Building Chassis

[AB3FL]

I work working on building a tube amplifier that may be used as a modulator.  What is the best way to drill the holes in the chassis for the tube sockets, tranformers, caps, etc......


thanks

Tom - AB3FL

[KX5JT]

I read an article a while back in Electric Radio that touts the benefits of Step-Bits.  Sounds like a great idea to me.

[K5WLF]

I've used Step-bits quite a bit on various projects and they work great. I drill a small pilot hole just to ensure the accuracy of the center point. Just have to be careful and not overshoot the step you want. Also, it's worth the money to get the good bits. And no, from experience, Harbor Freight does not sell the good ones.

[Detroit47]

Greenlee punches

[AB3FL]

Thanks All.   Looks like I need to get a good set up of punches.  That looks like the safeest way for me to make holes.  The step bits look good too, but I don't have a drill press.

Tom - AB3FL

[Jim, W5JO]

I've used Step-bits quite a bit on various projects and they work great. I drill a small pilot hole just to ensure the accuracy of the center point. Just have to be careful and not overshoot the step you want. Also, it's worth the money to get the good bits. And no, from experience, Harbor Freight does not sell the good ones.

What do you look for to determine if a bit is good or not?

[K5UJ]

I work working on building a tube amplifier that may be used as a modulator.  What is the best way to drill the holes in the chassis for the tube sockets, tranformers, caps, etc......

You have not even told us what metal you are working with.  That tells me you are already in over your head.

I don't know Jack about metal work either but sometimes a noob can help another noob best.  Get yourself a textbook on machine tool practicies.  the kind used in schools that teach metal shop.  You can get them used from abebooks.com
Start reading it.  You'll learn about how different types of metal behave; hand tools, cutting oils for different metals, taps, most important, safety practicies.   Before you go out and blow a ton of money on greenlee punches, you might discover there are other ways.   Good luck.

[AB3FL]

Either steel or aluminum is what I would be using.  I built a small chassis before, but the holes were terrible as I was using normal drill bits.  I looked for a video on punches on youtube and found one that looked good. 


Tom - AB3FL

[w3jn]

Feel free to use conduit punches; they're only slilghtly off-size of normal 7 and 9 pin miniatures, and octal sockets.

You don't need a drill press to use step bits, but you should clamp the chassis in something for when (not IF) the bit binds in the hole.  The other thing is there seems to be plenty of crap left over on the opposite side that needs to be filed/ground away using these bits.  Or maybe I'm just doing it wrong 

[W7TFO]

Here is a list I've compiled over the years:

Drill bit set.
Flat & rat tail files.
Greenlee punches.
Small triangle square.
Countersink bit.
Nibbler tool.

With these tools and some practice, you can build up some really pro-looking gear.

Punches are not cheap, but they do the best work and will last a lifetime.

73DG

[WQ9E]

If you are going to do any significant chassis work, a drill press should be on your short list.  Even an inexpensive one is going to outperform a handheld drill and will allow you to do much better and safer work. 

For any hole saw or fly type cutter you should use a sacrificial piece of scrap wood to back up the drilling surface.  This will provide a much cleaner cut and reduce binding and chatter.

Before cutting a hole in an expensive large chassis I would try your cutting tool in a cheap piece of aluminum to find the true resulting hole size.  Many hole saws will produce a hole slightly larger than the specified size and any runout in your drill or the cutting tool shaft will increase this discrepancy.

Consider using a subchassis mounted on the main chassis for high power final or modulator tubes as this will make future changes to a different tube type simple and won't result in a kludged up chassis.  You can also use a lighter gauge material for this subchassis which will decrease the difficulty of cutting large openings.

[W7TFO]

I didn't list hole saws in my previous post, as most of them are really hard to handle and don't provide fine results without much care & practice.

