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Cutting slots in sheet metal for a rookie

#1
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Pretty simple, how would you guys cut those slots out?

Also, how do you measure the center of an existing hole?

The parts pictured go together, so the slots need to be reasonably close

Thanks!
 

Johnwa

Active Member
#2
If you don’t require 0.001” precision then find a drill bit that just fits in the slot, measure from it and adjust for the radius to find the center.
It would be easy to do the slots on a mill, otherwise If the material isn’t too thick, I would drill a hole at each end of the slot and then clean up with a file.
 

PeterT

Ultra Member
Premium Member
#3
If you have trouble with the hole oblong-ing which can happen sometimes on sheet metal. I find these cone step bits (whatever they are called) can help. Drill a pilot hole & then it progressively increases diameter with each step. Then like John suggests, connect the 2 holes with straight segments, hand filing or rotary burr Dremel type tool.
 

Attachments

#5
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I was trying to improve my skills I guess, what I’ve done works fine and will never be see unless someone takes it apart.

I used an IR air die grinder with a carbide burr. Not exactly high precision fabricating
 

PeterT

Ultra Member
Premium Member
#9
With a die grinder you should be able to get pretty close to a scribe line. & be pretty much bang on Next time (there's ALWAYS a next time LOL) mark the metal with dark Sharpy marker, scribe the line from your pattern, or lay it out whatever the situation calls for. That way the witness line will be nice & bright against the dark marker (cheap mans layout blue). Center pop the hole centers & drill them a bit undersize if you are concerned about ovaling or wandering. Sheet metal can be a bit of a bugger that way. Then use the die grinder to open up the slot & work your way around until you just kiss the scribe line everywhere. Its better to remove metal in little arcs & nibble away at rather than trying to traverse the cutter in long lines. If its a burr cutter it may cut different in one direction than the other. A stone isn't as bad. Find the one that gives you best control. Hand files should do this equally well so grab your weapon of choice.
 

Janger

(John)
Administrator
Premium Member
#10
A drill press and decent drill bits would help a lot. Used. Not too expensive either. The step drills Peter mentioned are good too but the rigidity of a fixed shop tool drill or mill is much better.
 
#12
I’ve been looking for a decent drill press for awhile. The one you posted is too far away, but I’ll start checking kijiji again. A small older mill would be awesome

Two dumb questions- can you mount a fence on a drill press table? Piece of angle iron and vise grips?

Can you chuck up a carbide burr and feed material into the cutter? (In the drill press)

Or is that starting to sound too rednecky...?
 

Johnwa

Active Member
#13
On the small drill presses with screw on chucks it sort of works. The bearings aren’t designed for radial loads though. On larger drills with Morse taper mounts the mount comes loose and things become airborne.
 

Janger

(John)
Administrator
Premium Member
#14
Drills are for drilling holes. Mills are for milling (slots). But John's comment that it does work, kinda, is true. The other issue is how do you slide the material straight and true? You can't hold steady and move the part even in a vise with any accuracy. (obviously anybody don't try to hold it with your hands). An XY vise would help a lot and make a drill press into a poor milling machine. This approach is hard on the drill press and will ruin chucks.

The drill table often has T-slots for T-nuts that you can use to hold stuff down - like a fence.

Anybody trying stuff like this - don't hurt yourself.

Don't worry - you'll be blowing all kinds of money on mills and lathes pretty quick.
 

Attachments

#15
I said “dumb” questions!

I still think a fence on a drill press would work to help keep my holes in line. Like a mill, that way one axis is fixed. As long as it’s squared up properly?

We can forget I asked about chucking up a carbide burr :D
 

kevin.decelles

Well-Known Member
Premium Member
#16
I have one of those x-y tables....... a cheap one....... I regret using it on my drill press. It drilled really well before I used that table, not so much after (mostly aluminum work). I'm scared to check my spindle runout since doing that years ago..... I can see it with the naked eye...


X-y table sits ona shelf, I might make sacrifice it for a 'shaper project'
 
#17
In Sheet Metal I would do as follows,
*Mark slots with scribe by using the original plate.
*Pree-drill as much material as possible leaving about 1/8 material inside scribe line.
*Clamp the original Plate with a 1/2" spacer onto the new plate.
*Using a 1/4" Carbide Die Grinder to finish the holes. The (smooth) portion on the Die Grinder
rides on the upper plate. All you have to do is holding the Die grinder in a straight 90 otherwise just use a Router with the Die Grinder.

Cheers.
 
#18
I said “dumb” questions!

I still think a fence on a drill press would work to help keep my holes in line. Like a mill, that way one axis is fixed. As long as it’s squared up properly?

We can forget I asked about chucking up a carbide burr :D
John and Janger are both right in a "perfect world" but seldom are we hobbiers in that world...the fact is your idea of a fence bolted to the drill press table will work but I "would" use a fine fluted carbide rotary tool/burr (no upwards or downwards pull to work piece or cutter) with straight flutes instead of a spiral mill cutter and feed very slow . With a very slow feed of the work piece into the cutter I can't see that thin of sheet metal doing much damage to a spindle guide .
 
#19
John and Janger are both right in a "perfect world" but seldom are we hobbiers in that world...the fact is your idea of a fence bolted to the drill press table will work but I "would" use a fine fluted carbide rotary tool/burr (no upwards or downwards pull to work piece or cutter) with straight flutes instead of a spiral mill cutter and feed very slow . With a very slow feed of the work piece into the cutter I can't see that thin of sheet metal doing much damage to a spindle guide .
In the interest of safety I kind of dropped this idea. I agree that “probably” this could work, but this “shouldn’t” be tried at home without supervision.

The more I thought about dropping the chuck (quill?), into the material, holding it in place, trying to lock the spindle depth, then feeding the material slowly, all quickly brought up red flags.

I did look very briefly, a mini-lathe was $5-600 from Grizzly. I wonder what a mini-mill goes for?