TURNING A BOX WITH THREADED LID
By Mike Green and Peter Toch, April 23, 2002
IT IS EXTREMELY IMPORTANT THAT THE WOOD USED FOR THE BOX AND LID ARE THOROUGHLY DRY SO THEY DO NOT GO OUT OF ROUND AFTER COMPLETION .
See detailed diagrams (You will need Adobe Acrobat Reader to view them)
- Turn blank into cylinder approximately the O.D. of final box.
- Turn tenons on each end to fit your chuck..
- Mount and center cylinder on lathe by clamping one tenon in chuck. (Note: chucked end will become the lid)
- Mark lid at parting point to separate box from lid (may want to use 1/3 lid, 2/3 box proportions) and part off lid with a parting tool.
Note: top of lid and bottom of box are the ends with tenons
- Hollow inside of lid keeping enough wall thickness to allow for depth of threads plus desired wall thickness. Two recesses are cut into the inner rim of the lid. The inner recess will receive the threads and second outer recess has a slightly larger I.D. than the one to be threaded. This second recess is larger to allow clearance of the threads of the box. Make sure the inside walls of both recesses are cut parallel to the axis of the lid (not tapered). See attached drawing for details of preparing lid for treading. Measure and record I.D. of recess to be threaded. This measurement will be used later in Step #15.
- IMPORTANT: DO NOT REMOVE LID FORM LATHE CHUCK. Remove chuck from lathe with lid in it and mount chuck onto threading jig. Check for run out (wobble) when turning jig threading screw. If run out occurs, adjust chuck to eliminate wobble.
- Adjust cross feed vise, which holds threading cutter/motor, such that the cutter just touches the surface of the recess to be threaded. At this point set the graduated collar on the cross vise lead screw to zero (0)
- Back up the jig threading screw such that the cutter is clear of the wood. Now advance the cross vise lead screw such that the appropriate depth of thread will be cut into the recess upon advancing the jig threading screw.
For 16 TPI thread, advance cutter by 0.044 (1.1mm) as read on the cross vice graduated collar.
For 10 TPI thread advance cutter by 0.072 (1.8mm).
- Turn on cutter motor and adjust to proper speed for efficient cutting but not so fast as to cause burning of the wood.
- Slowly and steadily advance jig threading screw such that the wood is rotating and simultaneously advancing past the cutter which cuts the thread. When the full length of the thread has been reached, immediately back the cutter away from the wood using to cross vice screw. Shut off cutter motor.
- Replace chuck onto lathe and remove lid.
- Mount box bottom in chuck by its tenon. Align and true up the cylinder.
- Face-off end of cylinder.
- Establish length of tenon to be threaded. As a rule of thumb, the tenon length should be equivalent to 4 threads in length.
For 16 TPI thread 4 x 1/16 = ¼
For 10 TPI thread 4 x 1/10 = 0.4 (approx. 13/32)
- Establish O.D. of tenon to be threaded. Start with measured I.D. of recess in lid measured in Step 5. To this dimension add the following:
For 16 TPI Thread I.D. + 0.072 (1.8mm)
For 10 TPI Thread I.D. + 0.134 (3.4mm)
- Now cut tenon to the length established in Step 14 and approximately 1/16 larger in O.D. established in Step #15.
Note: Cutting tenon oversized allows for resizing in the event the box goes oval upon hollowing due stain relieving. It also gives a visual reference for hollowing.
- Hollow the box. Be sure to leave enough wall thickness in the area of the tenon to be threaded.
- Carefully cut tenon to final O.D. as established in Step #15. Chamfer outer edge.
- Again, leaving box in the chuck, mount chuck on threading jig.
- Thread O.D. of tenon in the same manner as described in Steps #7 through #10.
Note: Thread until cutter is just shy of touching shoulder at bottom of tenon and immediately back cutter completely clear of wood. Shut off cutter motor.
- Test fit lid onto box. If too tight, repeat cutting operation slightly increasing the depth of cut on box until lid fits satisfactorily.
- Leaving box in chuck, remount chuck onto lathe. Visually check for match-up of wood grain between lid and box. If grain does not match, remove lid and very carefully slightly cut back tenon shoulder on box. Replace lid and again check for matching of grain. Continue this operation until desired grain matching is achieved. Care should be taken as not to cut off too much from the box shoulder.
- Thread lid snuggly onto box and turn outside of box and lid to final shape.
- Sand and if desired, finish exterior of box and lid.
- Remove lid from box, then remove box from chuck.
- Reverse chuck box on lathe and turn foot to desired shape.
- Sand and apply finish as desired.
Source of 60° Double Angle 1/4 Shank Type Cutters:
Woodcraft Store, 313 Montvale Ave, Woburn, MA 01801, Phone: (781) 935-6414
Whiteside Machinery Thread Cutting Bit, Woodcraft Cat. No. 140944. Price: $27.99 plus tax
Note: This item is not available through Woodcrafts regular mail order service, but can be obtained at the Woodcraft Store in Woburn, MA. See Bill Smith (store manager) if you cant find it.
Source of 60° Double Angle 3/8 Shank Type Cutters:
MSC Industrial Supply Co., 75 Maxes Road, Melville, NY 11747-9415,
Phone: 1-800-645-7270, Website: www.mscdirect.com
Types of Steel: Order number: Price: (plus shipping & handling and tax)
Import HSS 03196052 $20.22
Import Cobalt 03198058 $34.61
USA Made HSS 73196057 $26.41
USA Made Cobalt 73196552 $35.45