fuel tank cleat attachment methods

Considering that the factory drilled then right into the floor during the 90s to expose the core to water on my boat, then anything you do will be better. I would agree that if you set something in epoxy like all-thread or a rod, it will be tough to get out if done right. If fact, I have some screws in a door at home I used epoxy on that will not come out, period. I guess I should have drilled and threaded them in instead of just sticking them into wet epoxy. Amazing stuff for sure......
 
Thanks fellas for your advise and words of wisdom (read encouragement). I think I'll try the threaded rod technique, since I have some on hand. As far as doing it right, my thoughts are as follows: First to drill out a pilot hole in the previous epoxy plug, tap with threads, wet out holes, mix in some cabosil in the remaining epoxy mix, apply to threads, thread to bottom and cure in place. Reattach cleats.
 
The issue with using a tap in a fairly short hole, is that you may not be able to get the tap all of the way into the hole. You need to use what is called Blind hole taps: You start with a tap which as flat threads and a modest taper, then the second tap, is beginning to cut the threads--the final tap is almost square threads, and gives good threads all of the way to the bottom.

taprep01.jpg


When using a blind hole tap you have to back it out more often than a thru tap, and best to use some compressed air to get debris and tailings out of the hole.

It is probably easier to over drill the hole, snug to the rid, and then put some epoxy into the hole, and also coat the threads with thickened epoxy,

The first way with blind hole, tap, you don't need much thickening.
 
thataway":1ryou5oe said:
It is probably easier to over drill the hole, snug to the rid, and then put some epoxy into the hole, and also coat the threads with thickened epoxy, .
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Thanks Bob. I do have taps like that for a blind hole. I simply picked up a cheap single and ground down the pointy end. It works fine.
As for above, I'm not sure what you meant by "snug to the rid". Please elaborate.
 
A couple of ideas/thoughts:

1) If you have a fastener epoxied into a hole, and you later want to remove it, try heating the fastener. I've had good luck with that method as epoxy is quite vulnerable to high heat (it softens). You can exploit that weakness.

2) Another way to do it in the first place (although it's more similar to tapping in that the fastener is not bonded into the hole) is to wax a fastener, then epoxy it into the hole, and then after the epoxy cures remove the fastener and de-wax it (or use an identical fresh fastener), and then use the hole much like you would a tapped one.

I've known the type of tap that can reach to the (flat) bottom of a hole as a bottoming tap, so perhaps that's another name for it. That's what I used on the trim tab fastener holes, for example.
 
There is a different between a blind hole tap and bottoming tap. The Blind hole comes in a set, and is more satisfactory for hard materials. The Bottoming tap only has chamfering for the first 1 to 2 threads-and will not fully thread to the bottom of the hole, unless there is a little taper (easy to do) on the last two threads of the bolt. The bottoming tap will also be a bit harder to use.
 
thataway":28jlhnye said:
There is a different between a blind hole tap and bottoming tap. The Blind hole comes in a set, and is more satisfactory for hard materials. The Bottoming tap only has chamfering for the first 1 to 2 threads-and will not fully thread to the bottom of the hole, unless there is a little taper (easy to do) on the last two threads of the bolt. The bottoming tap will also be a bit harder to use.
Click to expand...

I'm wonder if I'm just using terminology wrong or if I have the "wrong" taps: The sizes for which I have the (so called) bottoming tap have three taps in the set (all three the same thread size in a little box). One is labelled "taper," one "plug," and one "bottom." I've actually never used the "plug" one, but used the taper and bottom for tapping blind holes in my boat. Should I be using something else? These seemed to work well, but if there is something better I'm all ears (as I expect to continue to tap epoxy for this and that).

Thanks.

Edited to add: I decided to look this up on Wikipedia for starters, since it seems silly to have numerous sets of three taps and not ever use one of them (or know why). My sets look like the first line drawing you come to on the right as you scroll down, which is this one:

TapTypes.gif

http://en.wikipedia.org/wiki/Tap_and_die

I don't have tons of the sets, just a few in the sizes I use most often (1/4-20, 10-24, 8-32 IIRC)
 
You have the correct set--use the Taper, then the plug and finally the bottoming. There is another way to do it and that is to use only one tap--which has chamfer on the first one or two and a half threads. Your final tap, assures that there are threads all of the way to the bottom of the hole. The single tap will not have complete threads to the bottom--although you may force or cut threads with the threaded rod or bolt (or booger up the last two threads)...
 
Thanks for the confirmation. If I remember correctly, I went right from the taper to the bottoming tap and everything felt good; perhaps that worked because even "hard" epoxy is softer than, say, steel. (I did also sometimes use a drill one size down from what was recommended.)

Next time I'll try progressing through all three though - maybe it will work even better.
 
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