PA120.3 threading advice

[gojirasan]

I have found that merely threading the holes on my PA120.3 to #6-32 to give me inadequate holding power for my application. I am talking about the 6 holes on the top and bottom of the rad, not the fan holes. The thin sheet metal just isn't strong enough. So I tried to epoxy some nuts inside the holes with some JB Weld. In order to align the nut threads with the hole and to hold the nut down while the epoxy sets I used a 6-32 screw which I had to wax so that the screw wouldn't bond to the nut. But somehow the wax managed to squeeze into the seam and the nuts just pulled right off after the epoxy set. So I am trying to think of a way of accomplishing this without wax. I don't actually own a #6-32 tap, although I might consider buying one. I am considering the idea of just bonding some square head bolts with the threads sticking out the top and bottom of the radiator, but I am a little worried that those threads sticking out are eventually going to cause some problem that I haven't anticipated. I am also considering the idea of epoxying a 1/8" strip of aluminum or steel and then tapping holes into that, but I would rather figure out a way to just epoxy the nuts without getting epoxy in the threads. Is there something obvious that I am missing?

[evil-98]

well that would explain it "I don't actually own a #6-32 tap"
of course it wont hold it with out it being drill/tapped correctly
consider using a larger screw? 8-32? and tap it this time?

[lennox]

if you already used a 6-32 self tap screw then you should definately go up to 8-32.. but use a tap this time.

[Zaskar]

They make 6-32 self tap screws? kind of a fine thread to self tap id think.
Using a standard 6-32 machine screw to thread itself would most likely mess the hole up almost like how over tightening a screw would just pull out the threads.

[spotswood]

They make 6-32 self tap screws? kind of a fine thread to self tap id think.
Using a standard 6-32 machine screw to thread itself would most likely mess the hole up almost like how over tightening a screw would just pull out the threads.
I'd recommend bumping up to a #8 tap.

[Zaskar]

I'd recommend bumping up to a #8 tap.

Outta curiosity would that slight jump require redrilling the holes?

[gojirasan]

Ah. I see. I did re-drill the hole to 0.143" (IIRC), but i tried to just screw a fastener in to "tap" it. How can you properly tap 1/16" of sheet metal? I don't think that is even enough for one full thread. That's what I don't get. And why I feel that using a nut is the correct way to get the job done. But if a proper tap really does make such a difference then I will buy one. #8 huh? But all my fasteners are #6. I guess at this point I would have no choice though. All new fasteners and a #8 tap. Any recommendations for a specific tap? And what about the sticking a fastener up through the hole idea? I am kind of tempted by that. Can anyone foresee problems there? I am trying to mount some legs on the bottom, the thermochill shroud on the side, and a pump with reservoir top on the top. So lots of stuff is fastening to those holes. I guess I could even drill some more holes while I'm at it.

[spotswood]

Outta curiosity would that slight jump require redrilling the holes?
It would depend on how bad/big the new holes are. :shrug:

[spotswood]

Ah. I see. I did re-drill the hole to 0.143" (IIRC), but i tried to just screw a fastener in to "tap" it. How can you properly tap 1/16" of sheet metal? I don't think that is even enough for one full thread. That's what I don't get. And why I feel that using a nut is the correct way to get the job done. But if a proper tap really does make such a difference then I will buy one. #8 huh? But all my fasteners are #6. I guess at this point I would have no choice though. All new fasteners and a #8 tap. Any recommendations for a specific tap? And what about the sticking a fastener up through the hole idea? I am kind of tempted by that. Can anyone foresee problems there? I am trying to mount some legs on the bottom, the thermochill shroud on the side, and a pump with reservoir top on the top. So lots of stuff is fastening to those holes. I guess I could even drill some more holes while I'm at it.

Ugh, the rad's holes are (were) the correct size for a #6 tap. There wasn't any need to re-drill them. :shakes:

Yes, a #6 tap would have made enough threads in that gauge metal to hold really well.

To avoid puncturing the rad, I use a tap with very few "starter" threads (chamfer). Search for "hand taps" at mcmaster.com :up:

Rivet nuts seem to be popular here at XS, though I'm not sure if they would work in the holes you are using. Any chance you could post some pics of that rad setup?

