Drill Chuck Runout

[Chewy]

Looking advice from the experts! I am machining an arbor for a bench motor. I bought a fairly high dollar LFA 0-3/8 Drill chuck. Mounting is 1/2"-20 with a flat head 10-32 screw in the center. I am on my third arbor. The first one I totally screwed it up. I made an adapter from 1" 4130. A 1/2" reamed hole about 1-5/8" long in the motor side. I made a stub shaft for the three jaw and then put the arbor on it and turned the side for the chuck. I was lazy. Instead of single pointing the thread, I used a die and the chuck was so crooked that it would rap you on the knuckles. My bad.

I then made an arbor out of 5/8" 1018. Turned it down and single pointed the thread. Not much better.

I then made an arbor out of 1" 1018 in a collet. I turned the shaft down to .505. Left a little ledge, say .100 long for the chuck to sit on. Parted a thread relief area, turned the shaft down to .498 and single pointed the thread. At this point, the shaft and face are perfect. A dial indicator vibrates a little, but not enough to read. The thread itself has a .001 runout. When you install the chuck, the runout on the chuck body, just ahead of the holes is around .003-5. Installing a gauge pin, endmill, drill rod the runout is .005-6. Forget about measuring out an inch or two. I had readings of .007-10.

The chuck tightly touches the face of the arbor. I used a cigarette paper in between and was able to reduce the runout to around .002 on the chuck body. I have a replacement chuck coming to see if this one is bad. Getting a little hassle because the vendor considers it used. I guess screwing it on an arbor in a lathe must devalue it. I need a 0 closing chuck to handle the small number drills. I am expecting .001-2 or maybe a little better runout with a pin at the chuck it self.

I have less runout then this on a 50 year old Delta drill press, so am I expecting too much? What is a realistic runout expectation, or what other way would you solve the problem. Thanks Chewy

 

[mmcmdl]

Not following along here . Are you asking how to make an arbor for a bench motor or an arbor for your drill chuck ? Or , do you need one to make the other ?

 

[Chewy]

I am making an arbor to go from 1/2" shaft on the 1725 RPM motor to a drill chuck. It is more or less permanently attached. The problem is that the arbor itself has almost no runout. When attaching the drill chuck it goes to h--l. There is also a big counterweight/ flywheel that surround the arbor so you can hand turn it or rub it to slow down and stop quicker. Haven't got to that part yet.

The arbor has not made it to the motor. I turned it and checked it. Then attached the drill chuck and checked it and it is totally unusable.

 

[Chewy]

I should have done this. The shaft and face as you see it does not deflect the indicator, so it is way less then .0002 runout, if any. The assembled unit is indicated at the 1018 shaft, the drill chuck body and the drill rod inserted.

 

[mmcmdl]

Seems to be a rather large chuck for the smaller drills you mentioned . Why not use a pin chuck ?

 

[Chipper5783]

Like mmcmdl says - that doesn't seem like the right chuck for the task (plain bearing and too big). It seems you are getting as good as that chuck will do. You can get very nice little 1/8" chucks that are intended for the small drill bits.

 

[Chewy]

This is a copy of a commercial unit that sells for $600. It has 2 options, 3/8 & 1/2" It is used to handle small drills and also 1/4-3/8 buffing wheel shafts. Already spun the one up at another repair shop and it runs true. I didn't get the make and model of the chuck. This one you can see the runout.

I have in the past used a smaller drill chuck for small drills. It is mounted on a shaft and I use it with a 5/8" keyless chuck in the mill or in an R8 collet. It has a 5/16" shaft. I have a pin vise that was cut in half and can use the collets for itsy bitsy drill bits by putting the pin vise in the keyless chuck.

 

[darkzero]

Thread mount drill chucks aren't known for precision. Then again drill chucks in general aren't relied on for precision anyway, .003 TIR is acceptable for a drill chuck. But that doesn't mean a thread mount drill chuck can't have great TIR but it may not repeat well.

Does the drill chuck have a register/boss like a threaded lathe spindle would have?

How about chucking up something you trust in the drill chuck jaws, like a gauge pin or piece of linear shafting, then chuck that in a 4-jaw & indicate. Then with a very sharp cutter, take a light skim cut on the arbor you made to true it up.

If there's too much hang out & you get deflection, center drill the end of your arbor, then true up the drilled center with a boring bar, then use live center tailstock support (assuming your tailstock alignment is well adjusted).

 

[Chewy]

I have to think about what you are trying to do. I made the arbor so the face was perpendicular to the threaded shaft. I figured right or wrong that with nothing but threads to attach the chuck, that the back would be the reference surface. There is only about .1 of un-threaded bore to push on a shaft so that won't make it. I was thinking about lapping the back surface to correct the runout. I put a piece of cigarette paper in to shim the low side and it helped. You idea would use the lathe instead, which is a pretty good idea.

This is a name brand chuck from a reputable supplier, not an Amazon special. It is on a precision turned spindle, not a worn out drill press quill. That is what is bugging me, I hope that it is just defective and the replacement one will work or I will be custom fitting it to the spindle.

 

[darkzero]

Yep, I'm familiar with LFA, they are a quality chuck manufacturer. But in general thread mount drill chucks aren't as "precision" as taper mount chuck. They're usually for drill presses & handheld drills. But yeah I know the drill chuck you bought isn't meant for handheld drills & thread mount chucks are perfectly acceptable for use with machinery.

I don't have a lot experience with nicer thread mount drill chucks but I have had threaded drill chuck arbors that I've modified for other things. While the ones I've had did have ground flanges, I don't recall them having registers on them. Like a register/boss on a lathe spindle, that is what ensures accuracy & repeatability, not the threads. I don't recall seeing that on thread mount drill chucks. That's not to say just an accurate single pointed thread with no register can't be accurate but the drill chuck threads needs to be accurate as well. I would kinda expect that from LFA if it was a high dollar chuck but relying on just the threads for accuracy isn't ways best.

I've had taper mount drill chucks where I have had to clock the arbor to get better runout, more tedious to do with a thread mount & it sounds like you have been trying that somewhat. Thatxs why I suggested mounting it in the lathe with the drill chuck centerline to the lathe spindle centerline, then take a cut to true up the arbor. This in theory should take care of whatever is causing the runout error but only if the setup allows you to (ie, overhang, rigidity, deflection, etc).

I've actually done this to a lathe chuck to true up the register rather than attempting to grind the jaws (which I had no means of doing at the time). It actually worked in my case. Not this actual chuck & one much smaller but you get the idea.