Denford Software & Machines

Hello all,

I am in the process of upgrading my Triac spindle.

I have a 1.6kw 8000 rpm AC servo motor ordered for the spindle and for this i thought it was essential that i upgrade the spindle bearings.
So i went with bearings rated for 10000 rpm to give me a good headroom, link below.

https://simplybearings.co.uk/shop/p1325 ... _info.html

After installing the new bearings i thought id check the runout on the spindle taper and i was shocked to find 30 microns of runout!
regrettably i didn't check the runout before removing the spindle and replacing the bearings. (i am now kicking myself for not doing so)
is this within spec for the Triac? it seems way too much

I was meticulous when reassembling the spindle and pressing in the bearings that everything was clean and chip free.
im not sure what to do now. I hate the idea of re grinding the taper and this is an absolute LAST resort

Any advice would be appreciated.

Thank you!

I have a Triac PC and will be replacing the spindle motor and probably the bearings at the same time. The link below gives some great advice on the procedure for installing new bearings and adjusting the preload. Perhaps, this might improve your runout issue?

https://www.mycncuk.com/threads/10344-Y ... #post88817

The VMC 1300 Pro had a spindle that ran to higher speed (6000rpm) than the Triac, but to do so a matched pair of spindle bearings with a ground preload spacer were added (possibly Fafnir/Timkin 2MM208WIDUL). May be worth considering better bearings, since you are aiming for higher speeds.

That Mycncuk link is to my Triac retrofit

However I've never measured the spindle run out, and I've still never reconfigured it to run above the servo's 3000RPM rated speed (I replaced the DC motor with servo).
I was only going to push mine to 4500-5000RPM though, to get some improvement with smaller cutters in aluminium, without pushing things too much.

Thank you for the replies

i managed to improve on this in the end. it required me removing the spindle from the head and reinstalling it. with the help of a heat gun, which i used the first time round but probably used it more effectively this time, and also a slight change in method.

instead of installing both bearings in the head, heating them evenly then installing the spindle like the first time, i instead installed the top bearing in the head, then the lower bearing on the spindle. i then heated the head and top bearing and installed the spindle and lower bearing all together. once in i "held" it together by hand until cooled. not sure if this really benefitted but made me feel good .
i then adjusted the preload nut to what felt about right, no endplay but still ran smooth with a slight "springyness" before rotating as moray mentioned in the mycncuk post. i then checked the runout. 0.002mm! i was dead chuffed and happy to leave it there

After this success i went for a celebratory pint then came back the next day to install the bearing support. and this is were problems returned.
i thought to install this i would apply the same method of heating the bearing with the heat gun and slide it on. this didn't go quite to plan as i managed to only get the bearing on about 3/4 of the way before the heat from the bearing transferred onto the spindle and went tight. i had to resort to tapping the inner race to get it on, along with using the bolts to pull it down. once i did this the spindle runout had returned.

It looks like im going to have to disassemble the spindle again, as i cannot get rid of the runout.
on a positive note ive had some experience with rebuilding "splndley" things.
At work i rebuild the live tooling for our doosan lynx220 and while it was quite the learning curve its worked out well for us. custom sockets and press tooling is needed to be made to do this. Anyways thats by the by, as moray says in the mycncuk post it is a very touchy feely process not easily taught.

unfortunately removing the spindle from the head will almost certainly damage the angular contact bearings. which is a real shame. but i feel i have few other options. it is what it is.

in regards to getting better bearings, i am now strongly considering this. must be a touch of madness in me seeing as i just probably ruined a pair of decent bearings!
as you mentioned kfm36, the 2MM208WIDUL fafnir bearings with ground preload spacer is tempting. ive seen pairs go for around £300 on ebay.