Mag drill runout and how to measure Morse Taper alignment / angular offset

[keeena]

I picked up a used Milwaukee mag drill and I found it has a bit of visible runout which gets worse the farther you are away from the drill. The socket in this particular drill has a straight bore with two drive dogs. There is an adapter which mates with this socket and has a MT3 socket. I've ruled out the MT3 tooling by simply trying a known-good dead center. The drill sounds fine and I can't feel any wobble if I shake the tooling while in the drill.

The end of the MT3 is easy to test and it shows less than 0.0005" TIR. So I'm assuming that something along the works has an angular offset (H-M link, thanks RJ for that detailed post). The problem is either with the adapter, drill's socket, or internals (shaft, bearings).

I was thinking that I'd need to get a reading at the very top of the MT3 bore but my DTI cannot reach anywhere near that far. Are there other methods for testing or will I need a long-reach DTI?

I also want to run these same tests with the drill's straight bore; basically trying to rule things out in order before I have to pull the drill apart. The adapter looks in decent shape; no rust and socket feels clean, no burrs.

Here's a stock picture of the adapter:

 

[epanzella]

Put a small bend in the end of a piece of 3/16 music wire and stick the other end in your tailstock drill chuck. Put an indicator base on your xslide and put the indicator plunger against the music wire. Run the bent end into the bore with the bend rubbing it slightly and you get the runout on the indicator. They'll be a conversion factor between what you read and the actual runout that is dependent on how much wire is sticking out past the indicator. I had pics of this during a rifle build but I can't seem to find them.

 

[keeena]

I forgot to mention the TIR of the system. Using a MT3-to-straight shaft arbor, I'm seeing 0.008" TIR at 3.25" from the end of the drill. This seems to high and I'd think may be an issue for annular cutters, but if this is about normal then let me know too. The TIR is a bit worse when I use real tooling due to additive nature.

 

[keeena]

Put a small bend in the end of a piece of 3/16 music wire and stick the other end in your tailstock drill chuck...

Thanks, that's a creative way to measure. You mentioned how it could be setup to measure lathe chuck; would it work in my scenario where I'd have to anchor the fixed end of music wire on the table? I'm just wondering since the music wire anchor won't necessarily be in-line with the mag drill spindle. I -think- it would still work...

 

[RJSakowski]

I don't normally consider a drill to be a precision tool. No knowledge of the Milwaukee mag drill though.

You should be able to measure the runout of your adapter using your MT3-straight shaft adapter and a pair of vee blocks. First, determine the concentricity of your MT3 - straight shaft adapter to rule it out as the cause of the runout and then assemble the two adapters and measure runout.

 

[keeena]

You should be able to measure the runout of your adapter using your MT3-straight shaft adapter and a pair of vee blocks. First, determine the concentricity of your MT3 - straight shaft adapter to rule it out as the cause of the runout and then assemble the two adapters and measure runout.

The MT3-to-straight shaft is pretty dead-nuts straight & concentric (0.0002").

I mounted the shaft of the MT3 arbor in the lathe with a collet chuck, installed the drill's adapter and measured the OD of the adapter. The far end of the adapter OD is 0.0015" TIR and near-side is 0.004" OD...so it gets sloppier near the business end by the dogs.

I confirmed that the MT3 adapter itself not showing any appreciable runout anywhere along it's Morse taper.

Could this 0.0025" difference between the top and bottom of the drill's adapter be the problem?

 

[epanzella]

Thanks, that's a creative way to measure. You mentioned how it could be setup to measure lathe chuck; would it work in my scenario where I'd have to anchor the fixed end of music wire on the table? I'm just wondering since the music wire anchor won't necessarily be in-line with the mag drill spindle. I -think- it would still work...

AS long as you can get the music wire to rub against the bore that you want to check for runout and put an indicator against it it will work. The ratio of actual runout to the absolute indicator reading will vary depending on your exact setup.