Rough Stuff

[Cedge]

You've got a part to make and the parent block of metal is already bolted down to the mill table. You've got to move a lot of metal before you can even begin to zero in on the painstakingly applied markup lines you've made. It looks like a long boring stretch of mindless cranking before you get to use your brain a gain. By the time you remove the metal and scoot the bit into the last cut, on the mark, you're tired of having all this fun. What can you do to speed things up?

There are a few things that can be done and some are so obvious that a new guy can overlook them. I certainly did, at least for a while, so no one is calling anyone else a dummy in this post...LOL

1- Remove big chunks with a saw. Be it a Band saw, a Slitting saw, Jig saw, or one of the forum popular Carbide saw blades or scroll saw mods. Sawing will save you time, lots of cranking and it will leave you with nice pieces of metal for your "next project" metal bin. Sounds like this would be an obvious no brainer, but I cranked a lot of chips that could have been used on other things, by having missed the obvious. Ok... I was too busy trying to keep metal flying and not blood as I learned to use that beastly little milling machine...(grin)


2- Drill holes. Big holes, small holes, red hole, blue holes....even lots of holes. You can use a drilled hole to form a radius cut while removing lots of metal that already needs removal. Combine drilling with sawing and you can make short work of removing LOTS of metal using easy operations. You can follow a curved line with a series of drilled holes to create contours which are easily finish shaped with a file, dremel or grinding wheel. I've cut circles, S curves, even tapered pieces this way and with a bit of patience it does a good job. It can also be used to prep a piece before you mill it so that you are quickly into the final cuts.

3- Roughing End Mills..... Something I'd never heard of until an uncle who is a machinist took pity on me and handed me one. If you've never seen one, think of a spiral thread tap with razor sharp cutting end. It has what look to be tapping threads on side of the cutter flute. Now picture a steel eating beaver with an appetite for darned near any mystery metal you can toss in its spinning maw and you've got a Roughing End Mill. When you need to move lots of metal and don't want arms like Schwarzenegger these little beauties are sweet.

They take deeper cuts than a standard 2, 3 or 4 flute cutter and present less drag on the motor. They are not for finish work, since the leave very distinct marks as they pass through a cut. What they are good for is getting close to the accuracy zone in very little time. Then you swap out for your favorite finish cutter and take things on down to a fine finish. I've bought several of these ranging from very course to fine and in a couple of different lengths. I've used them on steel, brass, aluminum, cast iron and stainless without being disappointed. I use them often.

4- Can you say "Power Feeder"? It's a motorized crank turner for your mill. These can be built or bought for not a lot of money. They border on saintly when you have to move metal and suddenly you don't have to do the whole crank and return routine. Flip a switch and it takes your Metal beaver for a walk and then flip the switch again and it brings him back for another feeding. These things sure do make the process less work and you'll have time to scratch your watch and wind your backside..(grin)

Yeah... these all sound so simple, but I suspect I've just eased the pain and strain for at least one newbie who, like me, was too busy avoiding disaster to consider there had to be an easier way.

Steve

 

[Davyboy]

More tips on roughing:
1. Drill holes at inside corners to enable turning the band saw or scroll saw blade. Hole must be wider than the blade.
2. When milling a slot thru a plate, drill a hole near one end, then with an undersize endmill, plunge with the quill, nibbling away .010 or so at a time, along the length of the slot. It's a little rough on a endmill, so use a 'beater'. Finish up the sides and size conventionally.

 

[rake60]

Good Points Steve.

Regardless of the manufactures claims, small hobby machines are not really intended to be hogging rougher.
You CAN take a 1/4" deep cut with a 1/2" end mill in a mini-mill if you are working with brass or aluminium. Do that often enough and you'll get to learn how to replace spindle bearings.

Here's a case in point.
When I made the main frame for the Poppin Flame Licker it started our as a solid block of brass. To get it to this point,

required almost 50% of the original stock to be removed.
4) 1/2" holes drilled through from the side. The cylinder mounting hole was another drill bit in the old drill press.

Roughing with a drill bit and saw will help to give your hobby machines a longer more accurate life span.

Rick

 

[Cedge]

Rick
These little Mills are, as you say, not intended for overly aggressive cutting depths. The roughers I use are 3/8 two flutes with what appears to be about a 16 pitch "thread" and allow for less stress when making "heavy" non-critical cuts. The finer roughers have what looks like a 28 "thread" and are not quite as aggressive. A heavy cut, here, would be 3/16 x 3/8 in aluminum while the typical cut would be more like .050 x .100. The benefit is less chatter and stress. I've also made steel cuts .050 x .050 with ease. That sounds small for a bridgeport owner but it's happy time on a mini-mill....LOL.

I listen to the machine as much as I watch what it's doing. It's not difficult to tell when the machine is not happy, and when to back off a bit. The new belt drive also adds a bit of an advantage, since it will slip before anything goes "BANG".

I guess the point of the post is really just to mention that lots of work can be avoided by using simple, more efficient methods of removing large bits of unwanted metal before the piece goes on the mill for the finishing cuts. Your warning is well taken. Roughing in is a common sense sort of thing... overdoing it can certainly do your machine in over time. Done with proper care and a bit of thought, it will save time and aching joints.

Steve