hi im a wood butcher im asking how easy is it to use a router to widen a slot in cast iron using a tct router bit is there a certain amount i should only take off at a time ie 1/2mm or 1mm do i need to use colant i need to widen a 15mm track to 19mm
Be prepared for quite a bit of mess. Cast iron has a lot of 'free' carbon in it, so when machined it causes a lot of black dust, which gets everywhere. The rest of the metal usually comes off as smallish chippings rather than the long, curly swarf associated with metals like mild steel, so isn't usually much of a problem.
The fundamental parameters for cast iron are that the surface speed of the cutter should be about 100 metres/minute and the maximum feed rate 0.05 mm per tooth. When you know the size and number of flutes of your cutter you can then work out the ideal RPM. Yes clamp it very stiffly, but you inevitably have a very non-rigid system, namely your arms (compared with a milling machine). I would start off much nearer 0.1 mm depth of cut till you feel what you are doing, and then perhaps increase it in tiny amounts to 0.5 mm.
+1 for the super rigid set up (depending on the shape of the casting and where the slot is, CI can be very brittle so NO vibration at all while machining please); and also + 1 for VERY small/light cuts.
I was surprised to hear Wallace talk about 24 K rpm for router speed, but from his past posts he obviously knows 'is onions. I guess a lot depends on the router cutter spec itself (up or down cut, parallel, number of teeth, etc, etc) but personally - never having tried routing CI - I would have been inclined to go slowest speed possible. But just me being an old woman probably!
But CI is easy to machine (lathe, shaper, mill, etc) AND is also dead easy to file too. Personally I'd be inclined to use a decent file - if the slot is long then pre-drill a couple or three + times then enlarge with a round file - much less chance of accidentally damaging/cracking the casting that way.
If you do machine, as CC has said, you won't get swarf like from machining MS for example, but it can be an abrasive "sticky dust" so do protect the area (old sheet, towel, etc) first.
I for one would be interested to see the job, and hear how it went please.
i no this might sound silly but what about using a jigsaw to cut it instead and then filling it down or sanding it down with belt sander if i can get the sander to fit id asum id have to use the finest metal cutting blade on the jigsaw and also prevent it from bottoming out
the slot currently is a v slot with the widest part at the bottom and is the width i want but the uper part is only 15mm and bottom part 19mm
I don't think the idea of a jig saw is silly really, but I can see you having problems with squareness - especially because it's a vee slot I'll guess that the blade (being only supported at the top) will tend to veer off and follow the angled side of the slot rather than cutting square.
If I'm correct, you only need 2 mm off each side of an existing slot, right? If so then for me I'd just have at it with a pillar or warding file (2 actually, 1 coarse, the other smoother to finish off). "Easy peasy", really, and pretty quick plus minimum mess and virtually no chance of cracking the casting. Try it and you'll be pleasantly surprised.
Not blowing my own trumpet but if you're not familiar with files & fling there's a "tutorial" with that title by yours truly as a sticky at the top of this General Metalworking section. Several people have apparently found it helpful.
keep on forgetting about using files think i got a few arond i no i got a second cut around the place plus a few chainsaw files i will have a look and see if i can get a few more but not many places around here sell files what about using a belt sander to try and remove as much as i can befor using files?
Have you got a belt sander that is thin enough to go into that 15 mm slot? If not how would you re-join the belt? How would the belt be supported to ensure the finished slot ends up square?
Don't bother to buy any files, just clean one or two up with a wire brush and have at it! Honest, it'll be easy with a file and won't take any time at all!
Edit for P.S:
If your files are really no good and can't be un-clogged then I'm 99% sure that wherever you are any local DIY shed will have a cheapo set of warding files (in a plastic wallet probably) that will do your job. I repeat, it's only my own opinion (but based on experience) that by the time you've finished trying to find some machine to do that job successfully you could have done the job with a file "3-times over"!
The wadkin machine was the LYR I think and had the advantage that the motor head was controlled by big handles and a frame work preventing it from going off coarse. It was used for cast iron engine blocks, they were also used in the aircraft industry.