Thread: Measuring runout

What's runout?:confused:

Runout is when you realise you need two more whatsits to complete the current project, and that Bunnies closes in 15 mins.

I'd have thought option 2, as that's simpler, and a theoretical mean position may not relate to anything "in real life". Eg: a blob of weld on a shaft would cause a runout equal to its height, and the mean position would be in space above the surface of the shaft.

Just my thoughts - no engineering experience or qualifications to back them up.

Cheers,
Andrew

Hey Chris.
I'm new to the forum (in the US actually)...I had a problem with runout in a router. I made a jig to drill holes for shelf pins and used a 1/4" router bit (the pins measured .250"). The holes came out almost .020" oversize (.270") and the pins were obviously a no go.
I finally determined that there was .010" runout of the router shaft which I measured with a dial indicator at the shaft. This translated to making the holes .020" too large overall. (.010" all around the hole).
Did that help answer your question?

Thanks PlaneCrazy,

So your dial indicator would have read -0.01" then +0.01" as you rotated the shaft for a 0.01" runout? I thought that runout was the deviation from the mean position, but if I was wrong the total error was twice what I thought. I think you have clarified it for me, thanks.

Chris

Chris,
If my memory serves, I was told by the tech at Hitachi that they measure shaft runout 25mm from the base (bearing), and that the "acceptable" runout for their routers (M12V) was 3mm.
Keep in mind that the longer the cutting tool, the more pronounced the effect of the runout. I'm not sure, but I think the mean you are mentioning is at the selected point of measurement. And yes, the effective error will always be twice the mesusement of the runout.

Are you sure it was 3mm? That is quite a lot! Perhaps it was .03mm (.001")? Anyway, thanks for the help

Chris,
May have been .3mm (about .010"). I know it was alot more than I expected. I have a number of routers. The best of them, a Bosch, measures between .002"-.005" runout right at the base.
I ended up using a 6mm router bit to get a .25" hole. Wierd, huh?

Hi Chris,

You can have run out on something which is round and spinning eg shaft, drill bit. Or you can have runout on something stationary and parrallel eg support post on a router or the beds of a lathe.

Of course if its spinning it will be twice the deflection. But if is suppose to be parrallel it could have a plus or minus valve depending which way its out in relation to the specified demension.

Glen

Runout can be indicative thru either bearing alignment or trueness of shaft....I have checked with micrometer and feeler gauges to detemine if dial indicator is correct particularly on a shaft, often times a little bit of "slap" is apparent in bearings in acceptable terms to manufacturers and quite often the norm, but deflection can of course depend on the material being worked and the aggressive nature of person applying the tool.
Cheers