Your "sticking a fastener up through the hole idea" is a good one, but again I'm having trouble picturing it in my head.

You could go with a "layered" solution....buy some 1/8 thick aluminum and fasten everything to it by by drilling and taping that to your hearts content. Then fasten the plate to the rad with the existing rad's holes. :shrug:

[gojirasan]

Thanks for the advice. I see that I should have just bought a #6 tap in the first place. I should have asked this question before I went ahead and actually did anything to the rad :). I was going to wait to post pics of my setup until I was done, but I will see if I can post some pics this weekend. It's an almost completely external setup mounted on some homemade legs. My case is uATX. So I can't really fit anything in there. Actually the setup is even more complicated because I am trying to fasten two radiators together in addition to all the other stuff I just mentioned. But I also want it to be a modular setup so that I don't always have to use both rads.

[Zaskar]

To avoid puncturing the rad, I use a tap with very few "starter" threads (chamfer). Search for "hand taps" at mcmaster.com :up:

Whats a good amount of starter holes for this application?

They have 3

Bottoming Taps that have 1-2 starter threads
Plug which have 3-4
Taper which have 7-10 (I assume thats too many for this application)

[gojirasan]

Funny I was just on mcmaster looking at those. Put a 4-40, a 6-32 and a 8-32 in my cart. (Never know when you're going to need a tap and the shipping is a killer). I selected bottoming taps, but I wonder if I could get away using a plug type. How much harder to use is a bottom tap compared to a plug tap? And what about coatings? Is titanium nitride of any value other than looking cool?

[Zaskar]

From what mcmaster said for High Speed Steel Titanium-Nitrade is bad for wrought aluminum (unsure if that applies to the aluminum that we would be using here) but Nitrade was good for it.
But then there is Cobalt Steel Which they say is better then High Speed Steel for most metals (aluminum is one of them) and it comes in Titanium Nitrade or natural finish.

Difference is only like a buck or 2, wonder whats best.

[Waterlogged]

For most ppl here, High speed steel is more than good enough. Those specialized coatings are geared more towards production shops that need to be cost effective in a more parts over a shorter time span sense.

As far as which style tap, Plug would be best choice for open hole taping while Bottoming will yield better blind hole taping results (especially if it's shallow).

[Zaskar]

Cool man.

Did a bit of reading up on it last night, seems bottoming is not intended to be used for starting threads, but rather to repair pre existing threads.

Probably could be used in conjunction with a plug tap for deep holes, after using the plug to start the threading, and then using the bottoming to finish it up so you get threads al the way at the bottom, but that doesnt apply for this.

[Waterlogged]

Cool man.

Did a bit of reading up on it last night, seems bottoming is not intended to be used for starting threads, but rather to repair pre existing threads.

Probably could be used in conjunction with a plug tap for deep holes, after using the plug to start the threading, and then using the bottoming to finish it up so you get threads al the way at the bottom, but that doesnt apply for this.

BAH! The shops I worked at used bottoming to fully tap holes all the time. It does take a bit of extra care to start them properly (by this I mean straight) by hand though.


Rivet nuts are a really good idea, for TC rads, I'd recommend #98005A120 (SS) @ Mcmaster or #98560A531 (plain steel). These are 2 piece inserts that I've used on cars before with great success. I'll also use them on my TC's when the time comes a 6-32 will no longer hold tightly.

[Kilyin]

I threaded 5 Thermochills (fan holes, not the ones you're talking about) with 6-32 machine screws and they're all working as intended. I don't see why you need a tap?

[Zaskar]

I threaded 5 Thermochills (fan holes, not the ones you're talking about) with 6-32 machine screws and they're all working as intended. I don't see why you need a tap?

Cleaner threads, it will provide a stronger connection that will last longer under stress/load.

