[raychar1234]

Hi everyone,

I bought a new Kress spindle to replace the old one which had used for many years and had the brush commutators replaced several times. The old one was very good in quality, so I bought the second piece.

However, lately, I check the run-out on the both spindles' inner taper holes that used for the location of collet. The new one has 0.07mm T.I.R. while the old spindle has 0.01mm. I am desperate as I bought it for almost half year and can't return it for replacement.

Now,I want to fix it by doing a little touch up on the taper hole. Like; to mount it on lath and mount a hand grinder to grind the hole once while the Kress spindle run itself.
Is it possible? Or, will I make the thing worse?

Thanks in advance...

[LongRat]

First I would be checking the source of that run-out. I think it is more likely to come from bearings or bearing mounts than the machining of the spindle taper itself. If you do find it is the taper, it would be possible to remove it and clean it up in a lathe. When in the lathe you need to ensure you get it running true to the bearing surfaces (not the taper, known to be out) before cutting anything from the taper, which could be tricky on a small spindle like that - depends what kit you have. I'm not sure if the Kress spindles are hardened but they may not be - in which case grinding would not be essential and a much easier set up could be had using a small boring tool.

[raychar1234]

Just measured the run-out on the circumference of the spindle shaft. As there are two flat land areas on it for spannner locking use, there are no more complete 360 degree, only two 90 degree sectors, for me to measure. Anyhow, it reflected it is true concentric and i trust this.

If doing touching up the inner taper, I need to fix it using its diameter 43mm portion and manage to align it preciselyfirst. My mini lath has smalll spindle bore so it does no help in clamping. Luckily, I have a spare small diy z-axis which is of THK slide and a dia. 43mm spindle holder. I am now thinking the rest of set up in order to finish the work....will keep the posting when there are proceedings.