Enlarging pre existing holes

So Im in the process of building a drip Sta-Level  and have gotten a case from collective cases and the meter from instrument panel specialists that collective cases specified. model 27 6vac lamp / 200uA. so received the meter today and did a test fit and it doesn't fit! The hole diameter 2 .1" (~53mm) and the meter diameter is 2.75" (~70mm)

SO, I'm trying to figure out how to enlarge this hole with the tools i have:
Dremel, Drill press, jigsaw and the collective minds of GDIY.

-Cory

File?

JR

Yeah that is one way but I feel like that's a lot of material to file away. I'd probably use a sanding drum. I always find fabrication difficult, so before I start grinding away I wanted to know if there is an "easy" way to do it.

You have to remove about 7mm at each side, having a dremel I'd probably put the file away till I'm closer.

JS

joaquins said:

You have to remove about 7mm at each side, having a dremel I'd probably put the file away till I'm closer.

JS

Click to expand...

I would do the same thing, remove the bigger part with the Dremel and use the File for the final stage, just be careful not to remove too much with the Dremel

Since you have a drill press I'd use a hole saw (2.75" is a standard diameter). Clamp the panel well and use a piece of flat wood underneath. Use good cutting fluid/oil.

Best, M

Marik said:

Since you have a drill press I'd use a hole saw (2.75" is a standard diameter). Clamp the panel well and use a piece of flat wood underneath. Use good cutting fluid/oil.

Best, M

Click to expand...

Those are usually not good for enlarging existing holes, you need to center it in some way, for one off I'd still probably go with the dremel. Also if you don't have the hole saw for the size buying one for just one hole seems overkill...

JS

joaquins said:

you need to center it in some way

Click to expand...

You need to center those only working with a hand drill. If you use a drill press and clamp the panel well you don't need to center it. But... you need to have a wooden block underneath, anyway.

Best, M

Marik said:

joaquins said:

you need to center it in some way

Click to expand...

You need to center those only working with a hand drill. If you use a drill press and clamp the panel well you don't need to center it. But... you need to have a wooden block underneath, anyway.

Best, M

Click to expand...

I have a bad experience with it, it turned out more than ok for the application, just an acrylic board with two fans for the notebook, quite good results, I squeezed like 35% more and make it live 1+ year more. One pulling one pushing, rubber sealed around where it got  hot. Another story, anyway. Very soft material and the hole wasn't perfect, drilling conditions weren't best though.

It could be done, you still need the proper saw and if it could be done 1 or 2 mm smaller to ensure the final result with the file may be a good thing.

JS

If went the Dremel route would I use the sanding drum or some kind of grinding bit? I'm pretty sure it's aluminum.

Which do you have? This is not critical... just be careful you don't screw up and make the hole bigger than you want.

My file comment is half joking. When I was a young puke, still in HS, my summer job between junior and senior (11th and 12th grade) years, was working in a machine shop... Since I was technically underage, and too young to operate machinery, I started out on bottom of the barrel jobs (believe me) but by the end of that first summer I was working on the real machines.

Then I show up for senior year of HS and I take metal shop class, not to learn metal working but to gain access to the HS metal shop so I could work on various DIY projects (mini bike, etc). The first class project was to file a small square piece of metal...  I nearly got into an argument with the teacher pointing to the belt sander a few feet away that could finish that project in minutes. It started out a little awkward but we reached a better relationship when the shop teacher figured out that I had already worked in a real machine shop, and knew stuff.  ;D

So use a power grinder to rough out the hole and a hand file to finish it.

To answer your specific question, my dremel has a cutting tool that looks like a little end mill that can cut thin aluminum pretty easily. The sanding drum would be more for finishing the hole to smooth the edges. Dremel also has grinding wheels but they clog pretty easily on soft metal.

JR

Marik said:

Since you have a drill press I'd use a hole saw (2.75" is a standard diameter). Clamp the panel well and use a piece of flat wood underneath. Use good cutting fluid/oil.

Best, M

Click to expand...

Hi Marik,
what cutting fluid/oil do you recommend?

thanks

That you can find at home, for Al I like alcohol, for steel pig fat or the most similar thing you have around (cow fat, soap?)

For dedicated stuff there are some commercial ones in so many flavours I don't even know, in particular for steel the pig fat has been recommended to me by some professionals over the commercial options not only in price but also as better overall. There are some emultions  (water based) I've used when you need to cool down the pice, for big cutting, drilling etc you need some liquid flowing permanently, a water pump for small water fonts works a treat for as cheap as it gets. In some cases is essential to have such thing, 1" hole in a 10mm 6051 steel (quite hard, used in truck suspension bands). Without that the bit will get dull after 2 holes, when you have to sharpen your bit 50 times for one job you start to wonder and build a continuos cooling system...

JS

Zjcc56 said:

So Im in the process of building a drip Sta-Level  and have gotten a case from collective cases and the meter from instrument panel specialists that collective cases specified. model 27 6vac lamp / 200uA. so received the meter today and did a test fit and it doesn't fit! The hole diameter 2 .1" (~53mm) and the meter diameter is 2.75" (~70mm)

SO, I'm trying to figure out how to enlarge this hole with the tools i have:
Dremel, Drill press, jigsaw and the collective minds of GDIY.

-Cory

Click to expand...

Whatever the method you finally opt, remember that marking and protecting are paramount.
I start by drawing the existing and desired circles, printing 1:1 scale on thick paper that I glue with paper glue. Then I protect the remains with gaffer tape.

I am not familiar with that case so don't know how thick the metal is, drilling large holes in thin metal can be exciting. If the the drill tool grabs into the metal, it can start spinning violently and injure you.

Back during my machine shop days I had to cut some 4" or so (don't remember exact size since it was 50 years ago), holes in sheet metal, something like 16 ga galvanized steel. I ended up clamping it down to a serious big dog drill press, that was more like a milling machine. The table had X-Y controls and the drill head had a motorized feed. Long story short, if you decide to drill an almost 3" hole, secure the plate to the drill press so it can't shift or get loose.

My sheet metal got several sheets stacked together and I used a fly cutter tool, but that was on a serious machine, and the metal was securely clamped down to the drill press table. Even then I had to proceed with caution.

Be careful sheet metal can bite you...

JR

PS: Another way to make pretty holes is using a greenlee punch, but for the cost of a punch ($100), you could pay a local shop to make several holes. 

The one and only tool for this job is a CNC router,
or ... if you don't have a CNC,

use the poor mans CNC :

http://www.sfz-e.de/tz2/seiten/unterricht/fach-twz/album_werkzeug/slides/Laubs%C3%A4ge.jpg

...markus