Tankless Coil - Broken Bolts

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Old 06-15-11, 09:28 AM
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Tankless Coil - Broken Bolts

While removing the tankless coil from my Weil-McLain B-68 boiler, five of the six bolts broke off. The boiler was installed in 1988. The bolts are 3/8-16 3/4". I will need to drill out the bolts and tap the holes. Should I use a 3/8-16 tap, or should I go one size larger, say 7/16-14? Any advise will be greatly appreciated. Thanks!
 
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Old 06-15-11, 03:52 PM
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You should try to use the same size if possible.
 
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Old 06-20-11, 09:34 AM
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Thanks. Advice (spelled correctly this time) appreciated!

How much torque should be applied when tightening the bolts?
 
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Old 06-20-11, 10:49 AM
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How much torque should be applied when tightening the bolts?
It depends on the grade of hardware you use, and whether or not the threads are dry or lubed.

I personally would use some 'Lubriplate' anti-sieze compound, and this would lube the threads.

Standard torque chart should be followed, see:

Standard Torque Chart

If you've ever done any engine assembly you know that head bolts have recommended 'patterns' for tightening in order to pull the bolts down evenly. Do the same with these. Criss-cross back and forth and pull the bolts down evenly. Don't go to the max tight all at once, start with say 5 ft-lb, then 10, then 15, then 20 (assuming grade 5 bolts). I would stop at 20 and run for a while and watch. Run for a couple weeks and monitor for leaks. Then, re-torque to 20 and call it good.
 
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Old 06-20-11, 12:24 PM
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Would Permatex 80078 Anti-Seize Lubricant be okay?

I'm nervous about using the existing 3/8-16 holes because I'm afraid the bolts might not hold well. Is it hard to drill and and tap bolt holes in a cast iron boiler? I realize I would have to be careful with the drill because the holes are not through holes. I also know that I would have to buy a drill correctly sized for the tap. Since I am going to a larger size bolt (7/16), I would also need to drill the holes in the tankless coil flange to a bigger size. Is all this a bad idea in your opinion?
 
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Old 06-20-11, 03:14 PM
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Make sure you use a bottom tap if the holes don't go all the way through.
 
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Old 06-20-11, 03:27 PM
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Originally Posted by drooplug View Post
Make sure you use a bottom tap if the holes don't go all the way through.
But you usually need to start with a tapered or maybe plug tap.
 
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Old 06-20-11, 08:05 PM
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Yeah, Permatex, Lubriplate... I like the Lubriplate that comes in a 'chapstick' type dispenser, very handy.

Look at it this way... TRY to stick with the 3/8. You can always take metal away and go to the larger size if you can't do it. Then, I would even consider using a 'Heli-coil' thread repair kit, but I don't know if you can get the special tap that HeliCoil uses in a 'bottom tap'... Yes, you can, lots of info in this PDF.

http://emhartamericas.com/pdf/Heli%2...20Rev.5%20.pdf

And Ray is right, you do want to start with a standard tapered tap to get the threads started. Then switch to a bottom tap. And above ALL ELSE, USE THREAD CUTTING OIL! The very last thing you want is to break a tap in one of them holes... if you break a tap, you are kinda SOL... they are damn near impossible to get out. You will NEVER drill into a broken tap... take your time, in a little, out, clean the chips, GO SLOW!

Start with a small drill bit, exactly in the center of the bolt. If you are careful and can drill right down the center, and carefully step up in size you won't damage the existing threads. If you choose the final drill bit correctly, you might find that the old bolt threads just kinda spiral out as you tap.
 
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Old 06-20-11, 09:05 PM
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I don't know about your particular boiler but some have cast "bosses" for the studs or bolts. Going to a larger size could seriously weaken the bosses through removal of strengthening metal.

Also, I would suggest that you not use bolts but studs with flat washers and nuts.
 
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Old 06-21-11, 04:36 PM
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Great information! Thanks to everyone!
 
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Old 06-22-11, 06:32 AM
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I lost count of how many broken studs I removed over the years. I found that the moist important tool in your arsenal for this job is a set of high quality drill bits. As Trooper says, start dead center with a small bit keep increasing the bit size and you'll usually get to the point that the remaining thread material spins out.

I've never had to retap a hole per se. It's just cleaning out some rust and metal chips that might remain. I would not go a size bigger on the bolts and you really shouldn't have to if you're careful.
 
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Old 06-22-11, 04:17 PM
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Going with heatpro's lead... was just looking at a standard drill size chart, and at the dimensions of 3/8 bolt threads.

The 'minor' diameter of a 3/8-16 bolt or stud is 0.297 so you most definitely want to stay below that size. There are drill bits at both 0.290 and 0.295 but you most likely will be wanting to use something a smaller than that... unless you know that you are dead center down the middle of the bolt.
 
