Stainless Steel Chassis: Never Again

[cometazzi]

I will ask for some advice but first I must rant:

I'm attempting to build a 5E3 using a chassis I bought on eBay in Dec 2019. There's a minor saga of why it took me years to get around to this but I'll save it and try not to be too wordy. Turns out the chassis came from Soviet Russia, and while it looked AMAZING, I learned three things almost immediately:

1) All the holes are possibly for metric parts, or at least they were all just a smidge too small for everything. The only things that just 'bolt right up' are the PT and OT. All the jacks, switches, pots, pilot light, fuse holder, noval socket and octal socket holes are about 1-2mm too small. Or at least too small for the Mojotone Tweed Deluxe Small Parts Kit that I boughtenated.

Then I promptly discovered:

2) This chassis isn't chrome-plated mild steel. It is highly-polished stainless steel. Also, there are no board mounting holes, and I need a couple extra holes for the safety and power amp ground(s).

Then I quickly discovered:

3) Stainless steel is harder than [vulgar phrase]. My old "wood and metal" bits were probably fairly dull but they just couldn't get a bite.

So after some research I went to the Home Despot and bought some name-brand Cobalt bits that claim they can drill hard steel and cast iron. They worked better at first, but it still was probably 45 minutes and countless drops of 3-n-1 for each new hole. Including resting my wrists, it was 2 hours to drill two holes to mount the board, and of course there was drift.

Using the larger bits I was able to successfully embiggen the jacks/pots/switches/fuse holes but it was loud, difficult, and dangerous. Said bits have noticeable wear on the edges of the cutting surfaces.

I wrecked my step bit enlarging the noval sockets, and almost killed myself in the process. I have some alternative octal sockets that fit the octal holes, but I sure would have liked to use the nice Beltons for this build.

Finally, last night I went to start two more holes in the chassis (safety ground and power amp ground) and the 1/16" cobalt bits (2 in the set) wouldn't even bite. They weren't even getting warm. So it looks like I get about 2 holes with each cobalt bit until they're trash. I bought a single 1/16" cobalt bit to get the hole started, then it promptly snagged and broke. Cleaned the debris, added a fresh drop of oil, then moved up a size. Took four hours (!) to drill two holes for two #6 screws.

Plea for advice #1: Is it the wrong oil? The wrong bits? I've only got a hand-held drill but I'm going as slow as I can, and I'm putting firm but not excessive pressure down on the bits. Trying to keep them from getting hot, trying to keep them from going dull, however, I've ruined my "wood and metal" bits and just about all the useful sizes in the set of cobalt bits. I haven't found anywhere that sells carbide bits but I bet if they exist they are $$$.

Plea for advice #2: Any creative solutions to this next dilemma? Today, I discover that the strain relief hole in the chassis is too close to the weld on the side of the case:

To note, this chassis doesn't have the typical round-with-two-flat-sides type of cutout that takes the typical strain relief. Instead it's got a round 5/8" (16mm!) hole. I hunted down a gland-style cable anchor to use, but as you can see it's overlapping the side piece that's spot-welded on top of the bottom panel. I though about filing down the plastic nut on one side for clearance, but the spot weld is under it too. I'd have to remove so much material that I wouldn't trust its integrity. Would a narrow washer (to allow the nut to overlap the metal) be ok? Rubber, metal, plastic? Being that this is the primary power cord anchor I don't want to jank out. Safety!

Another option is to drill another (smaller) hole above that one and farther away from the edge, and use a 1/2" gland instead. Since I've wrecked over $80 in drilling implements on this chassis thusfar, I like that solution much less.

Plea for advice #3: What do you guys do, or where do you source "shiny and silkscreened" Tweed-type chassis? Mojotone has what appears to be a chrome-plated mild steel chassis. However, they strongly advise against drilling any holes in them as it will cause the chrome plating to start flaking off. Mojotone is a proponent of mounting grounds to PT bolts and thus don't have extra grounding holes. I'd have to drill them and then start the process of decay. There are plenty of bare-metal non-silkscreened chassis around, but in this build I'm trying for the full Fender Deluxe aesthetics.

