Home Forums Hunting & Shooting Ask The Gunwriters Question about metric conversion

All just complete nonsense. The reason you think the imperial system is easier is simply because that's what you're accustomed to and how you relate to measures. I'm a machinist. I work for one of the top 3 CNC machine tool manufacturers. I've worked in both metric and imperial shops in the past and can very easily converse in either units, and in fact am required to because we have both imperial and metric customers. Metric is much easier because everything is in increments of 10. I know a ton of people in industry and I'm not exaggerating when I say that every single person I know who has worked for years in shops using both units prefers the metric system.

What country do you live in? I have exactly the opposite reaction from the programmers and machinists I have known. In fact I could call and ask at least ten people and bet not one would say they prefer metric. By the way the inch works off of 10 also. Of course I only have 40 years of working in machine shops, job shops, Aerospace and oilfield.



The only reason you're finding conversions cumbersome is because you're doing conversions between the two systems in the first place. If you were to work in a shop that is entirely metric for just a short time, working from part prints that were designed in metric units, the math is no more "difficult" because you're not doing conversions.

Funny but the conversion factor is not the point actually it is the added numbers that make for much longer programs that are the annoyance. If you worked in a shop that only ran prints based on the inch you would find it easier simply because the inch itself is more useful than the millimeter or the centimeter. How you could not see this is beyond logic.


When the default units are specified in mm on a part print, then no, you don't need "to put mm at the end" of anything. That's what drawing title blocks are for. You also don't "put mm at the end" in any CNC program just as you don't put "inch" at the end of imperial numbers.

I never said that in a program I put mm or cm anywhere in the program using modern machines though there are instances where you have to do it, not in a program presently though it was necessary in some of the older CNC machines. Today you just put in G21 when running a metric program instead of the G20 for inch. Surface speed is also calculated differently. The difficulty is the added numbers required to make a metric program. The added figures/numbers are the complaint and they make finding the problem with the program more time consuming.


You define that in the units parameter on the machine control once. Metric doesn't "generally take(s) more numbers" necessarily, depending on the precision you're working with. Sure, metric requires another number or two on the left side of the decimal, but fewer numbers on the right of the decimal compared to inches. If you're talking about part prints and CNC programming, you're dealing with only one unit designator - millimeters. If parts are designed in metric to begin with, then the designer typically used dimensions in whole numbers, numbers with only 1 decimal place, and seldom to more than 2 decimal places, because the units used were always in metric to begin with, not converted over from inch.

This was not my experience at Bell Helicopter! And we received many prints in metric because we supplied parts all over the world.


The exception is if the part in question was designed in mm but intended to mate to another part designed in imperial units.

Yes!


As for programming, if you're manually fat-fingering in programs at the machine control or typing up a text file and uploading to the control, then you're either doing some really simple programming, you're only doing minor program editing, or your shop is behind the times and too cheap to invest in some good CAM software. If you have a good CAM software package, it doesn't make a damn whether you're working in metric or imperial units and neither have any influence on programming time.

When I first started running CNC lathes we floor programmed every part right off the print. Many of them were not simple at all and required hours in front of the machine punching in numbers and wearing out calculators. Mills of course are a different game altogether though we often wrote simple programs faster that the programmers running their CAD software could get them out.

Typically anymore the vast amount of time standing in front of the machines is editing/correcting CAD programs, not made easier by metric in any sense of the word. Second why do the identical programs written in metric have 25% more lines? Especially if you are writing in a .005 radius at every edge.

If you truly believe "the vast amount of precision measuring tools are in inch almost everywhere," then you've been hiding under a rock for a long time, and you certainly haven't been to IMTS lately. The exact opposite is true. The "vast amount" of everything in the manufacturing world, be it precision measuring tools, cutting tools, fasteners, etc are in metric because that is what the majority of the world works in. Open up a Sandvik catalog (you know, the world's largest cutting tools manufacturer) and compare the amount of offerings in metric vs imperial sizes. Ironically, every fastener on the CNC machine you're using every day to type in imperial units, and every part dimension on said machine is in metric dimensions. Now I totally believe the "vast amount" of stuff at your local Groves Industrial, MSC, Fastenal, etc are in imperial units. That's only because the shops local to you are predominantly working in inches, especially in oil and gas country, where shops are still clinging to imperial units with white knuckles. So, your local industrial supply stores are stocking what they will sell. In areas of the country where automotive and aerospace manufacturing dominates, metric is most common by far because all of the finished product is either predominantly or entirely in metric. In most manufacturing segments, metric rules...even in the United States.