How to cut a rectangular hole, smaller than 1", in sheet aluminum?

[rustythe4x4]

Originally Posted by rmack898

How about a DB punch.

http://www.mcmaster.com/#knockout-punches/=pslrz1

Exactly what I was thinking.
More specifically:
http://www.mcmaster.com/#3476a51/=psz1yn

A bit pricey, but flawless every time.

[johnyradio]

Originally Posted by rustythe4x4

Exactly what I was thinking.
More specifically:
http://www.mcmaster.com/#3476a51/=psz1yn

A bit pricey, but flawless every time.

thx, i'd love some, i'll take 15, please

covered that earlier in the thread, decided too pricey.

looking for something under $100.

Current plan is one of these:
a rotary dremel, electric scroll, or manual coping or jeweler's saw. Or maybe a die grinder (new suggestion).

new info which might change everything. This piece is not all aluminum. The outer material is 28 GA galvanized steel. Inner liner is aluminum.

Would that affect my plan to use a rotary dremel, electric scroll, or manual coping or jeweler's saw?

[cutter]

oookay, I knew it was going to happen and I should have said this sooner.
I was trying to let the conversation flow because of the worthwhile nature of this thread but Johnny, you need to read this part of our FAQ.

In short, we do not allow off-site hosting or embedded images for the reasons explain in the FAQ.
We upload them to our server instead.
That way, they are much more likely to remain viable years down the line.

So Johnny, we got ourselves some editing to do.
I would prefer that you do it but if you don't then I will.
What say you?

[johnyradio]

Originally Posted by cutter

I was trying to let the conversation flow because of the worthwhile nature of this thread but... we do not allow off-site hosting or embedded images ...So Johnny, we got ourselves some editing to do.
I would prefer that you do it but if you don't then I will.
What say you?

oops, well i'd be happy to make the edits if you tell me how, but cannot get to it for a couple days, atm i'm off to be one of the expert speakers, along with the Mayor Ed Lee of San Francisco, and several other distinguished speakers, at "Symposium for Sandy Hook: Gun Violence Reduction & Mental Health". I will explain how studies in Child Development and Public Mental Health form the underpinnings of my mentoring program.
http://www.highgroundhackers.org/sandy-hook/

anyhoo, i'm happy to do the edits, plz send me instructions, or if you can't wait feel free to do them, that would be very nice of you.

may i respectfully suggest you mod your forum, if possible, to prevent people from doing that?

ps, thanks for maintaining this great resource!

[cutter]

Done. When you get back we'll work on attaching images.
You've got a nice thread going here.

[GWIZ]

Originally Posted by johnyradio

even cheaper, incl shipping! sweet. thx! the customer reviews for it are generally very positive. "great value", etc. One review said had no trouble with 90 degree angles.

the Dremel scroll on the other hand got a lot of mediocre reviews on amazon. and it uses proprietary blades

it's looking good for the green machine.

that, or a Dremel (original Dremel rotary tool, not the Dremel scroll) with plunge router and/or depth cutter guide. Looks like about $20 to $40 for the rotary tool and $40 for the plunge router. Basically same price range as the green machine.

this Dremel rotary runs 8000 to 35,000 rpms, vs 400 to 1600 rpms for the green machine! Does it matter?
http://www.harborfreight.com/variabl...kit-68696.html

So that's the current decision.... Opinions/other options welcomed

Grinding stones you generally run them high so 8K - 35K rpm is OK if the stones are rated at that rpm or higher.

If the cutter has teeth then you have to go slower in metals, need to avoid heat and unnecessary rubbing that will kill the cutter.
I'll have to go back and look what they posted on the saw for speed.

Rotary tools are good for cleaning up and would work well with that nibbler I stated.
I would not recommend them for cutting out a slot as you want,
If you are thinking about the thin slitting disc, they are dangerous and I would not recommend them for students.

Do you have a Harbor-freight in your area ?

As for the saw make sure the blades are not also proprietary, at one time I was not able to find blades let alone for cutting steel, I found some at a discount so I don't know if you will be stuck getting them from HF. shop around other stores and see if you can better blades before you buy (fine tooth for metal).

