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Recent content by rhb

  1. R

    Looking for B&S 961 LVDT readout documentation

    FWIW I've started a teardown and analysis over on EEVblog: https://www.eevblog.com/forum/testgear/brown-sharpe-961-gage-amplifier-and-readout-teardown/msg4632409/#msg4632409 Eventually that should lead to full schematics if nothing else. I'll be posting any info I collect to that thread as...
  2. R

    Looking for B&S 961 LVDT readout documentation

    I am looking for *any* information. I bought one via ebay and it will not zero but pegs with either of my 599-988 sensors attached. The sensors clearly work. I've done a lot of looking, but found nothing. Not even a YouTube video describing them. Reg
  3. R

    Buying a used lathe a day's drive each way

    I'd like to thank the last few posters for offering practical comments. It is a welcome relief. Last night I went to bed intending to drop off PM. I can't tell someone what insert to use for a particular alloy. I don't know that. But I have other skills which are highly relevant. I ran...
  4. R

    Buying a used lathe a day's drive each way

    Yes, cast iron creeps at room temperature. The world is rubber if you measure accurately and precisely enough. All of the first rank machinists will say the same. Listen to Robin, Tom and Dan. I only mentioned it because of the bit about the floor moving. However, I learned this because a...
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    Buying a used lathe a day's drive each way

    I'm a geophysicist. I can calculate how long it will take for the floor to rebound after you move :-) A more significant issue is creep. If you level a lathe, it will take 4-5 hours for whatever viscous deformation, "creep", to relax. I recently learned the creep is actually quite large at...
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    Buying a used lathe a day's drive each way

    I don't *need* a new lathe. I just want one. I'm an old guy playing with stuff I didn't get to do when I was younger and which are important to me. Machining is one, electronics is the other. I've got what is really a ridiculous electronics lab that cost over $500k when new 25 years ago. My...
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    Buying a used lathe a day's drive each way

    I'm in central Arkansas 6 hours drive from DFW. Any well tooled small lathe in near new condition is of interest. I thought I'd found one, but except for collets and a 3 jaw there wasn't any tooling. I don't recognize "HGR". Can you provide a link? I have friends near Dallas so I can spend...
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    Buying a used lathe a day's drive each way

    I initially proposed Facetime and the sales guy was agreeable, but his boss said they "didn't have the ability to do that". I was going watch the bubble settle to avoid any deception or ignorance issues. All I really want is confidence that it's worth spending 2 days driving 1600 miles to...
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    Buying a used lathe a day's drive each way

    What is it reasonable to ask a distant dealer to do as a substitute for a personal inspection? The cost for a personal inspection and pickup is $500+ for a machine 800 miles away. That's a chunk of money and a lot of drive time to spend only to say no and drive home. On a $4000 purchase is...
  10. R

    Spotting medium thickness measurement

    Here's a photo of the underside showing the contact area in relation to the spindle.
  11. R

    Spotting medium thickness measurement

    Digital displays inherently have a 1 digit ambiguity, so this is not actually bad. The Mitutoyo 543-793 is spec'd at +/- a tenth which is the same performance as this. The Chinese now do so much contract manufacturing that the quality is much higher than 30 years ago. It will be interesting...
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    Spotting medium thickness measurement

    The photos clearly show that I'm using a ball tip (came with the indicator) bearing on a flexure (0.020" feeler gauge )to spread the load. The carbide feet and flexure contact surfaces have been lapped on a 1200 grit diamond lap. The flexure has less than 1 mm total travel in use. There...
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    Spotting medium thickness measurement

    I have been making a repeat-o-meter for checking surface plates using an ebay $31 Chinese electronic half tenth/1 um gauge. It seems to work properly so I decided to try measuring the thickness of my typical application of Canode using a Speedball soft rubber printer's brayer. Repeated...
  14. R

    Has anyone built an LVDT amplifier/signal conditioner?

    I can get 40 ppm accuracy from an HP 34401A and a Keysight 33622A (at 50 readings per second via GPIB IIRC :-) The rate limitation is the integration time for the 6.5 digit ADC. I found a 7" meter from a Daytronics 300D on ebay. Very nice with an aluminum housing. So I just need to sort out...
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    flatness measuring help

    I just stumbled across this while searching for other things: https://www.beyonddiscovery.org/balancing-machines/measurement-of-seal-face-flatness.html
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