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Archive for March 3rd, 2017

Mini-Lathe Carriage Stop: Spring Counterbore

While pondering the tailstock ways, I realized the spring on the LMS Adjustable Carriage Stop just needed a counterbore to make it work right:

LMS Carriage Stop - spring counterbore

LMS Carriage Stop – spring counterbore

The OEM spring now sits slightly compressed with the screw tip flush at the far end of the block:

LMS Carriage Stop - reassembled

LMS Carriage Stop – reassembled

That OEM screw head knurling leaves a bit to be desired, doesn’t it?

Actually boring the hole would be a remarkably tedious process for little gain. Instead, I lined up the block in the drill press using a ¼ inch drill (the OEM hole isn’t hard metric!) in the unthreaded section, enlarged it with progressively larger drills up to an O (0.316 inch = 8 mm), then finished with a P (0.323 in = 8.2 mm).

As it turned out, my guesstimated relaxed spring length was a bit off, so I turned a brass bushing to shorten the hole by 2 mm:

LMS Carriage Stop - screw bushing

LMS Carriage Stop – screw bushing

If I don’t mention it, nobody will ever know!

The original doodle, with close-enough sizes:

LMS Carriage Stop - spring counterbore doodle

LMS Carriage Stop – spring counterbore doodle

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