How critical is it to have balanced collet nuts on spindles intended for woodworking?
I alternate between 1/8", 1/4" and 1/2" mills quite frequently and was getting tired of removing the collet from the collet nut. So I purchased a pack of four ER20 nuts. Unfortunately, they do not have the balancing holes that the Sienci collet nut has. They might be well balanced without the holes but at the price I paid ($20 CAD for four), I doubt it. I tried one of them on the spindle at 20K RPM and it sounded fine. It didn’t appear as if there was any more vibration than with the stock collet nut.
I don’t know how critical it is but it occurred to me that you may be able to test the difference by cutting a couple of slots with the same bit using the balanced nut for one and the unknown for the other.
My thinking is if the nut is causing more wobble then the slot would be wider.
@_Michael Good idea. I might try that in aluminum. It might be hard to detect in wood. I’m more concerned about wear on the spindle’s bearing than any minor deviation in the cut.
That said, from what I’ve been reading, how you tighten the nut can affect runout as well. So maybe the impact of an unbalanced collet nut is negligible. I tend to tighten the nut by changing the position of the wrench 180°. Sort of like following a star pattern when tightening lug nuts on your car.
I didn’t occur to me that the bearings could be affected, I was only thinking about having some piece of mind about cut quality if the tests came out well.
As far as the bearings go I don’t have a clue how much faster they could wear.
Usual preface, I’m with PreciseBits. So while I try to only post general information take everything I say with the understanding that I have a bias.
For the most part, at least in this level of machining, you are mostly worried about the bearings with nut balance. By the time there something off enough for the average human to notice it’s not bad but horrible. So how much you want to roll the dice with your spindle is your call.
A couple other things…
First, I understand not wanting to mess with collet nuts every tool change. However, you should at a bare minimum be taking the nut and collet apart and blowing them out after use. Material getting stuck in the spindle, collet, or nut can not only add to runout but cause accelerated wear of all the parts.
Second, if I was getting nuts from somewhere that didn’t balance them (an industry standard) I would worry about what else they might be skimping on. If the angle or the position of the taper or thread is off in the nut that can cause the collet to get “pulled” off center leading to runout.
If you want more info on torque and runout let me know. I have some info. Although the short version is that you are probably more at risk of overtightening than under tightening for most applications with less than ER32 collets cutting metal.
Hope that’s useful. Let me know if there’s something I can help with.
@TDA Hey thanks. I’ve read your posts in the past and was hoping you’d chime in. Agree with everything you say and as soon as I find a Canadian supplier of balanced collet nuts at a reasonable price, I’ll buy one or two. I just wished Sienci carried them now that they sell extra collets.
I don’t think there’s anyone in Canada that makes them. I know there are distributors in Canada for Haimer (German) and Rego-Fix (Swiss (Link)). Those will be pricey and you’ll have to watch the thread type if this is for the Sienci ER16 (mini thread, A/UM head is not “standard”).
EM Precise Tool (Link) and Triumph Tool (Link) carry both. Neither is easy to order from or list pricing though. Never dealt with either or even know people that have. They are on the Rego-Fix distributor list for whatever that’s worth…
I’ve kept an eye out but haven’t run across anything else in Canada yet.
Out of curiosity - might it be worthwhile to ask Sienci if they could put collet nuts in their store? The nuts that come with the spindle are balanced so it should be made clear that the bare nuts should be balanced as well.
I think there is a large step between the nuts mentioned by @tda and unbalanced nuts. I would think that the nuts that come with the spindle are a good compromise that would be suitable for our application.
@Jens I will do that. I already asked them about replacement cutters for the large surfacing bit they now sell and they appeared to be open to that.
What bothers me about buying the nuts from an unknown source, is that you don’t really know if they are balanced or not, even if they have the holes. Come on, how hard would it be to drill a few random holes on a nut and claim it was balanced. Who would ever know? An unscrupulous seller could then sell their $5 nut for $60 and we’d be none the wiser.
@Jens Sienci’s response was that a decision to sell the collet nuts individually would depend on customer requests. So if people want the nuts, they would need to see a demand before buying them for resale.