First cut from my 8520...what is this god awful noise coming from...

[zakruvalcaba]

Thanks for the detailed response. I agree I'm fairly novice here but the one thing I know how to do is remove and seat collets. I've done it hundreds of times with my round column RF31. In that mill, the spindle shaft is made to use a 22mm wrench to hold the spindle while you loosen the drawbar about 1/2 a turn. I then give the drawbar a whack with a hammer to drop the collet slightly then continue to unscrew the drawbar until the collet comes free and drops into my hand. I fully understand this process and I imagined the process would be the same with this mill. Again, something isn't right.

What I'm telling you and perhaps you can see this clearer by looking at some of my earlier posts, is that my collet was entirely seized in the spindle. I don't have a brake on mine, the previous owner jerry-rigged some custom setup but that's neither here nor there. My collet holder has flat edges so I can hold the collet holder while I tighten the drawbar. The main point of my argument is that it appears as though the collet holder is not seating correctly in the spindle....so when I tighten the drawbar it's bringing the collet holder too far into the taper (for lack of a better description) and causing it to seize. I don't how else to describe it. Like I said, I finally got it out but I'm hesitant to put it back in because of how hard it was to remove. I literally had to beat the living #@$% out of the drawbar to @#%^#% get the collet out. It's not right. Simple taps should work and I'm concerned that perhaps I'm doing something wrong. If you look at the video I posted above you can see that the collet holder appears to not fully seat....it gets caught on the taper....

 

[Meta Key]

Good -- your procedure sounds correct.

In your video your toolholder seems to go way into the spindle before it encounters the drawbar. How many threads are engaging when you tighten the drawbar? I get 5 or 6 full turns of the wrench.

Here is a toolholder (not a collet, more like what you're using in terms of the shank) being inserted. First pic it has just contacted the drawbar, no threads engaged.


Second pic, drawbar fully engaged, about 5.5 full turns of the wrench.


Not sure what to make of your situation.
Please do confirm that the toolholder *and* the spindle are both MT #2 and not the optional BS #7.
You could also try some chalk or dykem blue on the toolholder to see if you're getting proper engagement of the toolholder in the spindle.

Meta Key

 

[wlburton]

Does the collet holder get jammed the same with both spindles? From your description it sounds like the MT2 might be galled, making the collet holder not slide in smoothly and then to become jammed. On my 8520 I've never even had to tap with a hammer--turning the little wrench (which I made out of an upside down 1/4" socket plus a handle) against the cap loosens the collet enough to remove it. Meta Key's point about checking to make sure it's not the BS #7 taper makes sense, too. I've never seen a BS #7 taper so I don't know if they look similar enough for one to be confused for the other, though.

Bill

 

[zakruvalcaba]

Collet holder shank is indeed MT2. I don't know anything about BS to be able to distinguish between BS and MT2 but the mill does say 8520 on it so I assume it's MT2. So I've attached 2 pictures. The first is the collet holder when it touches the drawbar in the spindle. I can then hand tighten the drawbar into the threads of the collet holder about 5 turns before I can't hand tighten any more. Then I use a small adjustable wrench, hold the collet holder in my hand and proceed to tighten the drawbar another half turn. Sounds identical to your procedure. The second image is the result of collet holder in the spindle after final tightening. I'm hesitant to tighten any further than that and end up in the same situation I was in before. Before, I used a large adjustable wrench, held the collet holder with the wrench in place by the visible flat areas and then tightened the drawbar tight. I'm wondering if too much force was placed on the drawbar when tightening, bringing the shank's taper of the collet holder too far into the spindle shaft causing it to seize once the force of the cutting motion was exerted onto the spindle / collet holder shank?

 

[zakruvalcaba]

Does the collet holder get jammed the same with both spindles? From your description it sounds like the MT2 might be galled, making the collet holder not slide in smoothly and then to become jammed. On my 8520 I've never even had to tap with a hammer--turning the little wrench (which I made out of an upside down 1/4" socket plus a handle) against the cap loosens the collet enough to remove it. Meta Key's point about checking to make sure it's not the BS #7 taper makes sense, too. I've never seen a BS #7 taper so I don't know if they look similar enough for one to be confused for the other, though.

Bill

Bill, here's the collet holder in my spare spindle. It seats about the same distance into the taper as the spindle on the mill currently. The drawbar is a little wonky but it tightens down fine. The chance of both of these spindles being BS I would say are darn near impossible....

 

[Meta Key]

OK, it looks like the toolholder is going in nicely and about the same as mine so I agree with you that the spindle is likely an MT2 taper. I brought up the possibility because the B&S taper was an option and who knows what has happened with your mill over the years. Sometimes guys will replace parts and not make a note of it -- kinda like the brake system on your machine. Who knows what else has gone on there?

Anyway, I'm with you Zak, I think the toolholder was just "in too tight" the first time. Tightening it up with a short wrench and while holding the toolholder by hand (or another short grip on the other wrench) should be plenty tight. I'd give it a try and see what happens. Ya do not want the toolholder to spin independent of the spindle but start with light cuts and see what happens. The Morse Taper is pretty dang grippy..

The other alternative is Bill's suggestion that the spindle might be galled in some way. If a lighter touch doesn't solve the problem then a bit of dykem on the toolholder should show you if there is a problem with the spindle socket.

Meta Key

 

[wa5cab]

And another possibility, if you find nothing wrong with the bore of the taper, is that the collet chuck had been in the spindle for a long time.

 

[zakruvalcaba]

And another possibility, if you find nothing wrong with the bore of the taper, is that the collet chuck had been in the spindle for a long time.

Good point but that wasn't the case. I just bought the set and it was in there for 1 project.

 

[wa5cab]

OK. I assumed that, like most stuck chucks on lathes, it was in the spindle when you bought the mill. You probably over-torqued the draw bar, then.

 

[zakruvalcaba]

Everything is back together and I made a few first passes on the mill using some 3/4" aluminum stock. At 600 RPM the noise is completely gone. The repair and new pulley bearings seemed to fix the noise problem. In terms of my stuck collet, I was very careful locking it down this time...so much so that I got some wobble on one of my passes....rocked the collet holder with my hands and it just popped loose. I need to find a happy medium between too damn tight and not tight enough. Anyway, tightened it down better and I made a second pass. Quality of the cut is just still not there. Destroyed a 1/4" Hertel 4 flute and I suspect my speed may be the culprit. I'll make some more passes at the 1900 RPM setting with a 3/8" 3 flute cutter and see if my quality improves. Thanks again for everyone's help. Progress here to be sure...this noob just needs more time on the machine....