Crooked draw bar threads in arbor

T

Tozguy

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A brand new drill chuck arbor came in this week. When the draw bar would only engage for one thread before binding I figured that the internal threads need to be chased. But when the tap was run into the threads there was no resistance. Before removing the tap I noticed that it was cocked off to one side and not by just a bit.
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My first reaction was 'ahh $hit' but then I realized that a draw bar would not be necessary for most of my set ups. So it is kinda funny now.

I might want to fix it eventually just for the challenge. Have you any suggestions on how to go about fixing it?
 
Yep, that's a POC return it. Wish Chinese stuff had more quality control. I don't know how that got drilled and tapped cocked like that. I would have thought it was an automated process that would naturally avoid that issue.
 
Tozguy, is that a Busy Bee arbor? If so, I have bought a couple of their arbors and they were okay but now that I see yours, I think I was lucky. never seen such crappy workmanship,.
 
Agree with the rest best choice is send it back. Unless you plug it you may forget about it and then try to use it one day where you really need the draw bar.
 
I would think that a good photo that graphically demonstrates the crooked threading sent to the vendor would get you a new arbor without your having to send the defective on back.

As to fix the defect, possibly using a Helicoil type solution would work if the thread is machinable. I would set the arbor up for boring and single point threading so that retapping doesn't follow the old hole. IMO though, unless I considered it a technical challenge, the job would be more trouble than it was worth. Arbors aren't expensive and it would be a lot of work to make it right.

In the past, I have made my own inserts. If the thread was a 3/8-16, I would look at making a 1/2-16 insert. Since you are single point threading, you are free to choose whatever o.d. you want. I would mount the arbor and bore it for the new thread. Then, I would, make the insert, threading the O.D. Then I would remount the arbor and single point thread it for the insert. Do not disengage the lead screw gearing or remove the threading tool so that you retain the synchronization between the lead screw and the spindle.Using permanent LocTite, I would screw in the insert. After the LocTite sets, I would drill out the hole and thread the 3/8-16 threads.
 
Yes it is from BB. I get lots of good stuff from them but this is an exception. I bought it for $8 to make a ball center. For that it is fine.
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The tapers are very good so I may even put a drill chuck on it eventually.
Its not worth the trouble to return it and I would rather take on the challenge of fixing it anyways, even if it is just for laughs. If I do get a good chuck for it then it could hold the arbor and make any drilling or boring of the draw bar end possible. (using a collet, 1/2'' stub, drill chuck, arbor, with a steady rest somewhere on the arbor). Then bore out and glue in an insert as suggested above.

Thanks for your ideas gentlemen.
 
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When you drilled that, out for the ball, was the shaft hardened?
If not, that's interesting. I would have expected it to be case hardened.
 
The arbor was first drilled with a HSS 8% Co center drill followed by a 3/8ths round carbide burr to finish.
It felt like the center drill struggled some but it did the job. The carbide burr of course just breezed through it. Cute little puppy.
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I'm not expecting the draw bar end to give me any trouble using carbide drills or boring bars.
 
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