Thanks.

Richard re:? ?"Replied" to the original mail!?

What does that mean? I just answered and hit Reply in my email reader (Gmail)?as far as I know I replied to the original mail, I think you have said this in the past on other subjects so there is something you are seeing that I am not.

Interesting, it will certainly be much easier to mount the stepper directly inline with the X leadscrew.

I have never found any guidance on sizing stepper motors; this?is?all guess?and bygolly.

And of course with my limited machining experiences I have no idea of required torques.

Ralph

On Sat, Sep 26, 2020 at 2:46 AM Richard <edelec@...> wrote:

Ralph, it would help if you "Replied" to the original mail!
As Peter has said OTT is "UK English" for Over the Top, meaning, a lot more than necessary.
In your case OTT referred to your suggestion of using a 3Nm motor with a 6:1 drive on your 1/2" 10tpi X leadscrew.
There are a number of problems with such a setup. First is adding the complication of a belt 6:1 ratio drive.
Secondly that amount of torque is just not needed. Thirdly as Bob indicates below the detent torque becomes a pain when working manually.
My X screw is 12mm x 2.5mm pitch so very close to yours and I have a 1.85Nm direct driving it. The detent torque is acceptable though there are times when I just unplug the motor to get rid of any loading. I have never had any cutting problems with my X feed though I do not take 5mm facing cuts in steel! I would suggest that you use your 3Nm motor but with an inline 1:1 drive.
Richard

On 26/09/2020 00:29, Ralph Hulslander wrote:

The X leadscrew is 1/2-10.

What is OTT?

Ralph

On Fri, Sep 25, 2020 at 6:33 PM Bob T <zs6bxi@...> wrote:

I’ve been playing with various stepper motor sizes and torques.?
I do have a 12 Nm stepper on my mill and have just upped the the sizing on my Hobbymat MD 65 Z drive from a 1 Nm to a 3 Nm drive nema 23 and from a 0.4Nm to a 0.65 Nm nema 17 on the X axis. My take on sizing (for what its worth) is that the larger the torque rating you have on a stepper the larger the “cogging” effect you feel when you turn it without the power connected. The 3Nm nema 23 on my Z axis has gotten just a little too big to be comfortable turning it when I’m not using the stepper drive (the hand wheel is 60 mm dia). On the other hand my 12 Nm beast works well with a 100mm dia. hand wheel without power on. I suspect that the “clogging or detent” effect varies with with the supplier and the length/diameter ?ratio of the stepper motor rotor. Of course any gearing will amplify the effect. For interests sake when I was “commissioning” my new ?X axis drive I put a digital dial gauge on the cross slide and measured what actual movement hat I was actually getting as I put steps on the motor. I was surprised to find that although a complete revolution of the stepper motor was a constant the angle change for a given number of steps did vary a bit.....probably in line with the spec sheet on the motor that said 5% linearity, not a problem for most folks but I will be looking at doing a 2 or 3 reduction in drive ratio to improve that.If I do that then I will have to look at a neat way of dis-engaging the drive when I don’t want it connected. It never ends !
The stepper in line folk also have a depot or agent in Australia so I get good response (and prices ) from them. But when you get to the larger sizes of stepper and drive things are no longer “cheap”.

Regards Bob

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Clausing 8520, Craftsman 12x36 Lathe, 4x12 mini lathe, 14" Delta drill press, 40 watt laser, Consew brushless DC motors and a non working 3D printer

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Clausing 8520, Craftsman 12x36 Lathe, 4x12 mini lathe, 14" Delta drill press, 40 watt laser, Consew brushless DC motors and a non working 3D printer