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Metric to american

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Brento

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#1
Has anyone done any project from books like these? My issue is all of the projects are in metric and id like to convert into american. I was curious if its easier to convert everything to american at known nominations or just make the part to the actual conversion from metric.
 

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Tony Wells

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That would depend largely on the complexity of the project and your design/engineering talents. That is, if you mean taking 10mm from print and subbing in 3/8"(0.375).

I'd probably convert the drawings to SAE/Imperial. Have done so for few commercial jobs. Just have to convert the tolerances too.
 

jocat54

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#3
Never done any from the books--but it's pretty easy to convert metric to imperial (25.4mm=1"). Think that's what I would do.
 

savarin

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#4
Why not follow the rest of the wold and use metric then you can just follow the projects as is.
My lathe is imperial but all my projects are metric so its no real problem. and seriously, Americans actually do use the metric system and have done so for years, you just divide an inch into 1/10ths, 1/100s, 1/1000s instead of a millimeter.
I use both systems and would just transcribe the measurements to the system I wanted. If done exactly and not to the nearest equivalent there should be no problems.
 

Brento

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There is alot of complex parts so the best thing is to maybe just convert to us to measure with my instruments but in the end keep dimensions the same.
 

Bi11Hudson

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I have been working with the metric system for more than 50 years building and modifying scale models. H-O trains....
The scale is 3.5mm to 1.0 foot. The end result is that I work as easily with the metric system as with imperial. Although imperial is what I grew up with, metric is somewhat easier. The important thing is to "get comfortable" with metric measurement. Most of my construction experience is with imperial. The machine work is maybe 30-70 metric.

A few years ago, I built an electric powered bicycle. The doner(?) was a late model Schwinn, made in China. So all the additions I made were done in metric. With few exceptions, such as I don't have metric keyway broaches. Had to finagle that. A three wheeler arrangement, it worked out well.

A few dimensions to get comforteble with:
25 mm is a fuzz less than an inch (25.4mm=1 inch)
1 mm is 0.03937 inch (roughly 40 thou)
10 mm X 1.5 thread is so close to 3/8-16 TPI you need to measure cose to find the difference.

With little expenditure, you can tool up for metric. A good metric caliper or micrometer along with the conversion factors for imperial leadscrews will yeild good metric measurements. On the other hand, conversion to imperial is just a matter of converting all the measurements, to the above listed factors. The bicycle mentioned was done in metric to make everything one system, no half and half, no two sets of wrenches, et al. My model building is done to imperial, because I must interact with others that have no grasp (nor want) of metric. Go for it, Dude. By whatever system is easiest for you.
Bill Hudson​
 

Brento

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I have been working with the metric system for more than 50 years building and modifying scale models. H-O trains....
The scale is 3.5mm to 1.0 foot. The end result is that I work as easily with the metric system as with imperial. Although imperial is what I grew up with, metric is somewhat easier. The important thing is to "get comfortable" with metric measurement. Most of my construction experience is with imperial. The machine work is maybe 30-70 metric.

A few years ago, I built an electric powered bicycle. The doner(?) was a late model Schwinn, made in China. So all the additions I made were done in metric. With few exceptions, such as I don't have metric keyway broaches. Had to finagle that. A three wheeler arrangement, it worked out well.

A few dimensions to get comforteble with:
25 mm is a fuzz less than an inch (25.4mm=1 inch)
1 mm is 0.03937 inch (roughly 40 thou)
10 mm X 1.5 thread is so close to 3/8-16 TPI you need to measure cose to find the difference.

With little expenditure, you can tool up for metric. A good metric caliper or micrometer along with the conversion factors for imperial leadscrews will yeild good metric measurements. On the other hand, conversion to imperial is just a matter of converting all the measurements, to the above listed factors. The bicycle mentioned was done in metric to make everything one system, no half and half, no two sets of wrenches, et al. My model building is done to imperial, because I must interact with others that have no grasp (nor want) of metric. Go for it, Dude. By whatever system is easiest for you.
Bill Hudson​
Thank you Bill perhaps once i get more into this hobby and some free cash i will pick up a metric micrometer or 2 all of my instruments are in imperial which is the only reason why im asking for opinions. I have found metric to be easier for drawings myself but due to everything in imperial through my last 3 jobs its hard to tool up on it without a good reason for it.
 

Hoover

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I am a machinist/ fabricator in new product development for one of the US power sport companies.
The company is global so everything is designed in metric.
The funny thing is that quite often when I convert to inches (I just can't think metric) dimensions convert to a nominal standard size.
It seems like a lot of parts are designed in US, converted to metric, then I convert back.
 

Bi11Hudson

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That makes good sense. For conversion factors, multiply any dimension in millimeters by 25.4. In centimeters, you can multiply by 10 and then convert. For decimeters, by 100 then convert. The result will be in inches. Run out 3 or 4 decimals and round it as fits. Some places it matters, some it doesn't. That's essentially what I do with my models.

