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Hole Center Distance Finder (for lack of a better name)
- Thread starter rwm
- Start date
- Joined
- Mar 25, 2013
- Messages
- 4,614
Testing:
I used my Sherline mill to drill 2 holes in a piece of scrap 100 mm apart. This mill does not have great capacity but is is very accurate.
I then measured the distance between the holes using my new tool:
Since the centers are 20.00 mm in diameter (ground shaft stock) you must subtract that from the caliper measurement.
Measuring to the outside of the centers:
This was a reproducible result. In fact, I tried to be sloppy and still got within .05 mm. 0.03 mm equals .0012 inches. I'm sure not all of my measurements will be this accurate but this impressed me. I think the key to making this tool accurately is to start with precision ground shaft stock for the centers. Then make sure your mill is perfectly trammed when you drill the cross holes. Then use a reamer to get to the final ID. I reamed .002 oversize and it feels crisp. Also, make sure the centers are on the rod in the same orientation they were drilled. That way any angular error is the same in both centers and will cancel out. For my purposes I would have been very pleased with a .005" error.
Robert
I used my Sherline mill to drill 2 holes in a piece of scrap 100 mm apart. This mill does not have great capacity but is is very accurate.
I then measured the distance between the holes using my new tool:
Since the centers are 20.00 mm in diameter (ground shaft stock) you must subtract that from the caliper measurement.
Measuring to the outside of the centers:
This was a reproducible result. In fact, I tried to be sloppy and still got within .05 mm. 0.03 mm equals .0012 inches. I'm sure not all of my measurements will be this accurate but this impressed me. I think the key to making this tool accurately is to start with precision ground shaft stock for the centers. Then make sure your mill is perfectly trammed when you drill the cross holes. Then use a reamer to get to the final ID. I reamed .002 oversize and it feels crisp. Also, make sure the centers are on the rod in the same orientation they were drilled. That way any angular error is the same in both centers and will cancel out. For my purposes I would have been very pleased with a .005" error.
Robert
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