Cutting shapes in sheet brass.

Hi All,

In my first post introducing myself, I warned that I would be asking some daft questions and so here is the first of many. I am afraid it will cause many of you to headbutt the keyboard and ask if this buffoon should really be allowed near tools without adult supervision but someone once told me that the only time a question is stupid is if the asker already knows the answer and since I don't....

How do I cut shapes in sheet brass? Or any sheet metal for that matter. I guess a straight line can be cut with a hacksaw but what about curves? If I was working with plywood I would use a fretsaw, with balsa I would use a scalpel but neither of these will work with metal. I'm thinking along the lines of approx 16 gauge brass or copper for a model steam engine. My initial inclination is to cut very conservatively on the waste side of the line with a jigsaw and then work at it with a grinding wheel in the chuck of my Dremel until I get the line I want. Any advance on that? I imagine there's an answer along the lines of "Everyone knows that you do it like this..." but I don't know so I'd appreciate your input...

Many thanks,

Jim

For intricate shapes a piercing saw can be used, very much like a narrow bladed coping or fret saw. For gentle curves you can sometimes get away with using a junior hacksaw with a new blade that cuts a reasonable sized kerf.

Brass does not grind that well but a sharp file or two will make easy work of it, external curves can be refined with a linisher or small bench belt/disc sander

This is clockmaker territory so here goes, what I do with a complicated shape is draw it in turbocad print it stick on the brass with 3m photomount and use a piercing saw (see Utube) to cut close to the line then file the last bit not familiar with CAD then use a layout blue and a scribe.

Thanks for the input guys, it's much appreciated. I use CAD for flying models so I'm reasonably proficient with it. I have a disc sander - never been used on anything harder than balsa but the instructions clearly state it can be used for non ferrous metals.... Erm... That includes brass and copper... Right? Sorry, sorry, sorry - I'm a clueless halfwit, I know, but to me ferrous means stuff that contains iron. Brass is made up of copper, zinc and carpet fluff if GCSE chemistry serves - so my Proxxon sander should be fine with brass and copper. I'm planning on making a steam boiler and I need to cut the U shaped sections out of the boiler housing.

Hi Jim

For long straight edges I use a filing guide made up of 2 pieces of rectangular steel bar pinned at each end. The pins are a close sliding fit and serve to keep the 2 bars in alignment. After cutting close to size with my jigsaw, the sheet metal is placed between the bars and the scribed line matched up with the edge of the bars, the bars are than clamped in the vice or with G clamps etc. Then filing the sheet down to the surface of the bars gives a very neat and accurate straight edge very quickly.

Hope that makes sense.

Nigel

Jim, I use a bandsaw for curved shapes both in brass and steel. A fine tooth blade about 24tpi and away you go.

Its very easy to cut shapes and if marked out carefully you can cut very close to the lines.

Clive

Hi Jim,

A couple of notes about using powered sanders on metals. They will work very well on many metalwork jobs along with saws as others have mentioned. However-

1. If you have been using it for wood, and the dust collection areas of the machine have wood dust present, be very careful if you sand any ferrous metals that give off sparks - they can set the wood dust on fire. (Don't ask me how I found that out.)

2. Never sand aluminum. Finely divided aluminum particles can explode or catch fire. Same goes for aluminum on a grinder, except on a grinder there is also a risk of the wheel bursting if it gets loaded up with aluminum. Don't do it!

Good luck, have fun. One thing you will find invaluable for model engineering is a full set of fractional 1/16" to 1/2", number 1 to 60, and letter A to Z size twist drills if you work in Imperial measure. These are often sold as 115 pc sets. If you want to work in metric, a 0.5 to 6 mm dia by 0.1mm increments, and 6 to 13 mm by 0.5 mm increments will be a good start. Whichever system you buy, spend a bit and get a good quality high speed steel (HSS) set, preferably US or British made, but some Taiwanese ones are also fine.

FYI brass is an alloy of copper and zinc, bronze is an alloy of copper and tin. For small pot boilers to published designs you can use brass, but copper sheet is far better for boilers and bronze is preferred for fittings on boilers since it is more corrosion resistant. The zinc can leach out of brass especially in hot water and the extent of this problem varies with geographic regions. Once the zinc goes, the brass loses much of its' strength. Best to be safe and use bronze and copper for small boilers, and only use silver solder for boilers for the same reason. For silver solder supplies and techniques, look up CuP Alloys on the web. They also advertise in ME and Keith from CuP is on this forum periodically.

JD

Thanks guys, there are some really useful points in all of the above! Nigel - I'm really sorry but you are going to have to explain "pinning" to me. You see, where I come from (aeromodelling) we use dress makers' pins to hold balsa in place over plans, so when you talk about pinning steel bar I can't help wondering if we are imagining different things. Sorry to ask a dumb question!

Jeff - great stuff, all things I need to get to grips with! I will google every word from your third paragraph between the words "fractional" and "good start". I was planning on using copper for the boiler but brass for the support. (Is that the right word? Support? Housing? The bit that holds the boiler in place above the burner.) I should point out that I am the sort of bloke who feels embarrassed walking into Screwfix because I never know whether I am supposed to ask for a cross head screw or a Phillips head screw - I know there's a difference but I don't know what it is. Do you see what I'm up against?