As an aside, I picked up a metric micrometer on eBay a while back for 3 or 4 bux. They paid shipping... It took 3 weeks plus to get here and I'm not sure how accurate it is. But I was getting it as a standby tool anyway. If I measure a 12mm shaft at 12.02mm, that's close enough for what I do.
 

Brento

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Ill keep that in mind thanks Bill. Just a question how wide does a set of metric micrometers measure? Equivalent to a 0-1?
 

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Does anyone have a chart as to what American threads are close enough to metric threads?
 

RJSakowski

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That makes good sense. For conversion factors, multiply any dimension in millimeters by 25.4. In centimeters, you can multiply by 10 and then convert. For decimeters, by 100 then convert. The result will be in inches. Run out 3 or 4 decimals and round it as fits. Some places it matters, some it doesn't. That's essentially what I do with my models.

As an aside, I picked up a metric micrometer on eBay a while back for 3 or 4 bux. They paid shipping... It took 3 weeks plus to get here and I'm not sure how accurate it is. But I was getting it as a standby tool anyway. If I measure a 12mm shaft at 12.02mm, that's close enough for what I do.
Bill, I believe that you meant to say divide by 25.4 to convert mm to inches. I multiply by ,3937 to convert to inche. If a rough calculation is OK, .4 works. I work with both but becuase my measurement tools are Imperial, I convert almost everything to inches
 

RJSakowski

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When I did layouts with a scribe and ruler, designing to nice round numbers was more or less a necessity. Nowadays, with CAD, DRO's, digital calipers, and CNC's, round numbers aren't as important. A consideration as to whether to design in metric or Imperial. In the U.S., Imperial measured stock is readily available while metric stock is not. In the rest of the world, metric stock is the most common one. Also true for fasteners. Here, you can find metric fasteners but usually they are more expensive.
 

Brento

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Well what i may do is keep everything metric but convert to imperial to make the part but when i have to use metric fasteners i will engineer it to be imperial fasteners.
 

Tony Wells

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RJ......I think you meant multiply by 0.03937 for mm to inch. Left out a zero:cool:

In general I like Metric, but I'm pretty well instrumented up for Imperial, plus some machines are cross-dialed, and some have DRO that speaks Metric. Too late in life to start buying a bunch of Metric instruments. Of course, some (the digital stuff) is bilingual.
 

Boswell

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I have a couple of digital tools that work great both ways. I particularly like my Mitutoyo Solar powered calipers. I also have a 0-1" digital micrometer but I pretty much only use it when I need to do Metric. I much prefer my mechanical micrometers because I don't have to search for batteries every time I need it.
 

Mitch Alsup

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I interchange metric and Imperial all the time.

Al you need is a calculator and 1 constant:: 25.4.

Imperial ince = metric mm / 25.4
metric mm = Imperial inch * 25.4

10mm = 10 / 25.4 = 0.393700
1 inch = 1 * 25.4 = 25.4 mm
 

Brento

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I have a machinest calc pro which is very sophisticated that i dont remember the button sequence to figure things out.
 

Dave Paine

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I have a machinest calc pro which is very sophisticated that i dont remember the button sequence to figure things out.
That calculator is indeed sophisticated. I looked at the User Guide. Easy to set for entering Imperial or Metric, but converting is not so easy, it is part of the Conversion menu.

The Staples calculator and others like it would be far simpler to convert between Imperial and Metric. I may have to get one for myself. I have an HP32 calculator which does all sorts of functions, but no Imperial to Metric, other than my entering 25.4/ or 25.4*.
 

pontiac428

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I interchange systems and don't have a preference, I just work with it.
My machine scales and leads are in inches, but the cutting tool does not have a preference, it just cuts.
You want to build something of a given size, then build it. The units of measurement are inconsequential.
Conversion factors are ratios, and ratios are proportions. We could convert to a different number base or work from log-10, either way we'd be watching some dimensional value and working towards it, cut by cut.
I am not trying to sound trite, it's just a number!

Edit: Microsoft Excel is your friend.
 

Bi11Hudson

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I seem to have stepped in it big time here... A calculater is nice...... if you're in a class. I prefer to have things where I can convert in my head, a pencil & paper at worst. Ya never know when the batteries will give out. And most times, I don't need an answer to 5 decimal places in imperial. I do use 5 places for a mm because the numbers are easy to remember. Point03937... Pi is 3point14159 Just the way my memory works. I take the measurement of a ...motor shaft with an imperial caliper. If it is 0.079~, it's a 2mm. If it's 0.092+, it's 3/32". In either case, it will work, just a matter of what type of coupling to use. Or what size fuel line. Or whatever I happen to be using for that install.

