chassis q ... unibit or punch?

[krash]

I tried the Harbor Freight punch kit with a very low success rate. The "shaft" bent and the punch wouldn't run true after the first hole. Well this kind of has soured me on punches. Anyway that was a heck of a lot of work to make 7 holes in a chassis.

So ... I hear for noval holes the unibit may be the way to go ... if I have $30 to spend on a tool to make 9-pin socket holes, should I go unibit, or a single greenlee punch? Is the greenlee punch really better/easier to use or just going to last longer than the cheapo? if it's the same pita quotient then I need another solution!

how long will a unibit last (as in, how many holes can I drill before replacing the tool)?

[Normster]

For 3/4" holes I really like using those flat drill bits used for wood. (Assuming you're using an aluminum chassis.) They make an ultra clean hole and they're cheap!

[rhinson]

ned at triode electronics sells a nice punch set for fairly cheap--i've got one i've used for yrs. also you can get a good quality inexpensive stepbit at your autozone or auto parts store---got one of them too i've used for a couple of yrs still going fine. i also have several pieces of the bimetal hole saws-----i've used these longer than any other method. which ever method you choose you need to lube the cutting piece with oil to assist in the cutting. rh

[Bob-I]

I tried the Harbor Freight punch kit with a very low success rate.

Garbage. plus you get their catalog 3-4 times a day.

single greenlee punch? Is the greenlee punch really better/easier to use or just going to last longer than the cheapo?

Worth every penny, they're great. You get a clean hole every time and they seem to last forever. Remember that these are for electrocal holes so the size is in standard electrical conduit sizes, not inches.

how long will a unibit last (as in, how many holes can I drill before replacing the tool)?

Again, it depends on the quality. The Harbour freight unibits last about 1/2 a hole, but a real quality tool will last forever.

I use both, depending on what I'm doing. You can't possibly buy all the greenlee punches you need, so I have 2 and a unibit.

[tubedogsmith]

Forstner bits and Greenlee punches leave the cleanest hole. I use lots of kerosene as a lube with the forstner bits. The unibit works fast but you'll have some cleaning up work on the hole usually with it.

[krash]

well I guess I need just the one greenlee punch. Seems like a lot of work to use it though. Unibit is probably much faster and less effort I'd guess...

Thanks for the replies. Maybe what I need is "both".

[lastwinj]

Remember that these are for electrocal holes so the size is in standard electrical conduit sizes, not inches.

not true. they have conduit punches, and regular punches. the conduit punches are the ones you are referring too.

jeremy

[lastwinj]

unibit or a greenlee. i have had wondeful success with either.

just got a set of unibits from harbor. works fine on aluminum if done properly. most holes done by any method will need some cleanup. always have a rotary deburring tool.

germ

[jaysg]

I actually have a set of Greenlee stepbits. They're also useful for opening holes in plexi material without cracking it. I always wish I had a drill press when using the step-bits.

I borrow punches when I need them. It's tiring to punch a bunch of holes in steel. If you can only get one thing right now, get a quality stepbit/unibit. hth

[NitroLiq]

Germ's right on the holes needing a bit of cleanup. I recently bought a titanium-coated step bit to widen a PT hole on my 36 watter. The titanium coating wore off and the hole had a burr on both the outsides and inside. A de-burring tool would've helped but I ended up just..um...de-burring it with a pair of needle-nosed pliers and sandpaper. It wasn't pretty but it worked and is covered with a grommet.

[jimipage]

I just started using Irwin Forstner bits. Wow! Nice and clean. They say the're made for wood, but I use Hammond aluminum chassis and it's just fine. For around $30 I was able to get a 3/4" and a 1".

[David Root]

I've used both unibit and greenlee punch. Greenlee is better in steel and aluminum unless chassis is real thick ( I have done one aluminum chassis in 0.125" T5). Unibit always needs cleanup, Greenlee doesn't.

Hammond 20 ga steel chassis are a pita with the unibit, 20 ga is NOT thick enough for a guitar amp chassis IMHO either, twists too easily.

Recently I am using a pre-punched steel chassis (Mojo BF Princeton Reverb knock-off) which saves a LOT of work. 18 ga, not as tuff as the original by any means but tuff enuff for a pro grade amp, and all the other cutouts and drilling have been done. I'm doing an original design, not a BFPR clone, so I may have to drill the odd hole, but in nicely braced 18 ga steel I see no problem.

[skyboltone]

There is an adjustable tool called a Fly Cutter that's dangerous as heck but will cut up to 4" diameter holes when used with a drill press. If you need to cut a hole for the power transformer to set in these are ideal.

I got mine at Aircraft Spruce and Specialty. Google it.

Clamp your work and use slow speed with slow feed. Don't try it with a hand drill. You'll regret it and may end up in the emergenncy room.

For smaller holes, forstner's are terrific.


Dan

[krash]

well Forstner bits look like the way to go... however I can't find any that are reccommended for aluminum. So what's the requirement to get Forstner bits that will drill aluminum? I suspect some titanium bit?

How long (how many cuts in alu) does a Forstner bit last drilling noval 7/8" holes?

Thx--

[glasman]

Try the Deltron punches available from Mouser. They are half the price of the comparable Greenlee and they work great.

Now if SOMEONE would make a reasonablly priced IEC punch.

Gary