Drilling/Punching a 24mm Hole In A Chassis

[Cathode Ray]

I have a "stepper bit" and it works great for drilling holes in project cases for 1/4" phone jacks, pots, switches...

But what tool is commonly used for a larger diameter hole ?

Looking at some of my amp chassis, it looks like some kind of punch was possibly used for the tube socket holes.


Thanks in advance

[Leo_Gnardo]

Since I have a 1 inch punch, I'd opt to use that. BUT some folks like their step drill bits. I don't think it would be wise to free-hand drill that big a hole though. If you have a step drill AND drill press, or access to that combination, I expect it would work well.

I'm sure more input from those who have used large step bits will follow, stay tuned!

[Phil_S]

Agreed that a drill press is the best way to drill metal, but I've drilled many chassis holes free hand. Clamp the work piece. Use a good variable speed drill and take your time. Slow speed is better for metal. Use lubricating oil on steel. Center punch is an essential tool. If you don't punch, the bit will wander and you can't easily undrill the off center hole. I start with a small bit and drill up to about 1/4". Then I use the step bit. One thing I don't like about a step bit is that, if you let it run too long, the hole will be sloped, so pay attention and stop as soon as the desired size enters the hole. Clean up with a deburring tool or round file if needed. Test on scrap if you aren't sure.

I have drilled many Octal size holes (1.125" or 1.25", depending on the socket) this way without any difficulty.

[pompeiisneaks]

I've got a pretty large stepper bit and it works great in my drill press. It was a lot harder with the hand drill, thus why I was happy to get the press .

I also bought a cheap harbor freight punch set that I used for some really large capacitors on my liverpool build and man that is so much easier, albeit more expensive to buy punches, but if you're going to do a lot, I'd do that every time if I could.

~Phil

[Cathode Ray]

Thanks guys!

Appreciate all the responses.

[martin manning]

A good quality step bit is worth the expense in my experience.

[Cathode Ray]

A good quality step bit is worth the expense in my experience.

Yeah, the bit I have appears to be about 1.5mm too small.

Going to pickup a larger step bit at hardware store tomorrow.

[Phil_S]

eBay can be a good source for name brand step bits at a decent discount. It takes patience. Look for "unibit" or "step bit." There are many crappy ones being sold. Often they have a TiN coating, which isn't a bad thing, but it is often a give-away that they are using the TiN to cover up the piece of junk it really is. Learn which ones they are and avoid them.
I have one of these and, for the price I think it's a winner. https://www.ebay.com/itm/Drill-Hog-USA- ... 0506.m3226
These guys buy surplus/closeout lots. I buy things from them and they ship quickly. This looks like a good deal. https://www.ebay.com/itm/Klein-Tools-59 ... rk:32:pf:0
Same Klein bit for less money: https://www.ebay.com/itm/Klein-Unibit-1 ... rk:33:pf:0

[bal704]

I'd use a hole saw. You can get them at lowe's or home depot etc. Not sure about 24mm, but a 1 inch (25.4 mm) hole saw is common. You attach it to your drill like a drill bit, and it has a small bit in the center for centering purposes. Drill a small pilot hole at the location of the center of the 24mm hole, then use the hole saw.

EDIT:
https://www.harborfreight.com/1-in-2-12 ... 68114.html

[M Fowler]

I use step bits from Harbor Freight (several sets), also have an expensive set, and ordered a metric set for pilot lights etc.

I mostly use special punches to fit Beldon tube sockets and another punch set to fit ceramic and older tube sockets.

So I do have a lot of tools but man do I use them.

Mark

[tubeswell]

I use chassis hole punches for tube socket and cap can socket holes. 24mm= 47/50ths of an inch, so a 1”punch* would mean a .75mm gap around the outside, which isn’t too much slop. YMMV

* 1”= 25.5mm