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Thread: Double lead threading...
10-12-2005, 01:42 AM #1
Anyone know if its possible with the Okuma LC10 with OSP3000L control? I can not find any reference in the book to it. IF the control wont handle it... whats the possibility that the start point for threads (as far as rotation) is always the same, that if the machine wont do it itself, I could do a single lead thread, and then rotate the part 108 degrees and locate it to the exact same Z base point? AM I crasy and just too big of a dreamer? Im wanting to do .613" x 44tpi doule lead threads.
10-12-2005, 02:19 AM #2
Here's a quick and dirty what that *usually* works.
Let's say you are threading from the right hand face of the part (Z=0) for a length of 2".
Program a thread from Z0 to Z-2 with a lead of .02272" (1/44) using a suitable finish diam which would be around .5835
That leaves you with a thread at 44 tpi around the part.
Now the magic - program another thread cycle just like the first one BUT start the thread at Z0+(1/2 lead). It should put the second thread right around the first one.
Looking at my numbers and your post I am not sure if you want 44tpi as a cut thread or that to be the doubled lead, etc, so check the math I used. Just remeber to start the 2nd thread 1/2*lead ahead of the first one.
10-12-2005, 02:19 AM #3
I'm not awake enough to do the math, but, generally as far as I know, your machine should take off from the same spindle rotation point, so because I can do the math in my head, 20tpi, double start. so your basically making two 10tpi 180 degrees from each other, or two threads .050 from each other. Run a thread with a lead of .1 starting at say Z+.050 then run the same thread starting at Z+.100, .050 off and you should have a good double thread.
10-12-2005, 02:33 AM #4
You guys are right on... I never thought about addressing it with starting Z instead of rotational position... Thats a heck of an idea... maybe a little dirty... but hey... most stuff that works great aint always text book clean...
Now to grab the calipers and the magnifying glass, and find out if that is 44 TPI 2x = 44tpi double lead or 22 tpi 2x = 44tpi double lead...
Thanks a ton!!
10-12-2005, 02:41 AM #5
It may be a little dirty but it should work out lots better than rechucking 180deg out
The CNC threading cycle should always start at the same spindle rotation, so by moving out the Z start to suit the thread will lay offset by the same amount.
You can use the trick for 4-lead, just cut eact one (Lead/4) to the right of the previous one.
Good luck with it!
10-12-2005, 02:51 AM #6
Awesome... thats all I can say...
I can see, there is going to be a whole new set of rules to add to my brain, so that I can get back to being productively creative with my processes... This is great!
10-12-2005, 03:37 AM #7
I've done exactly what Damonfg suggested before an it works perfectly. Two exact same canned cycles 1/2 pitch apart in z.
10-12-2005, 04:23 AM #8
G71 with a "Q" and the number of starts you need.
possible on my control, don't know if 3000 would do the same.
G71 X,Z, then B,D,U,H,F,E,L,J,Q, with feed paterns M32,M33,M34, and depth paterns M73,M74,M75 are all possible.
10-13-2005, 03:03 AM #9
The 5000 was the first Okuma control to allow you to specify the number of starts. On the 3000, just modify the z offset number by half the lead and re-run your same program. It'll cut your second thread right where you want it to be.
Anytime I make an acme lead nut, I use a tool thats less than full width, and then shift the Z offset fore and aft to bring the thread out to width. Gives a better finish, and allows you to create a nut with near zero backlash. The same offset shifting logic applies to multi-start threads. You don't have to physically move z, but rather just make it think its in a different spot when it starts to move
10-13-2005, 03:18 AM #10
Make it think its in a different spot... as in change the tool offset incrementally? or are you thinking doing it another way?
Thanks for the ideas everyone!!
10-13-2005, 10:24 AM #11
Multi start threads
Feed rate will be PITCH x # of starts
Each start will back up one pitch
3 start thread
32 tpi = .0313” pitch
feed = 3 x .0313” = .0938”
start 1st thread at .050”
second thread at .050” + .0313” = .0813”
third thread at .0813” + .0313 = .1126”
This would do a 3 start 32 pitch OD thread.
10-13-2005, 05:29 PM #12
I have never had to do a double thread before... Only single thread... But damn that sounds like a great idea... I really hope i get to do a double pitch thread just so i can use that trickery and smoothness...
So let me get this straight...
Lets say im doing a 1/2-13 threads with double pitch (13 tpi x 2 = 26 tpi)
I would start the first thread canned cycle as normal...
Then the second canned cycle would start 1/2 of a pitch distance further from the part ?
So i would start the second thread .0384 further back from the first thread... This way the second thread starts 180 degrees from the first ?
That is SOOOOooooo SWEET!!!!
10-14-2005, 01:37 AM #13Here's a quick and dirty what that *usually* works.
10-14-2005, 02:19 PM #14
Solar, yes. Just keep in mind that the thread depth needs to be cut shallower than the 13TPI would be cut at and you will do fine.
JS: I still have 3 teletypes keeping an old allen/bradley filled
10-14-2005, 08:39 PM #15
Im guessing the theory on thread depth is the same as the pitch calc? cut depth / number of starts?
10-14-2005, 10:12 PM #16
yep, set the depth based on the thread pitch, not lead.