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Anyone heard of invertabolt?

zippity do

May 20, 2005
I would be interested if anyone has some feedback on the use of invertabolt? Do they work good? What you use them for, etc?
Anybody got a picture of one in pieces so we can see how they are made?

It looks like they would have several rather sloppy threads in the insert and on the part that comes up. That would give you some leeway on getting the holes in exactly the right position.

At some point the sloppy threads have to disengage, and there must be a shoulder on the part that comes up so it can develop some clamping force as you continue to turn it into the workpiece.

The only downside I see is that you'd have some partially tapped holes in your workpiece after you're done.

Thanks Roger, I knew something wasn't "quite right" in my mental concept. The thread forms have to kind of converge to develop some clamping force.

Unless as you suggest the bottom thread is merely a "jack" to get the top thread started, then a flange allows load to be developed.

Seems as if the clamping stud would have to be spring loaded from below and not actually threaded into the piece it rides in. Otherwise it would tend to push the part up until the beginning of the thread on the stud came around to the proper angular orientation to engage the tapped hole in the part. If the stud had a finer pitch on the lower portion than on the section which goes into the part, then it could develop the clamping force via the differential movement of the two threads, but that would still mean it would push the part upward until it engaged the thread in the tapped hole.

If you watch the videos, it would seem there are some parts that this setup would be useful for, but with the necessity to drill and tap multiple holes plus the requirement to drill and ream dowel holes for the actual location of the stock, it looks to me as if its a thing you'd only want to use when nothing simpler would work.
"If the stud had a finer pitch on the lower portion than on the section which goes into the part"...

Different threads--I hadn't thought of that.

Looks ingenious to me. Obviously a differental thread pitch provides the hold-down force. And a CNC machine could be provided with an Allen tool to do the fastening and unfastening so the operator would only have to place the part on the studs and remove it after it's done.

I doubt that I will ever use it but, you never know.

Paul A.
The beauty of the Invert-A-Bolt we found at Cessna is that you can make a universal type fixture and run many, many parts over the same tool. In fact, 90% of the dedicated tools at Cessna were eliminated with this concept. Granted, you need to tab or picture frame your part, but that is a small cost compared to the savings in tooing, storage, maintenance and retrieval, plus, your bolts are ALWAYS right there.
The concept the Invertabolt is based on was first seen in the aircraft industry around the '80s. It was a homemade version made from a set screw welded to a washer with a pusher spring under it. The old LTV (now Vought) has been given credit by some, but I don't know.

Several aircraft companies have used variations of them. I'm not sure when invertabolt came out with their version but they work very well. I know at least one company that does almost all of their flat plate work on universal grid plates using these alternating with bushed holes. I believe Invertabolt or sombody else now sells plates similar to these.

One of the really great advantages to these things is the small footprint. With practice ( & a little guts) you learn to program cutter paths close to them &, since there is no bolt head, over the top of them.

bigrog, if you know Phil Simpson or Dennis Schroeder in NC Programming at Cessna (if they're still there) tell them hi from Jim Malia. Also, tell'em today's my last day at RAC & I start back at Bonex tommorow.
Jim, good luck back at "The Big Bummer Factory",(WWII terminology) better known lately as the Lazy B Ranch. What a great place to be away from.