What are your thoughts on making a mounting arbor for a drill chunk out of a grade 5 bolt? My mill uses a quick change tool holder and so far all I've gotten for it is a pair of collet holders with 3/8 & 3/16" collets. I also happen to have just picked up a 1/2 drill chuck with a 3/8-24 thread. What i was thinking of doing it screwing a grade 5 3/8-24 bolt I have lying around into the chunk then chopping the head off and holding the whole works in the collet. Might try to get creative and turn it down a touch first to make sure it's concentric, though I'm not sure it'd really help much. Main thing I'm look to do is hold center drills and the like - nothing too crazy.
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Drill Chuck Mounting Arbor
- Thread starter sdmuleman
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I have done that with a 1/4" chuck for holding bit's smaller than 1/8" . I did take a cleanup pass to true up the shank. If you wan't to run it in reverce you will need to drill and tap it for a 10-32 left hand screw. What quick change are you using?
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Bolts have rolled threads, not cut threads, and concentricity to any degree of accuracy is purely by accident. Since it appears that you have the ability to make an arbor in the lathe, I believe you would be better off making the arbor from raw bar stock.
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Andre
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In my failing travels to make a homemade lathe (Hey, I learned a lot even though it "failed") I used a 3/8" drill chuck with .375-24 threads. I made an arbor from a bolt, it ran true without the chuck but with the chuck it ran out like five thou as wermie said.
Machine takes an QC-30/NMTB-30. Old Bridgeport Boss CNC machine. Forgot about the direction of thread.... have to think on that. Maybe a locking screw.... I could turn one if I really wanted but I was trying to be lazy. Don't expect it to be perfect. Seems like if I put it on the chunk and then clamped the chunk down on something concentric then I could turn the shank down a bit that way.... may have to play around with it some. The real solution is to get a morse to QC adapter and use my lathe chuck, or get a real chunk arbor... but I saw this and thought it was worth thinking about at least.
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What I did was chucked a 1/4" by 1 1/2" dowel pin in a collet in my lathe and tighten the drill chuck to it and took a skim cut on the bolt so it runs true to chuck. The LH screw I drilled and taped the center of the bolt through the center of chuck. Just like it mounts on a drill.
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I don't think I'd go the bolt idea when just a little more work could produce a very accurate chuck, if your ever going to use a threaded chuck it can be made to run very accurately by turning a scrap piece to a size the chuck will mount on, mount the chuck to the pin you just turned, counter boar the chuck to produce a short register area and then a light facing cut, make a mating mandrel to suit, drill and taped the mandrel the same thread as the chuck, use a suitable bolt to make a stud, screw it all together.
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When you marriage a chuck to a threaded arbor. It is better to have a thread with shoulder so the chuck bottoms out on that shoulder. Instead of the threaded shaft bottoming out in the bottom of the threaded hole. Using a shoulder tends to yield better chuck accuracy...Good Luck
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I have tried over the years to make various chuck arbors and adapters and have seldom been satisfied with the results when taking any short cuts. Even using a well supported die in a tailstock holder left a thread with too much runout. I've resorted to turning down arbors from larger stock by turning between centers and single point cutting a tight thread and finishing with a final shoulder cut with a sharp tool.
In a pinch you can get a chuck turning reasonably true by clamping it's jaws on a true running piece of stock already chucked up in the lathe and then truing up the arbor sticking out of the back of the chuck. So much overhang makes this tricky but like I said, "In a pinch".
Without a good square shoulder to snug up against I don't think any chuck will run very true for you even if the bolt weren't a rolled thread. A rolled thread won't seat in the chuck the same way twice. You need both a concentric thread to reduce radial runout and a square shoulder to maintain axial runout to a minimum.
Sounds like a nice milling machine. I can't imagine not having a lathe. I'm sure you'll find a way to rectify that soon enough.
Mark
In a pinch you can get a chuck turning reasonably true by clamping it's jaws on a true running piece of stock already chucked up in the lathe and then truing up the arbor sticking out of the back of the chuck. So much overhang makes this tricky but like I said, "In a pinch".
Without a good square shoulder to snug up against I don't think any chuck will run very true for you even if the bolt weren't a rolled thread. A rolled thread won't seat in the chuck the same way twice. You need both a concentric thread to reduce radial runout and a square shoulder to maintain axial runout to a minimum.
Sounds like a nice milling machine. I can't imagine not having a lathe. I'm sure you'll find a way to rectify that soon enough.
Mark
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When made mine I didn't have eny change gears for the lathe. I have scence gotten a qc gearbox. Mine runs as true as my jacups super chuck and scence there is no reason to remove the arbor from the chuck that isn't a concern. Yes there is better ways to do it but you work with what you have.