hardwood profile cutout advice -- my first paying commission!

[bking1836]

For kicks and giggles,
If using a climb cut with the downcut...swap to a conventional profile pass.
Most of my downcut bits prefer it on profile passes.
Feed is in the ballpark, tweak rpm's and then increase both proportionally until quality suffers...then I usually back off 10%.
Like everyone has been saying...Listen to it
2 cents.
scott

So I tried switching to conventional, and wouldn't you know it, but the conventional cut edge quality is better than climb cutting! Not by a lot, but still better. Thanks! In this most recent run, I ended up pushing feed rate to 3 ips and, although I tinkered with rpm, I keep coming back to 12500. As I go higher than 12500 the pitch of the whine starts to get really high. As it is this 1/4" bit is pretty unbearable to listen to!

I didn't appreciate this at first, but having 32 slats to cut out is giving me quite the opportunity to tinker with settings...

[dlcw]

Last year I made chairs for my dining table out of solid bubinga. Bubinga is INCREDIBLY hard, dense wood. Legs were cut from 1.75" thick boards. I used a 3/8" 2-flute downcut spiral. Feed was 4IPS, spindle was at 13K RPM, with a 2.2HP spindle. Pass cut depth was set at .25" Went off without a hitch. All the legs and curved arm rests were cut perfectly.

As each machine is different, feeds and speeds will vary. I ALWAYS ramp when cutting, solid wood, plywood or other material. Don't get carried away with high spindle speeds. I tune speeds and feeds according to cutting sound. If the bit is screaming, it's hungry. You either need to speed up your feed rate or slow down your spindle speed. If the spindle appears to be lugging a little, speed up the spindle or slow down the speed. Eventually you will discover where YOUR machines sweet spot is for different types of material. Record this in a journal of some sort or create your own file of feeds and speeds. Manufacturer recommended settings are just that, recommended. It is just a starting point for you to determine your "right" settings.

When cutting any hard materials, I always climb cut leaving about 1/32" skin. I then conventional cut that last pass. I've noted flex in my machine, even though I tune it after every large cutting job. The climb cut pushes the bit away from the line. The conventional cut pulls the bit to the line. And since you are cutting very little material on that final pass, machine flex is minimal. Yes it takes longer but the results are predictable and of very high quality. Just part of the learning curve.

[Brady Watson]

Bubinga IS hard, Don. I forgot how hard it was until last weekend when I made a little something for the Mrs. I found myself going back and recutting the edges with .007" allowance full pass to clean up the stepdown marks.

-B

[dlcw]

Brady, I've found that with the flex in my machine, I don't have to leave an allowance when doing the climb/conventional cut process. There is enough slop that the conventional cut has material left over to cut after the climb cut is done. This is especially true with all the plywood I cut. I climb cut 3/4" ply with a 1/4" compression bit in two passes. That seems to be enough side force on the bit to push it away from my cut line a tiny fraction. Then the conventional cut cleans the cut up right to the line. The more force you apply to the bit in the climb cut, the further the bit will be pushed from your cut line.

Bubinga makes oak look like pine in regards to hardness. It is some tough stuff. However, because it is so dense it is also brittle. I've bought LARGE pieces over the years that had micro cracks in it from when the tree fell over. Kinda interesting.

Attached picture is of the chairs I made. The table can be seen also. The table is solid resinous (gummy) cherry with bubinga bread board ends. The base is solid bubinga.

[scottp55]

"I've bought LARGE pieces over the years that had micro cracks in it from when the tree fell over. Kinda interesting."

Interesting Don. JUST surfaced some Red Gum a Desktopper brought me in his suitcase from OZ almost 2 years ago. ZERO visible checking until I cut off the paint squaring the ends with a Freud thin kerf crosscut finish blade, and then surfaced it for 2 parallel sides. And 4 surface splits showed up in 24 hours, and one end is horrible checking now(even though coated Linseed/beeswax within 20 minutes and it was acclimated to shop)!

