Angle accuracy +- 10 minute

[Ken_Shea]

Am looking at a set of adjustable angle blocks and it list the angle accuracy as +- 10 minutes.

What does this equate to in layman’s terms?

Thanks

[Verboten]

I believe that a minute is 1/60th of 1 degree.

[Verboten]

Of course you probably already know that the "+-" before the 10 means that it could be 10 minutes of angle on either side of the angle specified.

[mrainey]

It means, in a functional sense, that for every inch of the block's length, it can be off +- .002909177

Since this error is cumulative, if the block was 10 inches long, it could be off as much as .02909 from theoretical. That seems pretty poor to me for any kind of precision work.

[Mortek]

Since they are adjustable, if you are using a cnc machine, just create a program to run back and forth at the angle you are trying to achieve, put an indicator in the spindle and run the program. Leave the tightening bolts close to snug, and tap the angle block in to the desired setting.

[M@T]

360 degree's in a circle. 60 minutes in a degree and 60 seconds in a minute.

So effectively, there are 3600 different degree's within one degree.

Very difficult to measure seconds though and I never worry about them. IMO, its just a pattern maker trying to make himself look good by designing some technical bollox drawing. I got sent a drawing once and they wanted a 2 degree/46 minutes/25 seconds angle. I just put 3 degree's on it and no-one ever complained.

[mrainey]

Seconds can be important when you're evaluating the indexing accuracy of the table on a horizontal machining center. +- 30 seconds vs +- 5 seconds can make all the difference in your ability to precisely locate a feature on the periphery of a large workpiece, or even to machine two faces perfectly parallel after indexing 180 degrees.

It all depends on what your parts look like and what sort of tolerances you have to hold.

[M@T]

Your quite right mate, I run lathes you see so even if the angle is slightly out, its barely noticable coz the OD's are never usually bigger than about 200mm. If your machining something a few feet long or even meters long then by the time you get to the end it will be out quite some way.

[tahlinc]

We have this rule of thumb that says:
.017 per degree per inch
This is reasonably accurate at angles close to zero.

In your case 10 min = 1/6 deg

.017/6 is about .003 per inch

That is not very accurate. But the accuracy in your case is the marking on the block not how accurately you can set them.