They could be used to grab something like a screw head but the end of the central part is flat so it would not engage a slot or other drive structure on a screw to transfer torque. The central part is threaded inside the knurled part so it moves up and down relative to the slotted/notched collar and could apply considerable force to whatever you put into the slot.Those look like they could be screwdrivers for starting screws in tight spots where you can't actually get your fingers in to hold the screw while it is starting... it is kind of hard to tell from the pictures on my monitor though.
I thought it might be something aircraft related but I could not find anything like it at The Yard Store or Aircraft Spruce.If you found it with clecos, it might well have to do with placing rivets in tight places on aircraft. Just a guess...
By the picture the end is totally how a rivet set is. It's not flat, it's kind of concave to fit the head of a solid rivet. Makes sense it would be used with clecos. I see how you load it by the side slot, but then what? I guess it can help you get the rivet in the hole but I'm not seeing what it does from there. Does the end open up, is there some kind of spring action when you push down on it? Never saw one of those in aircraft school.They could be used to grab something like a screw head but the end of the central part is flat so it would not engage a slot or other drive structure on a screw to transfer torque. The central part is threaded inside the knurled part so it moves up and down relative to the slotted/notched collar and could apply considerable force to whatever you put into the slot.
Here is another photo with a darker background to show the business end a little better.
View attachment 293864
By the picture the end is totally how a rivet set is. It's not flat, it's kind of concave to fit the head of a solid rivet. Makes sense it would be used with clecos. I see how you load it by the side slot, but then what? I guess it can help you get the rivet in the hole but I'm not seeing what it does from there. Does the end open up, is there some kind of spring action when you push down on it? Never saw one of those in aircraft school.
I think we have winner here hman. Solid rivets need a specific grip and length so when set the driven part is a specific witdth and height. I'll bet this is for holding rivets for making custom length rivets. I looked all through the aircraft tools and it only showed cleco pliers. I originally thought it was for popping the rivets into the holes but the lack of a quick release made that a no go.These look like lantern chuck-type screw holders. You'd use them to hold screws by the head when you want to work on the threaded section (shortening, grinding, cleanup, etc.)
Lantern Chuck
The Lantern Chuck shown is not my design. It was modeled after a Lantern Chuck from Model-Engineer in the UK which in turn may have originated from information gleaned from Tubal Cain’s Book, “Work holding in the Lathe”. There were no drawings for this tool only two photos’ showing a general...www.hobby-machinist.com