The ones from Blair are a cut above (pun intended), and work more like a precision milling tool than a rotary blade:

http://shop.blairequipment.com/SearchResults.asp?Cat=4&gclid=COCz4Ku2tK0CFaQbQgodiwFQnw

If you elect to use a holesaw, I highly recommend these...they are the deal for the $$.

73DG

[The Slab Bacon]

Here is a list I've compiled over the years:

Drill bit set.
Flat & rat tail files.
Greenlee punches.
Small triangle square.
Countersink bit.
Nibbler tool.

With these tools and some practice, you can build up some really pro-looking gear.

Punches are not cheap, but they do the best work and will last a lifetime.

73DG

That pretty much sez it all ! ! ! !  With PRACTICE being a key word here!
that is pretty much all I use.

But Dennis, you forgot 2 very important items......................
A fresh Sharpie and a bottle of alcohol.
Depending on the complexity of the item you are building, you WILL lay it out, clean the ink off and lay it out again quite a few times before you drill the first hole if you want a good professional looking layout.  

[w4bfs]

But Dennis, you forgot 2 very important items......................
A fresh Sharpie and a bottle of alcohol.
Depending on the complexity of the item you are building, you WILL lay it out, clean the ink off and lay it out again quite a few times before you drill the first hole if you want a good professional lookig layout.


I usually consume the alcohol after the drill walks away a makes a new hole location .... then I clean off the drill press like I shoulda in the first place

[KM1H]

Add a roll of masking tape to minimize marring when drilling.

[KC2ZFA]

all of the above and this too:

[K5UJ]

the title is building chassis.  if you are going to make your own chassis from sheet of metal you need to make bends.  i would like to own one of these:

http://www.grizzly.com/products/24-Box-and-Pan-Brake/G0557

I'd also like to own a milling machine but i would settle for a floor mounted drill press.  I'd also like to have a table top band saw.

[ssbothwell KJ6RSG]

are those nibbler tools any good for aluminium and steel or are they just meant for plastics?

[W2WDX]

OK, I'll bite.

Drill press! I can't emphasize this enough when using step drills. Actually I can. DRILL PRESS!!!  

Slow gradual drilling, using lubricant/coollant at the same time will eliminate burrs and erratic hole sizes when using step drills with Steel or Aluminum.

Greenlee punches are the only way to go. I have bought others (cheaper) and the aggravation created by them is worth the extra money you will spend to buy Greenlee.

I own a table top ten-speed Porter-Cable drill press that I bought from Loews. It's just fine, but make sure you firmly mount it to the table. I also added a nice milling vise for smaller projects. All told cost me about $250, including the milling vise.

Never buy cheap bits or mills, and always buy the right bit for the material. This is important for three reasons. Quality of the hole, durability & therefore longevity of the bits, and safety!

Also never put a piece to be drilled down without it being firmly mounted to something. Clamp it to the drill base, use a milling vise or a drill vise mounted to the base of the drill press. Most binding occurs because the piece moves, vibrates or is on angle not perpendicular to the drill. Rigid mounting of the piece and having a press is mission critical for perfect holes that need little hand work after drilling (deburring, etc) Safety is also a big issue here! Many a finger/arm/eye have been lost due to people drilling chassis held only by hand, being drilled with a hand drill with no lubricant. OUCH!

Clamps, various wood blocks, drill specific vises, correct drill types, etc will all make the job go well with high quality results, go quickly and happen safely. Here's the milling vise I bought, from [yikes] HarborFright (the mis-spelling was intentional.) It's not ultra-precision but works fine for most Amateur Radio uses.

http://youtu.be/3UakdVbLCHE

John

[WQ9E]

I second John's call for a drill press.  I generally have a cross slide vise mounted to both my straight and radial Delta presses.  The Harbor Freight vises have worked fine for me and I have had them for about 10 years.  I also have another mounted on my mortising machine and it has also performed flawlessly.

