Drilling and Tapping the Frame

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turbocruiser

turbocruiser

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Hi folks, I would like to ask how acceptable it is to drill and tap into the frame ( specifically the bottom face of the box frame channel )? I would like to thread two to three holes in specific places. These holes would match the size of some of the already existing holes in other places. IIRC most of the already existing holes take bolts between 12 to 14 mm heads to give an idea of the size of hole I'd want to drill and tap. Anyway, I would think that with all the various holes and slots and such on the frame from the factory, two to three small holes would make no difference at all but before I go for it, thought I'd ask!!!
 
I would not hesitate to drill a hole in there, structure strength wise, but isn't there stuff (wiring etc) in there that could be punctured?
E
 
There is nothing to tap into.

The threaded holes in the frame are captive nuts that are welded to the back side. Drilling in other areas will not give you enough wall thickness to do anything with.
 
[quote author=cruiserdan link=board=2;threadid=14169;start=msg132048#msg132048 date=1080973832]
There is nothing to tap into.

The threaded holes in the frame are captive nuts that are welded to the back side. Drilling in other areas will not give you enough wall thickness to do anything with.
[/quote]

Okay, I thought that was a possibility so, plan B is, is there a source for u-bolts similar to the ones that Slee uses for the sliders and skids but that would go from the top of the frame to the bottom with the bolts on the bottom? I need a safe and secure way to attach something to the bottom face of the box frame channel. Thanks. Dan, welcome back from fishin, wanna go fly fish some trout with me tomorrow? It'll be about forty degrees, some snow flurry and lots of schnapps to keep warm; a lot different from Sea of Cortez fishin, well except for the EtOH consumption!!! Thanks all, please keep the suggestions coming on this subject.
 
You can have u-bolts custom made by some spring shops. Depending on the area of the frame that you are planning on using it may be a challenge to get something that long over the top of the frame without interference from the body.
 
I have used them in several projects. I wonder about strength in this application.
 
Depending upon the application - the frame rails are thick enough for threads, i.e. mounting brakets, etc. Also depending how the frame was made, the bottom / top sections are (used to be in older cruisers) are two "C" sections or about 25 mm in depth.

General rule of thumb is the thread depth should at a minium -> equal to 1.5 times the diameter of the bolt.

What are you attaching to the bottom of the frame?
 
[quote author=Safado link=board=2;threadid=14169;start=msg132159#msg132159 date=1081013297]
What's the application?
[/quote]

Exhaust pipe skid plate! I hope I can finger it out.
 
[quote author=Warthog link=board=2;threadid=14169;start=msg132182#msg132182 date=1081017083]
Depending upon the application - the frame rails are thick enough for threads, i.e. mounting brakets, etc. Also depending how the frame was made, the bottom / top sections are (used to be in older cruisers) are two "C" sections or about 25 mm in depth.
[/quote]

Yes, this is what I was looking at, it seems that the metal is twice as thick on the top and bottom faces due to the overlapping of the channels. Also, luckily, I will be able to use about two already existing factory captured nuts so these other two would thread in for extra strength. Also the geometry of the exhaust pipe skid plate is such that the force will transmit up and back or forth but not down so not sure if that matters in terms of the natural strengths of bolts (pulling vs. shearing )? The upwards force would be handled by the frame so only the back and forth lateral forces from dragging over obstacles would be the concern. Perhaps custom u-bolts are better but I was hoping that there would be a source like McMaster that sells so many custom configurations that i would not have to have a spring shop make them? Anyway, I love welding and fabricating and I have all the time in the world for this project but as a start, finalizing a mounting method then dictates the design from there on. Thanks folks, I appreciate you thinking this through with me.
 
I would think that the inserts George mentioned would be OK for a project like you outlined. I think that the bottom of the fame would be marginal for tapping threads for a 6mm bolt. You would likely want 8 or 10mm. I suggest you use antisieze on any bolts used in these inserts to reduce the possibility of spinning the inserts during future disassembly.
I used this type of insert for my tailgate inner panel, license plate bracket and for my snorkel pillar bracket. In order to set the larger inserts you will likely need a hydraulic setting tool, they are pretty spendy.
 
25mm? that is about an inch! that is thick

could you fabricate a bracket that welds to the frame then bolt to the bracket? this would have the added benefit of spreading to load into the frame along a larger area
 
[quote author=cruiserdan link=board=2;threadid=14169;start=msg132205#msg132205 date=1081023902]
I would think that the inserts George mentioned would be OK for a project like you outlined. I think that the bottom of the fame would be marginal for tapping threads for a 6mm bolt. You would likely want 8 or 10mm. I suggest you use antisieze on any bolts used in these inserts to reduce the possibility of spinning the inserts during future disassembly.
I used this type of insert for my tailgate inner panel, license plate bracket and for my snorkel pillar bracket. In order to set the larger inserts you will likely need a hydraulic setting tool, they are pretty spendy.
[/quote]

I've used 8mm (or sae equivalent) and you don't need a hydraulic tool. There is a cheap tool that you can buy with the AVK fasteners - basically a bolt and special nut/collet with spurs on it - you just use two spanners to set the rivnut - real easy to do. The power of the lever (i.e. the thread on the bolt)... The big rivnuts seem easier to set than the small ones - because the spurs on the nut/collet are bigger and grip very well.

george.
 
