The above is my solid brass plumb bob in matching fitted brass case. I first produced these plumb bobs around 1984 and I made quite a few until being too busy with tooling for electronic circuit board assembly ...... so I stupidly discontinued the plumb bob somewhere around 1990 and hey presto a clone soon sprang up.  Yet it does not have my handmade approach......flattery indeed. And not the first time this has happened.




The above is at the smaller of my two flypresses, a no.1 Denbigh, somewhere 1900 /20 vintage pressing the plumb bob tube onto the bottom cover. An excellent piece of equipment that I bought from a Northampton machinery dealer 200 miles away when I first became self employed in 1983. The fit and function of the hand scraped slideways of the ram are still glassy with no metal pick up. I use it to press the polished / buffed tube onto the bottom cover as well as stamping my logo onto other finished product ie 'Richard Kell Made in England' as on my dovetail markers and centre finder.    





The bottom cover is an interference ie force fit into the tube and has a contour drilled hole to accept the lower part of the bob with minimum rattle. This is an interesting example of how the toolmaker / machinist has to be 'on the ball'. The internal diameter of the tube measures 0.5615 inch max when examining a batch of machined tubes, ie one and a half thou up on five hundred and sixty thou (imperial).  I use a small pair if internal calipers and a hand held imperial micrometer, also looking for ovality ie out of round. So, knowing my capstan lathe can achieve a two thou deviation I set my tolerance as two thou up from 0.560 to four thou up. This gives me a minimum of half a thou interference fit. An interesting example of what goes on in my workshop. Also, I compile a distribution chart of the actual sizes achieved as they come off the machine, thereby providing feedback as to any size drift and feasibility of the two thou tolerance on my 1945 Ward 1A capstan lathe. Imperial measurement is so much easier than metric, I defy anyone to use a metric micrometer as quick and easily as an imperial, the metric micrometer is so very liable to be misread ..... a foul instrument. The scrappage and frustration of engineering manufacture switching over to metric in the 1970's was absurd. Fine for scientific measurement but a needless changeover brought onn by misinformed and over zealous politicians. A lot like the pounds versus kilos changeover debacle here in the UK.





Out of interest above is one of my leg vices (very pre-1900) which is mounted next to the flypress and also a modern machinists bench vice is located at the other side of the flypress. To the left is my buffing spindle, an extractor is out of view at my feet ... essential. The layout is for efficiency ie speed.





Voila .... finished product. 

I have a youtube for this ...  http://www.youtube.com/watch?v=JncQCqKLBKY

Remember to wind the line clockwise from inside the bobbin and see how I hold the bob and rotate the case to screw assemble.
Its the same price as my no.1 honing guide, so just pop onto http://www.richardkell.co.uk  order as a no.1 honing guide and drop me an e-mail to say its actually the plumb bob you want. Delivery abt 14/21 days.

Finally, below is one of my size distribution charts for turned components produced on my Ward 1A manual capstan lathe. These are 'first op' ie from raw bar.  I produced one of these charts for the plumb bob tube bottom cover the one below is for honing guide brass bobbins, tolerance 0.700 inch diameter, plus zero, minus two thou. Its hard to make out, the half thou column is widened to about four off wide, so by far the most common size achieved is a half thou down from top tol on a two thou total tolerance. Not bad going all considered. And would you believe it some buyers for industrial  jobbing work will still not use me because of not having the dreaded British Standards 'quality system' installed with all the B/S which that entails.  Leg vices and flat belt drives .... how could they possibly entertain me ......

Tags: centre finder, dovetail marker, hand tools, honing guides, imperial measurement, metric micrometer, micrometer, plumb bob, quality systems, tolerances, tolerances achieved, turned components, woodworkers plumb bob