Helicoil Armacoil

[Forumadmin]

Helicoils are supplied as a kit with the correct drill, tap and insert tool - everything you need but at an eye-watering price (£73.59 including 20% discount). For this you get 10 helicoil inserts. With the kit (incidentally now marketed as Armstrong Precision Components - Armacoil Thread Repair Kit, Helicoil to you and me) came a table of drill sizes which I list below. To drill out prior to tapping for the Helicoil insert, very little extra metal has to be removed – really just the removal of the remnants of the old threads. This compares well with tapping out to the next size up. The special tap supplied is quite short and well tapered so care is required to keep it running straight and to avoid too much swarf build up. The helicoil inserts went in easily using the insert tool. The inserts are effectively springs and the tool slightly compresses them so they wind in easily. On release of the tool they grip tight.

Bolt size
.............Helicoil drill size BSF mm
........................Helicoil drill size BSW mm
3/16-------4.9-------5
1/4--------6.6-------6.7
5/16-------8.3-------8.4
3/8--------9.8-------9.8
7/16-------11.4-----11.4
1/2--------12.9-----12.9
9/16------14.5------14.5
5/8--------16.1------16.5
3/4--------19.3------19.7

[Leo Bolter]

To supplement Keith's graphic description here's the instructions that came with one of my "ReCoil" brand equivalent sets. (this one happens to be Metric (M8), but the principle remains the same).



Also, here's a repeat of the info regarding BSF and BSW Inserts.

[Mike Allfrey]

Hi Keith,

Sounds like the 'march of progress' has influenced the good old Helicoil. I wonder why they would change a name that has become the normal term in the industry for such a device. As Leo says, we have Recoils down here - but they are always referred to as 'Helicoils'!

They are a bit expensive, and your pricing about matches what we pay here in OZ. So, don't weep any more!

One point about these excellent threading devices. The coils that come in the kit are a bit short for use at the Jowett cylinder head stud threaded holes in the crankcase. Slightly longer coils are available, but rarely stocked where you purchase the kit, meaning a second trip to the retailer. I screw in a first coil to the bottom of the new thread, break off the tang and then, carefully, wind in the second coil on top. as soon as the tang contacts the top of the first coil, the second coil's tang is broken. It is then important to make sure the tangs are removed, and that the lead on the second coil starts slightly below the face of the crankcase. This procedure works for me.

Keep that tap absolutely square!

Regards to all,

Mike Allfrey.

[PJGD]

As mentioned before in this forum, I have been very happy with wire thread inserts from this company:
http://www.wireinserts.com/

The kits come with all the tools needed, and the inserts have been long enough as is; too long in some cases.

Philip