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heli-coil sizes

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  • heli-coil sizes

    well i broke off 3 bolts on the force 125 exhaust cover, which needed to be taken off to clean out the corrosion.....i got all 3 of them drilled out and i was going to try to go back with the same thread size...but i still have some steel threads left in the housing threads which makes going back with original size almost impossible with breaking some taps off in it....so i decided i need to put heli-coils in them...is there a chart or something that can tell me what is size bit/tap and heli-coil to use? i've installed some heli-coils at work a very long time ago just cant remember the specifics on them.
    Run it till the prop falls off!!!

  • #2
    Re: heli-coil sizes

    Hi,

    Go to helicoil.com and you should find the information you need.
    You can also get them online at McMaster Carr.

    Did you try to use a plug tap, 2 fluted to clean out the holes? They are much stronger, and the plug type have a nice lead on them. Then follow up with a bottom tap if needed. Most hardware type stores don't sell that type. You may have to go to a tool supply. Don't forget to use some oil when tapping the holes. Wd 40 is not good enough for that. Light greas works well too.

    Good luck,

    Mike

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    • #3
      Re: heli-coil sizes

      Originally posted by MWBROWN View Post
      Hi,

      Go to helicoil.com and you should find the information you need.
      You can also get them online at McMaster Carr.

      Did you try to use a plug tap, 2 fluted to clean out the holes? They are much stronger, and the plug type have a nice lead on them. Then follow up with a bottom tap if needed. Most hardware type stores don't sell that type. You may have to go to a tool supply. Don't forget to use some oil when tapping the holes. Wd 40 is not good enough for that. Light greas works well too.

      Good luck,

      Mike
      ...ditto, and right on. Follow this Kajun and you'll be done in time for dinner.
      ps: McMaster Carr are known for quick delivery...so if you order something on line often by/before noon...you'll have it the next day, not 2 weeks later. Have it sent to your work address if you can.
      Big Prairie
      90' Capri- 90 Force
      Apparently....Newt Gingrich has several Pete Seeger records that he hasn't disclosed.

      Comment


      • #4
        Re: heli-coil sizes

        Originally posted by MWBROWN View Post
        Hi,



        Did you try to use a plug tap, 2 fluted to clean out the holes? They are much stronger, and the plug type have a nice lead on them. Then follow up with a bottom tap if needed.

        not following you on this ...i tried to use a regular tap...it is flat on the end of it, which i believe is a bottoming tap....2 fluted?....also where is the charts that tell you the size drill bit and tap that i need to step the hole up too..i cant find it on helicoil.com...
        Run it till the prop falls off!!!

        Comment


        • #5
          Re: heli-coil sizes

          Because Heli-Coils are 1/4 X 20 internal threads, the external threads are also 20 tpi. therefore they are not standard and you must buy the kit containing the proper drill and tap. A kit with 6 Heli-coil inserts, the drill and tap costs about 20 bucks. And, There is not much meat on the exhaust cover bolt hole bosses. It is MUCH easier to just drill the hole deeper, tap 1/4 X20 deeper, and use a longer bolt.

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          • #6
            Re: heli-coil sizes

            HeliCoils use a special drill size, and a purpose built tap, AND insert tool.... get the kit...(21 years Machinist)

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            • #7
              Re: heli-coil sizes

              i have a kit at work....but i dont know which size to use.
              Run it till the prop falls off!!!

              Comment


              • #8
                Re: heli-coil sizes

                Ok, I will explain.

                Most home taps are 4 flutes. Flutes being the cutting edges.
                A good hardware store may have a two flute plug tap. Plug tap is tappered on the end, thus cuts easier. Take a bolt with you if you don't know the size and pitch. Guessing from Franks post that they are 1/4 x 20.
                If you drill them deeper you will need a .201 to .205 diameter drill.
                13/64 diameter drill will work.

                The kit will say 14/ x 20 repair kit. The drill and tap will be bigger of course than a standard drill.

                Sorry, I thought Mcmaster would have that info.

                Good luck,

                Mike (37 years making chips)

                Comment


                • #9
                  Re: heli-coil sizes

                  thanks for the help folks and mike thanks for the explanation on that...

                  i ended up not having to put a heli-coil in it..i stepped up to a 7/32 drill bit and it took out all the steel threads left over from the broken bolt..and ran my 1/4-20 tap and was able to make some good threads with it.....all 3 holes are ready to go!....now i got to get that old gasket off......anyone have a good way to get that black exhaust cover gasket off? its hard as a brick and ain't coming off by scraping it....i really dont want to sand it off cuz it looks like asbestos.
                  Run it till the prop falls off!!!

                  Comment


                  • #10
                    Re: heli-coil sizes

                    Tough it out with a single edged razor blade, lots of time, and lots of sore fingers.

                    When you go to replace the gaskets be sure to tighten all bolts securely starting from the center and working out--in steps, just like the head pattern. And use PLENTY of anti-sieze. The water tends to wick into the bolt holes and corrode the aluminum. Then after running, re check tightness. Good and tight but be careful not to strip them. I know--I know--factory says to install gaskets dry. I'm not a big fan of Permatex, but a light coat here may help to stop corrosion.

                    When replacing the gaskets, be doubly careful especially at the lower front. The gasket is only about 1/8 inch wide here and easily kinked, leading to water leaking into the bottom cylinder. If the engine is run frequently, no harm will come but once it is layed up, the bottom cylinder will rust, jamming the piston tight.

                    Comment


                    • #11
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                      Re: heli-coil sizes

                      Originally posted by Frank Acampora View Post
                      Tough it out with a single edged razor blade, lots of time, and lots of sore fingers.

                      dang..was hoping noone would say this lol
                      Run it till the prop falls off!!!

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