Your help - and patience - is enormously appreciated.

Jim

hi jim,

ive only ever used a hacksaw and file on brass (plus very occasionally a piercing saw). hacksaw blades and files used on brass get painted white in my workshop. i only use brass for tanks and tender - i use steel sheet 1/16" thick for all other platework. beware martin evans' designs where for ease of drawing he shows tank sides and cab and bunker etc all in one piece. a little bit of thought and making the parts in sub assemblies considerably simplifies construction. platework is quite a small part of building a loco in my book (and my least favourite part too) and joining a club with a bandsaw etc or knowing a local engineering form with a proper guillotine saves a lot of time and expense in machinery that wont get used much. all the plate work for my current loco was cut out of steel sheet at home with a hacksaw and filing to size and shape. laborious but very satisfying.

if it's your first boiler, stick to a well proven design with a decent construction series, and a trawl through back copies of ME for how others have done similar sized locos is well worth it too, and join a club and ask other members and the boiler inspector for their advice.

cheers,

julian

Just a word of warning. Do not get brass or copper filings in your eye - seems a stupid stupid remark as anything in your eye is bad news, but these metals (and many others) are non magnetic and not so easy to get out, also, brass is particularly nasty. Having said that, I have (as above) printed out a paper template and stuck this onto a brass sheet. Then placed the brass sheet on top of a piece of dense insulation 2" thick and used a fine metal cutting blade in a jigsaw (goggles on of course). Just be aware that you don't want to scratch the brass as it is quite soft, so clear the metal filings as you go.

BobH

Jim,

Re your query about pins

The pins you are used to are those 1" nickel plated jobs that my wife uses in her dressmaking. What we are using as a "pin" is a piece of round bar, can be straight or tapered, which is an interference fit (needs to be pushed in firmly) in a pair of matching holes to hold two pieces of metal bar (square or flat) in  perfect alignment, with no movement between them.

The diameter of the bar varies to suit the job in hand

The piece of sheet brass being cut will be placed between the two pieces, the cutting line lined up with one edge, and the pins inserted, and the assembly pressed tightly together; so brass held tightly and can be cut with hacksaw, piercing saw (small fretsaw) or whatever, using the metal bar as a guide fence.

That's it in brief, but like everything in this activity there can be much more to it.

If you use the stick-on paper pattern method, like the old fretsawing work, you can cut thin sheet with a scroll saw (power fretsaw), but it does need to be held tightly down on the table, and is best glued to a piece of ply, hardboard etc first, or the edge gets wobbly (another technical term).

Phil

Edited By Robbo on 23/10/2013 09:45:31

Yes, but for thin brass sheet the normal fretsaw blades are rather coarse you should aim to have at least three teeth in contact with the material at any one time. Try to get some piercing saw blades instead they are available from about 28 to 80 tpi.

Russell.

In theory a standard 24tpi hacksaw blade is too coarse to cut 16 gauge brass, but I have never had any problems. You'll find a junior hacksaw works OK, and even you razor saw blades for small precision cuts, but if you have a fretsaw you will need o get fine tooth blades as coarser ones will snap as soon as they look at a brass sheet.

Any gauge of brass up to about 16 can be cut with aero snips (less than a tenner for a set of three basic ones at Machine Mart), but if cutting heavier than 20 gauge you may or may not be able to get it flat again afterwards...

Another possibility is a nibbler. Drill held ones are wasteful but fast. I have a hand held one which is slow but accurate. I once cut through about 16" of light gauge stainless steel sink drainer to cut one down for a camper van. I think the feeling in my hand came back a few days later!

Neil

Edited By Stub Mandrel on 23/10/2013 19:32:18

When I need to cut 16 &18 gauge material on the bandsaw, I put double sided tape on to scrap pieces

of 6mm mdf board or plywood and stick the material to that. It works a treat.

Thanks chaps, I forgot to mention the blade pitch!

Hi Jim welcome
How about using a scroll saw with a fine blade . on mine I also fit small files as well and use it like a filing
machine . What you have to watch is that the teeth spacing/ pitch is less the the brass thickness
Mine has a support arm on it to stop job jumping up when sawing/filing
Nobby

The reason for needing fine teeth wrt the thickness is to stop the saw jumping forward as the material can fit well intothe gap between the teeth. Then it takes too big a cut and breaks. So if you can attach the brass to a thicker piece of wood that provides resistance to the too rapid advance.

Jim

PM sent

Phil

Not recently, but many time in the past I have used a jigsaw to cut sheet metal. I frequently created cutouts of various shapes in welded up steel electrical enclosures and panels. I tried marking out on masking tape which is fine for following a line, but swarf gets trapped under the soleplate and got hammered into the painted surface.

Eventually I found the best plan was to mark out on thin ply (hardboard is ideal) and sandwich that on the job.

Apart from cutting the noise down the biggest advantage was the sawdust, its a brilliant cutting lubricant!

I have used the same technique on anodised aluminium as its much easier to cut with sawdust than with a liquid cutting fluid. I did some test cuts on 6mm ali plate with and without hardboard and the wood won hands down compared with no lubricant at all (I never tried oil).

Ian P

PS, I used (and still use) a Bosch jigsaw I bought when they first introduced the 'pendulum' action. It must have cut dozens of kilometers by now!