Funny, even the Desktop will leave watermarks from .25" bit flex from woods B.Walnut up, but even making a last pass depth of .02" will clean it up a bit from Sugar Maple up in hardness. Spiral ramp profile pass will fool the eye until you try to sand the end grain to 400G.
Offsetting a full depth pass like Brady says with a spiral ramp, personally leaves the least sanding for me from Sugar Maple up to Teak/Bloodwood for me.
2 cents to the Masters
scott

[Brady Watson]

Beautiful stuff, Don. You're right - it really does make the common woods look like pallet material

I bet those chairs will last for 100 years+. They've got to be so dent/gouge resistant that they'd be too nice to get rid of...and I totally get the wheels! Sucker must weigh every bit of 40 lbs!

-B

[dlcw]

Beautiful stuff, Don. You're right - it really does make the common woods look like pallet material

I bet those chairs will last for 100 years+. They've got to be so dent/gouge resistant that they'd be too nice to get rid of...and I totally get the wheels! Sucker must weigh every bit of 40 lbs!

-B

Actually Brady the chairs weight in about 25lbs. Not to bad really considering the wood. For finish I used about 4 coats of MLCampbell Duravar. Tough stuff. One of my daughters has already put dibs on it when I kick the bucket. I think it's fair since she helped me build the table and all the chairs.

[bking1836]

Last year I made chairs for my dining table out of solid bubinga. Bubinga is INCREDIBLY hard, dense wood. Legs were cut from 1.75" thick boards. I used a 3/8" 2-flute downcut spiral. Feed was 4IPS, spindle was at 13K RPM, with a 2.2HP spindle. Pass cut depth was set at .25" Went off without a hitch. All the legs and curved arm rests were cut perfectly.

As each machine is different, feeds and speeds will vary. I ALWAYS ramp when cutting, solid wood, plywood or other material. Don't get carried away with high spindle speeds. I tune speeds and feeds according to cutting sound. If the bit is screaming, it's hungry. You either need to speed up your feed rate or slow down your spindle speed. If the spindle appears to be lugging a little, speed up the spindle or slow down the speed. Eventually you will discover where YOUR machines sweet spot is for different types of material. Record this in a journal of some sort or create your own file of feeds and speeds. Manufacturer recommended settings are just that, recommended. It is just a starting point for you to determine your "right" settings.

When cutting any hard materials, I always climb cut leaving about 1/32" skin. I then conventional cut that last pass. I've noted flex in my machine, even though I tune it after every large cutting job. The climb cut pushes the bit away from the line. The conventional cut pulls the bit to the line. And since you are cutting very little material on that final pass, machine flex is minimal. Yes it takes longer but the results are predictable and of very high quality. Just part of the learning curve.

Thank you Don. Very helpful. I should probably add a 3/8 downcut spiral with 1.25" or 1.5" CEL to my ever-growing inventory of bits.

So I'm happy to report that all 94 pieces have been cut successfully. In the end there was definitely more drama in my head than on the spoil board. The conventional cut left a better edge for sure, and I ended up being fine at 3ips and 12500 rpm with .162" passes and a 1/4" downcut bit. I wonder if I could have pushed the cut depth a little deeper...

All that ash turned into this pile of parts:

IMG_2922.jpg

And here's the rough assembly:

IMG_2928.jpg

I'm pleased with the design and how it all came together, but it was definitely more work than I had anticipated. And I'm not even done yet!

For this design to be commercially viable, I will need to find some efficiencies. Interestingly, the problem wasn't prepping the stock (my lumber mill will take rough sawn 4/4 stock to 3/4" S3S for pennies), nor is it the machining, which set up pretty easily and will run relatively efficiently next time. It's the 94 parts to thread onto rods, plus sanding and finishing, that takes so much time and effort!

I appreciate the wisdom and support of this forum.

Brian

[knight_toolworks]

Bubinga IS hard, Don. I forgot how hard it was until last weekend when I made a little something for the Mrs. I found myself going back and recutting the edges with .007" allowance full pass to clean up the stepdown marks.

-B

yep and purple heart and ipe. thats what I cut my teeth on and man wasted some wood. i tested on pdf then tried purple heart and learned the machine had slop (G)