I just finished punching 2560 holes in some angle on a Tommy Industrial 67 ton ironworker. Each part gets (4) 5/16" holes and (4) 9/16" holes.
I put up a fence with markings along it to place each hole which worked fine for my purposes but isn’t tight tolerance.
Curious if any of you have come up with a good fence and flip stop system to accurately locate holes for things like this? I’ve seen such things for woodworking drill presses.
It is important to consider what the holes are located relative to! Does the fully punched angle locate by one end? The other end? or is it located between two other parts?
Or maybe the punched angle locates by one of the holes? If that happens to be the case locating with an end stop to punch the holes may produce all the holes off location. But with “loose tolerances” you may never notice the difference.
1 Like
These angles it was carriage bolts through angle into wood for the big holes and a u bolt around a cable for the little bolts. The u bolt needed to fit so I made flip stops the right spacing for those holes.
Jeremy- It sounds like you have it in hand. I am always surprised when people are spacing holes with a disregard to the function of the holes. Some need to be precisely spaced, some can be very loosely located. Not sure which is worse, working hard to locate holes that are big enough to always work or not paying attention to where tighter holes wind up and having to reach for a rat-tail file.
While we’re on topic, how do you accurately locate multiple holes on the punch?
Here I used a pen mark on the fence for the not so accurate holes and a homemade flip stop for the more accurate holes.
I suppose one could accurately drill a custom fence with pin holes in just the right places. The pin could locate off either the end of the part or into previously punched holes depending on the need…
As with many good things in life, it depends. If you want to locate holes accurately it is critical to first know “located with respect to what?”
You mentioned that some PAIRS of holes are to accommodate U bolts; if a pair of those holes are too close together or too far apart you’ll never even get to whether the pair is in the right place. (There is a GD&T callout that specifically addresses this). For this spacing I’d suggest some sort of fixed length spacer or block that moves the workpiece just that distance from a fixed stop after punching the first hole of the pair.
There is also a GD&T callout that acknowledges that a bigger hole (within some limit of size!) will allow fit up where a smaller hole (also within size limits) will not. So punching your holes to the largest size the nut and washer will cover might be better than punching them to the smallest size to fit over the bolt.
These are some techniques that allow larger functional tolerances on your holes’ locations.
This is pretty much what I did. The holes were 5/16" to fit a 1/4" thread on the U bolts. It fit every time I checked it.
I made hole punching stops using a bolt that poked up from under the table on a hinge and weighted arm with a release handle to manually lower it to move to the next hole. It would be pushed down by the material till it found the hole and a quick and cheap hinge would be a 3/4" nut welded to the underside of the jig then thread in a bolt and weld the flipping arm to the bolt.