Mixing measurement systems, bad idea, or really bad idea?

[Downunder Bob]

Um, not really an issue IMHO. The fact that this is your hobby means you have learned to measure things, buy a cheap digital caliper if you don't want to do the math.

John

Yes a digital caliper will automatically measure in whatever system you set it to, then with the press of a button will display the same dimension in the other system. Problem solved.

 

[Eddyde]

We use both everyday. Metric is way better in my opinion. Less mistakes and more accurate.
Cheers
Martin

Less mistakes, perhaps but it certainly isn't anymore accurate.

 

[Eddyde]

Curiously, my former business partner, who was born, raised and learned his trade as a cabinetmaker in the south of France; told me, he actually preferred imperial measurements for cabinetmaking. He said he like the relative nature of fractional inch measurements.
Indeed, fractions can simplify doing layout in your head, Eg 4x ¾" = 3" as opposed to 4x 19mm = 76mm. When more precise measurements are required you can roll right into decimal inches.

 

[Bi11Hudson]

Less mistakes, perhaps but it certainly isn't anymore accurate.

Got to stick my nose in here. I have worked in the "fiber optics" business(splicing), where the "conductors", the fiber strands, were measured in microns. That's metric, the next step below millimeters. There's 1000 microns(micromillimeters) in a millimeter. Most machinists think in thousandths, or possibly tenths. 0.0001 inches. There's 39 thou, and change, to a millimeter. Just that mm isn't the smallest unit of measure there is.

The bottom line, either can be as accurate as the other, it's a matter of what one is most used to. I do both, essentially interchangably. If what I'm working on is metric, I try to stay metric. Doesn't always work out, but I try. On the other hand, my machines are calibrated in inches. If I was really good, I could work to a tenth of a thousandth. I'm not that good, but like to try. Further, my model trains are a mixed scale. HO, 3.5mm to the foot. Just how confusing can you get? 3.5mm ~ 0.1385inch. The metric is a little easier to work with here. A similar scale used in Europe is 4mm per foot. It's all a matter of what you're conversant with.

Most of the usage of a dial indicator is to determine out of round, eccentricity, things of that nature. The absolute measure doesn't really matter. As mentioned above, deviation from the "zero" is what matters, get that as small as possible. Whether it's 0.0004 in or 0.1 mm isn't important. Until you're comfortable juggling numbers in your head, a digital caliper does help.

.

 

[Cooter Brown]

I worked at tool and die shop, prints would come in all time with the measurements in millimeters and we would convert everything to inches before starting any work....

 

[Martin W]

Less mistakes, perhaps but it certainly isn't anymore accurate.

You are correct. It is not any more accurate than imperial. Like Bill said it is what ever you are confident with to add and subtract numbers in your head.
Our shop is a millwork shop and our machines have metric scales. It is easier for me to have a kid cut something say 750mm than just a hair over 29-1/2" or 29.527 or 29-17/32. This makes it more accurate for me.
Funny thing is I prefer imperial for myself. That's all I use in my hobby machine shop.
Cheers
Martin

 

[WCraig]

To me, the main problem with "Imperial" is that you're forced to mix decimal and fractional measurements. Eg the part is 0.800 wide and you want to put a 5/16" bolt just on one side of centre. So I've got to convert 5/16 to decimal...where did I put that @#%@ chart again?!? Oh, that's right, it is a four-decimal place number so I need to choose whether to round up or down. Etc.

Who among us has't made a blunder when mixing fractions and decimals?

Placing a 6 mm bolt on a 20 mm part is a lot less drama.

Craig
Despite what I've said, the machines I've got and all the tooling are Imperial-based so that's what I work in.

 

[WCraig]

BTW, how big are #6, #8 and #10 machine screws again?

 

[Janderso]

I have not had to use the metric system yet, and do not plan to change, at age 74+. Likely the metric system will not be adopted in the USA for a long time yet, if at all.

John,
In the Ford manufacturing world, every nut and bolt used in their vehicles has been 100% metric for over ten years. Before that it was mixed.
Granted, most of the products are assembled in Mexico, Turkey, Canada or wherever.
The trucks are made here.
The new techs only need to buy metric.

 

[Janderso]

BTW, how big are #6, #8 and #10 machine screws again?

I was curious,
#6. 0.13”. 9/64
#8. 0 .16”. 5/32
#10. 0 .19”. 3/16