I've been hacking on this chassis off and on for over a year, and I'm about to chuck it into the street. I'm going to cool off before doing anything rash, but I don't think buying a different one (with all the right holes) is off the table at this point.

What would a fellow Shock Brother do?

 

[Uncle Daddy]

You could have bought metric components!

 

[cometazzi]

You could have bought metric components!

I know, right? But I would still have to drill holes in this thing made of depleted Pripyat Uranium!

I don't know that the holes are actually metric, as I didn't actually measure them. I also didn't discover this until I had already bought the parts. It took me I don't know how long with a file to upsize the hole for the pilot light. It'll just barely fit if I cram it in with all my might, and I'll probably never get it back out if I do.

 

[bottlenecker]

#1 Your method is probably killing your twist drills, more than anything else. If you can clamp it to a block of wood or something so the chassis doesn't vibrate it will help. Try misting it with water to cool it instead of 3 in 1. Get better cobalt twist drills from MSC instead of whatever junk home depot carries.

 

[Uncle Daddy]

Yes for a washer under the plastic nut. Belt and braces, use a p- clip on the cable inside the cab.

 

[sds1]

Brutal. Avoid steel!

For the larger holes I would recommend the Irwin Unibits but it's still going to be brutal. Unibits are available down to 1/8".

 

[Dostradamas]

Drills cut metal away.
More pressure does not help the bit cut better.
Drill stainless at half the speed you drill mild steel.
Use cutting oil
wait for the tool to do its job.

 

[cometazzi]

#1 Your method is probably killing your twist drills, more than anything else. If you can clamp it to a block of wood or something so the chassis doesn't vibrate it will help. Try misting it with water to cool it instead of 3 in 1. Get better cobalt twist drills from MSC instead of whatever junk home depot carries.

Thanks for the advice.

By MSC is that mscdirect.com?

My next question is what brand should I look for? I see Milwaukee and Irwin there and an unnamed house brand.

 

[schmee]

Drilling SS is all about speed and feed. Too much pressure or speed and it burns, too little pressure and it doesn't bite into the metal. I rarely use any cutting oil. You can "feel" the bit bite and where to keep the pressure. Use lower speed. But a drill press makes it much easier than a hand drill. And there are some work hardened SS that are very difficult anyway.
Hard Chrome is just as bad, you still have to get through the chrome which is harder than SS!

Having said that, you just need two ground places, neither have to be drilled:
-The pots and input jacks to the chassis with the amp preamp end grounds going there also. You can just solder those to the pots or jacks. It grounds through the chassis.
-I have never had an issue grounding the power section to the transformer bolts.

 

[printer2]

I have two SS chassis, one virgin and the other one with most of the holes. I drilled holes and enlarged them with a round file rather than burning out my step bit. SS work hardens (there are a number of different types of SS with somewhat different properties) and is a pain to work with. I have more SS sheet to use, will I again? Maybe when I feel like beating myself up again.

 

[cometazzi]

Yes for a washer under the plastic nut. Belt and braces, use a p- clip on the cable inside the cab.

I do have a p-clip that I intend to use. However, what do you mean by the "belt and braces" part?

Thanks!

 

[bottlenecker]

Thanks for the advice.

By MSC is that mscdirect.com?

My next question is what brand should I look for? I see Milwaukee and Irwin there and an unnamed house brand.

That's the site. I'm not sure I've tried the house brand. We use a bunch of stuff, some hertel, accupro, mostly usa, but we are getting lots of parts out of them in machines. If you're going to beat them up in a hand drill, try the cheap stuff. MSC just because you will very likely get more drill for your money from them than home depot, and you have lots of options.
Also, I forgot to mention, push harder. You want a bigger chip with stainless, so push hard but make sure it's fixtured so you can do it safely. I'm guessing you'll get through it and just avoid SS chassis. If not get a cheap drill press.

