Another threading question

  1. Brad93

    Brad93 M J B Engineering

    Messages:
    10,397
    Location:
    Essex
    I’m having trouble with another thread.

    I’ve used a better quality steel, threading at 305rpm now, got a nice thread.

    I am trying to thread, M20 x 2.5mm pitch.

    My OD started at 20.06.

    My OD is now 19.88 and my threads are the full depth of the 2.5mm insert.

    I still can’t get a nut on?

    Any ideas?
     
  2. Seadog

    Seadog Forum Supporter

    Messages:
    6,976
    Location:
    NE London - UK
    You've cut a left-hand thread? :scared:
     
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  3. mtt.tr

    mtt.tr Member

    Messages:
    4,084
    Essex England
    I would advice investing in thread wires they are the only method i know of for proper sizing of threads.
     
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  4. Brad93

    Brad93 M J B Engineering

    Messages:
    10,397
    Location:
    Essex
    I took another two almost spring passes and the nut winds right on now

    some sort of thread measuring gear is definitely needed.
     
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    slim_boy_fat, doubleboost and Seadog like this.
  5. mtt.tr

    mtt.tr Member

    Messages:
    4,084
    Essex England
    Running a square file along the thread can help knock of any last burrs

    Well done for persevering
     
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  6. pressbrake1

    pressbrake1 Forum Supporter

    Messages:
    2,898
    essex england
    Move along a couple of thou on the compound and take another cut
     
    Brad93 likes this.
  7. Brad93

    Brad93 M J B Engineering

    Messages:
    10,397
    Location:
    Essex
    This is what I should of done to narrow the crests.

    know for next time now :thumbup:
     
  8. Kram

    Kram Member

    Messages:
    1,786
    Location:
    Sussex
    I measure all of my external threads, takes seconds, easy thanks to DrAl's calculator, here, www.cgtk.co.uk/metalwork/calculators/screwmeasurement

    Measure the OD before starting. Choose a suitable drill bit from the calculator wire size. Deburr the part and measure with your drill/peice of mig wire. Subtract the original radius and double the result. That is the easy way to do it.

    Youd be looking for 20.3mm with a single 1.5mm drill bit/wire

    Internal threads I have not worked out yet. It should be easy enough to turn pitch specific tips for a bore gauge.
     
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  9. mtt.tr

    mtt.tr Member

    Messages:
    4,084
    Essex England

    Internal threads either buy or make a guage
     
    Brad93 and pressbrake1 like this.
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