I recently picked up a nearly new Jet 3/4 HP, 16 speed drillpress at an estate sale for a great price. After getting it home and setting it up I prepared to drill some nice straight string holes in a classical bridge using a brad-point drill when I noticed that the tip of the bit was wandering around in a circular path. Thinking it might be a bent bit, I tried others and had the same result. I tried installing the bits very carefully, hand tightening the chuck while turning the bits to make sure they were contacting the jaws evenly, and tightening all 3 key-holes gradually. Same results. I have a .500" lathe-turned spindle. which is perfectly straight and circular, and using a dial indicator found the runout to be about .004" with 2" projecting from the end of the drill chuck. Obviously with a longer drill bit the runout is even greater. Not good. I've removed the quill and cleaned inside and outside to make sure nothing was throwing off the alignment, but still have the runout problem. Frankly, I'm stumped. Any suggestions as to what I might be missing and possible solutions are greatly appreciated. Larry
I'm not familiar with this machine (Jet is a generic brand down here) but suggest you remove the chuck/spindle/taper or whatever and check the drive shaft for trueness and driveshaft bearings for wear (take the belts off, put a long shaft in the chuck and use the extra leverage of the shaft to give the drive assembly/shaft a lateral shake and listen for clunks and feel for any movement). If the driveshaft is all good, its the chuck which is generally a replacement item. Anybody else familiar with this machine?
I presume it's a taper-mount chuck. You might take the chuck off and use your indicator on the taper itself to check runout. You could also remove the chuck, rotate it about ninety degrees, reinstall, and hope for better readings.
.004 total indicated runout would mean .002 off center, which isn't too terrible for a drill press chuck. 004 off center would be .008 runout, which is kinda nasty, but still workable for a lot of drilling operations.
I had the exact same problem with a floor standing Craftsman drill press. I had the service guy out and he replaced two chucks, and neither helped. Like Russell mentioned, you've got multiple parts to the head.of the machine that could be the culprit. The Sears guy also replaced the drive pulley with multiple sheaves....basically everything that was easily accessible. He didn't replace the cone-shaped pulley adapter, the splined arbor (driveshaft) or bearings inside the head. I ended up getting a replacement drill press, but Sears let me keep the old one for spare parts. I ordered the splined arbor and cone-shaped pulley adapter, tore the whole thing back apart and rebuilt it. I can't tell you which part was bad, but it had to be either the arbor/drive shaft, or the cone-shaped adapter. I did not replace the bearings, but they weren't very old. You probably have two or three sets of bearings. One up top where your belt/pulley is located. It will be visible once you remove the pulley. There will also be one or two more inside the head above the chuck. These are probably held in place by snap rings, and a little harder to access because you'll have to remove everything else to get to the darn things.. Most of these inexpensive drill presses are a variation of the same thing, but if you know the model number, you can probably find a user's or maintenance manual on-line. I've also heard that Jet provides fairly decent service, but if you don't mind getting your hands greasy, they just take a little time, patience, and back muscle. I kept my old parts, and snapped some pics for you. Hopefully they'll help.
Wow guys! Thanks for all the input. Gave me several options I hadn't considered, although I'm starting to think it may be the chuck itself, which is easily replaced, but I'll look into the spindle also.
Rusty: Jet is a fairly well-regarded machine here in the US, looks identical to the Delta drill presses and since they're all made in China now, about the same quality (for better or worse). I've got several other Jet machine tools and have been satisfied with their performance. Probably not professional/industrial quality, but good enough for what I need.
Frank: yes it's a #2 Morris taper chuck. I'll use my dial indicator to see if that may be the problem, but I've also considered locating the high spot and trying to wack it back to center. Maybe I need a bigger hammer.
Eric: thanks for the story and photos. I hope I don't have to go to that length, but I got this machine at such a good price I can afford to buy some replacement parts if needed
I'll let you guys know how it turns out once I get it fixed. Unfortunately we've got Emerald Ash-Borer here so I'm going to be spending the next week or so taking down about a dozen big white ashes in my woods so I can replant this spring (if it ever gets here). Does anyone have any experience using white ash for guitar necks? It makes great baseball bats (and firewood)!
A drill press is NOT a precision instrument, as mentioned previously 2 thou off centre is more than acceptable. While the spindle maybe very true, manufactures tend to stint on the bearings. Additionally there is the fit between the quill and the housing; the female taper; the taper of the chuck etc.. Then you have the chuck all of which can cause the drill to run out of true.
IMO a press with a bit in the chuck and running out .between 3 or 4 thou would be normal . Only if you intend to spend serious money could you expect better tolerances.
Even if you had the world’s most perfect drill press with no play at all you have the bit itself. The cutting edges of which may cause the hole not to be where you’d want it to be. If you want precision use a boring machine.
Robbie, you may also want to ensure there aren't any little burrs, chips, etc. up inside the shaft where you insert the chuck. As you apply force the inside surfaces may not have good contact, allowing the chuck to move as you pull on the handle to apply force. Just a thought.
If the bit is wandering when pressure is applied I would look at the speed at which the drill is running and the speed of the feed. Errors with either will give the problems you describe.
Thanks, Eric. I'll check that if I can figure out how to get the chuck off. Maybe heat it with my propane torch?
Steve...good advice. I usually (but not always) check my guide for proper speed. Feed rate is suspect since I'm naturally impatient.
One last thing which might help is something I was taught to do as an apprentice fitter/turner some 30 odd years ago.. When the chuck is placed in to the taper, place a stout piece of scrap timber on the bed and bring the chuck firmly down on to it 2 or 3 times. This will ensure that the male and female tapers are well in.
One or two people have suggested tightening all 3 holes in the chuck. IMO this will have no effect as the Jacobs type chuck is designed to be self-centring.
Great advice...thanks! I'll try looking for the book and trying these suggestions.