For the front bearing, I chose C63000 nickel aluminum bronze (known as QAL9-4 bronze here in China). This material has high strength because of the added nickel (needed for the thin mounting flange) and good wear resistance. The downside is this material is very “grabby” and tends to warp if you get it hot. Therefore, I’m going to machine it in two phases with a stress relieving operation in-between.
This is a great little Sandvik face grooving tool (insert MB-09FA150-02-14R). I didn’t have a left-handed version, so I’m going to mount the tool upside-down and run the lathe in reverse so I can rough the ridges on the face of the bearing.
While I’m leaving stock on all surfaces for finishing after stress relieving, I turned the center boss to a known dimension; 23.5mm in this case since I have a collet that size. I’ll be chucking on this to do the first part of the finish machining.
Note the upside down tool mentioned above.
With the 23.5mm boss chucked in a collet, the entire back-side is machined – including the 3.374″ O.D. and the bore. The bore was checked with a 0.594″ and a 0.595″ pin gage. The 0.594″ gage passed and spun freely while the 0.595″ gage did not enter.
With the part running true, the same face grooving tool as before was used to finish turn the complete face.
A simple drilling fixture for the bearing was made from a scrap of aluminum. The scrap was faced after clamping in the vise to be sure it was perpendicular to the mill spindle and a M10 hole was tapped near the center.
A 0.020″ recess was milled around the tapped hole to clear the boss on the backside of the bearing so that the majority of the bearing would be in contact with the tooling plate.
This step is a modification I made to both the front bearing and the cam retaining plate. I don’t like using fastener clearance holes for part locating so I added shallow counterbores to both the bearing and the retaining plate to register the O.D. of the spacers.
The last hole in the front bearing is the 1/4″ jackshaft hole. The cam retaining plate needs to be attached to the front bearing before this hole can be added. The plate is attached without removing the front bearing from the fixture.
A 0.375″ reamer prepares the cam retainer plate to receive the bronze bushing. The Oilite bushing was a McMaster-Carr part, #6338K411.
I used a 0.251″ reamer instead of the 0.250″ specified in the plans because I wanted to be sure the bronze bushing cleaned up. I’ll just need to make sure the jackshaft is sized accordingly.
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