Lathe/Mill/Press question

[JCH13]

If I get a machine with hand dials. What would be the better to have the dials graduated in?

Say I have a rod I want to cut into some sort of custom bolt.
I want to cut the shaft diameter in SAE, but the head in metric. Would it be easier to do that on a metric graduated mill/lathe, or on an SAE graduated mill/lathe

mm/25.4=in

One can be made into the other. Math FTW.

Get the units you are most comfortable using.

 

[Howard]

mm/25.4=in

One can be made into the other. Math FTW.

Get the units you are most comfortable using.

Actually, I'd say imperial would be a little easier, since it's a heck of a lot easier to multiply by 25.4 instead of divide (and end up with more whole numbers).

 

[JCH13]

Actually, I'd say imperial would be a little easier, since it's a heck of a lot easier to multiply by 25.4 instead of divide (and end up with more whole numbers).

I think you mean metric, not imperial, as inches (imperial)*25.4 = mm (metric) right?

Why is it easier to multiply instead of divide? Why are whole numbers easier than decimals? What's the practical difference in machining (for example) to 0.787in vs 20.00mm?

 

[Jaepheth]

Well, clearly you can convert the measurements.

What I was thinking though, was that with a metric machine you'd be able to get closer to an SAE measurement before having to interpolate the dial markings than the other way around

 

[JCH13]

Well, clearly you can convert the measurements.

What I was thinking though, was that with a metric machine you'd be able to get closer to an SAE measurement before having to interpolate the dial markings than the other way around

If you're worried about getting more accurate than 0.001in on an inexpensive bench-top machine you're doing it wrong. The machine prints I make at work rarely have tolerances tighter than +/- 0.003in, normally they are +/- 0.005 or +/- 0.010.

If you really need to hit 0.01mm/0.0005in precision on a regular basis without tearing your hair out you need a real knee mill. Of course if that's what you're doing, you're probably working for NASA :awe:

 

[infoiltrator]

The machinery does not care. It is a matter of blue prints.
I trained SAE and our measuring tools were SAE.
When we did metric it just meant the decimal inch sizes were equivalent to even metric sizes.
You may want a few metric drills and reamers for specific jobs, usually given fractional, number and letter sizes you are fine.
Switching between systems can be confusing. Now .939 inch +- .0015 vs ...

 

[Howard]

I think you mean metric, not imperial, as inches (imperial)*25.4 = mm (metric) right?

Why is it easier to multiply instead of divide? Why are whole numbers easier than decimals? What's the practical difference in machining (for example) to 0.787in vs 20.00mm?

Sorry, you're right. Metric is easier. I still think multiplying is easier than dividing since you end up with better numbers. Practically speaking there is little difference.

 

[Kirby]

Watch your hair when dealing with lathes.

http://www.nytimes.com/2011/04/14/nyregion/yale-student-dies-in-machine-shop-accident.html