Calculating steps per inch using metric screws.

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• I am using Mach 3 and a G100 on a lathe with metric screws. My screw is 1 turn per 5 millimeters and I am using G202 drivers. What shoud my steps per inch be?
Message 1 of 4 , Jul 31, 2007
I am using Mach 3 and a G100 on a lathe with metric screws. My screw
is 1 turn per 5 millimeters and I am using G202 drivers. What shoud my
steps per inch be? 9842.5xxxx? Steps per MM? 400?

I have been trying it both ways, (in/metric base unit measures) with
what seem like crazy results.

Steve T.
• Howdy, I m new.... I ll be able to tell ya if my calculations are correct next week. Here s how I came up with mine? 1 turn = 5 mm = 200 steps so 5 divided by
Message 2 of 4 , Jul 31, 2007
Howdy,

I'm new.... I'll be able to tell ya if my calculations are correct
next week. Here's how I came up with mine?

1 turn = 5 mm = 200 steps
so
5 divided by 200 = .025 mm per step
1 inch = 25.4 mm
5 turns = 25 mm so we need .4 mm more
.4 divided by .025 = 16 more steps
ok
5 turns = 1000 steps plus 16 more = 1016 steps
1016 steps times 10 micro steps = 10,160 steps = 1 inch = 25.4 mm

Hope this is right and good luck,
Jack

--- In mach1mach2cnc@yahoogroups.com, "stephenmtate"
<stephenmtate@...> wrote:
>
> I am using Mach 3 and a G100 on a lathe with metric screws. My screw
> is 1 turn per 5 millimeters and I am using G202 drivers. What shoud my
> steps per inch be? 9842.5xxxx? Steps per MM? 400?
>
> I have been trying it both ways, (in/metric base unit measures) with
> what seem like crazy results.
>
> Steve T.
>
• ... G202 is 10-microstep drive, so with a 200 step motor you need 2000 steps per turn, divided by 5mm for one full turn that gives you 400 steps per mm as you
Message 3 of 4 , Jul 31, 2007
stephenmtate wrote:
> I am using Mach 3 and a G100 on a lathe with metric screws. My screw
> is 1 turn per 5 millimeters and I am using G202 drivers. What shoud my
> steps per inch be? 9842.5xxxx? Steps per MM? 400?
>
> I have been trying it both ways, (in/metric base unit measures) with
> what seem like crazy results.

G202 is 10-microstep drive, so with a 200 step motor you need 2000 steps per
turn, divided by 5mm for one full turn that gives you 400 steps per mm as you
have said.

One inch = 25.4mm so 400 * 25.4 = 10160 steps per inch.

Set the 'units' on setup to inches, and the steps per unit to 10160 and
everything should be set up for inches. Move an inch and check the results.

I get problems with the different Taig controllers if the pulse polarity is
wrong, and you get moves that are out by around 50% so things are obviously
wrong. If you are only out by a little bit short, then the next step is to
slow things down and look for the drive simply missing steps.

--
Lester Caine - G8HFL
-----------------------------
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• ... Set it up in mm using config/set native units as mm and use 400 steps per unit then save and restart Mach. OR use config/native units setup in inches at
Message 4 of 4 , Aug 1, 2007
On Wed, 01 Aug 2007 04:02:11 -0000, you wrote:

>I am using Mach 3 and a G100 on a lathe with metric screws. My screw
>is 1 turn per 5 millimeters and I am using G202 drivers. What shoud my
>steps per inch be? 9842.5xxxx? Steps per MM? 400?

Set it up in mm using config/set native units as mm and use 400 steps
per unit then save and restart Mach. OR use config/native units setup in
inches at 10160 then save and restart Mach. Once you have done that
leave native units alone. Use G20 or G21 in the first line of your
program to set the units for each program. Don't change native units
without a restart - it may screw up.

Steve Blackmore
--
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