Shrink Fit Tool Holders

I've been wondering if shrink fit tool holders are single use.
You heat up the tool holder drop the tool in and let it cool. How do you
get the tool out when its worn out?
The reason I have been thinking about this is because I did a shrink fit a while back on a large ring on a tool (not a machine tool) for a friend a couple months ago. It worked fine, and I didn't care if it was permanent because the tool was beyond its intended life anyway. He's been using the tool everyday in his business. Its on its second life.
Now my success with that lead me to think about a toy I picked up a while back and the poor success I've had with tool holding with drill bits in a regular jacobs style chuck on the lathe. Particular 1/2 shank stuff. The toy is a turret for the tail stock. I'd have to go look, but I think the sockets on the turret are 5/8. The pieces are just held in with a set screw. Seems that anything you put in it would have to have a flat machined on it to have any chance of not spinning.
Now here is where the shrink fit comes. I have a part I make periodically that is quite simple and it makes a few dollars. I make up to a dozen at a time. Ideally if I was making hundred at a time I'd send it out to be CNC turned. Best practice is spot drill, pilot drill, drill, turn, part off, flip, drill, and then bore. That?s a lot of drill changing One drill bit is 1/2 inch, and one is 5/8. The part is aluminum, though so a sharp bit isn't too likely to spin. Aluminum isn't all I turn though.
My thought at first was to make set screw holders for a variety of bits to go in the turret. Then I'd have to grind flats on all the drills. Yuck. Then I thought about shrink fit. Then I'd only have to grind flats on the tool holders. Might be a bit dicey for a 1/2" shank drill in a 5/8 diameter holder though. LOL.
Of course I wondered if I could easily get a good enough fit that way to prevent a dull tool spinning in the shrink fit holder. I can soak the holders at close to 600F on the BBQ grill pretty easy. That would provide about .0025 expansion for a 0.500 hole in steel (apx), but for say a 1/4 hole 0.00125 (apx). I don't have a practical way to cool the tool much lower than 0F, so that's not going to gain much. I guess 100 under ambient most of the year is something, but on a small tool only about .00025. I'm using the rough approximation of .001 /1"/100F. I know not all steels shrink or grow the same.
Anyway, even if the whole shrink fit tool holder thing works. How do you get a broke tool out of the holder? Its not really material cost. A short piece of steel isn't all that expensive. Its the time to make it all. I suppose for a drill, unless I break it, its not all that big of a deal. When it gets dull I walk it over to the grinder, resharpen it, and pick up the rotary tool to touch up the split point. Probably not a big deal on the lathe since I'd mostly be using drills.
They do this for mills and drills and other things in relatively expensive shank tool holders for milling as well. Are those tool holders considered disposable?
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On Tuesday, October 30, 2018 at 11:42:39 AM UTC-4, Bob La Londe wrote:

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I'm not sure I follow all of your question, but tools are easily removed fr om heat-shrink holders. I've even seen them *drop* out in demonstrations.
The better heat-shrink systems work quickly enough that the holder is expan ded before the tool shank has much chance to expand. So, unless you wait to o long, you have plenty of clearance to remove the tool before the shank he ats up and expands.
--
Ed Huntress

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wrote in message
On Tuesday, October 30, 2018 at 11:42:39 AM UTC-4, Bob La Londe wrote:

I'm not sure I follow all of your question, but tools are easily removed from heat-shrink holders. I've even seen them *drop* out in demonstrations.
The better heat-shrink systems work quickly enough that the holder is expanded before the tool shank has much chance to expand. So, unless you wait too long, you have plenty of clearance to remove the tool before the shank heats up and expands.
********************** I was thinking maybe with induction heating instead of back yard BBQ grill that might be the case.
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On Tuesday, October 30, 2018 at 8:42:39 AM UTC-7, Bob La Londe wrote:

A hybrid approach worked for me; we made our cutting-tips with a taper, and pressed them into a tapered holder, but didn't use a locking taper (I think we turned 4.5 degrees half-angle). The only trick is, we applied superglue and pushed the tips in with a hydraulic press (known force, keeping our eyes on the oil pressure gage).
This was in conjunction with an ultrasound drill (impact grinding); when the tip wore, a sharp rap on its shank would remove it, and the holder could be solvent-cleaned and ready for the next tip to be inserted. On paper, it took about a ton of force to remove.
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    By using a special induction heater to heat the holder quickly, and get the tool out before it conducts enough heat from the holder to lock up again at the higher temperature.

    O.K.

    Hmm ... my bed turret for my Clausing has a different way to hold the tools (1" diameter in this case).
    There are vertical holes drilled to partially intersect the horizontal hole for the tool shank. You drop a stud into it which has a ')' milled into one side which is a continuation of the curve of the tool shank hole. The top of the stud is threaded and fitted with a nut and a washer. You slide the tool shank in, then tighten the nut which locks the tool shank in firmly enough so it does not spin. (FWIW, the turret has six stations, and automatic indexing from one station to the next as the turret ram in retracted.

    With the bed turret, you do all of the work on one end on a lot of workpieces, letting the turret advance to the next tool as needed. One station of the turret (as I use it) has both a depth stop and a retracting center drill, so I save one station. I then drill and tap under power (next time I'll probably do it with thread-forming taps so I don't have to drill as deep to clear chips from a gun tap). That is two more stations. Then a box tool to turn a set length to proper diameter, and a Geometric die head to thread it, using the last two stations in the turret.
    Then the parting tool on the carriage is used to make relief at the intersection of the thread with the shoulder, and then part it off, using a turret carriage stop.
    Obviously, this is for something specific, and a different product would require a different setup.

    I need some diameter-reducing holders for some of the tools, though most are 1" diameter. Mostly, I need the adaptors for smaller Geometric die heads, which don't apply that much torque -- at least working in brass as I normally do.

    The tools are installed and removed from the holders using the induction heating tool I mentioned. I don't have this, so I only know of its existence, no direct experience with it.

    The same way you are *supposed* to get it in -- with the quick induction heating tool. It produces the heat in the holder only, so it expands while the tool shank does not (at least not right away), so it falls out or can be pushed out, depending.

    Note that with these, the holders are designed to go into automatic tool changers in CNC milling machines, so you also need to record how far the end mill extends out of the holder, and enter this information into the G-code program, so it produces the dimensions desired.

    Nope -- they just have one of the relatively expensive induction heater to allow removal and replacement.          I don't think that a torch would heat the holder quickly enough to prevent heat transfer to the tool shank so both expand at the same rate.
    Good Luck,         DoN.
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On Saturday, November 17, 2018 at 9:54:44 PM UTC-5, DoN. Nichols wrote:

One thing to keep in mind with shrink-fit systems is that nearly any of them, including the cheapest, work fine with carbide tool shanks, but only the better ones -- which heat faster than the cheaper ones -- work well with HSS shanks.
The thermal coefficient of expansion for tungsten carbide is much lower than for steel, making the speed of heating much less critical than it is for steel.
I've watched comparative tests with different brands on both types of tool shanks. As a minor aside, solid tungsten ("heavy metal") shanks, used on some boring tools and other deep-hole insert-type tools, behave like tungsten carbide in this regard.
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