Thread cleaner/chaser?

  1. Jonathan Webb

    Jonathan Webb Member

    Messages:
    330
    Location:
    West Sussex, England
    Hello and help please.
    I'm trying to get a newly machined 316 stud 3/4" BSW into a cast iron threaded hole which has got a bit rusty. I've cleaned it out as as best I can,is repeatedly. Access is not good as it's under 2cm of fibreglass. The original stud goes in ok-ish. The new stud threads look good inasmuch as a nut freely runs along it. The other same sized stud that goes into the other hole gets stuck at the same place but goes into it's own hole ok.
    I suspect that the rust in the hole is the problem.
    I have seen articles about making a makeshift thread cleaning tap by cutting grooves into a similarly threaded bolt.

    My main question is: does that work?

    I haven't really got time to order a proper tap as this is holding up work that needs to be done by the end of the weekend.
    Any other tips or tricks - anything to dissolve loose surface rust?
    I can't get even a small wire brush in there, just a toothbrush & rags on a screwdriver, which I've been using.
    Many thanks.
     
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  2. brightspark

    brightspark Member

    Messages:
    30,770
    Location:
    yarm stockton on tees
    an internal thread cutting lathe tool would clean it out by hand if u had one
     
  3. Wozzaaah

    Wozzaaah The wizard of woz Staff Member

    Messages:
    15,049
    Wiltshire, UK
    Yes it does work, very well! It's an old trick that can get you out of trouble.
    I've always cut the grooves slightly diagonal.
    Brick acid is very good for getting rid of surface rust but anything you clean with it will quickly flash rust if you don't protect it.
     
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  4. Pete.

    Pete. Member

    Messages:
    9,490
    Location:
    Kent, UK
    If you're really stuck Jonathan I have a 3/4BSW tap here in Gravesend.
     
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  5. Jonathan Webb

    Jonathan Webb Member

    Messages:
    330
    Location:
    West Sussex, England
    I'm in a boat, in a remote corner of a car park.
    I've got power and hand tools, that's about it. The hole in question is in 500kg of cast iron that ain't going anywhere thanks anyway.
     
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  6. Jonathan Webb

    Jonathan Webb Member

    Messages:
    330
    Location:
    West Sussex, England
    Cheers wozzaah. That's the right answer. And I have hcl at home.
     
  7. Jonathan Webb

    Jonathan Webb Member

    Messages:
    330
    Location:
    West Sussex, England
    Thanks Pete. That's helpful to know. I'll try the DIY route first.
     
  8. Jonathan Webb

    Jonathan Webb Member

    Messages:
    330
    Location:
    West Sussex, England
    An old stud, with grooves added, goes in by hand. The new stud still gets stiff after a short while. All the other (1",3/4" and 1/2") studs have gone in ok so the machinist's work quality seems to be ok.
    I'll bring some HCl tomorrow & try that. I've found that epoxy grp has reasonable resistance to it do as long as I neutralise it I'll be ok.
    Well hacked off, got almost nowhere in a whole day and it's cold and noisy (wind). Bah.
     
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  9. Pete.

    Pete. Member

    Messages:
    9,490
    Location:
    Kent, UK
    You need to grind a whole bunch more off that bolt for it to work. Chop out two opposing pie slices.
     
  10. Bullet2012

    Bullet2012 Forum Supporter

    Messages:
    1,527
    Location:
    Berks
    Are the other studs the same material ? Just wondering if the stainless is “baulking” . Try a little lube on the thread.

    also will the new stud fit in a different hole ?
     
  11. winchman

    winchman Member

    Messages:
    3,635
    Location:
    Merseyside
    Make the bolt look like a tap
     
  12. Jonathan Webb

    Jonathan Webb Member

    Messages:
    330
    Location:
    West Sussex, England
    Thanks.
    Yes, they're all the same, 316 stainless.
    I'll remove one of the others tomorrow to try swapping them round, but a different stud sticks similarly. I've been using a bit of hypoid oil on it partly as lubricant and partly to attract the dust so I can clean it off the threads.
     
  13. brightspark

    brightspark Member

    Messages:
    30,770
    Location:
    yarm stockton on tees
    queer stuff stainless steel on threads they can gall up :)
     
  14. Jonathan Webb

    Jonathan Webb Member

    Messages:
    330
    Location:
    West Sussex, England
    Game over for today. . I cut down a brass wire suede brush to try and scrub the threads a bit more vigorously than the toothbrush snd the damn thing snapped off...
    I'm fairly sure that long nosed pliers will get it out or dissolve it with acetone. Still, a PITA.
     
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  15. Matchless

    Matchless I started with nothing, still have most of it left

    Messages:
    1,305
    Location:
    Essex UK
    job for a gynaecologist!
     
  16. Jonathan Webb

    Jonathan Webb Member

    Messages:
    330
    Location:
    West Sussex, England
    Yes. I'm working under that shadow.
     
  17. 500e

    500e Always buy fire insurance a flood is hard to start

    Messages:
    4,813
    Location:
    SWest UK
    2507 would be a better grade than 316, have seen 316 shackles eaten away in 18 months As @brightspark says SS also has a nasty habit of galling, if it starts goes tight before is should STOP & remove examine thread
    Would take @Pete.offer if you can get it in there length could be the problem though.
    Grinding of an old unit could be the way to go then blow out the hole dingy or air bed pump.
    I would also be wary of the brick acid hcy, neutralising the stuff if it seeps into fibreglass could be a disaster
    You want the glass to be as clean as possible free from oil & acids so when you cap the keel bolts they stay dry with no seepage
    Did the bolts on an Albin some years ago feel your pain that was in the corner of a car park as well
    https://www.ebay.com/itm/MRO-Soluti...ade-Ant-Seize-8-Oz-Brush-Top-NEW/223639697015
     
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