I have designed, built and tested an R8 collet release system for my Bridgeport J head mill that eliminates the hammering normally required to free the collet to take out the endmill.
The reason I did this was to save the life of the pricy bearings I assume could be damaged by the hammer impact caused by hitting the drawbar to release the endmill.
This design is easy to make using easily available materials .A picture and text are posted in the www.metalworking.com website unde " final R 8 collet release". I hope soon to learn to post this data to this site.
I posted this same stuff to another metalworking interest group and ony got one response saying only very few times do R 8 collets stick. I was dissapointed because I thought this design was the best thing since sliced bread. Mine always stick and wonder if I am wrong and if so what do you guys do to prevent sticking.
I kind of thought my reasoning was reinforced by at least one supplier sells a hammer along with a replacement drawbar.
Walt
R 8 collet release Bridgeport Mill
I like your gadget
Walt,
I think your gadget is useful.
I always been frustrated at the R-8 taper design. It is one of the hassles I don't like about using my mill.
Even with your quick release system, changing collets is still a bit of a hassle, because you have to do most of the other steps, coordinating the brake with tightening and untightening the drawbar.
Instead of a regular 3/4" combination wrench, I use an angle head (3/8) ratchet with a 3/4" socket. This helps a little bit. If I found a battery powered ratchet, that would make life a little bit easier.
Does anybody have experience with the Kurt power drawbar system?
Jon Spear
San Francisco, CA
I think your gadget is useful.
I always been frustrated at the R-8 taper design. It is one of the hassles I don't like about using my mill.
Even with your quick release system, changing collets is still a bit of a hassle, because you have to do most of the other steps, coordinating the brake with tightening and untightening the drawbar.
Instead of a regular 3/4" combination wrench, I use an angle head (3/8) ratchet with a 3/4" socket. This helps a little bit. If I found a battery powered ratchet, that would make life a little bit easier.
Does anybody have experience with the Kurt power drawbar system?
Jon Spear
San Francisco, CA
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AndrewMawson
- Posts: 286
- Joined: Sat Jan 04, 2003 5:46 pm
- Location: Battle, East Sussex
Re: R 8 collet release Bridgeport Mill
Walt, Yes my R8 collets stick as well, but only need the slightest tap with a spanner (= wrench US speak)to release. I keep a 3/4" double ended ring spanner hanging on a hook beside my Bridgeport, and find hand tightening with that, and releasing by partially undoing with the spanner, and tapping the drawbar nut with the other end works fine.
I had intended to saw off the other end, and cast a lead hammer head onto it, but it really insn't necessary.
I had intended to saw off the other end, and cast a lead hammer head onto it, but it really insn't necessary.
Andrew Mawson
Battle, East Sussex, UK
Battle, East Sussex, UK
A brass block on other end of the wrench
At one place where I worked, the shop people had bolted a brass block on the opposite end of the combination wrench ("spanner"), which could be used to tap the top of the drawbar.
One thing that is nice about Walt's device is that the collet can be released from below, rather than on top. This is particularly convenient, for example, when the collet is holding something that you don't want to drop out and hit the table, like a drill chuck on a straight shank. With Walt's thing, you don't have to reach both the top and bottom ends of the drawbar simultaneously.
One thing that is nice about Walt's device is that the collet can be released from below, rather than on top. This is particularly convenient, for example, when the collet is holding something that you don't want to drop out and hit the table, like a drill chuck on a straight shank. With Walt's thing, you don't have to reach both the top and bottom ends of the drawbar simultaneously.
Re: R 8 collet release Bridgeport Mill
Thats a neat looking tool. I use a leather mallet on the draw bar to knock the holder out. You could beat on the draw bar many times a day for 20 years and not hurt the bearings on a BP. You might replace the draw bar a few times.
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Matt_Isserstedt
El Cheapo Power Drawbar
I can't seem to remember the catalog, but the last cheapo power drawbar was based on a 3/8" butterfly impact wrench. I think there was a little air logic (timer?) and a lubricator for the tool.
My take was that the impact wrench was fixed and thus applied axial thrust to the drawbar as it unscrewed and expelled the collet via the screwthread.
I don't recall how it attached to the mill...last time I looked at the top of the head it appears smooth...
Seems like an enterprising scrounger could make one of these for a little less than catalog prices...... [img]/ubb/images/graemlins/smirk.gif"%20alt="[/img]
My take was that the impact wrench was fixed and thus applied axial thrust to the drawbar as it unscrewed and expelled the collet via the screwthread.
I don't recall how it attached to the mill...last time I looked at the top of the head it appears smooth...
Seems like an enterprising scrounger could make one of these for a little less than catalog prices...... [img]/ubb/images/graemlins/smirk.gif"%20alt="[/img]
Re: El Cheapo Power Drawbar: the difficulty
Matt,
I think that one of the hard things to design in a homemade power drawbar would be a feature to make sure that the ratchet or impact wrench would NOT EVER be engaged while the spindle is turning.
I guess you need to have a sort of vertical actuator that would lower the wrench down onto the drawbar, and the actuator would not turn on if there was power to the spindle. Is that what you mean by air logic?
I'm not sure how to attach one to the top of the head either. I think that there is supposed to be an open space for air cooling.
I want to see a real-life power drawbar system in action some time. Maybe I'll ask Kurt to send me an instruction manual for their system.
I think that one of the hard things to design in a homemade power drawbar would be a feature to make sure that the ratchet or impact wrench would NOT EVER be engaged while the spindle is turning.
I guess you need to have a sort of vertical actuator that would lower the wrench down onto the drawbar, and the actuator would not turn on if there was power to the spindle. Is that what you mean by air logic?
I'm not sure how to attach one to the top of the head either. I think that there is supposed to be an open space for air cooling.
I want to see a real-life power drawbar system in action some time. Maybe I'll ask Kurt to send me an instruction manual for their system.
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Matt_Isserstedt
Re: El Cheapo Power Drawbar: the difficulty
Jon,
Completely forgot about this feature. I recall seeing some heavy springs on two vertical tie rods, then there's gotta be an air cylinder which forces the socket down for both 'tighten' and 'loosen' with a spring return. But yes, this would probably involve a timer.
I'll see if I can find the photo and scan it....
Completely forgot about this feature. I recall seeing some heavy springs on two vertical tie rods, then there's gotta be an air cylinder which forces the socket down for both 'tighten' and 'loosen' with a spring return. But yes, this would probably involve a timer.
I'll see if I can find the photo and scan it....
Re: R 8 collet release Bridgeport Mill
I have used the kurt draw bar an my local votech and was not impressed. I have a quil hammer, it has a 3/4" socket on one end and a brass cap on the other. The handle is about 12" long and in padded. I like the use on the hammer more the kurt devise.