Oversize or same size holes in structural steel

[NPloysa]

Ok, so say I want to sandwhich my frame with a bracket for air ride. The bottom and outside of the bracket will be one piece. The bolts will go through bracket, then the frame (both sides), then a "strap" to spread out the bolt tension



Kind of like this. The catch is, the weight will be sitting on the bottom of the bracket also. The bottom of the "L" would be sitting under the frame.



L [] I



Should I try to drill the holes just bigger than the bolts, 5/8" Grade 8, to 3/4" or can I go bigger? The bolts won't be doing any weight supporting. I am a fairly good machinist but probably can't drill a straight hole through a box frame, which the oversize holes will help me with for getting the bolts straight.



Thanks!



Nick

 

[rbattelle]

If the bolts aren't supporting any of the load, I don't see any reason you can't bore them oversize.



Be careful not to overtighten them, of course!



Ryan

 

[NPloysa]

That's what I was thinking also, and I won't overtighten! Thank you!

 

[DJW]

If you have trouble drilling through a box frame to match up, could you drill pilot holes first, then the drill would pick up the pilot holes easier? Even if the bolts are not load bearing, all steel fabrication I've ever worked on Structual, High Pressure, Machinery Building etc. unless holes were reamed, just clearance was called for,most of my work was Code, and a Rattling Good Fit was frowned on.

 

[NPloysa]

One idea I just thought of was drill pilots in the bracket, clamp it to to the frame, then drill through those holes like a template, switch sides, and do the same. That way I will have my 1/4" pilots in all 4 places for the holes... .



Thanks guys!

 

[GHarman]

Just a thought. Dont know how much clearance you have to work with? A small magnetic based drill motor and your bracket with the pilot holes might do a perfect job. You can rent the mag. base drill motor. GregH.

 

[NVR FNSH]

Weld tubes thru the frame rail to prevent crush or weld a tube to one side of your air ride bracket so it goes thru the frame and provides for a bottoming surface from the other side. Not a real clear description but I think you'll get the idea.



Brian

 

[NPloysa]

Yep, I get the idea, thank Brian. But in that case I will just weld the bracket on the frame!



Nick

 

[2-ND TIME]

Over sized holes!!

Sorry must be toooooo tired yet, this isn't making any sense to me. Sorry pilot sizes shouldn't be larger then the ???? the sized across the cutting edge. I usually use a # 33 or 1/8" for everything and grease if you don't want it to run every where or cutting fluid. I say just make the holes a 1/64" over the size if you can fit it. For if you drill the hole correctly or are able to drill it correctly a 0. 625 bolt won't fit a 0. 625" hole . If not go up in 1/64" to get it to fit. Do use flat washers on both sizes and lock washer and have at least 2 threads out past the nut.

 

[y-knot]

Welding anything to the frame is not the way to go, it just makes things too hard down the road if repairs to the truck are needed.

If you are going to be drilling thru the frame, you need to use and inner sleeve. You can buy them in different sizes at places like KarTek Off-Road, or similar. What you do is get a sleeve that has the inside diameter to mach the bolts you will be using, say 1/2", which would typically have an outside diameter of 3/4". Drill the frame on one side to 3/4" and on the other side to 1/2". Now insert the sleeve, that has been trimmed to fit so it passes thru the frame and rest on the inside of the frame rail, and comes out flush with the outside of the frame rail, on the 3/4" size side. Now add your washer, lock washer and nut, you can tighten down the 1/2" bolt all you want and it will not crush the frame rail. Yes it will take slightly longer to do it this way, but it usually does take more effort to do it right.

If you have a steel source ne'er, you can simply buy a section of round tube steel of the proper dimension and make your own sleeves. Good luck.