Drill Press Chuck Runout

sean69

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I have a 1980s Busy Bee 18" benchtop drill press, got it at auction for $150 a few years ago. It looks brand new, seldom or very lightly used.

But: I had always had trouble drilling straight holes (usually 11"-14" deep) so I finally got around to checking it for runout.

Turns out the spindle is good, solid, no play and +/- 0.0005 runout... as is the chuck shank (arbour?) about the same runout. measuring a ground shaft in the chuck itself, I get +/- 0.0050 runout (!)
Checked the jaws, no dirt looking clean and clear. so:

Is there a way to correct the existing chuck or am I looking at a new chuck?

-thanks
-sean
 
You will always have trouble drilling holes that deep without the drill wandering to some extent; what material ate you drilling? The only way to drill really deep straight holes is the process of "gun drilling", which requires special tools and equipment.
Bottom line, do not expect a new chuck to equal straight holes when drilling that deep.
 
You will always have trouble drilling holes that deep without the drill wandering to some extent; what material ate you drilling? The only way to drill really deep straight holes is the process of "gun drilling", which requires special tools and equipment.
Bottom line, do not expect a new chuck to equal straight holes when drilling that deep.

I have some little processes to compensate for crooked holes - mostly into endgrain in hardwoods. (holes for magazine tubes in rifle fore ends)

But I can see the end of the bits wobbling - it affects other work as well - more distressing are out of round holes in metals. I bought a set of reamers a couple weeks back & completely ruined a ram rod tube trying to ream it out ...
 
But I can see the end of the bits wobbling - it affects other work as well - more distressing are out of round holes in metals. I bought a set of reamers a couple weeks back & completely ruined a ram rod tube trying to ream it out ...

Sean, I totally agree with John re the deep holes. Accuracy with an Asian drill press in deep drilling is probably not gonna happen.

If your spindle is accurate, and 0.0005" is pretty good for a drill press, then an increase to 0.005" of run out on a rod in the chuck suggests that a) the arbor is bad, b) the chuck's internal taper is bad, c) that a and b are okay but the chuck was not mounted on the arbor accurately, d) the jaws are damaged or not holding the rod concentric to the chuck body, or e) the chuck is a POS and needs to be changed to a precision chuck.

You sort of need some frame of reference as to how much a properly mounted chuck in good condition will run out on an Asian drill press. There is no such standard, at least to my knowledge, but I have a Craftsman 15" drill press in which I replaced the spindle, spindle and drive sleeve bearings, mounted an Albrecht keyless chuck in pristine condition on a brand new Albrecht arbor with great care paid to how I installed the chuck in the spindle and I have under 0.0005" TIR at the arbor and under 0.001" on a 3/8" dowel pin measured 1/2" beyond the chuck. It is pretty accurate when drilling holes but even I understand that this only handles the driving end of the hole making process.

So, do you need a new chuck? Dunno', maybe. If your chuck is the OEM chuck that came with that drill press then I would say dump it and use an Albrecht, Rohm or Jacobs Super Chuck. The OEM Chinese chucks are worthless other than for drilling holes in wood, in my opinion. I would also dump that OEM arbor and get a decent one from Albrecht, Jacobs, Rohm or some other reputable maker.

The biggest issues when we get out of round holes are chatter and vibration. This has little to do with the drill press directly; it has more to do with the drills and how we use them. About 3-4 years ago, I looked into this subject and am "speaking" off the top of my head about what I recall but chatter is a really big deal. As you might expect, speeds have a lot to do with chatter. If you drill a partial depth hole and you see a sunray pattern, like spokes on a wheel, at the bottom of the hole instead of a smooth surface then you have chatter. Just like on a lathe, the solution is to reduce speed and increase feed. It may surprise you to find that this works rather well, crude as it may seem. This is why I tend to run my drills slower and feed harder nowadays and it works.

The other issue is vibration. As I recall, you can modify your tool web to be thicker and use less relief behind the cutting edge. I may be wrong on this but increasing the contact area at the cutting tip dampens vibration, leading to less out of roundness.

To be honest, I don't modify my drill geometry. Too lazy, I think. What works for me is:
  • Use spotting drills to get my drill started well and I make sure the drill flute ends are buried in the hole before I clear chips the first time. This makes a hole my drill can re-enter accurately.
  • Avoid pilot drills when I can. Pilot drills are thin and will wander, and any drill that follows will follow the same path. Using a main drill works better, for me at least.
  • Use lower speeds and harder feeds. This works better than you might think.
  • Clear chips after going in 2-3 drill diameters.
  • Always use lube.
  • For reamers, spot, then drill with a drill one size smaller than your pre-reamer drill to rough out the hole, then use your pre-reamer drill, then ream. I tried all kinds of things to figure out how to ream an accurate hole and this works best for me. I also run the reamer at about 100 rpm on the mill or the slowest I can on the drill press (about 250 rpm) and make a steady controlled pass on the infeed only, then I shut off the machine and manually withdraw the reamer. This gives me a better finish, a more accurate hole and my reamers stay sharp longer. I use a lot of lubricant, too.
It matters which drills you use before running a reamer in the hole. See the attached file.

