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Author: Subject: Helicoil without special tools - Can it be done safely
John P

posted on 24/6/20 at 02:00 PM Reply With Quote
Helicoil without special tools - Can it be done safely

Hi,

I have a classic car which has stripped a 5/16" BSW thread in the aluminium crankcase casting.

I can't readily take it to a local company so am considering fitting a Helicoil but have a couple of queries:

Firstly, without completely stripping the engine I will have to drill the old thread out with a pistol drill. Do you think that because it's following the existing damaged thread the drill will naturally keep itself in line?

Secondly, whilst I can buy a suitable Helicoil tap for around £9.00 and some inserts for £5.00 the complete kit would be over £32 which is a lot for something I'm unlikely to ever use again. Is it possible to wind the insert in and break the tank off with say pliers and a flat headed punch or am I asking for trouble trying this.

John.

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02GF74

posted on 24/6/20 at 02:19 PM Reply With Quote
I bought a helicoil kit, metric, off ebay for £22, covers M5, m6, m8, m10 and m12 with inserts dell's, taps and tools.

The winder tool is nothing more than a rod with a slot cut in, the tool to remove the tang is a rod without the slot

You can make these yourself.

The drill should follow the threaded hole, worst case could you open up the hole on the other piece that the bolt goes through?


You may be able to make a jig with a tube to guide the drill bit to bolt on to the crankcase, simplest would a thick section of steel with a guide hole that bolts on using a nearby hole?

It's doable, juneeds a bit of thought to avoid bollocking it up, may be try it out on a scrap piece.

[Edited on 24/6/20 by 02GF74]

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rusty nuts

posted on 24/6/20 at 02:36 PM Reply With Quote
The proper Helicoil tools I have use a sleeve with a female thread and a threaded bar with a machined end to locate with the tang on the Helicoil , The cheaper Rethread tools use the slotted rod , Iíve never had any problems with either, in fact the rod is quicker , just donít force any of them .
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steve m

posted on 24/6/20 at 02:42 PM Reply With Quote
Ive used the proper helicoil setup many many times, and for the mild inconvenience of having to wait for delivery, I would use the proper tools and taps to do the job properly

5/16 comes in unc and unf, attached link is unc

https://www.ebay.co.uk/itm/5-16-UNC-Helicoil-Thread-Repair-Kit-Race-Rally-Design/321677426254?hash=item4ae577fe4e:g:XzUAAOSwICpaAdkP





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cliftyhanger

posted on 24/6/20 at 03:03 PM Reply With Quote
There is nothing special about the winding in tool. An old screwdriver with a suitable mod should do it?
I can't understand what else you get besides tap, inserts and wind-in tool?

My classics are all UNF/UNC, but I use metric helicoils as I am a tight bstard. Just a thought.....

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paulf

posted on 24/6/20 at 05:21 PM Reply With Quote
I have fitted many helicoils over the years and there is nothing special about the job,the tapping drill is about the outside diameter of the existing thread and easily follows the original hole ,just get someone to eye up the drill as you line it up to drill.
Then tap carefully and clean out with an airline before winding in the insert with a length of bar of a suitable size with a slot in the end and snap of the tang with a sharp tap on the bar..
As long as you have the correct tap the other parts of a kit just make it a bit easier if doing a lot at once.
Paul.

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Irony

posted on 25/6/20 at 08:37 AM Reply With Quote
I thought that the drill bits were a specific diameter with regards to the Tap?
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907

posted on 25/6/20 at 09:58 AM Reply With Quote
Is it possible to drill 8mm and take out the 5/16 thread, then tap 3/8" UNC. Blind holes would need a plug tap.

In the past I've drilled out another bolt hole so the item being bolted on had two matching (slightly larger) bolts.
Obviously you need to drill out the flange to suit the bigger bolts/studs.


Just a thought.
Paul G

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coyoteboy

posted on 25/6/20 at 11:37 AM Reply With Quote
quote:
Originally posted by Irony
I thought that the drill bits were a specific diameter with regards to the Tap?


They are, for example the M6 has a major diameter of 6mm on the male thread and the female tap is very slightly larger for a normal M6 (6.1-6.2). The repair tap for an M6 requires 6.3mm drill diam, which just clears the old thread out and the tap inserts the new (non-standard) thread size as you say.

Ultimately, so long as the right size drill and tap are used for the helicoil, the process of fitting it is super simple with a forked tool (not pliers!).