[Big_Daddy]

He's talking about these

http://farm3.static.flickr.com/2378/2558332797_2bb4f6c229_m.jpg (http://www.flickr.com/photos/bigdaddy501/2558332797/sizes/l/)

http://farm4.static.flickr.com/3065/2558332995_c32d29c0a0_m.jpg (http://www.flickr.com/photos/bigdaddy501/2558332995/sizes/l/)

And I so recommend you drill and put in rivet nuts on those as well. They'd work perfectly. Hold much longer, and be much more sturdy then just tapping. Also, you could stay with 6/32" screws (bolts that is)

[gojirasan]

98560A531 Very nice indeed if you have a rivet gun/tool. I have access to some machine shop stuff, but not to rivet tools. Definitely the Right Way to do business though.

[Zaskar]

Is any tap lubricant needed for tapping it, or can you get just as high quality a threading without it on the thin metal?

Also if you have to rethread a hole with the same size tap, can you still use a plug tap (slight taper) or will the tapered threads not allow it to align properly with the old threads and risk cutting into them and cross threading?

[Waterlogged]

Very nice indeed if you have a rivet gun/tool. I have access to some machine shop stuff, but not to rivet tools. Definitely the Right Way to do business though.

Well, I bought a complete kit from J.C. Whitney a very very long time ago that had steel RN's in 6-32, 8-32, 10-32, 10-24, & 1/4-20 and alum RN's in 5/16-18 & 3/8-16. It also had the gun, mandrels and nose pieces. Unfortunately, they don't sell that kit anymore as it looks like they've opted to carry crappier versions from another company. As a substitute, you can get a decent inserting tool from Mcmaster, 98590A220 looks to be a very good tool for inserting rivet nuts.

[gojirasan]

It's described as "6-32 Thread Mandrel for Rivet Nut Insert Tool". That seems to imply that I still need a "rivet nut insert tool". I have to admit I don't really know anything about how rivets work. I've just seen the end result :). I'm still considering the idea of bending some 6-32 threaded rod into a right angle and JB Weld ing one branch of the angle to the inside lip so that the other leg sticks up through the hole maybe 3/4" or something. It would be the cheapest solution. So it is tempting. But at this point I don't have a lot of trust in the structural integrity of the JB Weld. Epoxy tends to be strong, but it depends so much on perfectly clean surfaces and just the right amount fo scratches to grab onto. I don't like having to rely on it when fasteners are an option. I should really post some pics of my setup so that I can request more specific advice, but I am reluctant to do that until I can actually show what the final product looks like.

[Big_Daddy]

I've posted it a hundred times now. ALL you need is this (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94100). It's $17 at Harbor Freight. It's got the 6/32" nose piece and a few others. Plus it does regular rivets too.

http://www.harborfreight.com/cpi/photos/94100-94199/94100.gif

[Waterlogged]

It's described as "6-32 Thread Mandrel for Rivet Nut Insert Tool". That seems to imply that I still need a "rivet nut insert tool". I have to admit I don't really know anything about how rivets work. I've just seen the end result :). I'm still considering the idea of bending some 6-32 threaded rod into a right angle and JB Weld ing one branch of the angle to the inside lip so that the other leg sticks up through the hole maybe 3/4" or something. It would be the cheapest solution. So it is tempting. But at this point I don't have a lot of trust in the structural integrity of the JB Weld. Epoxy tends to be strong, but it depends so much on perfectly clean surfaces and just the right amount fo scratches to grab onto. I don't like having to rely on it when fasteners are an option. I should really post some pics of my setup so that I can request more specific advice, but I am reluctant to do that until I can actually show what the final product looks like.

:doh: Your absolutely right :brick: The proper tool minus any mandrels is $52.36 so I'll rule that out.

Another "decent" option is 96349A101. All you need is an Allen and a open end or box wrench.

I've posted it a hundred times now. ALL you need is this (http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=94100). It's $17 at Harbor Freight. It's got the 6/32" nose piece and a few others. Plus it does regular rivets too.

http://www.harborfreight.com/cpi/photos/94100-94199/94100.gif

I have one similar to that and it can be quite clumsy at times, don't like it at all.

[Big_Daddy]

Clumsy is as Clums... nevermind.. :) It took me 3 rivet nuts to figure out the best way to do it. After that, the rest went in like butter.. (is that really good? :)) And for the 10 or 20 that you will use.. I think it's very worth it.

