Using a Bridgeport Slotting Head as a nibbler ???

[awemawson]

Recently had to make some rectangular cut outs in 2 mm aluminium sheet with a hand held nibbler which is always a pain to get neat, so I was casting about for easier methods.

There are 'Throatless nibblers' where the die pokes out of a table and cuts on the down stroke - very handy, but not cheap and they take up floor space.

There are punch and die sets for Fly Presses, but the depth of sheet is very limited by the upright of the structure and again they take up much floor space for the arm to swing.

Then I cast eyes on my Richmond 3 foot radial arm drill. Very heavy construction, lots of room for biggish panels, perhaps I could make some sort of reciprocating punch holder, and rig the corresponding die on the table with guides for the sheet.

Then I thought - don't be daft - you've got precisely that hung on the back of the Bridgeport in the form of a slotting head.  Crank woggles a cutter up and down at a rate set by change gearing, and again masses of room for a biggish sheet of metal. Only issue that I can see is arranging some form of 'stripper' to stop the sheet being pulled back up by the punch as it withdraws.

Anyone been there and done this? Or have any comments on the strength of 'push' of the standard Bridgeport slotting head. How much force does it take to ram (say) a 3 mm circular punch through 2 mm aluminium sheet or 1.6 mm galvanised sheet?

[philf]

Andrew,

Depending on the grade of aluminium, the force required for punching a 3mm hole in 2mm thick material could be anywhere between 100 & 400 kgf (220 - 880 lbf) which isn't inconsiderable.

Phil

[BillTodd]

Hmmm,  Looking at my roper whitney punch and thinking how much leverage has it got and how much force to punch 2mm ally? 

Well the punch moves not much more than the thickness of the piece, while the handle goes from a  hand-full to about an inch and half.  so say 20:1 . I recon I can easily lift 40kg with my fingers so say 400N max at the handles making a maximum force of about 8000N at the punch  (close on a ton)

That's gonna give that bridgeport a shaking ;-)

Bill

[JHovel]

I would think that its wll within the capability of a Bridgeport head. That force is not created by a stationary weight, but by the 'decelration' of all the inertia in the ram and drive of the entire mill. I'll be very interested in your attempt! Looks like a great out pf the box use of a slotting head.
Cheers,
Joe

[awemawson]

First results are very encouraging 

Not having a suitable punch and die to hand, I reached for a 5 mm slotting tool that I already had for the slotting head - but what to use as a die  For a rough and ready test, just really to see if there was enough ooomph in the system to slot 2 mm aluminium I hit on the idea of setting the vice jaws slightly over 5 mm and using them as the die. OK no shear action at the front and back, only on the sides. But this is just 'proof of concept' not full implementation 

How do we space the jaws - suspend a 5.2 mm drill on a parallel, screw the vice tight and see what happens. Turned out far better than I'd expected, and certainly worth developing as an idea. Only issue was the lack of a stripper plate to stop the victim aluminium sheet being lifted by the punch as it withdraws. But for a first attempt I'm very pleased.

[Mark Rand]

The stripper plate can be mounted on the tool with a die spring to propel it. If the "stripper plate" is thick enough, the tool can always be in stripper plate's hole, so self aligning.


I knew there was a reason to get a slotting head for the mill.

[mattinker]

Your using it like a slotter which it is, the plate needs to be bolted down which could be done in such a way as to act like a stripper.

Regards, Matthew

[BillTodd]

Nice

how about making a nibbler type tool? one with a stepped profile so it controls the size of the bite .

[JHovel]

 
Thanks for the details! Keep documenting the progress.
Bill's comment is important. If you want to be able to do 'off-hand' nibbling, you will need to controll the step distance.
Cheers,
Joe

[hermetic]

Hi Andrew,
I have a desoutter air nibbler in which the blade is C shaped in section and reciprocates up and down a guide rod which is inside the C. as you feed in the metal, when the blade goes up, the edge of the metal hits the guide rod, and as it comes down it removes a crescent moon shapet cutting from the sheet, the metal then can move in the distance equal to the thickness of the blade for the next cut. Does that make any sense to you, and will that be any help?
Phil.

[awemawson]

Phil, yes thanks I have one that sounds very similar !

Bridgeport had to be turned back into a mill today so I had to break down the trial set up. I'm coming round to the idea of a conventional nibbler arrangement set into some form of fixed table. I have several nibblers ranging from the air one mentioned, up to a monster that will cut through 6 mm mild steel and scares the wits out of me when I use it I may investigate mounting the big scary one in a table and see how I get on !

[dawesy]

Wow a 6mm cut with a nibbler. Think I'd be cautious of that too.

[awemawson]

It spits out 6 mm cubes of mild steel at a great rate of knots  It's also pretty heavy to hold. I took a few pictures - it eats through 6 mm plate at an alarming rate !!!

[Meldonmech]

Hi Andrew
                 I would use a hand held jigsaw with a metal cutting Blade. No fiddling around setting up just drill one hole to enter the blade and away you go.

                                                              Cheers David

[awemawson]

David,

it's horse for courses I think. A jig saw is fine BUT the edge is always a bit nasty and needs filing to size, AND in a soft metal like aluminium the face inevitably gets scarred. For thicker steel - 3 mm plus - a jig saw is probably what I'd reach for - being harder it doesn't scar from the saw vibrating. For open cuts I have a very nice Gabro notcher that cuts cleanly and doesn't distort either side of the cut, but it cannot be used for internal openings. They do do a punch press that would be nice, but they take up a lot of real estate and fetch silly money.

[dawesy]

That's a beast
Only issue I've had with jigsaws are the quick change type blade holders letting go.
I now use one of the evolution cutting discs in my circular saw. Is has a metal guard and the speed rating is ok. Works well but can only do straight cuts.

[DMIOM]

....... I'm coming round to the idea of a conventional nibbler arrangement set into some form of fixed table.................

Andrew, that's what I did. Some time ago I had a unit which comprised table/frame with NVR switch and replaceable insert tables. The one for the router was OK for a 1/4" router but flexed too much for a 1/2" ELU, so that insert got re-purposed to hold a power nibbler.

Dave

[awemawson]

  Nice 

So does it perform as you'd hoped - is it nice and controllable ?