The kits are £27 quid delivered.
https://www.ebay.co.uk/itm/5-16-BSW-V-Coil-Fits-Helicoil-Wire-Thread-Repair-Insert-Kit/123751334218?hash=item1cd027814a:g:mTMAAOxybLpRiSNF

[Edited on 25/6/20 by coyoteboy]





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Big T

posted on 25/6/20 at 01:55 PM Reply With Quote
You should be fine drilling with a hand drill I tot he existing hole. The hole should sort of ďself-CentreĒ on the whole.

I canít see why you couldnít wind the thread in with a set of needle nose pliers and then snap the light off with a screwdriver. Itís aids law that if you donít buy a kit, you will soon enough need to re-thread another fixing.

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coyoteboy

posted on 25/6/20 at 02:23 PM Reply With Quote
i mean you could do it with pliers, but I've seen so many messed up and cross threaded that way.





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Big T

posted on 25/6/20 at 02:25 PM Reply With Quote
quote:
Originally posted by coyoteboy
i mean you could do it with pliers, but I've seen so many messed up and cross threaded that way.


I would recommend just buying a kit, the ones Iíve used are just like a bit of bar with a slot in the end which I suppose you could knock up quick enough, but if youíve got to order the pets, just grab a kit. Anyone you know who could possibly do you a lend?

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MikeR

posted on 25/6/20 at 06:54 PM Reply With Quote
Ask yourself what you'll do when you mess it I up. Then ask is that worth the extra 20 quid. Simple decision for me, but it's your call.

(I'd get the proper kit)

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John P

posted on 25/6/20 at 08:25 PM Reply With Quote
OK, you've all convinced me. I'll order a proper kit rather than risk mucking it up.

Think I may change from 5/16 BSW to UNC though as the Rally Design UNC kit is something like 1/3rd of the cost of a BSW one and I'm not that much of a purist.

Thanks for all the help and advice.

John.

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907

posted on 25/6/20 at 08:56 PM Reply With Quote
quote:
Originally posted by John P
OK, you've all convinced me. I'll order a proper kit rather than risk mucking it up.

Think I may change from 5/16 BSW to UNC though as the Rally Design UNC kit is something like 1/3rd of the cost of a BSW one and I'm not that much of a purist.

Thanks for all the help and advice.

John.






5/16 BSW and 5/16 UNC are both the same TPI, 18

Paul G

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tegwin

posted on 25/6/20 at 10:12 PM Reply With Quote
I needed a Helicoil in a spark plug hole a few years back and rang around the local garages until I found someone with the kit who would do a house visit. I was worried that if I stuffed it up myself it would be game over.





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britishtrident

posted on 26/6/20 at 06:14 PM Reply With Quote
The red boxed kits on ebay work fine I have more than a few M6 cam cover and engine cover threads with them.

With spark plug threads my first choice is the metal sleeve insert type rather than helicoil.





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coyoteboy

posted on 27/6/20 at 11:51 AM Reply With Quote
Keenserts work nicely but require more material removal. I like the replaceable nature of a helicoil. We use both at work as preventative thread enhancements on any aluminum parts.





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John P

posted on 6/7/20 at 12:54 PM Reply With Quote
I've just received the Rally Design kit which looks fine except that the inserts are only something like 8mm overall length so presumably 1D.

Will this be OK in aluminium bearing in mind the original thread stripped out when the thread engagement was around 6mm although this was an old thread in the aluminium of a 1929 crankcase.

I would buy some longer inserts but Rally Design don't seem to list them separately and I don't really know if other inserts can be use with the Rally Design tooling. The tap supplied is marked ST5/16-18.

Any advice?

John.

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rusty nuts

posted on 6/7/20 at 04:33 PM Reply With Quote
You can put multiple inserts in if you need to, Ive had to a few times without any problems,
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steve m

posted on 6/7/20 at 04:53 PM Reply With Quote
Helicoils are about 8mm long, and quite sufficient on there own
However, I have also doubled up,
but found that inserting first helicoil into the hole, and then loading the bolt up with the second helicoil,
and refitting worked fine also

steve





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coyoteboy

posted on 7/7/20 at 02:54 PM Reply With Quote
Helicoils come in a selection of lengths (specified as 1D, 1.5D and 2D) - i.e. multiples of the major diameter of the thread. You'll also find that they, in the in-packet form, are shorter than the deployed form which extends as it goes down the bore.

The more heavily loaded the fastener, the longer you'd want. Generally the fisrt 1D takes 75% of the fastener load. Generally since it's stronger than the base fastener you could assume a 1.5D will be stronger than original anyway even if the original was 2D thread depth.

But yes, you can double up but do so carefully - if you insert it with a few threads gap between, you won't get much benefit.





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