[Mavigogun]

I have no direct experience with ISO30 anything; mid-purchase of a used S30C spindle and tool holders, reported to have low hours. While inspecting the tool holders, all the tapers include markings- some kind of generally blotchy in bands near top and bottom, some with many longitudinal marks starting at the wide end of the tapper and fading out.

The spindle was used with aluminium pretty much exclusively; the tool holders and machine had fine bits of aluminium glitter most everywhere.
Are these markings normal? Obviously, the concern is runout and possible spindle damage. What do your tool holders look like after ~100 hours use?

Images attached.

[Mavigogun]

I applied a soft chemise and denatured alcohol to the holders- see attached images for the results on the two holders previously pictured. The chemise came away with lots of (presumably) aluminium glitter; a finger nail ran over the surface can detect some of the marks, most with effort.

[metalmayhem]

I'm guessing if the holders look like that then the spindle taper must be a mess . On the holders I'd just clean them up with a fine scotchbrite pad and wd40 . For cat 40 and 50 spindles my preferred method was to grind and taper a wood block , spray a bit of wd40 then run the spindle at a few hundred rpm . The wood has a certain amount of abrasion which helps to clean the spindle without scoring it . The key thing is with this method is to not make the wooden piece so that it can get wedged in the spindle , make it smaller than the taper and run it up and down on one side as the spindle is turning . I am sure this will make some people in these forums cringe safety-wise but it is effective in competent hands , and is why I said a few hundred rpm . I actually used to do it at about 1000rpm . There are tapered spindle cleaners for this purpose but they aren't so great for getting mashed chips out of a spindle taper

If the machine has an atc then something is needs to be changed in order to protect the holders from collecting crap . It isn't uncommon to pick up a chip or two after thousands of hours , but holders looking like that after 100 hrs is a problem . The good thing about aluminum is it won't have caused any damage , and it's merely a mess

[pippin88]

If multiple tool holders have similar marks, the spindle taper is damaged.
Probably had chips jammed in.

Often fixable with some work.

A ding / scratch in metal will usually result in a depression/low area, but also raised/high areas. These high areas in the spindle taper will cause run out and damage tool holders

The spindle taper can be reground, or sometimes stoning of high spots can remedy the situation.
A few low spots don't matter - a small reduction in spindle taper contact area is not an issue