'BHI 150' Flying Tourbillon Anniversary Watch Offer
Lathe Tips
The British Horological Institute has archived and edited the following from e-mails sent to the Clock/Clockers mailing lists on the Internet. The information here does not necessarily indicate a method approved by the BHI, we are only publishing this digest so that others can decide for themselves whether the methods listed below will suit them.
From: Steve Callihan, Dewey Clark, Thomas Roma
Index
Advice for buying a lathe
Homemade collets
Chucks
Advice for buying a lathe
1) Buy a complete setup (full set of collets minimum, but look for a setup that includes 3 jaw, 4 jaw, milling attach, slide rest, etc.). You will spend more in that very instant, but over 2 years you will spend far less. No one ever listens to this rule, but 3 years later they understand it.
2) All tools should be purchased with the idea that our family will sell them for us when we are done. Two implications: a) buy tools that you won't need to replace (see rule 1); b) buy tools that have demonstrated consistent demand (Levin, Derby, Boley, Lorch).
3) If you can afford it, or if you will primarily be working on clocks, get a 10mm lathe. These are more expensive, but they are held to the same tolerances, are more robust and were generally purchased by people who knew how to use and care for them. Every hack knew he had to have a bright chrome 8 mm lathe on his bench to impress customers. Only true machinists bothered to pay extra for the 10mm lathes.
4) Buy from someone you can trust . This has major implications for buying at the MARTs; unless you are buying a complete setup from someone for $3000. If you are buying pieces/parts, you need to know who you are dealing with and you had better know what you are looking at. There are several established used tool dealers you can access. Established dealers usually understand the short-sightedness of sticking someone with a bad piece.
5) Bear in mind that lathes do not wear out, they are destroyed. Buying new equipment leaves out the middle man. I think you could get a pretty complete Sherline outfit for less than $1000.
6) Take a course on practical lathe work
7) Download Bill Smiths articles on graver preparation from the clock site in Florida http://www.netwide.net/users/clockdoc/
Home made collets
You must have the following items: A lathe, a new number 40 collet, 5/32 inch wood dowel or brass rod to fit the #40 collet, a jewellers saw {or Back saw}, a set of good quality twist drills from #1 to # 80, A T-rest for your lathe, and a good sharp graver.
If you can't afford a full set of collets, you must make them as needed. To do this, pick a drill to produce the hole you need for your collet. Place a piece of 5/32 inch brass stock in the # 40 collet and tighten the drawbar. Part off the rod about a 1/4 inch from the face of the collet. Face off the end of the rod.
The following sizes make up the bulk of my hand-mades. The largest is 1/4 inch {6.35mm} #63 or 64 collet. The next is .2095 inch {5.32mm} #53 collet. The smallest is 5/32 inch {3.95mm] #40 collet.
1/2 to 5/8 inch length works pretty well for these sub-collets.
Use your graver to locate centre. Put the drill you selected in a pinvise and drill all the way through the rod. Remove the rod from the lathe and use the saw to make two slits 90 degrees from each other so that the end of the rod now has four fingers.
Carefully cut the slits to within 1/4 to 3/8 inch of the end of the rod. Now you have a usable Sub-collet to slip inside the # 40 which ,when you tighten the drawbar, will tighten the fingers on the sub-collet down on your workpiece.
Chucks
A Jacob's chuck will work for rough work like pivot polishing. More precise work such as re-pivoting will require a chuck with greater repeatable accuracy.
A four-jaw chuck is very versatile. In experienced hands these can produce amazing results. They are less user friendly than the 3-jaw self-centring chucks though.
