanks thehomeengineer! We've added your Square Stock Clocking Method to our Measuring and Marking category,
as well as to your builder page: thehomeengineer's Homemade Tools. Your receipt:

Square Stock Clocking Method by thehomeengineer

tags: lathe, measurement