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02-28-2008, 12:55 AM #1
My R-8 arbor spun in the spindle of my mill, what now?
I have a bridgeport clone (a Doall) and the R-8 arbor spun in the spindle and smeared the "tit" that aligns the R-8 shank in the grove. I had a hell of a time getting it out but finially did. How do I replace this tit? I hope The spindle doesn't have to come out but i cant see how to do it w/o pulling it. Do I need to have the tit in there or can I just carefully finish grinding it down and avoid it all together. Any advice will be appreciated,
02-28-2008, 01:13 AM #2
Your term "tit" does not convey the meaning to me that you expect the majority to understand and that could be my problem.
You did say that your Bridgeport clone had an R8 taper and that has more meaning.
My first concern is what happened to the draw-in bolt that holds the arbor into the R8 spindle when the arbor spun? I would expect that the draw-in bolt would self-tighten stretching the thread and maybe breaking the draw-in bolt.
I understand that all R8 tapers have a keyway that apparently nobody uses, relying on the short taper alone to drive the cutter. If so, then why so?
Please provide more information because as we all know knowledge is no burden to carry.
02-28-2008, 01:13 AM #3
On a bridgeport on the bottom of the quill there is a silver ring that the spindle nose goes through. If you lower your quill about 1 1/2 inches, you will see the joint between the ring and the rest of the quill column. On the bottom of this ring, by the spindle, there are two holes for a spanner wrench. You need either a spanner or some sort of post type tool to loosen this up. However, there is a hex set screw to loosen on this ring before it loosens as I recall. Loosen this ring up and spin it off.
You will have an open part of the quill. On this part you will find another set screw that you loosen out of the hole. Under this is your key for your collett keyway. Get this out and check it, the end is usually square as I recall. If it is either square or round, check it for burrs that may impeed the collett from catching properly by checking it on a collet keyway.
Put it back in, have a collett in the nose to help set the depth of the drive key. I usually make it catch, bottom it out on the colley keyway then back it off so things move freely and there is plenty - but not too much clearance.
Check it over than re-assemble. Your first set screw that goes in after you set the key depth should fit set against your key, but check to be sure you did not re-advance the key further by re-checking the collett. The rest is simple re-assembly.
Probably clear as mud, but may work for you.
02-28-2008, 01:13 AM #4
You have to remove the quill to replace the key in the spindle.
you don't need the key in the spindle for the collets. If you want to replace it you have to remove the quill and disassemble it to get to the key. I think it's threaded in. They get damaged eventually on most mills.
The cure I have used several times is to use a die grinder to grind the key flat with the bore. The collets will work fine without the key.
02-28-2008, 01:17 AM #5
Just grind the tit off. It is just a little dog point set screw that goes in when you put the spindle together, so yes, it has to come out of the quill to remove it properly. Many have removed the alignment dog when using power drawbars, since this can be a real headache with a production machine. Given the size of the dog, it isn't intended to transfer any real power, just prevent the tool from spinning when tightening the drawbar.
02-28-2008, 01:17 AM #6
Leave it out. Makes collet changes a lot quicker without trying to line up the key. This is one time that no "Tit" is a good thing....
02-28-2008, 01:19 AM #7
Don't replace the dogpoint crew. It's supposed to align the collet but when the spindle tooling slips it takes the dog point screw tip with it. Unscrew the retainer (strap wrench job) from the end of the quill. Trun the spindle until you can see the tapped hole for the setscrew. Unscrew the set screw and look inside to see if there is a second setscrew take that out as well. Replace the retainer and go back to work.
I don't know why they install that damn setscrew. If doesn't do any good, it has practically zero resistance to torque, and it soon gets buggered up. Experieced hands remove them and never reinstall them.
02-28-2008, 01:35 AM #8
Hold the cutter and collet with fingers of one had, tighten drawbar to good finger tight with
other hand and then use spindle brake and wrench . That cursed "tit" is worse than useless.
...lew... I see others have been typing while I hunt and peck. :-)
02-28-2008, 01:45 AM #9
We just discussed this 2 days back at another post. Look up 'posts made by piniongear' to find the discussion.
To repeat, a lot of people will tell you not to use the dog nose set screw. I do not count myself among that crowd. The key is there to align the R8 arbor and the taper is to hold the R8 in place. Your collet spun because you did not have it tightened properly, not because of the pin.
Make a wrench...... I used a half inch square bar for the 'handle' and 2 pins 3/16 inch diameter to go into the ring nut. My other post gives the center to center dimension, or just measure yours. The pins on the tool I made stick out 1-5/16 inch from the handle and the handle was drilled 1/4 inch deep in both places.
And then here are the instructions for replacing the key....
02-28-2008, 01:48 AM #10
I will remove the set screw and go on with life.
02-28-2008, 01:53 AM #11
Muleworks, it sounds like you are planning on doing a titectomy.