Everything2Stroke - How to install thread inserts
  • Thread Inserts "How it's Done"

    Continuing along with the RM250: The cylinder is relined ready for finish honing. After taking a look at the head studs, Iíve decided to replace all of the threads with Stainless Steel inserts.

    The stainless alloy inserts have a small tang at the bottom to allow a way to grab while inserting.

    #2 & 8 are stripping & #6 is snapped off. Take a good look at the photo and learn what to look for. After seeing all of the cylinders with blown pistons on this site, Iíll guess that there are a lot more stripped stud threads then it would seem.

    Back to the snapped off #6 stud. You shouldnít just attempt to drill out a snapped stud with an electric drill. The bit can walk off of center line and cause more problems. Now we have replaced the drill press with a vertical milling machine. Instead of a drill bit, Iím using a 2 flute center cut end mill to remove the snapped stud.

    The end mill does a straight down plunge and removes the stud without walking off the center.

    Next, on all locations, I tap drill the hole and cut the threads.

    You can see how handy the Parallel mounting plate is while working with the cylinder. No matter what the operation is, itís always a problem getting a proper hold on the Dang thing. "Trade Secrets"

    Last, install the inserts in all of the threaded holes.

    The top of the new liner is decked with a .005Ē squeeze fit to seal the head gasket.

    The small smudge above the reed valve pocket is from my 500 deg. Temp stick. I use the temp stick to keep track of the cylinder temperature when removing & replacing the new liner.

    Iíve ordered a few lengths of 8x1mm threaded rod for machining new stainless head studs. When we receive a cylinder for thread replacement, Iíll supply new Stainless head studs to go along with the job.
    18 & 8 Stainless steel, 18% Chrome, 8% Nickel. "Trade secret"
    After the last few cylinder repair jobs, we are starting to work from the bottom so we wonít have to disturb any existing head studs. As seen earlier in this thread, pulling head studs is a pain.

    As you have learned, assembling a tool box and shop with the proper equipment can be a life long project. If your young and have the ambition, you can do this too. Never give up on your education.

    All for now ďOld DogĒ
    This article was originally published in forum thread: How It's Done - Trade Secrets inside. started by John Tice View original post
    Comments 16 Comments
    1. Morph0906's Avatar
      Morph0906 -
      good read John thanks
    1. Tangles's Avatar
      Tangles -
      Stainless and Ally don't like each other.
    1. John Tice's Avatar
      John Tice -
      Hello Tangles: I don’t understand your statement, “Stainless and Ally don't like each other. “ Stainless steel is an alloy. Mainly T-300, Non magnetic. Typically 18 & 8 is how stainless is coined. 18% chrome & 8% nickel. The rest is iron & about 3% carbon with some trace of other materials.
      Thank you for your comments. I’m somewhat disappointed by the lack of comments & questions from “How it’s Done” & my other posts. I’ve gathered a wealth of information from my 45 plus years in the shop, some more, some less. I’m here to help as I can.
    1. Larry's Shee's Avatar
      Larry's Shee -
      I know that steel bolts in the alum cases don't like each other, hence bolts that may have been in place 20+ yrs forming that white powdery substance. Two dissimular metals: http://www.cdxetextbook.com/engines/...ctrolysis.html
      Maybe he ment aluminum for ally?

      Unfortunatly it's hard to show each little step in say setting up a cyl for boreing, or facing. Many might not know what question to ask, or how to ask it. Short of vidieos it's hard to show every step.
    1. John Tice's Avatar
      John Tice -
      That's a good clip. Even while handling aluminum around our shop a person will get black oxide all over the hands. This is why it's a good idea to replace the old head studs with new ones made from stainless steel.
      Thanks for the comment
    1. 97kx250guy's Avatar
      97kx250guy -
      What helicoil kit should I buy for a 97kx250 stripped head bolts?
    1. John Tice's Avatar
      John Tice -
      97KX: You need to measure the studs, they are most likely 8x1.25mm. Just about all of the cylinders we work on are 8x1.25. There are some 8x1.25 one end by 10x1.25mm, I'm not sure which ones they are. The older Honda CR's use the dual sized. If you look at my site under threaded products you will see the 2 different types. I hope that helps.
    1. 97kx250guy's Avatar
      97kx250guy -
      Quote Originally Posted by John Tice View Post
      97KX: You need to measure the studs, they are most likely 8x1.25mm. Just about all of the cylinders we work on are 8x1.25. There are some 8x1.25 one end by 10x1.25mm, I'm not sure which ones they are. The older Honda CR's use the dual sized. If you look at my site under threaded products you will see the 2 different types. I hope that helps.
      Thank you, that does help but how do I measure the studs? And when I look on a site to buy the helicoil it says a third number. For example M12 X1.25 X 16.3MM. What does that number mean?
    1. Dangerouspower's Avatar
      Dangerouspower -
      Length probably.
    1. John Tice's Avatar
      John Tice -
      DP is correct: The length of a coil is usually 1-1/2 times the diameter of the bolt. Anything longer serves no purpose as far as strength goes.
    1. 97kx250guy's Avatar
      97kx250guy -
      How do I find out the pitch?
    1. John Tice's Avatar
      John Tice -
      This is what the typical thread gauges look like.

      One is for metric and the other is for standard SAE threads. (Society of Automotive Engineers)

      These are available at most any tool store & probably on line somewhere. They are also in the Harbor Freight tap & die sets. The H.F. tap & die sets are a rather Cheezy. You are better off to buy taps in good quality as you need them.

      Standard tap & die set, Harbor Freight. The thread pitch gauge is in the center.

      As long as we're on the subject, here are examples of some standard types of high speed taps.

      1. Bottom
      2. Gun tap, pushes the chips forward & doesn't work well in blind holes.
      3. DRAP, combination drill & tap
      4. Express tap, Neatly swages the threads and leaves NO chips. Tap drill size is critical.

      There are other types but seldom seen in most machine shops. Always purchase High Speed steel taps when available.

      When you have more time, Read through "How it's Done" for more ideas.

    1. seattle smitty's Avatar
      seattle smitty -
      I think "tangles" meant to type "Alloy," which is what some of the Brits used to call aluminum . . . if they weren't calling it "al-yu-MIN-i-um." "Alloy" is plainly a bad, confusing term, and it's unfortunate that was taken up by some here back in the days of MGs and frogeye Sprites and open-back leather driving gloves.

      FWIW, on some occasions, and when there's room to install them, Keen-Serts might be better or handier than Heli-Coils, particularly where you may be screwing the fastener in or out from time to time, unlike studs.
    1. John Tice's Avatar
      John Tice -
      Smitty: It’s Bug Eyed, not Frog Eyed. With the inserts, I use what the tool store has in stock.
    1. seattle smitty's Avatar
      seattle smitty -
      "frog-eyed sprite" got me 184,000 results on Google.
      "frog-eye sprite got 163,000
      total frog hits: 347,000

      "bug-eyed sprite" got 37,300 results
      "bug-eye sprite" got 274,000
      total bug hits: 311,300

      I win, Tice!

      (Wikipedia explains that "Frog-eye" was the Brit term, whereas "Bug-eye" was USA).

      It was a British car . . .

      Good article as usual, John. I'd never heard the term, "drap;" that's a keeper! As to the inserts, I'm not advocating one or other, just mentioning an option that is sometimes useful. The Boeing tooling shop I was in long ago used a lot of Keen-Serts, which was how I got accustomed to using them, but I use Heli-coils most often for my stuff.
    1. John Tice's Avatar
      John Tice -

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