Cutting square holes in styrene

Jim, You raise a very good question, l have been doing this the way you mentioned, but maybe try a good sharp wood chisel and back up the styrene with a piece of hardwood, never tried this, but may have to try myself.

Ray

Many window openings have been cut out using my Delta scroll saw. One of my most go to power tools in the shop for a variety of cutting task.

Corner punch

https://www.micromark.com/5-16-Inch-Corner-Punch

Or use an knife and straight edge to cut them out. 

I am not kidding:  There used to be available drill bits for cutting square holes in wood.  They must be used in a drill press  I have a few but have never used them.  These are in two pieces.  The inner is a normal round bit.  The outer is a square chamber in which the round bit spins; it is restrained from spinning.  At the end from which the round bit protrudes, all 4 sides of the outer chamber have very sharp edges.  AS the inner bit cuts the round hole, the outer shell slices the hold square.

I usually just use a scalpel and the metal straight edge, but here's an option that should work.

What kind of drill is needed for the square hole drill?  I confess, that's something I never saw before.

I have two, but since I haven't used them in the past 40 years or so, I don't recall where in my massive tool room I have stored them.  So I dug out videos on the internet:

https://www.youtube.com/watch?v=Zo8Xk4jMtco

https://www.youtube.com/watch?v=3dGfm-uEpCk

Or to buy:

https://www.amazon.com/Woodwor...orking/dp/B078XQN2YJ

https://www.amazon.com/Woodwor...Chisel/dp/B015A3DPZ8

Well, they're showing them in a special press that holds both pieces, I was led to believe there's a way to do it with a standard drill press.  From seeing those videos, that doesn't seem to be the case.

No sense in buying bits if I can't use them.

I believe that in the Machine Shop they are called Broaching tools. They can be used for square holes and keyways in metal. Last year I attended a Machine Tools show for the first time and saw them in action.

My memory is a bit fuzzy about exactly how they work, but I used one of these on a standard drill press to make square holes back in high school wood shop. I know for a fact that they do work.

GRJ, it's not a special press.  There is an attachment that fits onto a standard drill press that holds it.  It appears on one of the videos on-line.  You remove the chuck, and this clamps to the drill press moving housing.  I have a floor standing Atlas industrial drill press, sort of ancient, on which it does fit.  I don't know about the table presses or the residential presses.

I do remember someone, probably a woodworking instructor, saying one must be careful not to overheat these.

Start with a round hole (small) and nibble out to size with a PCB nibbler. Finish square with a file. Has worked fine with the styrene scratch building I do.

I suspect it would have to be a larger drill press than I have.  I noticed the special holder, wasn't sure how it was attached.

It's a nice idea, I'll keep my file handy for square holes.

Thanks, everyone. I hadn't thought about using a mortising attachment. A friend of mine is a retired shop teacher and has one …  and the drill press to go with it. I think I'll try it first on some scrap styrene to see how it works.

Plan B is to use my tried-and-true method.

Hi John, I just read the spec's and questions further down. It states you can buy a special attachment for a Bench top drill. But it is an extra$125.00

Then one from Micro Mark states its 1/4" at the holding end !

The problem with the tools mentioned is they are only good for a single pane windows, basically putting one square hole in plastic. The won't work for windows with multipanes or muntins. The cutting force will just break them out.

Pete

gunrunnerjohn posted:

Well, they're showing them in a special press that holds both pieces, I was led to believe there's a way to do it with a standard drill press.  From seeing those videos, that doesn't seem to be the case.

No sense in buying bits if I can't use them.

Looking at those Special bits, I can't see why they would NOT work in a regular drill press. IT appears the drill is held by the square via ball bearings so the drill will spin and the edge of the ball bearing  hits the head of the chuck [not forumite Allentown]

This set here says need regular drill:

https://www.amazon.com/dp/B07B...pa_dk_detail_2?psc=1

It says "regular drill", but I don't believe it.  All the stuff I see on them requires you to hold the outside part from rotating while the bit does the dirty work inside the square chisel bit.

I do this the old fashioned way - because I'm old...

Mark the four corner locations accurately with a pen (or a center punch). Use a hobby knife or single-edge razor and start a cut along each of the diagonals from each of the marks to the center. Then use a metal straight-edge to cut along each of the four sides. Triangular pieces will fall out and you can then fit windows and clean up with a file. Requires care and patience - which is a virtue. Some of my wood structure walls shown below.

MELGAR

Almost all windows that I do end up having their holes being hidden by wooden millwork of one kind or another, so the holes don't have to be perfect. If I were doing a modern skyscraper, that would be different. But I don't do that.

gunrunnerjohn posted:

What kind of drill is needed for the square hole drill?  I confess, that's something I never saw before.

John - the machine you saw is a mortise machine. The drill bit is inside the rectangular punch. As you press down on the handle the drill makes a hole and the bit squares it off. The machine is expensive.

The bit pictured earlier that fits in a normal drill press is meant to be used with the press off. You simply apply downward pressure. Obviously this is used on thin stock. One can also purchase a hand held version and used a hammer.

Jim:

Two ways I use

1. drill a 3/8 inch hole and use the nibble shown above.

2. If you have a large sheet and a lot of windows and especially if you have to line up rows or columns precisely then use what I call the cookie cutter method. Cut strips leaving out space for the widows and glue together. Obviously this method only works if you laminate later. See below.

Boilermaker1 posted:

Corner punch

https://www.micromark.com/5-16-Inch-Corner-Punch

 

Or use an knife and straight edge to cut them out. 

This gizmo really works I bought a worn out table top drill press and threw the motor and running gear away.  I use it just for making windows and doors.

I use a number of ways even the old fashioned method of drill and saw using a saw with teeth not a blade, that's using 3mm styrene sheets. I like to also cut strips then leave the window spaces and glue it altogether and brick clad it. Lots of ways, maybe 3mm MDF and laser cut the holes is the next way to go not that I know any laser cutters in West Australia.  I thank the Lord I only have one large structure left to build on the layout with no windows and that's it for the rest of my life no more structures ! Bring out the locomotives. Roo.

Here's a picture of the adapter that holds the outer sleeve of the square bit, and the sleeve without the internal round bit, sitting on my drill table.  Clamps above the chuck

I have a dedicated mortising machine (a Delta) which I use for mortise and tenon joints in woodworking. The bits, as shown above, are a combination square chisel surrounding a round drill bit. When used in a standard drill press, the chisel/drill bit is not used by itself, but rather with an attachment that keeps the chisel from rotating. Using either machine, the chisel squares off the round hole created by the inner drill bit. While I admit to never having tried it on styrene or any other plastic, I don't see the chisel cutting cleanly through such material. A sharp blade will easily slice along the edge of a piece of styrene but not through it's flat side, since it would be attempting to punch rather than slice through it. 

I use Boilermaker 1' s method of cutting with a knife and using a square. I use a boxcutter because that is what I got used to from working in a supermarket as a kid. The trick with cutting is to press firmly on the blade and cut through in multiple scribes rather than at one time. I cut from .010 to .125 this way. If you use a boxcutter with single edge blades, buy the most heavy duty blades you can. The cheaper blades snap and can get dull quickly.

The round drill inside of the square broach is a mortising tool for making joints in wood furniture. This technology is over 100 years old.

There is nothing magical about those mortising tools. They are simply a combination of a drill and four corner chisels very much like the corner punch that MicroMark sells. This is extremely handy in woodworking if you need a mortise and have the tool of exactly the right size. For making window openings in styrene, balsa or bristol board, it is just as easy to simply drill corner holes and cut, chisel, or file the corners square.