Re: Tapered Threads?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Linc Reed-Nickerson
<w7hie@d...> wrote:

> Hi,
>
> I'm new to lathe programming, I have a Bridgeport with a

Microkinetics

> conversation and just converted my lathe.
>
>
> I need to turn some tapered threads for making studs for a steam

locomotive

> boiler. 12 tpi, 1 in 12 taper... various diameters... all boiler

threads

> are 12 tpi.
>
> I understand the G33 command to set the threads, but not how to

make a

> taper... is that set in G33 or by a previous command?
>
> Anyone able to help with a few lines of G-Code?
>
> Linc Reed-Nickerson

Assuming you don't have a canned cycle for threading, then you have
to do it with a series of G33's.

N100 G00 X1.0 Z1.0
N200 G33 X3.0 Z-11.0 F.0833

This would be one pass. I tried to use your example of a 1 in 12
taper. Position the tool 1" off the end of the part (for this
example I used a 1" diameter as the start point). The G33 would
then end 12" from the start with a 1" taper. The start point doesn't
need to be 1" off the end, it does need some distance for the
spindle/axis synchronizing though.

Generally you can't single point a thread in one pass so you have to
re-position back to the start and make repeated passes until correct
depth is reached. Each pass needs to start with a slight infeed
from the previous pass, the amount of infeed is sometimes calculated
based on removing appoximately equal volumes of material per pass.

G00 X.980 Z1.0
G33 X2.980 Z-11.0 F.0833

Here I used a straight infeed, usually angular infeed is used, but I
didn't want to do the math.

Doug