The frames are definitely not anywhere near 25mm in thickness. More likely around 8mm where it's doubled. For H.D. ubolts, contact a boat trailer company such as EZ Loader. They're all over boat trailers because of the need to alter them for different boat configurations. I also had a trailer fabricator locally make a set of large U bolts a couple years back. Cheap and did it on the spot for me. I think these will provide enough strength for what you're doing. Getting them around the frame with the floorpan sitting on it will be tough, though. What about drilling sideways through the frame and using reinforcing plates and through bolts to essentially clamp a mount onto the frame?

DougM
 
[quote author=RavenTai link=board=2;threadid=14169;start=msg132207#msg132207 date=1081024947]
25mm? that is about an inch! that is thick

could you fabricate a bracket that welds to the frame then bolt to the bracket? this would have the added benefit of spreading to load into the frame along a larger area
[/quote]

Yes, I thought of using some flat stock like 3/16 thick and two inch wide and having that mount to the frame and then tap into that for the structure of the skid plate system. The problem is clearance with the u-bolts for the slee step sliders and the slee transfercase skid. Not much room to get the flat stock in there. With the sliders and with the skids, I would have to run the flat stock between two or three u-bolts and the frame which would make removal of any single thing tougher. I'm starting to think that u-bolts that were about 2.75 inches wide and 8 inches long would work best but I have not had any luck finding those short of custom ordering. If I could find these, I could use two of these for the skid thing and they would not interfere with the u-bolts for the sliders and skid. Lastly I cannot imagine that the frame is almost an inch thick at the overlap...I think 250mm would equal an inch wouldnt it? 2.5cm = 1 inch IIRC. That's another subject but sure wish we would convert to metric...has nothing to do with Red, White and Blue if you ask me, no advantage I can think though for "standard" which really should be referred to as the anti-standard if you think about it! Anyway, I'm rambling, again thanks for the thoughts, anyone know a superb source for u-bolts that might stock the size I would want for this application? Thanks.
 
[quote author=IdahoDoug link=board=2;threadid=14169;start=msg132216#msg132216 date=1081026663]
The frames are definitely not anywhere near 25mm in thickness. More likely around 8mm where it's doubled.

What about drilling sideways through the frame and using reinforcing plates and through bolts to essentially clamp a mount onto the frame?

DougM
[/quote]

Damn I thought I typed fast but this came in while I was working on a response! Now that's great thinking Doug; I could use channel to go over the bottom face of the box frame channel and then through bolt it on both sides, should be super strong!!! See, that's why this forum thing rocks! I'll go look at all the clearances and conclude whether this would work. Then I'll go look at my "standard" stocked steel supply catalog and see if they have something slightly wider than 2.5 inches to fit over the frame tightly without wiggling around, then I can through bolt the thing. Great thinking, thanks. Also thanks for the trailer supply suggestion, another great thought. Off to the imagineering department, ohh, but first to the fridge for some sixes.
 
[quote author=turbocruiser link=board=2;threadid=14169;start=msg132218#msg132218 date=1081027097]
I think 250mm would equal an inch wouldnt it? 2.5cm = 1 inch IIRC. That's another subject but sure wish we would convert to metric....
[/quote]

you are correct that 2.5cm is about an inch but there are only 10 MM in a CM not 100 so 25.4mm is 1"
 
[quote author=IdahoDoug link=board=2;threadid=14169;start=msg132216#msg132216 date=1081026663]
The frames are definitely not anywhere near 25mm in thickness. More likely around 8mm where it's doubled.[/quote]

Thanks for catching my mistake :slap::beer::slap::beer::slap:, and yes I was thing a 1/4" in thickness when I miss typed 25mm & should of been 8mm like Doug mentions.

I've drilled / tapped the frame on the bottom / top / and sides in both my older crusiers, which have held up fine - the FJ40 skid plate is attached to the frame with drilled / tapped holes - no problems on the rocks.

Drilled & tapped, or Nutzert (overkill) approach is adequate for an exhaust skid plate

2.54 Cm = 25.4 mm = 1.0 inch

Joe :bust2:
 
FWIW...

I have my bumber off this weekend and looked down the frame rail...it's not twice as thick on the bottom and top as som of you described. The tube is made up of one C chanel and another that barely has enough of a lip to weld on....something like this ] for you to have an idea. Anway, all sides are about 1\8 inch.
 
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