And btw, From Mcmasters 94370A260 has 6-32, 8-32, 10-24, and 1/4"-20 Included, for $39.50

Also, any reason your using rivet nut inserts, instead of rivet nuts? With the small flange, there really isn't much for the nut to grab on to. If you use standard rivet nuts, it works much better. I'm using the ALU ones, but you could get steel as well. 93482A605 are the ones that I used with great success.

[Zaskar]

About to place order, just want to be sure on 1 last detail. When tapping the radiator you dont need to use tapping lubricant like you would for normal deeper threadings do you (to get the same quality tapping atleast, I know you don't need to use it to get it to tap, but I don't want the threads to be of lower quality)

[Big_Daddy]

No, you don't need any taping lube, not in the least

[Kilyin]

Cleaner threads, it will provide a stronger connection that will last longer under stress/load.

Not trying to be argumentative here, but I can grasp my rads by the fans and violently shake them and they are rock solid (with 2 screws per fan, machine screw threaded). I don't see how you're going to get a stronger connection?

[Zaskar]

Not trying to be argumentative here, but I can grasp my rads by the fans and violently shake them and they are rock solid (with 2 screws per fan, machine screw threaded). I don't see how you're going to get a stronger connection?

Well thats the theory :P The threads should be sharper and cleaner when using a tap, but if you got it strong enough without then thats great :D
I just wouldn't recommend it cause that may not always be the case.

And thanks Big_Daddy, that was the last thing I needed to know, placing the McMaster order in a few then, just gotta make sure im not forgetting anything :D

[Kilyin]

Well thats the theory :P The threads should be sharper and cleaner when using a tap, but if you got it strong enough without then thats great :D
I just wouldn't recommend it cause that may not always be the case.

And thanks Big_Daddy, that was the last thing I needed to know, placing the McMaster order in a few then, just gotta make sure im not forgetting anything :D

Well if anyone is as lazy as I am (and I'm sure there are some) the thing to do is use a fan for the actual threading to hold the screw 'straight'... while using a credit card or similar under the hole to prevent accidentally piercing anything (although if you can pierce the rad without a pointed tip self tapper, you're doing it wrong). After that it's just a matter of elbow grease and turning the screwdriver. Worked a treat for me.

[gojirasan]

I just realized rivets aren't going to work for me. And neither is going with male threads sticking out of the rad. The main point of securing extra threads to the rad in the first place is so that I can secure my Thermochill shroud which slides over and secures to the top holes (that may be what the top holes are there for). Since it slides over and needs to seal as tightly as possible (even thinking about using a gasket or some silicone), I can't have any protrusions at the top/bottom. So it looks like either tapping to 8-32 or using adhesive to hold down a nut of some kind (possibly a homemade one though) are the only choices. I'm really hesitant to go with the larger fasteners, so I think I am going to try the adhesive route again. If I make my own nuts I can make them say 3/8" x 2". With all that extra surface to epoxy it should be strong and I shouldn't have to use wax or oil to protect the hold down thread from bonding to the nut. As far as bond strength, it just needs to hold the nut from falling out when I thread into it, but it needs to be a reliable bond.

[spotswood]

I just realized rivets aren't going to work for me. And neither is going with male threads sticking out of the rad. The main point of securing extra threads to the rad in the first place is so that I can secure my Thermochill shroud which slides over and secures to the top holes (that may be what the top holes are there for). Since it slides over and needs to seal as tightly as possible (even thinking about using a gasket or some silicone), I can't have any protrusions at the top/bottom. So it looks like either tapping to 8-32 or using adhesive to hold down a nut of some kind (possibly a homemade one though) are the only choices. I'm really hesitant to go with the larger fasteners, so I think I am going to try the adhesive route again. If I make my own nuts I can make them say 3/8" x 2". With all that extra surface to epoxy it should be strong and I shouldn't have to use wax or oil to protect the hold down thread from bonding to the nut. As far as bond strength, it just needs to hold the nut from falling out when I thread into it, but it needs to be a reliable bond.

Then how about using double-sided tape to hold the nut in place? :shrug: