Feeds and Speeds

[jay]

I have a couple of hundred of curved stair treads to make from 1" thick oak blanks. Also have some from 1" thick Maple blanks. I will be cutting these on my PRT96 with a 3.5 Hp Variable Speed Porter Cable Router.

Has anyone had experience cutting either of these at 1" thick? Looking for suggestions for bit size, bit style, depth of stepdown and feed rates.

[Brady Watson]

Jay,
I cut 100 pieces of 4/4 Hard Maple last winter using the Colombo. I was referred by another botter to the customer because they were using a 3.25 PC router and had trouble with the maple burning and tearing out. I found that I needed twice as many tabs as I thought I did (4" X 14" piece actually flew off of table!)...and that it was very sensative to RPM. 13000 made the tool chatter...14000 burned the maple and 13,500 was just right. I also discovered that the outside profiles were best done with a Conventional profile pass and insides with a Climb mill strategy. The harder woods seem to leave little 'scales' on the scrap piece instead of the finsihed part.

I recommend sticking to 3/8 or 1/2" diameter cutters because they handle the hardwood better than a 1/4" tool. I used a 1/2" spiral and 1/2" straight and went with the 1/2" straight. I ran 1 to 1.5 IPS with a .375 stepdown using the DOS software.

I found that it is best to offset the vectors about .02" and leave about .125" skin at the bottom. Then go back in and profile the original vectors with a cleanup pass at full depth using tabs. This will eliminate tool marks in the profile which are rather apparent in hard woods.

-Brady

[jay]

If I had enough power coming to the shop I would already have a spindle but in this old building it is not worth the cost to upgrade the wiring and panel, so until a building in an area with 3 phase can be found for reasonable rent I will have to make do with the PC. We need more room as it is anyway.

If you were cutting with a Colombo at 1 to 1.5 IPS with a .375 stepdown, I hate to think how little I will be able to get away with using the PC... Thank you for the info it is a place to start experimenting.

In the picture below I have to radius the left and right edge of the red area and make a 45 deg corner down at the lower right. In the blue area the left edge (approx 7" long) has to have the same radius as the right side of the red area. The right edge of the blue (approx. 14" long) has a different radius.

Tread Picture.

4812

[srwtlc]

Jay,

I cut 12-14 1"+ thick red oak spiral treads a while ago with my PC. I used a 3/8" upcut with a speed of 1.65"/sec at 19,000 rpm in four passes at approx. 0.30"/pass. They were cut two at a time from a 32" x 32" blank. If I remember all went well. I had to cut them to fit around the steel posts, so they had a bunch of in and outs.

Scott

4813

[beacon14]

I cut some guitar blanks on my old PR machine with a PC router out of 1 3/4" stock using a 1/2" diameter spiral upcut, 2" cutting length bit, using 4 passes, then a final clean up pass for the last 1/16" or so at full depth. There was some sanding required, especially when cutting against the grain, but I was happy with the results.

[Brady Watson]

Jay,
Keep in mind that all the numbers I gave were for maple...not red oak. I haven't cut any oak on the bot yet...

Remember your settings may vary and you never know what will work until you jump in a cut some samples.

-Brady