INT/ISO30 collets

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spro
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Re: INT/ISO30 collets

Post by spro » Thu Mar 01, 2018 8:47 pm

I agree, earlgo. I'm not liking a "pin" for this location purpose. If something more like a key exists and works, leave it be. If they wear to where they slip, they do damage.

pete
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Re: INT/ISO30 collets

Post by pete » Thu Mar 01, 2018 10:25 pm

Your welcome Earl, however I'm not saying my explanation is 100% correct, it may or may not be. I've spent more than a bit of time reading various threads and trying to figure out why Bridgeport added it when they developed the R8 taper and it's the only logical explanation I can come up with since the drawbar can still be tightened without it. A nice set of at least ball park numbers you worked up and it's appreciated. No doubt spinning a collet or tool holder during a crash helps tighten the drawbar a bit further so helping the numbers and that pin a bit. As Badog pointed out a full shear would take a lot. Likely it's progressive where the pin finally shears after being damaged a few times previously. The only good reason for me to have one in the spindle is the use of a Haimer 3d taster where the tool gets zeroed to the tool holder and the spindles C/L. The index positioning with the pin makes sure the tool holder is always positioned in the spindle the same. Marking the end of the spindle and tool holder and aligning them each time does the same without having that set screw installed. I've read enough on PM about the problems that can be caused with a sheared pin I personaly don't think it's worth leaving them in place.

Harold_V
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Re: INT/ISO30 collets

Post by Harold_V » Fri Mar 02, 2018 4:30 am

pete wrote:
Thu Mar 01, 2018 10:25 pm
it's the only logical explanation I can come up with since the drawbar can still be tightened without it.
Quite true under normal circumstances, but it isn't beyond reason to find the bar won't turn without dragging the collet along. The key is intended to prevent that from happening. It's real irritating when the collet wants to spin.

I've owned two BP's in my many years. Bought both of them new. I wouldn't have considered removing the key, regardless of the claims made by many who insist it isn't needed. Might not be for them, but I don't permit others to make my decisions when I have my own opinion.

In support of removal----if collets are closed randomly, the resulting wear pattern will also be random. With the key, there's a distinct pattern developed, and can be detected with a good indicator.

Some folks like the key. Some folks don't. That's true in many things in life.

Don't think for a moment that the key can't take a load. I crashed my 3" boring head years ago, with my first mill. The key did NOT fail. The shank of the boring head (a Bridgeport) has a nasty notch to remind me of the crash. Yeah, I had one hell of a time removing the head from the spindle, but I got it out, and continued to use the mill until it was replaced when it was ten years old.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

earlgo
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Re: INT/ISO30 collets

Post by earlgo » Fri Mar 02, 2018 10:18 am

I am fairly certain that whatever holds the R-8 collet from turning may or may not be a pin or set screw dog point, but I chose that as the lower extreme that might be fitted. (The 5-C collet blocks I have just have a dog point screw preventing rotation.) Some "keys/pins" may be a larger set screw with a dog point flattened on both sides to fit the keyway. And some may have an actual key. To calculate the shear on a full length key would not be very useful to the discussion, so I chose the minimum plausible situation.
I think Pete's research and Harold's experience on the why has brought the two best reasons to the foreground: anti-rotation during the first stages of tightening and indexing/location of critical tools.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.

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BadDog
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Re: INT/ISO30 collets

Post by BadDog » Fri Mar 02, 2018 12:54 pm

On the BP (at lest mine and those I have seen/read of), it actually is a set screw with a locking set screw on top. The end isn't actually a dog point, but rather both flat and ground round such that the screw threads are gone on the portion that sticks out. So you have the collet key bearing tangent on the resulting cylindrical surface. Not ideal by a long shot if it's actually intended as a driving torque resisting feature.

Tightening things like an R8 shank boring head or whatever, obviously not a problem with or without key. You're holding it anyway, so the only impact is not having to rotate/find the screw to align with the key to insert. IMO, win for no screw. With collets going in, I put the tooling in, and lightly hold the tool (particularly if sharp there) between 2 fingers that are also pushing up on the collet in the spindle. Again, no pin means no fussing around to align. Not a huge deal of course, but I still find it nice. As I hold it up, a modest firm up pressure readily locks the collet in the spindle as the draw bar comes up. I've never had the least problem with rotation while tightening. However, I've heard folks tell that they wanted/needed the key with power drawbars, which makes sense given you have to restrain it without the taper as it rapidly sucks up into the spindle. I wouldn't know, I don't have a power drawbar.