It sounds like you're a gun guy and I'm not sure which brand of reamer works best for your needs. For my simple needs, I prefer Alvord Polk, L&I and PTD reamers.
 

Attachments

  • Yankee Reamer sizing info.pdf
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It might not be the run out that is causing your issue; most drill especially in smaller diameters will flex and follow a started hole. It might be that the drill press spindle is not perfectly square/perpendicular with the table that your work piece is sitting on. Check this the same way you would tram in a vertical mill head, like a Bridgeport head.

If the work piece is not set perfectly square with the spindle there is no way the drilled hole will be square in the work piece regardless how true a chuck runs.

Just a thought,
Ted
 
Sometimes a picture is worth a thousand words. Here's an illustration I drew up in Fusion 360 of a two inch wide block 14 inches long. The bottom right edge is skewed off the horizontal by 0.002" which you would see as 0.002" dial indicator error per side if your arch from center in your drill press spindle was 2 inches (4 inch total swinging diameter).

As you can see, the center line of a vertical line (which would be your spindle) starts at 1" at top but over the 14 inches moves 0.014" (almost a 1/64") off from it's original entry (the two dimensions in ( ).

This demonstrates only a error of 0.002 per side so if your table is off more than this it obviously gets worse. Also, errors like this magnify with the length of the piece, so 14" can show a lot of error where you wouldn't really notice it on a very short piece.

If you drill press table is not trammed in very closely on these long pieces you are going to see this error, just as you would on a milling machine.

Maybe I'm barking up the wrong tree, but this is something that gets overlooked sometimes...

Hope this makes sense,
Ted

Tram error.jpg
 
I have a 1980s Busy Bee 18" benchtop drill press, got it at auction for $150 a few years ago. It looks brand new, seldom or very lightly used.

But: I had always had trouble drilling straight holes (usually 11"-14" deep) so I finally got around to checking it for runout.

Turns out the spindle is good, solid, no play and +/- 0.0005 runout... as is the chuck shank (arbour?) about the same runout. measuring a ground shaft in the chuck itself, I get +/- 0.0050 runout (!)
Checked the jaws, no dirt looking clean and clear. so:

Is there a way to correct the existing chuck or am I looking at a new chuck?

-thanks
-sean


You might try taper shank drills for the holes that require more accuracy.

Although that is a fairly deep hole your drilling.

How off line does it go ?


Stu
 
Sean69, my suggestion re the question of what gives with the chuck is to take it apart and see. I would expect that it could use a bit of deburring and cleaning. Once you have done that it will be clearer whether the chuck can meet your precision requirement.
As mentioned above, common drill chucks are not considered good for precision work. To get the best results from any drill chuck you need to have the best drill bit for the job. I would even say that the drill bit might be more important than the chuck for quality work. You might not have exhausted all your drilling options yet.
 
Assuming that you can separate the chuck from the arbour, you can then indicate the arbour for runout. Likely the issue is with the chuck, replacing to a better quality will help.

Deep hole drilling is always a problem, wood or metal makes no difference. There are special drills with a grind for deep holes. Wood with its differing hardness especially in end grain is a problem. I would drill a smaller hole about an inch and follow with the either finish drill or just under would be better. Repeat until done. 1 inch at the time, using the previous hole as a bushing to help guide the drill straighter. Use the finish drill to clean out the hole. Best I can suggest at the moment.
 
It might not be the run out that is causing your issue; most drill especially in smaller diameters will flex and follow a started hole. It might be that the drill press spindle is not perfectly square/perpendicular with the table that your work piece is sitting on. Check this the same way you would tram in a vertical mill head, like a Bridgeport head.

If the work piece is not set perfectly square with the spindle there is no way the drilled hole will be square in the work piece regardless how true a chuck runs.

Just a thought,
Ted

magazines are generally somewhere in the 0.660" range, I use a 5/8 brad point (very expensive lee valley HSS) to start & then ream the rest of the way with an adjustable hand reamer and extensions.

I've made up a jig for this purpose and use a laser to line it up parallel with the tool, the jig gets blocked up at the bottom to compensate for any flex in the DP column - I then can drill 1/2 way through, flip it end for end and drill from the other side (on a very meticulously squared piece of material)
Once (and only once) I had a little wooden button drop out where the brad points met perfectly in the middle.

Anyway - if that hole is under 1/16" out then I can compensate a little by reaming it a little larger, but any more than that I have to square up the material again to the bore before doing anything else. A "true" hole would save me a couple hours easy.

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