Red Oak

[chunkstyle]

Well it's finally happened and I've been asked to cut some solid oak on my machine for a stair builder. Never having cut solid wood before I took some oak I've had lying around and did some test cuts.
Using a .25" M.C. traveling at 2 ips. Pass depth was .25" requiring 3 passes. Went in climb mode thinking it would have less chip out but I think I will try a final clean up pass in conventional.
Having a limited amount of solid oak on hand to test cuts I wondered if anyone else would be able to share any insights in getting the cleanest cuts besides a final conventional pass. 'll be burning up the last boards I have in the rack to practice on tomorrow.
Machines a PRS standard with a 2.2 hp spindle. Thanks for any advice.

Tim

[Brady Watson]

Tim,
It sounds like you are on the right track. I think 'you got this'...don't over-think it or you might mess yourself all up. Just be deliberate...It's only oak, not old growth Mahogany, so if you did make a boo-boo, it isn't the end of the world. It's important to take things to the limit to make sure you can pay for your mistakes in a worst case scenario. I think you will do fine.

Be vigilant and observant as you cut the parts out, noting if there is any tear out (on face) or blow out (in the outside corners) and take appropriate actions to correct on the next board. You might have to get creative - like making a few vector 'lead-ins' that relieve the corners so they have no chance of blowing out when you do the profile cut...so keep that in mind. Many times, the specific board itself and the way the grain runs through it fights you no matter what you do, and that is something to consider when working in natural materials.

Hope that helps, never 2nd guess yourself & go make some money!

-B

[Bob Eustace]

Just love red oak mainly because about zero fuzzies on vee carve. On profile we use 13000, 3ips at .2 depth. Very kind on cutters.

[chunkstyle]

Thanks guys,

Brady, I'll keep What you said in mind. I noticed the parts coming off my test peices had minor inconsistencies and wondered if it wasn't in the grain. I do have to cut some mohagany in the next week or so. This red oak will be a good way to ease into the water. Thanks for the advice.
Bob, thanks for the feed speeds and spindle rpm's. I was testing with 2.25"/sec. at 10.5k rpm's. 3 ips with a standard in solid oak?! Guess I'll have to try that. That will be great if it works. Thanks.
I'll post back the results.

[gene]

I think that you are on track. I cut a bottom step for a staircase that was rounded on both ends 69 " . Then i did a dado on the underside and curved plywood for the riser . also machined the radius trim for the ends . i will try to get the photos posted . it sounds like you should not have any problems..

[garyc]

Weedhopper....
Some info for you here: http://www.talkshopbot.com/forum/showthread.php?t=961
;)

[blackhawk]

Tim - I cut red oak quite often. I normally go 1/4" deep per pass, 2 IPS, and 19,000 rpm when using a 1/4" endmill. I use the Centurion Tool down spirals. My machine is a PRT Alpha with a PC router.

I really don't notice a huge difference in cut quality between conventional or climb. But normally, I cut in climb leaving an onion skin. Then do a final pass in conventional to cut through. This method makes the cuts more accurate just like cutting plywood.

[twelchPTM]

this all probly goes with out saying but i figured i'd throw it in there ...good sharp bits, dull bits (even slightly) will rip apart your wood. and no mater what you do get your wood from a reputable yard. big box wood is asking for trouble

[chunkstyle]

Thanks for all of the advice.
Went in at 2.75" at 10500 rpm with a m.c. bit. The spindle speed was drifted up and down some in an effort to get rid of the chatter but not up so far as to lose chips and start making dust. The stack is the last of the 39 peices that were cut out.
Two things I noticed were the chatter marks in one of the semicircles were consistently more pronounced thru out all the parts I cut. This would seem like there is an issue on the X rail for some reason. You can see the chatter marks in the photo. Worse in the semicircle towards the bottom of the picture and less so towards the top. This was not the case on the other side of the part, though, so I'm puzzled why it was worse in just this one area. The picture of the boards on edge shows the variation in cut quality between semicircle better.
The second problem was at the end of the cut (conventional removing onion skin with Vac running) the bit would shave a small bit of wood off in the last part of the tool path before it retracted. This extra bite only happened at the onion skin pass. I noticed that the amount of bite increased as parts were coming off the table so I swapped out the bit for a new one. The bite decreased but was still there with new bit. My guess is that the bit, in slowing down at the end of the tool path travel, was moving into the material more as it was traveling in conventional mode?
Since the parts were made over length it won't matter but it is this normal?
All stepper motors were snugged up to the racks before the cutting session and re-snugged during bit change. Didn't help any though. Would anyone have any ideas on what to check?
Thanks for all the help. Made tackling this job a lot easier.

Tim

[bobmoore]

It looks like you are getting the chatter when coming across end grain rather than most of the cut with the grain. I think something is slightly loose allowing chatter to occur during the increased stress. Judging by the deflection at the end of the cut maybe your hold down clamp (vaccum?) is flexing slightly at 2.75. Try a slower cut, maybe half speed and compare cut quality. could save a lot of sanding.
Bob