35 mm Precision
Work Spindles

By J. Malcolm Wild, FBHI

 

 

 

The 35 mm work spindle was brought to my notice by Derek Pratt.  These are often termed as de-mountable spindles or quills and were used in the Swiss toolmaking industry.  Work is held in either the chuck, collet or faceplate and can be transferred from machine to machine without the necessity of removing the work from its work holding, therefore complete accuracy would be maintained. Figure 1 and Figure 2 show the quill holder mounted on the Schaublin 70 lathe. Originally a special headstock was supplied which was shorter and gave more room for the cross slide and tailstock, Figure 3. Note the drive from the headstock; a catch plate with driving pin is fitted to the rear end of the spindle shaft and a slotted faceplate mounted on the Schaublin 70 lathe headstock, Figure 3a. This arrangement ensures there is no sideways thrust on the spindle/quill when in position. The original Schaublin drive was similar to an Oldham coupling, (i.e. a male and female key arrangement). You will see there is a space between the carrier to allow room for the end of the drawbar.  It had always been my belief that the bed of the 70 should have been made another 50 mm longer, which would have been an advantage, giving more room for the cross slide, tailstock, etc. Various 35 mm diameter work spindles were produced, some with plain nose and machined to accept standard collets such as W8 and W12.  Others had the collet facility plus the spindle nose threaded to accept chucks. 
 
Other sizes of quill were available. The 25 mm spindle was used on the vertical slide in conjunction with the Isoma microscope, Figure 3b.  Also on the lever feed tailstock the barrel can be replaced with a high-speed spindle for the precision drilling where higher accuracy of contra-rotating of work and drill is required, the spindle being driven by the overhead drive, Figure 3b.
 

AWCI members can access the complete article in the HT Archives (35 mm Precision Work Spindles).