Cutting mahogany

[Rocco.G]

Hi all

I do some railings, etc. for a local woodworking shop and have used 3/4"- 1" pvc. Now he would like me to cut some decorative brackets out of 1" mahogany. Can anyone provide insite on how best to cut this wood? i have a couple of small scraps to experiment on, but this is expensive stuff and don't want to waste it. Would both sides of the brackets will be seen so IDK what is the best bit and the speeds to use.

Thanks
Rocco

[scottp55]

Hey Rocco,
To a small extant it depends on WHICH Mahogany;
https://www.wood-database.com/wood-a...s-the-lowdown/

So testing would be a good idea.
Only Mahogany I've done on machine was a piece of Honduran gifted.
It was 3D, so only of marginal use for you,
but a SHARP bit I used had really nice slivers at 3D rates of
1.5,1.5,16K and started off the piece but cutting full .45" depth
at 6% stepover.
Only a light horsehair brushing, and it's as you see it.

Came out Great, so now looking at the 8' S2S slab my aunt gave me in exchange for a fox carving
scott

[scottp55]

For some reason it wouldn't take the pics...try again

[Rocco.G]

Scott

Thanks for the info. I make electric signs so dealing with wood is new territory for me. i've gotten cutting materials like aluminum, plastic, HDU, etc. pretty much figured out but not so much wood. I had no idea there were many varieties of mahogany.

The customer is going to give me a 1' x 1' piece to experiment on. I had assumed a brand new bit would be best. i'm going to play-around with it on Saturday. i'll report back on how the experiment goes.

Great head carving by the way! I can imagine that took a while to run.

[scottp55]

I should have asked what kind of cuts you were making Rocco.
New bits for the job and charge customer for it.
Profile cuts/
VCarve?
3D or moulding toolpath cuts?

It's very hard to go wrong if you start slow with lower rpm,and once bit stays cool with good chips...gradually increase both proportionally to best speeds.
I kinda like that my 2014 Desktop has to be manually speed controlled...I can guestimate on new stuff with my hand on VFD and watching chips,dial a speed in without knowing what the speed is until best finish/chips are going

Depending on the bit, an X,Y feed of 60-90IPM and 13-15K will probably get you in the ball park(depending on bit size/flutes,etc.).

A good way for depth of cut is either 1/2 diameter to start, or do a zig-zag "Z" Fluting toolpath at guestimates "Linear""Start and End" at 3/4 bit diameter, and inspect finish(for profile cuts).

Any questions, feel free to e-mail me if you want to send bit questions with pics.

"Wise Man" was about 3hrs at 6% step
scott

Seemed like a GREAT cutting wood capable of fine detail. Forgiving it seemed

[Rocco.G]

This job is to replicate some victorian corner brackets, so it's all thru-cuts. It's one corner bracket that gets a mirror copy. if the customer likes the sample, there will be at least nine more pairs for this building. And them perhaps more groups of ten pairs down the road. I've attached a picture of some PVC brackets/railing pieces we did for this customer and then the bracket that i have to replicate. I'm going to assume that I'll need to put a sacrifical layer under the mahogany to avoid tear out. the customer gave me a 12" x 12" X 1" piece to play around with. At least he gave me a template cut out of 3/8" material. I'm going to trace it and see how well the Corel auto-trace program will work. If it takes too long to clean up, I'll send it to the Vector Doctor. He always gives me nice clean files.


IMG_5005 (1).jpg736889033 (1).jpg

[scottp55]

Except for the fact that the painter is going to Heck,and one spot I see, the wood looks good Rocco.

Doesn't look to hard to do from scratch(and mirror)compared to a trace.

IF spoilboard is in good shape and freshly flattened,AND held down firmly,
downcut bits with a last pass at .05" usually cut cleanly, and downward
pressure helps hold workpiece against spoilboard so not much material movement.(others will disagree
Brady liked to start with a downcut, and then finish with an upcut IF not comfortable with a compression bit.
I used to use the twobit method, but the got lazy one day, and downcut only was fine with that last skim pass.

Only you and the owner can decide how big a radius in the corners is
good.

IF something like a 3/8" bit is fine, you May consider "Pocket" cutting the interior cuts to eliminate tabs/trim router finishing.
(or maybe just for the smaller pockets?)
40% stepover is pretty much standard.

I'd ramp all cut 2XDiameter(at least).

On perimeter cut, a Profile cut with a spiral ramp usually cuts smoother(steady bit pressure),and fools the eye a bit on the lines(reduces sanding

For a downcut to cut bottom cleanly...it must NOT have gaps under workpiece...so yes, a clean and surfaced 2'nd spoilboard might be a good idea.

I KNOW a couple others have done Victorian renovations, so I HOPe they'll chime in!

My 2 cents
scott

[8Ball]

Compression bit or a two sided file using spiral down cut bit.

Do an actual trace with a pencil. That will give cleaner lines for digital tracing and eliminate the shadows that cause issues.

[Rocco.G]

i did some test cuts with bits that i have, just two of the smaller inside curves. i tried a three flute bit (not sure of the exact item #) and also a two flute aluminum cutting bit. Both cut nicely and didn't tear out unless I went beyond 1.75 IPS. IIRC I was turning at 12500 RPM. Photos are below of both sides. The section that looks like tear out was just a wet spot. I use coroplast under whatever I'm cutting so I don't go into the bed. Some 3m spray glue holds the material to the sacrificial sheet. I learned this trick from a friend who has an older Gerber machine and no sacrificial board. If he cuts into his bed he might damage the vaccum strips.

My customer made a template out of 3/8" plywood and I tried tracing it but I had too many stray points to clean up, even after using the Corel auto-trace routine. i eventually took a scrap piece of black sign vinyl, traced and then cut the pattern with an exacto, pulled out the cuts to expose the white liner. Then I stood on my work table and took a photo straight down. After another run through the auto trace, it didn't take long to clean it all up.

i didn't ramp anything, just a straight profile cut for the tests. With the corrugated plastic underneath the wood, both sides were pretty clean because the last pass was deeper than the wood. The one that looks like it had tearout was just a wet spot on the plastic sheet. For the perimeter I'll leave tabs but I suspect that the vac would hold it.

And of course, after all of this, my customers client is dragging thier feet before placing the order. At least I have a better udnerstanding of cutting wood. if the order ever gets placed I'll post pictures of the finished brackets. The same wood worker just asked me about cutting some ABS plastic but i'll post another thread asking for advice there.

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[scottp55]

Looks clean Rocco....welcome to wood!
scott