inch to mm conversion table

[crashtestheli]

I have this posted at home - might be useful

inch thou mm
1/64 0.016 0.397
1/32 0.031 0.794
3/64 0.047 1.191
1/16 0.063 1.588
5/64 0.078 1.984
3/32 0.094 2.381
7/64 0.109 2.778
1/8 0.125 3.175
9/64 0.141 3.572
5/32 0.156 3.969
11/64 0.172 4.366
3/16 0.188 4.763
13/64 0.203 5.159
7/32 0.219 5.556
15/64 0.234 5.953
1/4 0.250 6.350

[Robbob]

/25.4 ............... only mathematical equation I ever remembered

[bob1961]

I just use this web site, lets you know any conversion you ever need ....

Online Conversion - Convert just about anything to anything else

[EeePee]

Google does it also.

[crashtestheli]

haha nice one.

I like to measure all bolts with a caliper prior to drilling a hole.
I have the above list taped to my drill bit case so I can QUICKLY choose a bit to drill the required hole.

ie:3mm screws are typically 2.8mm in real life

[bob1961]

yes 2.8 hole needs to be drilled to tap it 3mm....

[crashtestheli]

Originally Posted by bob1961

yes 2.8 hole needs to be drilled to tap it 3mm....

Almost
A 7/64 bit would be used to drill a 2.8mm hole that the screw will slip through.

A 1/8" bit would make a 3.2 mm hole and would be close enough to tap for a 4mm bolt.
A 3/32 bit would be good to tap for a 3 mm bolt

[bob1961]

2.4 sorry....

[BigSki]

easy conversion- 25.4mm= 1", .0394" = 1mm.

[Meatwad]

There's an app for that as well. The old machinists hate me for it but it's handy.

[802coma]

Yeah I convert stuff every day haha.

.03937 never use the 25.4 for some reason maybe because I'm working in 10ths and millionths of a inch

[Etype R]

I just let the software figure that crap out

[Eric0424]

Originally Posted by bob1961

yes 2.8 hole needs to be drilled to tap it 3mm....


2.4 sorry....

Nope, pre-tap drill bit for plastic and soft metals is 2.5mm (75% thread), some recommend 2.7mm for harder metals like steel, stainless, etc.

Tap/Drill formula is nominal diameter (3.00) minus thread pitch (.50mm), we get a 2.5mm drill bit for the M3x.50 screw.

Calculator if anyone is interested.
Tap Drill Size Calculator -- Technical Notes

A couple of metric charts if someone wants to save or print them. I keep both SAE and metric charts in the garage close to the lathe and drill press for quick reference.

[Hal]

Old thread but my 2cents.... .03937 is close for converting but 25.4 is the way to go. .03937 is rounded off. If you are working in realy tight tolerances it is not close enough. Inch /25.4=mm and mm x 25.4 will get inches. Very simple. I work in metric all day and it is way easier than inch. Realy, who thought inches was a good idea? Parts of an inch 1/8, 1/16, 1/32. 12 inches make a foot. 3 feet make a yard. How many yards in a mile? Nope lets go back to feet for that one. Metric is all about multiplying by 10 ( or dividing) imo metric is way easier. I work in microns ( .001mm or .00003937 inch) and measure a lot of our product using waves of light witch convert to metric very easily also. Our hobby doesnt require these tight tolerances but once you start its hard not to continue. JMHO

[kincer]

For me I just go to my phone and tell Google to convert it for me lol, but yeah you're right for our hobby really tight tolerance isn't an issue.

[JatoTheRipper]

Necro thread.

Google is the best too. All you have to do is type "1" to mm" in Google and it'll convert for you. That's true for pretty much any units. Google has become much more than a search engine. It's a powerful tool.

You can also download this handy little app (no installation necessary so it may even work on your work computer). It's Convert.exe. It has conversions for a lot of things I use as an engineer. https://joshmadison.com/convert-for-windows/

[celticsun33]

metric to SAE mm x .03937
SAE to metric SAE X 25.4

easy peasy