Play in new arbour for mill

Hi,

Ok thanks for the help and info on my issue… this afternoon I check the following and can report back.

So, when measuring the arbour at speed I got 0.15mm runout under speed, turning the spindle by hand the runout was only 0.09mm.

Following the advice, I removed the arbour and measured the spindle, I couldn’t get to the inside but found a clean section outside. At speed I got a runout of 0.05mm but manual turning the spindle got 0.02mm runout.

Regarding the above difference in readings could this be down to a cheap dial gauge? I have had this for many years now…. Would imagine it was about £15 to £20.

The other observation I note, can feel a very slight movement in the spindle when trying to move it side by side. Not too sure if it’s the motor belt I am moving or play in the spindle. But following the reading taken about is this bad or good?

So……. Note sure where this leaves me...!!!!

Q1 = due to the different measurements I am getting, this could be due to a cheap dial gauge bouncing under speed of the rotating item, or due to play in the spindle.

Q2 = if the runout of the arbour was only 0.09mm, generally would this be acceptable?

Q3 = not looking forward to the answers on this one…!!!! If I have the runout in the spindle what options do I have to solve this? Would this hopefully be just changing out bearings and collars? On a scale of 1 to 5 is this very hard to do ?

The plunge type are not ideal for measuring small amounts of run out, a lever DTI rather than your dial gauge would be better. Not good to run at too fast a speed but not sure what your lowest is.

I'd like to see less than 0.09mm

The spindle bearings may just need some adjustment if you think you can feel movement, I assume they are taper roller type.

This is almost a bit fast but the problem with turning by hand if there is bearing play is you can be moving the spindle with uneven hand pressure. This is the type of runout you should be looking for, one of those divisions is the same as one of yours so about 0.003mm on the arbor or spindle, drill in the chuck won't be as good

Edited By JasonB on 17/09/2023 18:29:52

I advise against starting with high accuracy measuring. Trouble is it's skilled work that's easy to get wrong. Dozens of booby traps. One is not making sure the instruments are OK before starting, check that dial and learn how to use it!

As unpractised measuring applied randomly with dodgy kit is dangerously misleading, I suggest better to start simply by cutting metal with the machine. If it cuts OK, stop worrying. Measure the work it produces, not the machine. Distinctly ratty tools can still produce good results. Takes longer because the operator has to compensate and double-check, but quite severe backlash and bearing wear can be tolerated.

Only take measurements if the machine doesn't perform adequately, and remember measurement is only one of several ways of pinning down problems.

Best engineering advice ever: if it ain't bust don't fix it.

Dave

0.09mm TIR is miles more than you should see in any mill spindle. Don't measure it on the outside, do it on the taper and do it at low speed.

Have you inspected the taper for embedded debris or burrs on the edge? Try roatating the head so that you can get a good view of it.

Running the spindle at the lowest speed is really only OK if its very slow, say less than 100 rpm. In any event the speed must not be fast enough to cause any bounce.

Whilst your plunger type indicator is not ideal you could probably just get the tip of it to bear on the on the inner surface at the mouth of the spindle taper bore.

Regarding the 'side by side' play you mentioned, its not really clear what you mean. I take it to be that you are turning the spindle slightly (CW and ACW) and seeing play in the driving splines? (if so, nothing to worry about).

If its 'side to side' movement and its not play in the bearings then it could be the quill is loose fit in the head casting.

Ian P

Put the chuck on the arbor. Then put a known accurate part in the chuck, and I suggest a hardened dowel pin of around 12mm diameter. Then clock the dowel pin to see if it runs true.

What I wonder do you intend to fit in the chuck when working? A drill perhaps? If so after checking the pin put a known size drill in and drill a hole about half an inch deep. Then check the diameter of the hole produced, and using a lever clock check if it is actually truly circular. If it the size that you expected and is round, rather than oval then everything is fine.

Obsessing about theoretical "run out" is not important. The important thing is what the machine produces. If the run ouit is still unacceptable I would suggest that you check the mill spindle for accuracy. You say it is a second hand mill and of course it may have wear and need new bearings or adjustment,

The movement you suspect in the spindle may be the quill in the body, put all quill and axis locks on and check they are effective before taking any measurements.

Mike

Hi Guys,

Thank you for all the great advice and can see I need to do more digging into my issue. As I haven’t use this mill before and is my first one, I only have this arbour to work with.

I will have a go and getting the dial indicator on the inside face of the taper and will report back.

On a side note if anyone can point me on any info in to checking the bearings and how to adjust fitment that would be much appreciated.

So as an update I did manage to get the dial indicator on to the internal taper spindle and got a runout of 0.11mm while on a slow rotation 100 rpm, which I understand is far from acceptable. And yes, would imagine the route of my arbour runout.

Thank you all for your help and guidance on this, and smile…. now need to start a new post in “how do I sort out this runout”.

Last couple of replies moved to new thread here