Cutting 3/4" pvc: Speeds and feeds

[Chuck Keysor]

Hello Shopbot friends and cloud of experts:

I have to cut out 32 flowers as show in the attachment. The material is 3/4" exterior grade PVC. The flower/diamonds fit into a big lattice in the front gable of a Victorian house, shown in the second picture.

I don't normally make so many of any one thing. When I saw that using a 1/2" end mill, a 1/4" end mill, a 1/2" ball nose end mill and a 1/6th" end mill, it will take (according to Aspire's estimate) 19 hours to cut all of these, I went "Yikes!"

I always default to the pass depth of 1/2 the bit diameter. I normally just adjust my spindle speed with the controller to get chips, instead of dust. But I haven't experimented with pushing the inches per minute speed, which is what I need to do now. And I also have to worry about breaking the 1/16th inch bits. And I haven't cut much PVC.

I did look at some charts from Onsrud, and then looked at old posts here. And it seemed as though people push faster than the numbers I got from the Onsrud chart (for two flute cutters). If the info from both sources matched, I wouldn't ask now, but I'd like to go on the more aggressive side.

Any recommended PVC cutting speeds and feeds for cutting 3/4" PVC with 1/2", 1/4" and 1/16" two flute bits would be appreciated.

Thank you, Chuck

[jerry_stanek]

How about a 1/8 inch bit instead of the 1/16 you can go deeper and faster and not lose much detail

[Chuck Keysor]

Hello Shopbot friends. Last fall,I had two threads running on this project which involved Victorian house carvings. In the other thread, Joe Crumley asked me to post pictures when the work was done. I decided to put the end on this thread since it already included the important original photo.

Everything is made from PVC, and the home owners did all the painting, and handled the installation. Chuckhttp://www.talkshopbot.com/forum/attachment.php?attachmentid=29045&stc=1http://www.talkshopbot.com/forum/attachment.php?attachmentid=29046&stc=1http://www.talkshopbot.com/forum/attachment.php?attachmentid=29047&stc=1

[guitarwes]

Great work. Lots of tedious painting on the homeowner's part.

Did you cut each square out individually and fit them in a lattice or did you use a full sheet of PVC and carve the patterns in that? How did you get the bullnose of the gold trim around each square?

[Chuck Keysor]

Thank you Wes. Yes, the diamonds were cut from 8 foot long PVC boards, that were 12 inches wide and a full one inch thick. None of the cutting was done as 3D work. It was all just 2D pockets and profiles using a 1/4" endmill, a 1/8" endmill and a ball nose endmill (to make the cove).

There were 32 diamonds in total, and by the time I was done, I had spent an hour to fabricate each one. (But that included a couple of bouts of having "COM errors" which loused things up.)

Each diamond had to be custom fitted to each opening of the lattice, which I did easily with a block plane. The strips you asked about (I think are called stop moldings...)were mitered then painted by the homeowners and glued in place.

I cut the "stop" moldings from PVC (everything is PVC) on a table saw (1/4" thick) with a simple radius on the end, done on a router table. I cut the stop molding to the height that would have it standing proud of the lattice, which added a great detail. The homeowners also did the cleaning up of the PVC. (The PVC did not cut as nicely as the foam did in the attached pictures.)

A couple of friends here in town when shown the sample diamond wondered that the level of detail was excessive, since they felt it couldn't be seen 3 stories up. But when you stand on the ground, you can in fact see that it is very detailed, which makes it much more pleasing to view. And there are a couple of decorative panels on local Victorian houses, that are way up high that are also very detailed, so that means this is not without historic precedent.

Thanks again, Chuck http://www.talkshopbot.com/forum/attachment.php?attachmentid=29052&stc=1http://www.talkshopbot.com/forum/attachment.php?attachmentid=29053&stc=1http://www.talkshopbot.com/forum/attachment.php?attachmentid=29054&stc=1

[guitarwes]

Great work. Thanks for the reply. You could have almost carved them in rows in several of the long pieces of material leaving the border and stepping down 1 square each time and attached them together then cut off the bottom making a triangle. But why make it easy right? :D May not have worked but that's just my brain firing off.