Technical I need to know about blind screwing

Tried to think of a catchy title. Here's my situation. 6" long 3/8" bolts need to be threaded deep into this thing with no access to the back, and no way to see what and where I'm doing..
I'm building my own version of cage nuts to be welded inside, using 1' deep nuts. I can get to everything while welding it up, but not when assembling it for the last time.
I can trial run it as many times as I need, but Murphy's Law and the possible movement during some of the welding may complicate stuff.
So the simple question is should I grind down a few threads on the 6" bolts to make them easier to start into the nuts, and if so, how? Just take the top off of the threads ? Would think 3 or 4 threads would be enough, and that number would pass through the 1" nuts, so they don't have to hold any torque.
Sorry, no pics, don't think they could help or show what I'm doing very well. TIA.

 

Can you use a floating cage nut so slight discrepancies are not as big a deal?

https://www.jhpfasteners.com/welding-fasteners/nuts/floating-cage#1

 

usually tapering just a couple threads SLIGHTLY is all you need to get them started

 

Can you weld a thick piece of metal behind instead of cage nuts? Then you can drill and tap a hole afterwards.
But give me more info about blind screwing in case I lose my eyesight..

 

What Tman said^^. First couple of threads only and file the slopes of the threads, good luck

 

Yeah, I do that all the time. I'll take a bolt and run a nut all the way up. Then on the belt sander, roll it in my fingers at about a 45 degree angle...it gets hot...and it doesn't have to be all that accurate. I usually grind it until I can no longer see the first full thread. Take it over to the wire wheel to clean it up and then run the nut back down to re-align any of the ground threads. Works every time.

 

Dependent upon what you're screwing , you may be better off blind !

 

Been there....done that....

 

Just clicked on the thread for the first joke. Not disappointed.

 

This stud is made to be able to put a nut on quickly, without having to take time to line it up. As in pit stop roundy round tire change quick. It's been developed and refined over decades.

 

Thanks to everyone for your help. Good tips.

 

Well at first I was going to tell him just to close his eyes.

 

SIREN!!!! Wow Wow Wut Mr. Police Man....
With wuts going on in the news lately and then throw some political stuff in there , which is not allowed on the H.A.M.B anyways....do I smell a dirty cop?
hahahuh...

Sent from my SM-T387V using The H.A.M.B. mobile app

 

I don't have a good picture of what you plan to do. Be sure you finish with a bottoming tap so the studs don't seize. Bob

 

Yeah, ol Darin is a real comedian. HAHA.

Mick

 

Likewise. If you could provide a sketch maybe someone will have a helpful idea.

 

@squirrel has it right.

IMO, tapering the threads increases the likelihood of cross threading the bolts not decreasing. Whereas, the parallel reduced diameter tip of the bolt insures the ‘piloted’ bolt is axially concentric with the ‘nut’ threads.

Ray

 

is the hole sloppy? yeah, yeah, seriously either the nut or the long bolt have to have some movement to align with out cross threading. can you use a long stud and an acorn nut?

 

Thanks again for everyone's ideas. Much appreciated. Won't need a bottoming tap, the long bolts pass through the 1" deep nuts. My concern isn't the nuts down on the inside, but guiding, and screwing everything together blindly, after I weld the pieces together, and possibly warping shit just enough to cause problems. TB33, if I could use studs, I would. Can't make that work in my convoluted, overkill, "Rainman" world. If I did shit the easy, proper, reasonable way, my project would already be on the road.
I've finally gotten used to doing stuff the hard, stupid way, can't seem to help it. Sometimes it even works out OK.
Thanks, folks ! I've got more ideas now .

 

Are you going to use my idea .

 

Sure, what could go wrong? Can't hurt.

 

Keep it simple...just turn off the lights!

 

Regarding turning off the lights......it’s not only the men who may make that call.....

There is an old saying......”In the dark, all cats are grey”.....

Ray

 

...and all women are beautiful...

 

Can you use a couple temporary studs to get things aligned and loosely assembled, then screw in your bolts, remove the temporary studs, and install the last couple bolts?

Roger

 

Thanks Roger, but no, there isn't anywhere to use temporary studs in the bottom.

 

Yep, works for both parties! Now someone explain the purpose of a "temporary stud?".

 

when the usual stud is either unavailable or out of commission??!!

 

Screwing blind, studs, do it in the dark....nobody mentioned ALCOHOL here yet!....seriously, Squirrel as always is right on target. Many factory fender and hood etc. bolts have the first 1/4 to 3/8ths of the bolt diameter the same as the ID the clip nut, J nut , captured drilled and tapped bar etc.

 

Ok, I can't resist!...I never went to bed with an ugly captured thing to screw into but I did wake up with one or two....