Archive for August 3rd, 2012
A three-pack of 100-tooth 2 inch cutoff saw blades followed me home from Harbor Freight a while ago. Although they’re intended for a craptastic HF tabletop saw, I thought they might come in handy on the Sherline for slicing lengths of brass tubing. The reviews for the saw indicate the blades are no good for steel, barely adequate for brass, and dandy for wood; they have nowhere near enough teeth for a screw cutoff blade.
None of the arbors in my collection fit a blade with a 3/8 inch hole, so a bit of lathe work produced one while the 3D printer cranked out a GPS+audio case:
The shaft is 3/8 inch drill rod and the collars are 3/4 inch drill rod, both of O1 oil-hardening steel that will remain forever unhardened, fitting into a Sherline endmill toolholder. I drilled-and-bored the collars to a slip fit on the shaft, then epoxied the rear one in place:
I drilled a 0.6 inch deep blind hole in the shaft and tapped it 10-32 all the way down for a 1/2 inch SHCS. A bag of assorted 10-32 taps produced a bottoming tap that came in handy, but I put tapping in the same category as parallel parking: I’ll walk half a mile to not parallel park the van. Couldn’t avoid it this time.
The flat on the shaft came from a bit of hand filing, which was easier than setting up the mill.
The front collar’s undercut ensures just the rim contacts the blade. The photo shows the vanishingly thin layer of epoxy on the rear collar that mooshed out as I clamped the stack together:
- Fixed (rear) collar
- Waxed paper with a 3/8 inch hole punched in the middle
- Cutoff blade
- Split lockwasher for a bit of space
- Loose (front) collar
- Socket head cap screw
After the epoxy cured, a pass through the lathe skimmed off that thin epoxy layer and trued up the fixed collar face to eliminate the last bit of wobble. The radial runout remains just enough so that one tooth tings before the others engage, but I’m not entirely convinced that’s due to the (minimal) shaft-to-blade clearance.
In use, putting the split lockwasher between the loose collar and the SHCS provides a little clamping compliance.
At some point, I’m sure this thing will come in handy…