I’m using a 2" think blue styrofoam baseboard, and I need to remove a section which is 4"x6"x1", with the 1" being the depth. How does one make a cut like that? Thanks.
A serrated edged bread knife can cut a hole like that, and it won’t damage the knife at all. You’ll have to cut all the way through the foam, split it into two 1" thick pieces, and then glue a plug back into the hole. The only tool I know of that could cut only 1" deep in a 2" piece of foam would be a router.
A hot wire tool with a long stiff wire will do it. I’ve done similar cuts but you have to have a steady hand and bend the wire properly.
a router is the tool you’re looking for.
I use a gun soldering iron that I’ve replaced the tip with a stiff wire in a long skinny “U” shape loop. Be careful with heat type cutters because they will “consume” material on both sides. Be certain to cut way to the waste side of the line, until you figure out where the unit will actually “cut”.
if this is a one time thing, and you don’t have the router or just don’t want to take the time to set it up, and if the bottom of the hole doesn’t have to be perfectly flat, then:
draw your lines.
set your utility knife to a 1" depth.
carefully cut the outline to your hole.
slice up the foam to be removed with many parallel cuts (like sliced bread).
remove one of the slices as best you can (a little bite at a time).
as more slices are removed, it will be easier to break off the foam at the 1" depth.
this will leave you with clean perimeter cuts, and a not so smooth bottom roughly one inch deep.
There is another way, depending on how accurate the 1" depth needs to be.
Use one of those cheap, disposable hobby knives (the kind that have snap-off blade sections). With the blade fully extended, it is fairly flexible.
Make a verticle cut around the perimeter of the hole you want, approximately as deep as you want. Cutting inside the perimeter, hold the blade at an angle to the vertical cut and slice out a wedge-shaped section, repeating until you have a wedge-shaped trough around the perimeter. Make several more vertical cuts across the middle section and slice more wedge-shaped pieces out of the middle. You can now carefully bend the blade and keep slicing thin pieces out of the middle until you reach the depth you want. This will give you the hole you are looking for. Accuracy will depend on how much care you use in making the cuts.
Here is a photo of a Thomas layout I made for my grandson. It shows the track recessed in a groove, or channel, carved directly into the 2" foam.
This picture shows where the track went under the bridge. I carved the channel deeper to allow more clearance under the bridge. The channel is about 1 1/2" wide and up to 3/4" deep.
I could have used a router, but particles of cut foam have static cling and I didn’t want that big of a mess to have to try to clean up. Foam bits that cling from static resent being vacuumed!! Carving took longer than a router, but cleanup was much faster and easier!
Hope this helps.
Darrell, static-free and quiet…for now
Thanks to all who replied. Very helpful info in every message.