I have a number of project books, some from the U.S., some from England, and some for pure metrics. Some very old, some recent. The only place I have any trouble is with English fasteners (Whitworth) and pipe fittings. What's called British Standard. But that's just a matter of a different method of measuring. I don't use the English systems very often, so must brush up on them when I have a project from that area. But you've got to watch the English. They started out imperial and converted to metric only recently. Sometimes the systems get a little mixed up. As in both systems side by side. A shaft 2 inches long by 1.5mm diameter. Ya got to think, 2X1/16", more or less. Or 50mmX1.5 if you're trying to stay metric all the way. If the shaft fits into something, can the something be reamed to 1/16. Or is it just to stand off something.

Most metric micrometers read to 25mm, or just a whisker fuzz under 1.0 inch. Making an imperial leadscrew cut (true)metric threads requires a 127/120 conversion gear. If you backtrack the numbers, the 127 gear is to convert 25.4 to a solid number, one without a partial remainder. The most important factor is to get comfortable with the idea of a fuzz and if it's important. A cylinder/piston/rings of any larger size won't matter that much. A shaft, especially a small one, fitting into a bearing, will. It's one of those calls you must make for yourself based on what the book says. The book you have posted is for machine parts. Take a dovetail cross-slide. The angle is important but will be the same, imperial or metric. The width (distance between) may be metric, but a fuzz too full won't really matter because of the gib and setscrews to adjust it. If it calls for 25mm, make it an inch. That's what I was refering to for you to make the call. And the worst case: As a hobbyist, if your call isn't right, ya make it again, watching the dimensions a little closer.

I'm not trying to denigrate one system under the other here. I'm only trying to give a little insight into the process of making a conversion from one to the other. I responded to a post the other day regarding need vs want. You need a set of manual calipers and a feeler guage. Anything else is a want, or time saver. Chew on that for a while.

Bill Hudson​
 

Bi11Hudson

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#24
Quote:
Bill, I believe that you meant to say divide by 25.4 to convert mm to inches. I multiply by ,3937 to convert to inche. If a rough calculation is OK, .4 works. I work with both but becuase my measurement tools are Imperial, I convert almost everything to inches

Answer:
That is for centimeters;
A millimeter is 0.03937" (40 thou)
A centimeter(10mm) is 0.3937" (400 thou)
A decimeter(100mm) is 3.937" (4 inches)
A meter(1000mm of course) is 39.37" (40 inches)

I prefer the multipliers rather than the divide process. Usually I don't consider rods, yards, feet, whatever. Unless I'm doing construction work. Most times, under 20 feet I stick with inches and fractions. To a sixteenth, as a rule. It's a matter of what fits best. When I am surveying something, I measure in feet and tenths(possibly 100ths) of a foot. I have a tape measure with 10 "inches" per foot. A lot of fun with a helper that can't read a tape that well. I have another tape with 12 inches per foot, but in tenths of an inch. Used to setup a machine where I used to work.

Bill Hudson​
 

RJSakowski

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RJ......I think you meant multiply by 0.03937 for mm to inch. Left out a zero:cool:

In general I like Metric, but I'm pretty well instrumented up for Imperial, plus some machines are cross-dialed, and some have DRO that speaks Metric. Too late in life to start buying a bunch of Metric instruments. Of course, some (the digital stuff) is bilingual.
Yes, I did:face slap: I know better! Thank you Tony & Bill for catching it. Muscle memory makes running the conversion almost automatic.
I am going to chalk it up to the late hour and the half a snifter of brandy. Anyway, that's my story and I'm sticking to it.
 

BenW

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Ill keep that in mind thanks Bill. Just a question how wide does a set of metric micrometers measure? Equivalent to a 0-1?
Metric mikes are ususally 25mm travel, so same as imperial ones.

Sent from my SM-G930F using Tapatalk
 

P. Waller

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#28
If the engineer is thoughtful they will dual dimension each drawing in inch and millimeters like so.
This is from one of todays jobs.


Same customer and same assembly but this one is not dual dimensioned as above, this part is mostly in whole 1/16s of an inch, go figure.
Simply use a calculator to convert and write the inch numbers next to the metric numbers as I do, I do this 6 days per week 52 weeks per year.
As mentioned the international standard is 25.4
It does not get any simpler than that.
 

Brento

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What is your rule for rounding up when converting the metric to inches.
 
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royesses

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I have a machinest calc pro which is very sophisticated that i dont remember the button sequence to figure things out.
I have the machinistcalcpro2. On it I enter a number then inch. Then tap mm and it converts the displayed number to metric. Tap inch again and it converts back to inch. Do the reverse to convert to inch. I don't know if your version is the same. I also have a calculated industries conversioncalc plus that does this and many other conversions including torque units.

Roy
 
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