Big wooden Threads

Topics related to wrapped rotary machining in Aspire or VCarve Pro
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Ring Shake
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Big wooden Threads

Post by Ring Shake »

I drew a 4" diameter threaded section in Rhino and am cutting it on my 4th axis.
It's going to be a coffee table leg threaded into a big nut which is mounted to a burl slab.
I had machined some grooves in the aluminum mounting plates of my indexer so they would locate into the clamping rails.
I cut a spline / tenon to fit into the rails and machined groove.
I had dis-assembled the indexer for machining. After re-assembly it would rotate by hand but not by G-code command???
After an hour of bewilderment I just tried dry running my program and everything worked, go figure!
I made a Z-zero error on my initial run by having it .25" too low. I zero'd of the top of the indexer and added half the tool diameter to my offset for some reason!!??

I realized on a roughing program it travels over parts already cut which can really rack up the machining time!
My solution was to draw geometry for 3 zones, and ran different programs for each. Only the end zones had the deeper passes.
Attachments
IMG_5171[1].JPG
Rough Ends.jpg
Cut Zones Rough.jpg

Ring Shake
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Re: Big wooden Threads

Post by Ring Shake »

Here is a section of the thread and the model
Attachments
RH leg 1.jpg
Thread Section.jpg

Ring Shake
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Re: Big wooden Threads

Post by Ring Shake »

One the tailstock end there is an outer ring which just slides off. It's just used for locating.
I have a plywood disc on the indexer end as well with a 1.5" sq block glued to it.
I beveled the corners of on the table saw and used a power planer for my " roughing pass".
I'm running a tapered ball .125" for the finish pass at 70 ipm and 10% step-over.
The first piece I tried 6% and the finish was amazing but crazy long run time.
Attachments
IMG_5183[1].JPG
IMG_5185[1].JPG
IMG_5196[1].JPG
IMG_5194[1].JPG
IMG_5197[1].JPG

Ring Shake
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Re: Big wooden Threads

Post by Ring Shake »

317 minutes later...tadaaah! That was for the threaded section with the taper bit. Bottom hex area was programmed with a .5" ball end with 7% stepover.
Attachments
IMG_5228[1].JPG
IMG_5208[1].JPG

Ring Shake
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Re: Big wooden Threads

Post by Ring Shake »

Next I'll take a crack at the nut. My plan is to machine it from 3 pieces and bond it together.
Attachments
Nut_3.jpg

Bobtail Farm
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Big wooden Threads

Post by Bobtail Farm »

thanks for your post.

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TReischl
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Re: Big wooden Threads

Post by TReischl »

Thanks for all that info!

Hmmm, here is something that might help you if you are going to do a lot of threads like that:

Manual programming! OMG!!!! No, seriously....

You could save a ton of time by doing the roughing with some simple lines of g code.

Here is an example:

Assume the left end by the indexer is X0 and the diameter of the thread is 2 inches and you want 8 threads per inch over a distance of 10 inches. (this is wrapping Y)

G0Z1.5 (make sure tool is above workpiece)
G0X10.25A0 (move to X value and rotate indexer to 0)
G1Z.875F35 (feed to take a cut .125 deep)
G1X0A2880F150 (do the rough cut)
G0ZZ1.5 (retract)
G0X10.25A0 (position for next roughing cut)

All of this is pretty straight forward until you get to the line with the A2880 in it.

The 2880 is obtained by knowing that you are cutting 8 threads per inch and you are doing it for 10 inches. So you have 80 turns. There are 360 degrees in one turn, so 80 X 360 = 2880.

I have made quite a few screws for guys in the woodworking clamp to build wooden vises. I learned very quickly to stick with 60 degree threads for a bunch of reasons. Most importantly is that finding a cutter to use in making the nut is tricky enough without using some obscure shape. I have 2 inch, 8 TPI on my workbench that have been used for about 20 years now with no chipout. Had an antique bench that was all beat to hades and the only really good parts were the nuts and screws.
"If you see a good fight, get in it." Dr. Vernon Jones

Ring Shake
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Re: Big wooden Threads

Post by Ring Shake »

I finally managed to spend some time cutting the nuts. I cut the first set and it was obvious something was not fitting correctly.
Well, turns out my threaded rod section was cut mirrored with the threads reversed compared to the CAD drawing.
I had modified the post P to correct a lettering test which initially cut backwards. Will have to sort that out!
I mirrored the nut parts so that the " backwards" leg could still be used.
Again i thought I had an error somewhere as the threads weren't meshing fully.
Turns out that there was some untrimmed wood on the edges of the threads at the surface of the bolt.
I trimmed that clear and it solved it.
I just taped them together and it turns like a charm!
Attachments
IMG_5265[1].JPG
IMG_5267[1].JPG
IMG_5272[1].JPG
IMG_5279[1].JPG
IMG_5281[1].JPG

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highpockets
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Re: Big wooden Threads

Post by highpockets »

I'm very impress! Great work.
John
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dwilli9013
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Re: Big wooden Threads

Post by dwilli9013 »

Wow. Quite the accomplishment. What are these to be used in?
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mikeacg
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Re: Big wooden Threads

Post by mikeacg »

That is incredible!

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TReischl
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Re: Big wooden Threads

Post by TReischl »

Nicely done! Impressive!

I particularly like the way you fixtured the parts for cutting. Very creative.

Now you got me thinking!
"If you see a good fight, get in it." Dr. Vernon Jones

dtorney
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Re: Big wooden Threads

Post by dtorney »

I want to make a threaded dowel extension as part of a new leg for an old table.
The dowel is approximately 4 1/2" long and 1 1/2" in diameter.
Threading at top of table legs
Threading at top of table legs

I'm assembling an Axiom Pro 8 machine, without a rotary accessory. For making these new legs, I may need a different machine.
Table, circa 1870
Table, circa 1870

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scubanimal
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Re: Big wooden Threads

Post by scubanimal »

FYI, Axiom will have a 4th axis upgrade in about 2 months, per what I was told. I couldn't wait so am not getting an axiom, but your situation may be different.
V/R,
Ian

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