End mill won't sit square in collet

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RONALD
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Re: End mill won't sit square in collet

Post by RONALD »

I have had Proxxon machines, and in my opinion they are for hobbyists like HO or O gaugers, not machinists.

Nicely made, but at under $400 you may be expecting too much.

If you want well built machines try Servo or the other types used in industry.

I picked up my Servo off of eBay a decade ago, used but in good condition.
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John Hasler
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Re: End mill won't sit square in collet

Post by John Hasler »

The collet system is this one:

https://www.proxxon.com/en/micromot/28940.php

It's the same as the one on Proxxon die grinders (I have one). The end of the spindle is threaded on the OD and is .1875" ID. You'll need a ball tip indicator such as a DTI to get on the inside of it.

That collet system is not suitable for end mills IMHO but the runout you are seeing seems excessive anyway.
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Harold_V
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Re: End mill won't sit square in collet

Post by Harold_V »

R.W. Parker wrote: Tue Mar 30, 2021 8:56 am Just noticed this:

<The variation increases the further down the bit I measure. At that location, it's .005"; about 7mm further down, it's .007">

Have you trammed the head of your machine? Sounds like it's not perpendicular to the table.

Richie
That wouldn't make a difference for the issue being discussed.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
James Temple
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Re: End mill won't sit square in collet

Post by James Temple »

Hello, Russ! Yes, it's me. Like everyone else who was lucky enough to stay in his house, I suddenly found myself in need of a new hobby about this time last year. So I've been slowly re-learning what's important, and so far have an A+ in keeping all my eyeballs and fingers intact.

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Lacking a true DTI, my micrometer does include an indicator point that can reach inside the spindle (see picture). The results are not encouraging; moving up through it in 1mm increments, there's a pretty consistent .002"-.003" of runout. It's starting to sound like the issue is that, given a parts chain of dubious solidity, this ~$400 machine was never really meant for semi-serious machining operations. My choices now are either rebuild it extensively (new spindle, etc.) or upgrade to something like a Sherline or Servo.

In the meantime, it was still useful. It's my theory that a lack of skill easily cancels out whatever gains are made by fancy equipment, and it's actually encouraging to know one's skills have grown beyond one's machines. For the model I'm rebuilding (pictured below), the standard for machining generally runs more toward 'if it looks right, it is right' rather than smooth functioning, but it seems certain I'll want to level up for subsequent projects.

IMG_6034.JPG

Hey, Russ, if you can think of a budget micro-mill that's a step up from the Proxxon, I might be in the market shortly ...
John Hasler
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Re: End mill won't sit square in collet

Post by John Hasler »

How long have you owned the Proxxon? Seems to me that spindle is defective even allowing for the low price. I doubt that the spindle on my Proxxon die grinder is that bad.
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NP317
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Re: End mill won't sit square in collet

Post by NP317 »

James:
Great to hear from you!!
You've been bitten by The Bug, for sure.
Check your "Private Messages" above.
To be continued.
RussN
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tornitore45
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Re: End mill won't sit square in collet

Post by tornitore45 »

It could be anything but Proxxon is a quality tool and the spindle should be true, still need to check.
My bet is a damaged collet or the nut or the thread. If the nut goes on crooked or was deformed it can move the tool.
Those collet are quite delicate.
Did this tool work well before and this problem appear all of a sudden?
Mauro Gaetano
in Austin TX
John Hasler
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Re: End mill won't sit square in collet

Post by John Hasler »

I checked my Proxxon die grinder. .002" TIR. Disappointing.
James Temple
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Re: End mill won't sit square in collet

Post by James Temple »

I was very much a beginner when I got this machine. I've only just gotten good enough to perceive there's a problem. Theoretically, at least, it could have been there the whole time.

I haven't seen a difference in the work because the main mechanical parts of the project (frames, siderods, etc.) are scavenged from other model locomotives; nearly everything I've milled just needs to stay together and look about right. But I also had distant plans of graduating to cutting my own frames and siderods. That looks doubtful with this machine.

Attached are a few pictures of the collet set that came with the mill. The collet nut has always gone on easily, never felt cross-threaded. I got the mill in May of last year, so it's still under Proxxon's two-year warranty, but John's results suggest that for them, .002-003" is 'within spec.'

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One thing I do notice: The ER-11 collets I looked up online appear to be slotted their whole length, whereas these slots end roughly two-thirds up. That suggests to me that an ER-11 can compress and grip the shank its entire length, while these can only grab ~10mm or maybe less.

The main problem still appears to be TIR in the spindle, but it seems likely the collets aren't helping.
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tornitore45
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Re: End mill won't sit square in collet

Post by tornitore45 »

ER collet are called double cone and are designed to collapse parallel gripping the tool along the entire shank.
The Proxxon collets, although they have a douple cone shape are collapsed by the front cone and grip the tool on the front (Nut Side)
Like any collet the closer the tool diameter fits the collet the better and straighter the hold.
I would not give up so soon on Proxxon honoring their warranty. They are only responsible for the holding accuracy of a dowel pin of the exact collet size, but 0.002" on a 0.125" collet is not defensible because it renders a 1/8" END Mill practically useless.
Mauro Gaetano
in Austin TX
Mr Ron
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Re: End mill won't sit square in collet

Post by Mr Ron »

In the picture posted, how much clamping force are you putting on the shank of the DI? What DI are you using. I have found some erratic readings with certain DI's, specifically those from Harbor Freight.
Mr.Ron from South Mississippi
pete
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Re: End mill won't sit square in collet

Post by pete »

With slits on only one end of each of those collets I think they'd be very critical about only holding the single diameter each was built to hold. Using for example imperial dimension tooling in metric dimension collets or the opposite won't work because anything even slightly under sized will give possible large amounts of run out even if they fit and the collet will hold them. ER collets are of course a much better design, but there certainly not all equal. In fact most of the cheaper off shore ER's won't even list any guaranteed run out numbers. And some cheaper sets I've seen on Youtube show numbers I sure wouldn't be happy seeing even with a drill chuck. But ER collets are also not slotted there whole length, check again. There slotted from both ends almost to each end. That allows the collet to collapse at both ends and hold the tool that way. ER 11 collets are 18 mm in length and the recommendation's I've seen will usually say the tool shank to be held should be inserted into at least 75-80% of the collets length to maintain the tool holding concentricity. So if your thinking of upgrading to ER's it might be worth checking your tool shank lengths first to be sure. I'm unsure of the exact cut off point for where it happens, but the smaller ER series collets will only collapse by .5 mm verses the larger collets that have a full 1 mm holding range. I seem to recall reading both the ER 8 and 11 sized collets and possibly the ER 16's have those lesser holding ranges.
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