cutting square hole cast iron table top

I have an old cast iron table from a table saw. It has a small
rectangular hole in the center of the table that I want to enlarge for
a router. I thought of a metal blade and a jigsaw yet, that sounds
like it might not realistically work.
Looking for any suggestions..
Thank you,
Keith
Reply to
kbozek
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A square file?. CI files really easily unless the edge is chilled, in that case you might need to start with a TC grit file. This should not take long unless the hole needs to be greatly enlarged.
Reply to
David Billington
Thanks,
I have to double the opening essentially making it fit a router template. I'm not familiar with a TC grit file and I am assuming this is a diamond hand file? Seems like that might take a while by hand.
Keith
Reply to
kbozek
TC grit file, a file with tungsten carbide grit sort of brazed to the surface. In the UK, readily available from good DIY stores and elsewhere, often used on tiles and the other ceramics, glass etc. I have not seen them in square but have never looked, I do have a round and half round though. That should only be required if the edge of the CI is chilled in which case a normal file will just skate over the surface, once you have removed the chilled surface a normal file should make quick work of it, saying that you haven't given dimensions. If you intend to enlarge the hole from 1/2" x 1/2" to 2" x 2" then that would take a bit of work and a jig saw could help remove the bulk of the material. Same applies, you can get TC coated jigsaw blades for cutting ceramic materials, also work on stainless fairly well if nothing better is to hand.
Reply to
David Billington
Thanks. I should have realized Carbide. I have to actually remove about 8 inches of material going from a 8 in by 4 in wide opening to an 12 in by 12 in opening. I'lll give it a try thanks.
Keith
Reply to
kbozek
In that case I would try the jigsaw route first, if the table permits, as that would be quite a bit of filing, or a grinder and cutoff disc to do most of the cuts. You can get good straight edges with a cutoff disc by clamping a steel bar like CRS to the surface and using it as a guide. If you can see the edge of the hole and it appears as cast then it may be chilled, if machined then the any chilled surface may already have been removed. I guess you don't know someone with a mill, that would be easy work. I hope the advice was of some help.
Reply to
David Billington
If I had your limited equipment Id mark out where the square holewill be, comein say 1/4in. scribe lines then center punch every 1/4 in. Drill through 1st with say ani/8 in drill, then with a 1/4. a lot of holes but te fastest way. This will take out most of the metal. then file up the rest to et the hole square and strait edged. You should be able to take out most ofthe rough with anangle grinder. Wear amask as the iron dust will make you cough. Ted Dorset UK.
Reply to
Ted Frater
--Been there, done that for another guy. Remove table, fasten to mill table, enlarge hole with endmill, create 1/4" deep 'ledge' for router base insert. Round corners of insert to match endmill and you're done: no need to square corners in iron. Stronger, too, that way.
Reply to
steamer

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