Metric vs Imperial lead screws

[DavidR8]

Hi all, in my continued search for a mill, I wonder how much the pitch type (I don't think that the right term) of the lead screw matters.
I know that some of the small mills have metric lead screws but dials in thousands with some weird fraction left over.
I would put a DRO on any mill I buy so I would think that it wouldn't matter whether the lead screws were metric or imperial.
Or am I missing something completely obvious?

 

[MontanaLon]

I would suspect it matters not a bit if you plan to put a DRO on it. It isn't like a lathe where you need the lead screw that drives the carriage to cut threads. Unless maybe you are planning to CNC it in the future to go all high tech and stuff. Even then I doubt it would matter as the software would be able to compensate.

 

[darkzero]

I work in imperial so I wanted an imperial lathe. Mill doesn't matter much if you have a DRO but I would still rather have imperial leadscrews.

Many beginners will buy a DRO right off the bat but IMO you should know how to you use your machines without a DRO. Should be familiar with how to use your dials, how accurate they are, edge finding/locating, dealing with backlash etc. I purchased my machines without DROs & installed them later. What happenes if your DRO system ever goes down?

I'm completely lost when it comes to metric measurements. I mean when I wrenched on cars for a living I worked mostly with metric so I can tell a bolt head size by looking at it. Fasteners I prefer to use metric. I can picture how much 1 thou or 100 thou of an inch is but if you ask me 1 tenth or 1 hundreth of a mm I'm clueless. Even though I have DROs I still use my dials for DOC & reference often.

 

[DavidR8]

Thanks gents, agreed on the need to learn to use the machine before diving into a DRO. I have since learned that the dials are actually metric so that takes away the insanity of imperial dials on a metric lead screw.

 

[darkzero]

Many people have learned to use both which is great. I have been using imperial measurements all my life, long before I even knew what a lathe was so that's what I'm used to. All my measuring tools are imperial. I do work with metric measurements but I always convert to imperial when making a part. It's just easier for me. I'd like to get familiar with metric measurements as far as machining but to be honest I doubt I ever will.

So in reference to ToT, I will always say "dead nuts" instead of "spot on" for the metric guys.

 

[mksj]

I had a mill with imperial dials and supposedly imperial lead screws, but were in fact metric. Nothing worked-out correctly and it was very confusing until I figured out the problem. This does occur on some of the cheaper machines and the dials are an approximation in inches. With this mill it forced me to buy a DRO which at the time was around $800, so wasn't happy about that. If your DRO ever goes out or you want to verify it to the dials, it is a lost cause. Also the Z axis for the head did not have a scale, and the dial was absolutely useless for measuring height adjustment. On a lathe it is a bigger issue because the lead screw pitch dictates the threading dial alignment, so you want the lead screw pitch to match the predominate measurement system you plan to use. In addition the tailstock and tool post dials you would also want to follow the predominate measurement system. I do quite a bit of work in metric, so one area where the DRO's come in real handy. Now that they have come down in price worth considering, I find that they significantly decrease my work time and help reduce mistakes.

Also from a resale point of view, it could have an impact.

 

[stupoty]

 

[DavidR8]

The lead screws are on a mill not a lathe

 

[stupoty]

The lead screws are on a mill not a lathe

I think I have lathe on the brain today

opps

 

[darkzero]

I think I have lathe on the brain today

opps

But yes, to answer what you were talking about, it would just be vice versa. Lathe with metric leadscrew can use the half nuts to disengage/engage but not with imperial threads. Well you can if you keep track of the dial when disengaging/engaging. That's how I thread metric on my imperial lathe.