Regarding Harold's boring head crash, to me, his scenario is exactly what I described and expect. He notes he had "one hell of a time" getting it out, with the shank damaged. But imagine if that had been say a 3/4" shank in an R8 collet. In my head at least, the moment you get any slack at all, I think the 3/4" shank is likely to start turning in the R8 collet long before you can coax the screw out of it's well gripping notch. Of course, depending on hardness and surface finish, it might have spun in the collet before it spun the collet in the spindle, so might never have happened and instead damaged collet (much better than spindle spin!). And that reduced chance of collet spinning in spindle counts as a win for leaving the screw in place, though I expect if the spindle taper and collet are good and properly tightened, I think the tooling is far more likely to spin in the collet anyway. But that's just an opinion based on how I think the forces and grip would work out. I lack the engineering or machinist experience to do more than think it through as best I can.

In the end, I don't think it's a slam dunk unless you have a power drawbar. Beyond that, I really don't know how it shakes out over all, but I remain happy with mine removed.
Russ
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pete
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Re: INT/ISO30 collets

Post by pete » Fri Mar 02, 2018 3:08 pm

My tooling doesn't yet include proper R8 collets so I'm either using the ER integral shank collet chuck or R8 shanked tooling such as end mill holders. Much easier to grab the fat end and hold it upwards while the drawbar gets tightened until the taper starts to seat without the set screw in the taper. Plus that collet chuck results in quite a few less tool changes the spindle see's, but I understand your point Harold. Maybe it's not for everyone since I guess it depends on how your using the machine. And I never thought about that power drawbar issue since mine doesn't have one either, but good to know that set screw might be needed if I ever add one BadDog. My mill is a BP clone built in Taiwan and has the usual double set screw as well. Using the word "pin" was misleading and lazy on my part. And same thing the inner set screw has a dog point with the first few threads turned off as well. I removed mine well before there was any damage to the screw tip and as a trial that if any problems came up later it's only a few minutes to replace it.

There might be for some users one further benefit to removing it tho. Some threads on various sites have mentioned that some of the cheaper offshore tooling has come with an under sized slot in the R8 shank that don't meet the specifications for the slot depth. So if the set screw isn't readjusted the tool or collet shank won't insert into the spindle. Myself I think I'd return anything that didn't fit before I'd start readjusting and lessening even more the set screws shear resistance. Checking Wiki just now they mention that it's the R8 taper that's meant to resist the torque and the setscrew is for use while tightening and releasing the drawbar.

Chipper5783
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Re: INT/ISO30 collets

Post by Chipper5783 » Tue Mar 13, 2018 7:02 pm

wally318 wrote:
Sun Dec 31, 2017 2:56 pm
In my rebuilding 4my Rockwell vert./Horz. mill and deciding on
tooling needed, I have often wondered whether there was such
an animal as 30 taper collet. Like in the pic.
I'm thinking they would come in very handy for using with
reduced shank drills in the Horizontal mode. Rather than giving up room
by putting a collet chuck in between.
Anyone ever see any of these or know where to get them?
The only ones I could find online are Asian made, but in metric and
not imperial sizes.
Yes. I have two mills, both with #40 tapers. I like having lots of options for tool holding. I think your thought process is good, you just need to figure out how to make it happen.

My Maho has a #40 taper with the S20x2 buttress external thread. I have the full Imperial set of #40 collets that would have been offered with this machine. I understand that these collets are no longer being made - it took me a couple years waiting on ebay to get them. There are two collet systems for these European mills (U2 with a sleeve and #40 direct - or MT4 depending on how Maho built the machine). The collets are a nice set up because the MH 600 is a pretty small machine and it is nice to have the extra bit of head room. I have had an e-mill walk out - but I'd thrashed the end mill and was still pushing it (should have quit that end mill earlier).

My Cinc Toolmaster has a #40 taper with the regular 5/8-11 pull thread. I thought the direct collets were pretty cool on the Maho, so when I had the chance to get a couple that would fit the Cinci - I bought them (1/4" & 3/4" the last ones the guy had). I have never seen these before - they may have been some sort of custom thing (they are branded). I have not used these collets, the Cinci has plenty of head room for the jobs I do - so I've gotten by fine with either endmill adapters (with the set screw) or a collet chuck (OZ25).
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David C. Lathes: Enterprise 1550, Smart & Brown 1024, Mills: Maho MH 600 x2, Cinci Toolmaster, Kasto hacksaw PSB 210, Grinders: Cinc#2 T&C, Ingar 618 SG all but the first came as projects, now they support an endless list of more projects. Good thing I have a day job!

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