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Drill Press Tir

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Long Roof

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I have a mid-80’s vintage floor model Craftsman 113.213850 drill press that I bought new back in the day. It has always had quite a bit of TIR on the chuck but I just accepted it. After reading some posts on this forum I got inspired and thought it was time for a new chuck.

The drill press takes a JT33 chuck with locking collar. Not a lot of choices for JT33 with locking collar but I found a Jacobs brand 34-33C and just tried it out.

First, using a dial gauge I checked the arbor without the drill chuck mounted and the TIR is nearly 0. I had to check to make sure I was making contact as there was virtually no movement of the needle on the dial gauge. With the new chuck, the lowest I can get is 0.007 at the body of the chuck and about 0.012 at the base of a drill bit. This isn’t much better than my old chuck.

What kind of runout should I expect from a new name brand drill chuck?
 

47convertible

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Short answer: everyone has their own standard but .003 to .004 at end of drill is what I shoot for from a drill press and using good technique.

Arbor needs to be checked for TIR when fully extended as well as at rest but accepting that your old chuck is the primary culprit I had the same issue with a 20 inch Jet I purchased new about 10 years ago--excessive runout. Replacing the bearings took out a few thousandths at the extended arbor but the factory chuck was also a bit wobbly. Replacing it got me maybe .002" added reduction. When using a piece of round test bar about 4" long I was able to reduce TIR to .003. For a drill press that's pretty darn good-- about the thickness of a human hair. The eye can pick up 'wobble' down to that range and cause unnecessary worry.

That said I think .007 at the chuck would be beyond my acceptable level for metal drilling or reaming and .012 at the end of a bit is unacceptable. I was never able to measure run out with a bit very well. Maybe I don't have a good technique. Good drilling technique is necessary including the use of centering drill to peck out a starting hole. Just grabbing a hole-size drill and muscling it down on the metal will almost always cause deflection and an unsatisfactory result.
Jerry
 

mikey

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#3
Measuring run out on a drill press is a good lesson in stacking tolerances - sooo many interfaces and each one capable of adding run out. If your bearings are stock Craftsman bearings then they are likely asian shielded bearings, and if they are original then they're 25 year old bearings that probably have significant wear. Even when the bearing has low run out at low speeds they will run out much more under load. If you really feel the need to reduce run out on your drill press I suggest you change both the spindle and drive sleeve bearings to deep groove bearings because it makes a huge difference in run out.

The arbor also makes a difference, as does the method used to install it. A good arbor is accurately ground. If you used the original arbor then it is probably made in Taiwan. It might be okay but an Albrecht or Jacobs arbor would probably be better and I would opt for one if you can find one.

Jacobs chucks vary in quality, especially the lower end chucks. The better chucks, like the made in the US Super Chucks were much better. Personally, I prefer keyless chucks for drills up to 1/2"; I use an Albrecht for these smaller drills and a Jacobs Super Chuck for larger drills. These higher end chucks have very accurately ground mounting tapers so they install more accurately and tend to run better. The Albrechts are dynamically balanced to run at 10K if I'm not mistaken.

I have a Craftman drill press, too. I changed the bearings as above, installed an Albrecht chuck on an Albrecht arbor and I have 0.0005" TIR on a 4" long piece of 1/2" OD drill rod. I also have a Jacobs 14N on an Albrecht arbor that runs out at less than 0.001". A running drill in either of these chucks looks like its standing still.

Pretty good, right? Well, what is the bit doing when drilling into a piece of steel? I do not know! My press is accurate, yes, but under load all drills are influenced by the quality and symmetry of the drill tip so all bets are off.

My point is that my personal approach is to do what I can to get the drill running well and to use good chucks and arbors and to sharpen my drills as well as I can. Then I don't worry about run out on my drill press.
 

Long Roof

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Quick update, first thanks Jerry and Mike for your comments. I went through the drill press, got things cleaned up, installed the new Jacobs chuck and it is a little better than the original chuck that I replaced. I think I realized that this was not intended to be a precision piece of machinery. I suspect that the bearings could be replaced to improve TIR. When I pushed on the step pulley at the top end of the spindle my dial indicator on the chuck showed quite a bit of movement.

I think at this time I will continue to use it as is. It is not a bad drill press for general work. It has done what I needed it to do over the years. I may replace the spindle bearings at some time to see what improvements that would make but that is kind of low on the priority list now. Too much time at work and not enough time in the shop.
 

mikey

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When you do get around to it, you'll find it isn't a difficult job to change the bearings and that it is well worth doing. The fact that you can get movement by pushing on the pulley suggests the drive sleeve bearings are shot and that will magnify run out big time. Most of the run out will be in the spindle bearings, though, so if you change bearings you should change them all. I suggest Nachi deep groove bearings for the drive sleeve. If you can find a pair of single row angular contact bearings for the quill, that would be ideal. Otherwise, deep groove bearings work well.
 
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