bearing failure

[baldric]

I have decided to go for ER 25 collet system,as opposed to using the mt 3 system of holding the cutters. The reason why,is because to (break) the mt 3 taper, I have to loosen the draw bolt two turns then belt it with a hammer, I noticed the drawbar (nut ) is not screwed on but pinned.
and I thought I might sheer the pin one of these days, The other reason , is everytime I strike the drawbar theshock load goes onto the bottom bearing to, I think this could damage the bearing surface, (brinelling) and shorten its life, what do you think? just a newbie question without any foundation, regards Bob

 

[baldric]

Hi Dave , I do realize that I would have to tap the collet holder out, but i could interchange any number of collets using the same holder which would not have to be removed every time tool change is required, that is the point I am trying to make, regards Bob

 

[Pacer]

Your mill has a MT-3 spindle taper?? If so, then my choice would be hands down the ER system - actually even if its not MT-3... (unless its one of the larger, beefier commercial type mills)

As you already noted, the feature of only having to change collets is most convenient, and its a good true running system along with an affordable price. I have a ER-40 system for my Bridgeport clone, and it stays on there 90% of the time. I think you'll love a ER system...

As for your worry about bearing problems, I dont think theres reason for concern, the spindle bearings gets far more loads under conventional usage. Side load on the bearing with an end mill or fly cutter, etc - drilling a hole would put way more load on the bearing than the taps to free the collet.

Another 'for instance' -- many of us mill users adapt/make a "power draw bar" using a 3/8" air impact driver and when its 'hammering' the draw bar loose, its putting more force on it than the taps by hand.

 

[Cal Haines]

author=baldric link=topic=3853.msg28245#msg28245 date=1317663946
I have decided to go for ER 25 collet system,as opposed to using the mt 3 system of holding the cutters. The reason why,is because to (break) the mt 3 taper, I have to loosen the draw bolt two turns then belt it with a hammer, I noticed the drawbar (nut ) is not screwed on but pinned.
and I thought I might sheer the pin one of these days, The other reason , is everytime I strike the drawbar theshock load goes onto the bottom bearing ...

Actually, it's the top bearing that would take the shock, but you're right, too much of a shock is a problem. If it takes more than a light tap or two to loosen the collet, then something is wrong. I have a similar problem with my Hauser 3BA Jig Boring machine, which has an MT2 spindle. You're supposed to be able to release the tool by turning the large knob on the drawbar but something has happened and some (but not all) tools will get stuck but good. Often I can't even knock it out with a drift (I support the end of the spindle when I'm using the drift so I don't risk the bearings). I'll be darned if I can see any problem with the spindle and I don't want to try reaming it. If I could find an MT2 lap I might give that a shot, but so far I'm just living with it.

My solution was to go the ER collet route as well. I have ER-32 and ER-25 chucks and collets but I find myself reaching for the ER-25 unless I need the extra capacity. The ER-25 chuck stays in the spindle most of the time. When I need to use a drill chuck or boring head I use a pair of Jacobs taper removal wedges (#6) to pop the chuck loose and that works great:


That trick only works when you have something in the spindle that has a shoulder on it so that you can get the wedges around the shank of the tool, between the back of the tool and the front of the spindle.

You don't need to remove an ER chuck to change collets. You use a spanner on the nut on the front of the chuck to loosen or remove the collet. If you've never used an ER collet chuck before, the collet snaps into the nut and then you thread the nut onto the chuck; don't make the rookie mistake of putting the collet in the chuck and then trying to tighten the nut or you'll damage something.

I got my ER chucks and collets from CTC Tools. They have ER-25 chucks with MT3 drawbar shanks (M12 or 3/8-16 thread) for $17 and collets sets for $38. They used to offer inch collets, but they only seem to carry metric now but. That's OK since an ER collet will collapse to the next size below it, that is, a 7mm collet will hold anything from 6 to 7mm. You really have to chinch down on a 7mm collet to tighten up on a 1/4" end mill (6.34mm) but it works fine. CTC ships out of Hong Kong, but it's worth the wait.

[size=18pt]Cal[/size]

 

[baldric]

Hi guys , thanks for your imput! Its just that i remember years ago machines arriveing from England by boat, the static machines were subject to the vibrations of the main engine ! six weeks of constant vibration, brinelled the bearings, they were buggerd by the time they got to the colonies ??? your thoughts ??? regards Bob

 

[baldric]

Thanks Cal, there is a lot of good info there, I have one of those wedges in my tool box, I could never figure out what it was for :-\ As for the link for the collets, boy they are cheap! $149 plus postage for the ER 25 collet set and $74 for the chuck +post. No I haven't got a thread on top of my drawbar, in fact the (nut) is actually pinned on. just had to make a new drawbar, because my mill came with a 10 mm thread, regards Bob

 

[flutedchamber]

I use the Bison ER40 chuck on my Bridgeport and am very happy with it. Super accurate collets (.0004 TIR) are available for a lot less than standard R8 units. Plus the ease of not having to reach up to loosen or tap collets free is a great benefit.

Honestly tho..in almost 45 years I have never seen a Bridgeport spindle bearing harmed by the tap that is needed to loosen collets. Most are harmed by incorrect lubricant/no lubricant or dirt.