BTW, If you decide on the HF saw I have a 25% off coupon that may work their wording is a bit funny that it is not allowed with a discount, but most of the time the coupons works on sale items and is worth a try.

[GWIZ]

new info which might change everything. This piece is not all aluminum. The outer material is 28 GA galvanized steel. Inner liner is aluminum.

Would that affect my plan to use a rotary dremel, electric scroll, or manual coping or jeweler's saw?

Yes it would affect something, get more information.
We still do not know the total thickness and as you questioned, is that two sheets of 28ga steel with what ga aluminum ?
Also a reciprocating saw blade may force the layers apart on the return stroke.

===
The rule for sawing is,
Three teeth of the blade must be in contact with the workpiece at all times or you run the risk of chatter and breaking off the teeth and/or breaking the blade.

Here is a pdf on sawing.
http://uhv.cheme.cmu.edu/procedures/machining/ch6.pdf

The speed on the saw is 400 - 1600 SPM
Strokes per minute. (not rpm).

That may be a bit fast in respects to blade life.

[johnyradio]

Originally Posted by Ironman

I would recommend making this in a drill press, but with care and patience you could do it with a hand drill.

doing it with a hand-drill seems pretty hardcore but yes, i have a old-timer buddy who could help me do this with a press. will try it just for the experience, tho i think it might not be a practical way to equip my makers. On the other hand, if i can get the technique down, maybe one of our requirements will be that youth-makers have to fab their own punch as part of their training. That would be impressive. If i can send a 17 yr old to a job interview, and he/she can show off a tool they fabbed theirself, they might just get the job.

A rectangular punch would be possible with two drilled holes, figure the spacing right. Much more complex, but the idea is to achieve a hollowed centre with a sharp edge. And you would definitely need a drill press to control the depth of the larger drill bit so all edges were even.

i knew you were going to say that What about a router instead of a drill?

[johnyradio]

Originally Posted by GWIZ

Grinding stones you generally run them high so 8K - 35K rpm is OK if the stones are rated at that rpm or higher. If the cutter has teeth then you have to go slower in metals, need to avoid heat and unnecessary rubbing that will kill the cutter.

ok, so stone can run faster because they don't overheat the way metal cutters do? thx for that!

Rotary tools are good for cleaning up and would work well with that nibbler I stated.

hoping for a one-tool solution....

I would not recommend them for cutting out a slot as you want, If you are thinking about the thin slitting disc, they are dangerous and I would not recommend them for students.

i'm not sure, here are the suggestions that were made:

Dremel's plunge router attachment, then make a jig/template of the D-sub cutout, and just trace around the template. A proper router bit should cut through the aluminum like butter.
http://www.workshopaddict.com/forum/...html#post20593

and

for what your doing you cannot beat a dremel tool, there is the depth cutter guide attachment that could easily be adapted to follow a pattern. Id get a die grinder and set it up like a vertical spindle sander
http://www.workshopaddict.com/forum/...html#post20578

Do you have a Harbor-freight in your area ?

nope

As for the saw make sure the blades are not also proprietary

yes, that's why i nixed the Dremel scroll saw, above.

BTW, If you decide on the HF saw I have a 25% off coupon that may work their wording is a bit funny that it is not allowed with a discount, but most of the time the coupons works on sale items and is worth a try.

wow, many many thanks, i really appreciate that!!! i know we'll need to buy something at harbor freight, if not this item something else. Would be great if you could donate that!

[johnyradio]

Originally Posted by GWIZ

Yes it would affect something, get more information.
We still do not know the total thickness and as you questioned, is that two sheets of 28ga steel with what ga aluminum ?

Will call selkirk monday...

Also a reciprocating saw blade may force the layers apart on the return stroke.

and a scroll and jig would both be considered reciprocating, right?

The rule for sawing is, Three teeth of the blade must be in contact with the workpiece

ok, i have read 2 teeth elsewhere. Can you have too many teeth? Won't a lot more teeth just give a cleaner, faster cut?