A quickie from Saturday.
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The 8x1x1 Norton grinding wheel was wobbling on the shaft of my cheaptastic Delta bench grinder. I thought the plastic bushings might be to blame, so I ran this up. But it didn’t completely solve the problem, which is that the dished washers have too much of a radius and too much slop, and don’t seat reliably square in the shaft. Making this bushing tight enough to prevent that might risk the wheel if the bushing expands with heat.
So I’m going to make new washers. I may make the inside washer integral with a bushing like this.
Rick “so many stupid things I lived with because I didn’t have a lathe” Denney
Here’s the replacement. This is the first time I’ve machined 1045, and this was cut from a hydraulic ram.
It cuts easy on the bandsaw.
But that was the last of the easy. The stuff turns with long stringy chips that are blued from heat and ready to burn, lacerate, or bird’s-nest at any moment. I switched from a CNMG insert to a CCMT insert, and that helped. I was running at 640 RPM, with .100 depth of cut and .005 feed rate with the CCMT insert, I got tight curls, but I had to manually break them by peck-feeding. But that was far better than the hot, sharp lassos the CNMG insert was throwing at me.
The CNMG faced fine, and left a pretty good finish when turning. It was just impossible chip management.
But boring the hole was a challenge. 1045 is hard on drills and the chips jam up instantly and throw the drill off-center. When I poked through with a 15/32 drill, I could see the runout from a mile. I used a thin brazed-carbide boring bar to try to straighten the hole, but the bar just deflected and bell-mouthed the hole.
I made the hole big enough and straight enough to get rid of the bell-mouth, and then stepped it up to 1/2” using drills. Then, I could barely fit a much stiffer boring bar and used that to work it up to 5/8. That was also brazed carbide and I honed to to very sharp. That finally cleaned up the hole and I was able to hit the dimension within a few tenths and restored concentricity.
Here’s the finished part:
Installed on the grinder shaft:
With the 8x1x1 wheel install:
And finally the wheel running true:
Rick “hard stuff to cut” Denney