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+--- Thread: How to start (/thread-3854.html)
RE: How to start - EdK - 05-26-2018
(05-26-2018, 03:30 PM)Nikon1975 Wrote: Is it a bad idea to buy second hand micrometers?
Not at all. Just stick to known quality brands.
Ed
RE: How to start - TomG - 05-26-2018
I have lots of used ones. Look for paint wear on the frames to tell how much use they've seen and check to see if the frame has been sprung (dropped) by running the spindle against the anvil and looking for any gap against a bright light. There should be none.
Tom
RE: How to start - Highpower - 05-26-2018
No there is nothing wrong with buying second hand measuring instruments as long as they are in fairly good condition and haven't been abused by previous owners.
1) Thimble rotates smoothly and can travel the full distance of it's capacity.
2) Condition of the faces on both the spindle and anvil. Clean and smooth. No chipped, pitted or heavily scratched surfaces.
3) Missing parts. Used micrometers are commonly found with the ratchet knob missing if they were so equipped originally.
4) Alignment of the faces. They should be perfectly in line with each other. If the spindle is slightly off center from the anvil, there is something bent and those should be avoided.
There are plenty of good used micrometers out there to be had for the fraction of the cost of a new one. You can afford to take your time in picking out a good one. They are out there.
RE: How to start - Nikon1975 - 06-27-2018
Some progress here. I built a power feed to have more consistent feed rates and improve the surface finish. It looks like it works. I have a set of micrometers, still working on the accuracy. Not having children screaming around might help on that aspect.
In the process I snapped my first drill bit: I was not drilling anything, just testing the software for the Arduino that controls the power feed. I forgot a 7mm drill bit in the chuck and it was snapped by the vise like a cookie. It was a bit scary, mostly because I was not aware of any risk as the spindle was not rotating.
I am now quite happy with the controller as it preserve knowledge of the absolute position of the table so it prevent to hit the end of the run.
[attachment=15770]
The old and a new block
[attachment=15771]
DIY motor mount
[attachment=15772]
Controller prototype (he needs a proper box)
[attachment=15773]
RE: How to start - TomG - 06-27-2018
Good progress!
Screaming kids definitely add to the challenge.
Tom