 

[bottlenecker]

Drills cut metal away.
More pressure does not help the bit cut better.
Drill stainless at half the speed you drill mild steel.
Use cutting oil
wait for the tool to do its job.

More pressure can help, depending how much pressure we are talking about. If there's not enough pressure the drill is rubbing, getting hot, and getting dull at the tip. Most SS especially likes a bigger chip. The right size chip will pull heat away from the drill and keep heat in the chip.

 

[jrblue]

But when you're done you won't have to worry about unsightly stains on your chassis. But more seriously -- I love stainless but it really does feel bad to work with, and of course it's physically difficult, too. Since it's overkill anyway, I just avoid it. Good luck getting through it.

 

[Kev-wilson]

As said above ss can work harden and would be hard work to anneal, can you slow your drill speed down any? Can you hand sharpen your bits as if so flatten the angle! There's a silicon spray called 'break free' that may help, or roocol cutting lubricant, better brand hss drills too(dormer etc).

A handy hole enlarging hand tool when the hole's a little small is a 'tapered reamer' tho that's not what the tool is designed for...

 

[BigDaddy23]

SS is a real bugger but here's my advice, some of which echoes what others have already added:

- low speed and high torque in your drill settings. If you run too fast, you work harden the SS and it becomes a problem.
- Proper cutting oil like Rocol, Trefolex. I've also had good success with gunsmith cutting oil from Brownells which stinks to high heaven!
- Sometimes center punching the crater half way through the process helps the drill to bite and cut.
- Sharpen your drills (or learn how to do this) - dull bits will just work harden the SS and essentially work against themselves.
- I avoid step bits with SS. You will ruin them quickly and they are difficult to sharpen.
- If enlarging existing bigger holes by a few mm's, use a triangular file to cut a few notches around the hole. This will help the drill to catch the edge and cut. For smaller enlargements, just use a round file.

 

[sax4blues]

This suggestion is anything but DIY. How about pay a machine shop to drill the holes. They will do it fast, possibly not much more costly than running through specialized bits. This is a one time operation for you, as you will not purchase SS chassis again.

 

[old wrench]

Stainless alloy steel has a lot of chromium added as an alloy - that is what makes it "stainless" -

Chromium is also what makes stainless tougher to work than regular mild steel

I've got a Makita power "nibbler" that works really well for opening up chassis holes or cutting square or rectangular holes for power, etc. - it's very handy for re-working panels and "stretching" existing holes

A nibbler does require a small diameter entrance hole just big enough to poke the head of the nibbler through the panel so the cut can be started

It takes small bites of metal and is very controllable - between my Makita nibbler and a hand file I can cut just about any size or shape hole in a panel

A die-grinder (or even a Dremel) with a grinding point or wheel is another option, but if the stainless over-heats it will darken due to oxides forming from the heat

.

 

[chas.wahl]

And oxides in the stainless will turn to rust, unless the chromium oxidizes first ("passivates") and thereby prevents iron from oxidizing -- that's the "stainless" part. Stainless is, as you've found, quite a bit harder than carbon steel, but strangely it does not have as much bending strength. And it's less conductive.

 

[King Fan]

Lots of good advice here. I watched a long and convincing YouTube when I did mine -- the essence was low speed but high downforce (compared to mild steel). But also, bigger (socket size) step drills are asking for trouble.

I learned two things I didn't see above. One may help you keep your fingers and "other junk", the other may help you keep your sanity.

1. Clamp the living daylights out of the work. When the drill 'breaks through' SS, it has a tendency to seize up. Chassis as propeller is not nice.

2. Buff the shiny inside of the chassis with coarse steel wool or fine sandpaper after drilling and before building. The 'hall of mirrors' effect in there is famously nasty in photos (wires appear doubled by their reflections), but it's actually pretty distracting in real life, too.