For chassis use, you will often need to build a simple jig that will go into the vise and support the chassis, generally a piece of plywood with attached cleats to clamp to the chassis sides and to clamp into the vise.  This style vise takes most of the frustration out of putting smooth cuts exactly where you want them.

[N6YW]

I have to jump in here.
I have built close to 100 amplifiers so far and may offer some wisdom in no particular order.
Plan, plan and re-plan. Your end results are ONLY going to be as good as your planning and layout.
Once you have arrived at this critical place, the best quality tools you can afford is a safe and sure investment.
Your drill bits should be as sharp as possible, and the use of a "Uni-Bit" is encouraged.
You should consider using a high quality snap punch. If you plan on fabricating your own chassis, be sure
to accommodate the radius of your bends with your finished measurements. Once you bend, that's it... you can't go back. Using a block of wood behind your material while drilling will help to eliminate "blowout" or slagging of leftover material from the hole. A plumbers pipe reamer or hand trimmer is ideal for clean holes.
The use of green masking tape is also encouraged when laying out your drill marks and helps to keep the material clean and also helps in case you "dance" a tool or bit across your chassis.
I should also stress the use of high quality files and this includes fine jewelers files. And please, buy a file card to keep your files clean. They can build up aluminum in a hurry and foul out.
NEVER use a hole saw on a drill press!!! This is fool hardy and dangerous as hell. Use the slowest drill speed you can to make your drilling operations not only clean but safe and it helps to maintain the structural integrity of your drill by not overheating them. It is best to use real cutting agents intended for cutting and drilling metal because they can handle the heat. Certain types of lubricants like light machine oil and WD-40 should be avoided.
Back to the layout...
If you can afford the space, make sure you have an adequate area to layout and fabricate. Working in cramped quarters can cause mistakes. Making absolutely sure that your measurements are truly square is made easy by having at least a Tri-Square and a T-Square. The cool thing about most Tri-Squares is they include a handy scribe that nests in the square so you can make scribe marks along a line.
More to follow.

[KL7OF]

All this stuff has been covered ad nauseum on this forum, some very recently....do a search...All the varied opinions will drive you nuts....There are many ways to do this...Most all work for the most part....My opinion.......I am a metal guy...made my living as a sheet metal worker, machinist, welder.....I've homebrewed 3 big rigs and modified many others...I have all the tools...My advice... if you are only building a chassis or two....KEEP IT SIMPLE....You don't need to spend a boatload of money for tooling......Good luck and keep on homebrewing!!!

[K5WLF]

I've used Step-bits quite a bit on various projects and they work great. I drill a small pilot hole just to ensure the accuracy of the center point. Just have to be careful and not overshoot the step you want. Also, it's worth the money to get the good bits. And no, from experience, Harbor Freight does not sell the good ones.

What do you look for to determine if a bit is good or not?

Quality of workmanship in the bit and how long it lasts. I ordered my Harbor Freight ones on-line and wasn't impressed when I got 'em. The cutting edges didn't last either. Just bad metallurgy. I bit the bullet and paid the price for Irwin brand at the local ACE hardware. They look like a high quality piece and live a lot longer. Reminded me not to grumble about the price for good quality tools.

[KC2ZFA]

I'm a newbie, and the "keep it simple" advice given above has been good to me.

I've been doing a fair bit of metal work with two hole saws, two step-drills, a nibbler, a reamer, a collection of files, a collection of drill bits, a black&decker, a dremmel, a pair of lab goggles, a hand saw, and my own two hands. I also use my thighs and feet to hold stuff in various orientations during drilling. Finally, a bunch of wood pieces and clamps are sometimes used.

Here's something I've been putting together recently (I've cannibalized the aluminum enclosure and other parts of a BC-375 tuning unit in which I put a chassis cover with angle stock):

http://imageshack.us/f/215/img1655gf.jpg/

http://imageshack.us/f/853/img1671m.jpg/

[AB3FL]

Now where can I get a chassis from that doesn't cost a fortune?