Heavy Metal - cutting cast iron table saw top

[Bruce Seidner]

What is the best practice for cutting a hole in a cast iron table saw top. I happened onto a marginal old Craftsman table saw that I picked up cheap and have dissembled the unit and want to cut out the top for a router plate. It matches my working Craftsman contractor saw at 27" and I thought that with all these sagging router tables being discussed there would be little chance of a cast iron top sagging.

My first thought is to use my jig saw with a metal specific blade and then use a file to the template line. My second thought is to use a router with an appropriate spiral bit. I'll start looking around for bits but imagine that the speed of a wood working router is a bit fast for metal. I Googled routing metal and did not come up with much at all.

As always, comments and suggestions are appreciated.

Bruce

[Brian Cosgrove]

I would put a cut-off wheel (6-7") in an angle grinder and cut it that way. I cut metal that way frequently. The router is an accident waiting to happen. Good luck, Brian

By the way, if you don't have an angle grinder, Harbor Freight Tools has a 7" for $39 right now, which is good for a few uses.

[Dave MacArthur]

My Dad did this on his craftsman contractor saw, he just took the wing off and took it to a machine shop, they cut the hole, cleaned it up, and tapped some bolt holes for the router all for $30, well worth it IMHO.

[John Fabre]

I think the machine shop is the best way to go too.

[Bruce Seidner]

I thought a grinder was a type of sandwich. I truly like the idea of getting a shop to do it and will call around tomorrow.

The grinder's look like they can use a number of wheels which is cool. But how do you control what looks like a Dremel on steroids? Is there some kind of jig or attachment that keeps it square to the material. I have a Dremel and there are some nifty attachments for it. I have done some serious damage using it free hand.

[John Fabre]

You might burn up a Dremel, HD or Lowes will rent a grinder, if it doesn't work, you can always take it to a machine shop.

[Scott T Smith]

Using a vertical mill in a machine shop would be best.

Options for doing it yourself - lay it out and drill corner holes (slightly inside of where you want the final dimensions to be). Cut between the holes with a jigsaw, leving 1/8" or so. Build a template for a rounter, and use a carbide or HSS spiral cut bit to clean up the edges.

Cast iron is soft and mills easily. I have a vertical mill, but would not hesitate to use the drilling and router routine if I didn't.

[Bruce Seidner]

Using a vertical mill in a machine shop would be best.

Options for doing it yourself - lay it out and drill corner holes (slightly inside of where you want the final dimensions to be). Cut between the holes with a jigsaw, leving 1/8" or so. Build a template for a rounter, and use a carbide or HSS spiral cut bit to clean up the edges.

Cast iron is soft and mills easily. I have a vertical mill, but would not hesitate to use the drilling and router routine if I didn't.

I know from experience that cast iron cuts easily. I have several cuts made by an errant saw using my cast iron table saw wings as an ad hoc saw horse.

I was unable to find information on routing cast iron. Milling machines are even slower than shapers. A router sounds like a humming bird by comparison. I too was thinking that an HSS spiral cut bit would clean up the edges using a template.

But this was just my theory, hence this post. Have you actually used a router and a spiral cut bit to cut thin cast iron? Is the speed of the router going to be a problem? I can get a cheap voltage controller to further slow it down if my lowest setting is still too fast.

[Mike Seals]

My vote it the machine shop. They'll get the hole perfect for you.

Grinder would work but your holes will not be as clean and a grinder will jump around on you.

[Jim Rimmer]

I had a C'man TS that I made into a RT. Got a friend who had a home machine shop to do it. One thing you have to look at is the webbing underneath the table. Mine was not solid everywhere. We started with the existing opening for the blade and just made it bigger. It does make a great router table but I'm a little concerned about longevity. There a some areas where there is not much material and I'm worried the vibration will eventually win out. I also have a T2 fence on it. I also remounted one of the wings on the back of the table (after the pics were taken) so I have more outfeed support but I need to get a relief slot machined in the wing for the miter gage bar.

If you can get a machine shop to do it cheaply, it's worth a try. Good luck.
IMG_2329.JPG

IMG_2334.JPG

IMG_2336.JPG

[Mark Woodmark]

Cast Iron is a tough one. You can drill it. I would be afraid to try to rout it. What type bit do you have that will cut cast? I know aluminum can be routed with a wood router and a carbide bit if you dont mind light weight aluminum flakes everywhere on you and your shop. Cast cracks easy and cutting it with heat produces a lot of slag

[Ray McCullie]

One thing to keep in mind is when you drill metal you want to lower you're speed. A drill may get 2700rpm at top speed say. A router may do 30,000 rpm. WAY too fast. Set you're drill press for a low rpm and take small bites so you don't overheat the bit.

Clean up the edges with a sander or file.

That's my two cents, worth every penny...

[Marty Paulus]

I would think any bi-metal hole saw would work. Orange Borg Bi-Metal hole saws say they will cut into Stainless Steel. If they will cut Stainless they will cut cast. Just be sure to use a lube/coolant. Some people use kerosene others will use WD-40. Get a good center punch and drill a pilot hole first before chasing the hole with the pilot bit in the hole saw.

From there I would just get a good file to clean up the hole. A router, as mentioned, would just make a mess and I am sure would screw up the bit. Tapping the mounting holes is no bid deal either. Again slow and lube/coolant.

[John Coloccia]

Machine shop is the way to go. Even if you cut it out with a jigsaw, you still need to make the rabbet for the ledge the plate will sit on. I could toss that on a mill and be done in 10 or 15 minutes. The shop you take it to will probably toss it in their CNC machine and just jog it by hand. Square holes are a piece of cake.

If you want to get fancy, bring the router insert in with you when you go there. They'll match up the cutter with the radius of the corner on the insert for a nice fit. I'd probably ask them to give you about .010" clearance on all sides (that's about 2 or 3 sheets of typical paper).

[Scott T Smith]

I know from experience that cast iron cuts easily. I have several cuts made by an errant saw using my cast iron table saw wings as an ad hoc saw horse.

I was unable to find information on routing cast iron. Milling machines are even slower than shapers. A router sounds like a humming bird by comparison. I too was thinking that an HSS spiral cut bit would clean up the edges using a template.

But this was just my theory, hence this post. Have you actually used a router and a spiral cut bit to cut thin cast iron? Is the speed of the router going to be a problem? I can get a cheap voltage controller to further slow it down if my lowest setting is still too fast.

Bruce, before I bought my vertical mill I cut both CI and aluminum with a router, and yes you need to slow the bit down. If you have a variable speed router, then no problem.

Take your time, make shallow cuts, and you should not need a lubricant. The router does not need to be as slow as a drill, but still fairly slow - maybe around 1000 rpm or so. Feed the router very slowly.

You can do a series of shallow plunge cuts from the top, or make a shallow but full depth cut from the side. The last time that I did this I removed about .030 at a whack via a plunge cut method, using an end mill that would chuck directly into the router collett. The end mill was around .250 diameter as I recall.