Have 12mm helicoil inserts, what size tap?

Hi guys, I got 12mm helicoil inserts to use for one of my spark plug threads, what size tap do I need, 12mm? Should it not be a bit bigger than that because the helicoil is acting like a spacer?

 

from the helicoil site, page 17:
http://www.helicoil.in/pdf/Helicoil__Catalohue.pdf

You bought only an insert, not a kit? Kits I have bought in the past include a drill and a tap.
http://www.helicoil.in/helicoil.htm

Steve

 

If you are doing this with the head still on the bike, be very carefull. Make sure the valves are CLOSED!!! Take off the valve cover and make sure that the cam lobe for that cyl. is looking horizontal. <---> . Dont ask, been there done that and still have the tshirt and the screwed up valve somewhere!!!!. If it were me I would pull the head, this way you do not have to worry about shavings from the drill or tap and the helicoil tang getting into the combustion chamber.
But if you are doing this while the head is off of the engine, have fun, its really easy to do just make sure you remove the tang with a quick rap from a centerpunch.

 

I am doing it with the head still on, don't want to remove it and then have to get a new gasket, and have a possible bolt break, or nut strip. Not today lol.

I know that I am suppose to use a 31/64" drill bit, but I am still trying to track down the tap that works with that. I checked one local shop and they only had a 12mm tap in a kit that was 60 bucks, and I don't need the whole kit, just the tap...

Going to check a few other places too...

 

Heli Coil taps are special, since they are not true thread sizes, but an oversized hole with the same thread pitch of an actual metric sized bolt, or sparkplug. They are useless for tapping threads or chasing threads, they are a single purpose tool. You must buy a Heli Coil tap.

 

Ok then, anyone know where I could try and pick up a 12mm Helicoil tap? I tried ebay, but they only have the kits?

 

Contact the people at this link"

http://xjbikes.com/Forums/viewtopic/t=2 ... panel.html

They'll hook you right up.
Emhart is B&D's HeliCoil Division.

Email this HeliCoil Rep. He'll provide you with the information you need, immediately.

stephen.devine@bdk.com

 

Dont ask, been there done that and still have the tshirt and the screwed up valve somewhere!!!!. If it were me I would pull the head

 

Even Better Take the Poor Bike to a Shop to have it done professionally it's quite inexpensive.
You REALLY? want to learn .. for the very first time...how to do a Helicoil on your Engine.

Not the cleverest place to experiment imo

 

Not only do you need the special tap but you also need the insertion tool.

Return the insert refills and get the kit.

 

Anthony:

Have you given any thought to having someone with a great deal of experience repairing a stripped Spark Plug Hole render you some assistance.

It might be a wise choice to not try and do the whole job by yourself and turn it over to a Pro who had everything he needs to do the job right ... the first time.

 

Good point.

Plus, it'll probably be cheaper than buying the tools. Owning the tools only makes sense if you'll be doing a number of them.

 

I'm not sure how to describe the HeliCoil Job.

Just getting it right in a stripped-out Housing with wide-open access requires some finesse.
The Job becomes more demanding when you consider that you will be repairing a Spark Plug Threaded Hole in a recessed cavity.

It one of those things, ... like ...: You need to get it right -- the first time -- because you don't get a second chance with Aluminum.