Tube Socket Holes

[GregS]

Is a chassis punch necessary to do a reasonably neat job of making tube socket holes in a chassis or could a drill bit do a good enough job of this? The reason I ask is chassis punches seem to be very expensive.

Thanks,

Greg

[zhyla]

Cheapest tool for this I could find:

http://www.acehardware.com/product/i...Id=37733771534

There's a mandrel that it attaches to so that you can mount it on a drill. The two large holes on the lower-left of the attached I cut with this tool. Works fine, but you have to go slow at first until it gets a little groove started. Greenlee punches are more convenient but what do you want for $10 .

[Jag]

I've used hole punches and hole saws. I find the hole saw works fine (actually I like it better for steel chassis). Make sure you get a bi-metal hole saw or you'll be going through them failry quickly.

I prefer a step bit for holes 3/4" and smaller.

As Zhyla said, go low RPM to start.

[stingray_65]

Hi Greg!

I've not built an amp before, however I do have over 2 decades of metal fabrication experience.

depending on your chassis material and thickness and the diameter of the hole, you could use a twist drill bit.

I wouldn't, an inexpensive alternative to a die punch is a hole saw.
a drill press is a huge plus here , but in lieu of that a VARIABLE speed hand drill can be used.

back the area you want to drill with a piece of 3/4 plywood or other such thing.

if your chassis is aluminum, use kerosene or charcoal lighter fluid for a lubricant.
if your chassis is steel use a light machine oil or transmission fluid for a lubricant
if it is stainless steel you need a special sulfur based lubricant like RIDGID DARK PIPE CUTTING

in all casses turn the hole saw SLOW AS POSSIBLE.

if your using the hand drill "orbit " your drill. that is to say tilt the drill slightly and slowly rotate the drill in a CCW orbit.
optimlaly the hole saw should hit flat againt the metal, this is un realistic using a hand dril, so deliberatly only let a small section of the saw touch the metal at one time and orbit it.

beware what is happening when you "break through"
this is when the hole saw really grabs.
go slow
real slow
practice on a few scraps before you go ahead with your chassis.

if i'm unclear on anything here let m know i'll be happy to walk yo through it

[tubeswell]

Or you can look around 2nd-hand tool shops and find chassis punches for good prices. That's what I did

[GregS]

Thanks a lot for the info from everyone. I think the hole saw will likely be the approach I'll take.

Stingray_65, your tips are very helpful as I don't have a drill press and will be using a hand drill. Good to know these things rather than learning the hard way!

Thanks again,

Greg

[Mandopicker]

I have had excellent luck with step-bits. Real clean holes.

Not terribly expensive, but as you all know...build one amp and you can't stop with building more.

The investment in a good set of punches or step bits will pay for themselves in no time, and assure a quality build.

[daz]

I did my first 2 with hole saws and it was a biotch. then someone told me about step bits and pointed me to harbor freight where i always seem to find great deals. sure enough they had a 2 pack, one that goes to i think 7/8" and the other 1-3/8". The larger one was much slower for some reason, even on the steps that were the same size as the smaller bit. the smaller one went thru like butter on aluminum.

a customer who saw me looking at them told me he's bought them there and his have been used forever and still work. And the 2 pack was $20. Other places charge as much as 30 or 40 bucks for one. Anyways, i did every holein the amp from pot holes to the cap can with them. they aren't perfectly clean like a punch, but they're fast and clean enough. Put it this way....when i look at the amp i never even notice the quality of the hole edges. if you look for it then you'll see they aren't lazer cut or whatever, but they're perfectly fine. the hole saws i used on the first 2 took forever, were a pain, and the holes weren't nearly as clean. Thats my experience anyways.
By the way, HF also had a set of punches for $15 i think it was. But only 2 of them were of a usable size....one the same as a 9 pin socket and the other for octals. But i would have had to use something else for the cap can and other holes, while the step bits were used for every single hole in the amp ! Highly recommended unless lazer clean holes are a must for you. then i'd say you'll need to bite the bullet and pay the big dollars.

[GregS]

The step bit sounds ideal. I'm not exactly familiar with what it is but I assume it's a bit that gets progressively larger in steps. Correct? Are they available in regular hardware stores? Is Harbor Freight an online store?

Thanks,

Greg

[daz]

exactly. The $15.99 set is what i got. they will cut any size up to 1-3/8, which is a tad under a cap can but big enough for octals. A can hole just needs to be enlarged a tiny bit with a dremel.

http://search.harborfreight.com/cpis...+bit&Submit=Go

[GregS]

OK, great.

Thanks

[wyatt]

Unibit's work great and can be used with a simple drill press (which has a million uses).

For real chassis punches, you can get used Greenlee Radio Punches for less than $10 a piece. Unlike modern Greenlee punches which are sized for conduits and such, the radio punches are the (considered obsolete) tube socket sizes like 1-3/16" and even square-shaped transformer punches.

[GregS]

I have a set of step bits ordered that should arrive any day. My chassis is steel. I was wondering if I should lubricate the bits when drilling and if so what is the best lubricant to use.

Thanks,

Greg

[tubeswell]

I have a set of step bits ordered that should arrive any day. My chassis is steel. I was wondering if I should lubricate the bits when drilling and if so what is the best lubricant to use.

Thanks,

Greg

Don't use anything flamable (unless you want scorch marks)

[stingray_65]

OK
first thing to remember is the bigger the hole the slower (rpm's) you go
use a variable speed drill

second is the bigger the hole the liklier it will grab and swing the chassis toward you at a hip bruising, chasss twistng speed.

its best to use ANY lubricant even water! if it smokes your pushing too hard or going to fast.

you wont want to clamp your chassis in a vise, so if you have a wooden bench just cleat it between some old lumber (2x4's) screwed to the bench

in lieu of that maybe clamp some boards to your table top, just make sure your chassis wont rotate.

not knowing your chassis depth, you may want to check to see the length of your bit vs the depth of your chassis and the liklihood of it drilling into your workspace.

LOL with all that said you will spend more time setting up than you will drilling