Thread: 2 start internal taper threds

hi we have a HASS TL2 I am having trouble with a 2 start int taper thread ,at the moment ive used the caned cycle using the taper mode finishing the cycle then runing it again at 50 rpm and tripping out of the program by lifting the guard which stops the cut at the end of the thred mark the spindle with a marker escape back to mdi and mark a centre line on the work put the tool to the g54 undo the chuck on the spindle mark then rotate the work 180 tighten the chuck and re run the program at the right rpm this was ok for a one off ?.
so the question is is there a code that can be( inserted, changed) in the caned cycle to indicate a multi start
thanks in advance
andy

Originally Posted by andy fx

hi we have a HASS TL2 I am having trouble with a 2 start int taper thread ,at the moment ive used the caned cycle using the taper mode finishing the cycle then runing it again at 50 rpm and tripping out of the program by lifting the guard which stops the cut at the end of the thred mark the spindle with a marker escape back to mdi and mark a centre line on the work put the tool to the g54 undo the chuck on the spindle mark then rotate the work 180 tighten the chuck and re run the program at the right rpm this was ok for a one off ?.
so the question is is there a code that can be( inserted, changed) in the caned cycle to indicate a multi start
thanks in advance
andy

Hi Andy,
Cutting a Multi Start Thread is relatively simple; you just move the Z start point by the pitch (not the lead) of the thread.

The lead of a thread is defined as the axial movement along the thread in one rotation, and it’s the lead that’s used as the feed rate in the threading operation irrespective of the number of starts. The lead is often described as the Pitch x the Number of Starts.

The pitch of the thread is the distance from a point on the Thread Form to a corresponding point on the next Thread Form. The pitch is often described as the Lead / the Number of Starts. Accordingly, to cut a two start thread, you move the Z start point by the Thread Pitch (Thread Lead / 2). For example:

6mm Lead / 2 Start Thread

The first start could be cut with the tool starting at Z6.0 and the second start with the tool starting at Z9.0 (6mm Lead / 2)

Regards,

Bill

simples, thanks Bill


andy

also being that its a tapered thread to keep the same offset at the same depth you will have to figure out the x start point for however much you moved over in z

ex. 8pitch 2 start tapered thread .75 taper per foot

1st starting point X1.5 Z0.2

2nd starting point X? Z.325 (.125 for the pitch)

figure taper per inch .75/12= 0.0625

Multiply that by how much you moved over .0625 x .125 = 0.0078

Add it to your 1st starting point 1.5 + .0078 = 1.5078

Now you have your 2nd start point in X - X1.5 Z.325

if you move in just subtract instead.

also if you are using a tapered ring gage the formula works for that too

Taper per inch x how much you need the gage to move in = value for offset

also being that its a tapered thread to keep the same offset at the same depth you will have to figure out the x start point for however much you moved over in z

Methinks NOT.
Given that canned cycle x and z values are to destination, not start, at least on Fanuc controls, jacking the z start point one way or the other necessitates recalculation of the taper per pass, according to the differing length of the pass, not start x value.
But I might be full of shit, not living in the Haas world...

Don't forget about Q.

On a Haas lathe Q is the start angle. Q0. on the first G76 cycle and Q180000. on the second G76 cycle will cut your double start thread without all the extra math.

Check it out in lathe manual.

http://haascnc.com/doclib/manual/96-8700an.pdf

p230

Originally Posted by John Willliams

also being that its a tapered thread to keep the same offset at the same depth you will have to figure out the x start point for however much you moved over in z

Methinks NOT.
Given that canned cycle x and z values are to destination, not start, at least on Fanuc controls, jacking the z start point one way or the other necessitates recalculation of the taper per pass, according to the differing length of the pass, not start x value.
But I might be full of shit, not living in the Haas world...

its the I or R number that would need to be changed as the difference of the taper would be more or less. i don't know what made me think start point in X. Edit: just remembered i got that from mazatrol

OT - what's the purpose of such a thread?

Originally Posted by kvom01

OT - what's the purpose of such a thread?

To connect to a magnatomitor simpler to what they drag behind boats to find wreaks but to be pushed into the ground to find geo features and needs to be quick release
Thanks for all the input sorted now
When I get time will post a copy of programme up so if anyone else needs it it will be available