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Old 07-11-11, 01:25 PM
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I'm ready to install the new tankless coil. It came with a rubber gasket. No instructions were included. Should I put any kind of sealant on the gasket? I thought a saw a forum posting somewhere that recommended applying a high temperature silicone sealant of some sort to the gasket.
 
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Old 07-15-11, 04:36 PM
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Anybody ever try easy-out bits.I used em on my car for head bolts and they work great.Didn't need a tap ether.

And I like Furds idea with the studs.When I did my coil if I would have thought of it I would have definitely used studs instead of bolts.
 
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Old 07-15-11, 04:53 PM
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I have never been successful in trying to use easy outs on a boiler.
 
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Old 07-15-11, 05:00 PM
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Someone (permatex?) makes a sealant which comes in a copper colored tube. Can't remember what it's called but often comes with replacement coils. I use a bead inside & outside of the stud holes on both sides of the gasket. Never had a leak.
 
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Old 07-16-11, 03:44 PM
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Thanks, Grady. Is it Permatex 81878?
Permatex 81878 | Liquid Gasketing & Silicone Sealants
 
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Old 07-17-11, 03:00 PM
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That's the stuff. Works well.
 
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Old 07-18-11, 04:36 PM
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also use never-seez compound on your studs/bolts. this will make life heavenly when it comes time to remove them again.
 
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Old 07-18-11, 04:55 PM
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Originally Posted by RDSTEAM View Post
also use never-seez compound on your studs/bolts. this will make life heavenly when it comes time to remove them again.
Good point. If not heavenly, at least not hellish. If using studs, I generally don't use never-seez on the boiler end but most certainly on the coil end.
 
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Old 07-18-11, 05:15 PM
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I think it's 'Loctite' that makes the anti-sieze in a very convenient 'chapstick' type tube. I'll never go back to the can and brush...


image courtesy amazon.com

hmmmm... whatever happened to the rule, I before E except after C ?

Oh, one more unrelated point. Do NOT use this stuff on wheel lugs on your car/truck! and please don't ask how I know!
 
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Old 07-31-11, 12:10 PM
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I installed the new tankless coil a few weeks ago. The new tankless coil came with steel studs and brass nuts. I torqued the nuts gradually to 20 ft-lb over a period of about two weeks.

Now it's time to do the soldering. I need to install copper 1/2" male pipe fittings into the female inlet and outlet fittings on the tankless coil. Elbows will need to be soldered onto the 1/2" male pipe fittings. Is it okay to screw the 1/2" pipe fittings into the inlet and outlet first, then solder the elbows on? I'm a little concerned about all the heat. I would prefer to solder the elbows on before screwing the fittings into tankless coil, but I worry that I will either have to over tighten or under tighten the fittings to get the elbows in the correct position.

Thanks for any advice, and all the prior help.

Joe
 
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Old 08-01-11, 07:03 PM
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I suggest using brass nipples & fittings until you get a foot or so from the coil. Then you can switch to copper.
 
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Old 08-04-11, 02:38 AM
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Thanks, Grady. Would you use pipe dope, or teflon tape?
 
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Old 08-04-11, 06:09 AM
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I'll let Grady answer for himself, but in meantime I'll tell you what I would use.

First let me say that tape and/or dope is NOT a pipe 'sealant' even though they may be labeled as such. They are more rightly called LUBRICANTS. They should not be relied upon to act as a sealant.

Pipe threads are designed to create a METAL TO METAL seal when they are properly tightened. This is why they are tapered threads. In general, they are designed for EIGHT threads to be engaged when properly installed. (more or less depending on the size of the pipe).

You will see many installers wrapping six , eight , ten wraps of teflon around the threads... do NOT use that much! You will not be able to tighten the fitting enough to get the required metal to metal seal. I would not use more than TWO wraps and I recommend only do ONE *or one and a half... just enough to hold the tape to the pipe with a little overlap of the tape*. Then I would smear a small amount of dope on top of that.

Keep tape and/or dope OFF the first two to three threads of the fitting. You want those CLEAN in order to get your metal to metal seal. This also prevents slivers of the teflon tape from getting into the water system.

The bottom line is that in order to get the required metal to metal seal on the threads you must use a minimum amount of 'stuff' on the threads which would prevent you from tightening the joint enough to achieve the seal.

Be careful when working with brass and copper... it IS possible to OVER tighten them and deform the threads.
 
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Old 08-04-11, 03:22 PM
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Trooper pretty well covered it. I generally use a non gritty teflon based paste but on domestic water it's your choice as far as dope or tape. Use either sparingly. If little is good, a lot is better? NOT!!!!!
 
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