helicoil fight

[DCoul]

I know this shouldn't be so hard. I'm putting helicoils in case where the scavenger pump is attached on my 1942 WLA. I've gone through a bunch of helicoils. They seem to bind before I can get the recessed far enough.

When it binds, it bends the tang at the far end of the helicoil. It there something to lubricate it well enough to not bind? I've tried locktite, bearing grease, motor oil, eventually tried WD 40. Seem like the aluminum is soft and/or has imperfectons the coil binds on.

Any tips.

Thanks all.

[exeric]

Are you using the Heli-coil insertion tool? Also, what size insert? Needless to say, if the tapped hole is not deep enough, the insert will stop and the tang will break. You may need to use a bottoming Heli-coil tap to maximize thread depth. . . Heli-coils can be frustrating.

[DCoul]

I'm using the 1/4-24 tap that came with the kit. It had the pointed end which wasn't allowing me to go nearly deep enough. I squared/rounded the end off so that I could go deeper. Still using all the initial threads at the point. I feel like the tip of the oil catches on the softer aluminum and then the tang breaks. Or, the threads are not perfect. This last one I chased with a 1/4"-24 bolt. Still no love. I've gotten pretty good at removing them because the don't go all the way in. I've had to cut off a couple coils because they are too long for the threaded hole. I was trying to keep the holes the original bolt size.

[T. Cotten]

DCoul!

1/4"-24 is the one size that doesn't need a special tap, as a 5/16"-24 tap does the job quite well, and they are a lot easier to find with a bottoming cut.

Still, I would carefully drill the hole a little deeper if possible,

Good luck!

....Cotten
PS: There probably hundreds of two-brush generators running now on earlier motorcases without drilling out their 1/4" mounting holes, since the Helicoil fits into the generators' 5/16" holes. If they are strong enough to hang a generator on, I'm sure they will hold an oilpump....
PPS: A piece of #7 (~.200") rod and a hacksaw makes a better insertion tool than the kit's, too!

[BigLakeBob]

I'm using the 1/4-24 tap that came with the kit. It had the pointed end which wasn't allowing me to go nearly deep enough. I squared/rounded the end off so that I could go deeper. Still using all the initial threads at the point. I feel like the tip of the oil catches on the softer aluminum and then the tang breaks. Or, the threads are not perfect. This last one I chased with a 1/4"-24 bolt. Still no love. I've gotten pretty good at removing them because the don't go all the way in. I've had to cut off a couple coils because they are too long for the threaded hole. I was trying to keep the holes the original bolt size.

At this point I would take a separate block of aluminum longer than your helicoil. Drill and tap thru using what was provided in your kit. Countersink the hole as said in the instructions or slightly larger than the O.D. of the helicoil. The helicoil should be able to be inserted all the way through the block of aluminum. If not, your drill is the incorrect size or the tap isn't correct for the helicoil. I don't know what you mean by 'This last one I chased with a 1/4"-24 bolt. Still no love'? Helicoils are difficult to shorten without throwing a burr, the best method I have found is to either use a grinder, cutoff wheel, or dikes then deburr. Either way it needs done before installation!

[larry]

A Helicoil can be shortened after installation by using a 3 corner needle file to make a notch then breaking off. The tang is notched and breaks cleanly, this method will break the same.

[DCoul]

Thanks Cotton. I don't feel like that insertion tool that came with the kit has a very good grip on the tang. I like your tool. I think I'll make my own. It seems like as soon as I get some resistance it bends or breaks the tang

[DCoul]

Thanks Big Lake. What I meant was, after drilling and tapping the hole, I wanted to test the threads before wasting and removing another helicoil. I took my tap and it fit in a nut that I have. The bolt that fits the nut is the same threads as the tapped hole. I threaded the bolt into the tapped hole, no helicoil and it went in fine. Pretty tight actually. The bolt went in so it seems like the helicoil would but it still got hung up and broke the tang.

[BigLakeBob]

Thanks Big Lake. What I meant was, after drilling and tapping the hole, I wanted to test the threads before wasting and removing another helicoil. I took my tap and it fit in a nut that I have. The bolt that fits the nut is the same threads as the tapped hole. I threaded the bolt into the tapped hole, no helicoil and it went in fine. Pretty tight actually. The bolt went in so it seems like the helicoil would but it still got hung up and broke the tang.

You say you threaded the bolt into the tapped hole without the helicoil and it went in but was pretty tight. Without the helicoil the bolt should fall into the hole. The tap drill size for a 1/4-24 helicoil is 17/64 (.265) where the major diameter of a 1/4-24 bolt is 1/4 (.250). With 1/64 (.015) difference there should be no resistance on the bolt going in the hole. Something doesn't seem right here. Are you drilling it the correct size before tapping, maybe you were supplied the wrong drill? You also say the tap fit into the nut you have, this doesn't make sense. The helicoil tap is a lot larger and should not fit any standard nut.

[DCoul]

I'll take a photo of what I was sent. I believe it is the 5540-4. I'm using a 1/4" bit. It sounds like I should be using a 17/64 bit? The bit didn't come with the kit. If so, this would make sense as to why I'm getting so much resistance while screwing in the helicoil. I've got a feeling I'm going to be drilling the scavenger pump holes to fit 1/4-24 studs.

edit: Damn! You're correct BigLakeBob. How am I going to fix this one?! I'm a 1/64 too small!

[BigLakeBob]

If you are doing this manually, do not try and drill the 1/64 out. The drill will grab and ruin your day. I would get a 17/64 reamer to open the holes up, even a cheap one will work. If you have the means or a friend with a milling machine, a guide block to keep the reamer straight would definitely be a plus. Good luck, at least the problem has been found.

[T. Cotten]

...edit: Damn! You're correct BigLakeBob. How am I going to fix this one?! I'm a 1/64 too small!

DCoul!

Your Helicoil tap should have already relieved the inside diameter.
It has a cutting edge ahead of the threads, as do most taps.

I still suspect the issue is one of depth, not diameter.

....Cotten

[DCoul]

reamer.jpg

I see some that are like a real coarse drill bit and then there is this type. This type looks like it would work best if by hand. Sound right?

[BigLakeBob]

DCoul!

Your Helicoil tap should have already relieved the inside diameter.
It has a cutting edge ahead of the threads, as do most taps.

I still suspect the issue is one of depth, not diameter.

....Cotten

I'm sorry Mr. Cotten but you are incorrect, taps do not size the minor diameter. I am aware they do make a drill/ tap combination for production work but we are not talking that here. Even if what you are saying could be remotely correct, which it isn't, if you read post #3 you will see he took the lead off of the tap. So what you are saying is that from now on I do not need to use the correct size drill as stated in the machinery handbook or on any tap/drill chart hanging on every machine shop wall across the globe, this will be some sad news for the drill manufacturers. DCoul could also have a depth issue but why in the hell would you not make the minor diameter of the tap the correct size?

[BigLakeBob]

[ATTACH=CONFIG]20975[/ATTACH]

I see some that are like a real coarse drill bit and then there is this type. This type looks like it would work best if by hand. Sound right?

Yes, in my opinion (I'm sure someone will disagree), a straight flutted reamer works best by hand. If it were me I would use a standard tap wrench holding onto the reamer diameter and run it through the holes using some type of cutting fluid. I still suggest a guide block to keep the reamer straight. Take your time, its your engine case. As I said previously, if you can test (duplicate) all this in a spare piece of aluminum it could prove all this out without spoiling the case. Good luck, I believe you have found the problem.