Greenlee punch question

I haven't used Greenlee 730 series punches in a long time. My remembrance is that I used a pilot hole the diameter of the draw stud (bolt). I know now that there probably should be some allowance. However in looking at the Greenlee datasheet, the minimum pilot hole diameter specified is much larger than the draw stud diameter.

For example, the 1/2 inch punch has a 1/4 inch draw stud, but a 3/8 inch minimum pilot hole size. The 15/16 inch punch has a 3/8 inch draw stud, but a 1/2 inch minimum pilot hole size.

If one puts a 3/8 inch bolt into a 1/2 inch hole, what keeps the punch centered in the hole?
 
For the few I have punched I drew on the piece directly with pencil and a plastic drafting circle template producing a penciled circle the same diameter as the punch.
Then aligned the actual edges of the cutting edge on the penciled circle. I then tightened it up by hand, and then carefully tightened more with a wrench checking alignment as I tightened.

Once the punch dug in to the surface it did not move.
 
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I searched before I posted my topic. I could not find any other threads that addressed the question. Oh, I know what may have happened: I refreshed my screen but nothing happened. I then had to reboot my router and then refreshed. I can see where that may have created a duplicate thread. Very sorry.
 
I read elsewhere that Greenlee marks the die at 90 degree points for alignment. Sure enough I looked and the marks are there. Never noticed that before. Unfortunately I am not scribing my locations, so I have no marks on my work to align with.

What do people think of just directly drilling the half inch holes, rather than using the Greenlee? This in is 1/8 inch extruded powder coated aluminum. The holes are for mounting pairs of binding posts. One consideration is I have the Greenlee and I don't have a half inch bit. However I don't want the hole locations to be off.
 
Thanks for pointing out the itsy-bitsy-tiny-winy (never mind the rest of the song) marks on the great Greenlee punches. In all the instructions that came with my sets (5/8" to 2" conduit) was their a mention of that mark I (re-reading) noticed. 25 years and counting!
I normally drill the hole to fit the bolt size accurately, than "unscrew" the slug out of the die. Lots of lubricant used to protect the Grade 8 (or better) steel used in the screw.
Anything smaller than 5/8" I pre-drill to max, and than ream and file to size.
 
The panel does not feel to me like it would warp. Not sure though. Here is a link to the drawing:

http://www.hammfg.com/files/parts/pdf/RM2U19BKFP.pdf


My worry is that if I drill the half inch holes I will get burrs but if I punch the holes I will not be able to achieve the positional accuracy I need. I am leaning towards drilling.

In any event I will have to punch the larger holes for the panel as I do not have equipment that can drill a 15/16ths hole. However for the 15/16ths holes I do not need as much accuracy as for the half inch holes.
 
Rather than anything fancy I ordered HSS TiN coated 135 deg split point bits: 1/4 inch for the half inch punch pilot hole, 3/8 inch for the 15/16ths pilot hole, and 1/2 inch, should I decide to drill the 1/2 inch holes.

I plan to punch the 15/16ths holes, see how it goes, then either punch or drill the 1/2 inch holes, depending. Sadly I have a taste for expensive bits but I hope the HSS will make acceptable holes here.

I have never used a hole saw. I googled around a bit but did not find a carbide hole saw as small as half an inch.
 
Yesterday I punched one of my 15/16ths holes in 1/8 inch die cast aluminum. It was quite a bit of work, and I almost gave up. But the hole looks very nice. I had no trouble unscrewing the bolt from the slug and die.


The problem is the slug is wedged in the die and I cannot get it out. Anyone have suggestions?
 
If you didn't oversize the center hole, you can sort of thread the bolt back in a few turns, then whack the bolt head on the floor.

That's how I have always done it. Just seemed logical:cool:

Anyone have any advice as to how to avoid the paint flaking around the punch hole on the Hammond black powdercoat steel chassis? I normally cover the chassis in blue painters tape for marking all of my holes but that does not help much..

(Hope this is not thread-jackin'?)
 
If you didn't oversize the center hole, you can sort of thread the bolt back in a few turns, then whack the bolt head on the floor.

Wow, thanks! (Except instead of the floor I put the die in a vise and tapped the bolt with a rubber mallet.) I am embarressed I did not think of this myself.

My aluminum panel is Hammond black powdercoat but I did not notice any flaking.