Installing Heilicoil in cast iron - advice wanted.

[Junkmaster]

Background: I made the mistake of purchasing a heavy duty drill press vice at a garage sale for $5. I've spent hours and about $40 so far and still have a ways to go.

The jaws of the vice were damaged or custom modified for some purpose. So I decided replacement was needed. In doing this I found one of the 2 bolt holes in the movable jaw was completely stripped. I've purchased a helicoil replacement kit with the tap, installation tool and 10 inserts.

I have never worked on cast iron, or installed a helicoil. It seems straight forward, but I don't get any do-overs. So I'm looking for advice.

I was planning on holding the jaw in a milling vice on my Smithy 1220, with the stripped hole facing up, towards the milling spindle. I'll drill the recommended size hole.
I'll exchange the drill for the provided tap and tap the hole. I am guessing at this point I'll exchange the tap for the installation tool and insert the coil according to instructions.

The two items that give me the most pause: holding the movable jaw in the milling vice, and drilling in cast iron. The movable jaw has two flat surfaces that I can grab with the milling vice, but the rest of it is curved/rounded. I need to support the side where I'll be repairing the threads. I will probably just carve up a wood block to wedge under it.

I'll go research drilling in cast iron, I'm pretty sure someone has done this before...

After the thread repair, I have to make new threaded rod (square thread, 4 tpi, 7/8" diameter) as the current one is bent about 2 degrees half way down the length. I've never threaded anything on the lathe, so I'll be practicing for a while.

I'll try to get some pictures and post them.

Evan R.

 

[george wilson]

Not sure of what the question is. Why can't you just drill and tap a LARGER screw instead of using helicons? If it is possible to just use a larger screw,it would be better all around.

Drill at a slow speed as cast iron can dull your drill bit. Use COARSE threads in cast iron,Fine threads for steel. That's why we have coarse and fine thread series.

 

[7HC]

I have never worked on cast iron, or installed a helicoil. It seems straight forward, but I don't get any do-overs. So I'm looking for advice.......
........After the thread repair, I have to make new threaded rod (square thread, 4 tpi, 7/8" diameter) as the current one is bent about 2 degrees half way down the length. I've never threaded anything on the lathe, so I'll be practicing for a while.

I'll try to get some pictures and post them.

Evan R.

Yes, pics will make it easier to see what you're describing.
Helicoils make for a good repair if you want/need to keep to the existing size securing bolt and don't want to enlarge the clearance hole in the jaw.
They're easy to install, just make sure you drill and tap squarely. Check the other threads while you're at it and still have a bunch of coils available.

In regard to the threaded rod, it's a very coarse thread and pretty thick, so I think I'd try straightening it before cutting a new one; there's not really anything to lose.


M

 

[Bill Gruby]

With regards to the Heli-coils, I would not use them unless it was absolutely necessary. Do as George recommends, go to a larger screw.

I also would try to straighten the threaded part.


"Billy G"

 

[wawoodman]

I've used helicoils in CI with no problems at all.

While you have your part clamped up for drilling, keep it in the same place and use a tap guide to keep the tap straight. The helicoil taps only have a few starting threads, so starting straight can be a problem.

 

[7HC]

With regards to the Heli-coils, I would not use them unless it was absolutely necessary.............

Could you expand on that Bill? I respect your opinion, but the reason I ask is that I've used Helicoils on many, many, occasions, both fine and coarse thread, metric and imperial, in cast iron, aluminum, and even plastics.

I've repaired cylinder block threads for both studs and bolts, which are often heavily torqued and are under significant load in use and never had one fail.

As far as I'm concerned the most significant advantage is that the original (or an original size) fastner can still be used instead of tapping to the next size up, with its additional issues of fit and clearance


M

 

[kd4gij]

Use red locktight on the Heilicoil when you install it and it will be alot stronger than the threaads in the castiron. let it dry over night before running the bolt in.

 

[7HC]

Use red locktight on the Heilicoil when you install it and it will be alot stronger than the threaads in the castiron. let it dry over night before running the bolt in.

Yes, that last bit is important. If you're going to use Locktite, let it set up before installing the bolt, screw, or stud.
Otherwise the Locktite will seep through the threads as they expand slightly when the bolt is installed, and you'll have to use heat if you ever want to remove it.


M

 

[Bill Gruby]

Could you expand on that Bill? I respect your opinion, but the reason I ask is that I've used Helicoils on many, many, occasions, both fine and coarse thread, metric and imperial, in cast iron, aluminum, and even plastics.

I've repaired cylinder block threads for both studs and bolts, which are often heavily torqued and are under significant load in use and never had one fail.

As far as I'm concerned the most significant advantage is that the original (or an original size) fastner can still be used instead of tapping to the next size up, with its additional issues of fit and clearance


M

Mike;

I shy away from the Heli-coils because I've had many pull out over the years. I probably shouldn't have said it the way I did without this explanation. I use only the smaller one 4-40 or less and they were used in aluminum alloy 356. I have used 1/4-32 special order for glo plugs in model engine heads. I now use a brass insert. The failures that I have had were not due to the heli-coil itself but by user neglegence from over tightening.

Sorry if this was misleading in any way. Sometime I forget the long answer is needed rather than a short one.


"Billy G"

 

[7HC]

Mike;

I shy away from the Heli-coils because I've had many pull out over the years. I probably shouldn't have said it the way I did without this explanation. I use only the smaller one 4-40 or less and they were used in aluminum alloy 356. I have used 1/4-32 special order for glo plugs in model engine heads. I now use a brass insert. The failures that I have had were not due to the heli-coil itself but by user neglegence from over tightening.

Sorry if this was misleading in any way. Sometime I forget the long answer is needed rather than a short one.


"Billy G"

Thanks Bill, I understand where you're coming from, and it's obvious that your experience has been different to mine.
Incidentally, although I've never had to repair glowplug threads, I have made a few successful spark plug thread repairs with Helicoils.
They're the ones I worried about the most, not because of the process, but because I knew that unskilled hands would be wrenching on the plugs eventually. :banghead:


M