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Thread: Question on JT33 taper
05-02-2011, 03:52 AM #1
Question on JT33 taper
I have a question regarding a JT33 taper. I am restoring my Dad's old craftsman drill press (model # 113.21370), which he purchased in 1974 and which I used growing up. Everything is in great shape and the drill press works fine. I have replaced the bearings on the spindle shaft (which the chuck attaches to).
On the end of the spindle shaft, there is a JT33 taper, which the chuck attaches to. The original Craftsman chuck has a collar, which threads onto a threaded collar, which is pinned to the spindle shaft (just above the taper). When you thread the chuck onto this collar, it pulls it up tight and keeps the chuck from coming loose.
Okay, so here is my question:
I purchased two extra chucks - both of which have a JT33 taper. However, these new chucks don't have the little threaded locking collar affair - they just engage onto the JT33 taper as normal. If I push the chuck onto the taper and twist, it mounts very tightly. I have checked the specs of the JT33 taper and it appears to be fine. I have also polished up the surface and checked it using Dykem blue. If I blue it and then put the chuck on (and twist it up and secure it), then it pretty much evenly wipes away the blue - which indicates to me that it's making good surface to surface mating.
My problem is that when using the chucks without the locking collar, the chucks seem to have a nasty habit of dismounting. If the drill chatters on the work (or if I use an end mill or something which produces excessive vibration), then the chuck will loosen up and drop off.
Shouldn't the JT33 taper be enough to secure the chuck and hold it? Or am I expecting too much? My assumption was that the locking collar was there simply as an added margin of safety (for example, in case someone uses the drill press with a buffing wheel or something), but now I'm wondering if it's there because the JT33 taper alone isn't able to hold the chuck up on the drill press.
I don't have any experience with morse tapers or anything like that. This JT33 is my first experience with tapers. Should the taper, by itself, be enough to hold the chuck on the spindle while drilling metal? Or am I expecting too much?
Any information would be most appreciated. Thanks!
05-02-2011, 07:21 AM #2
Jacobs was the only company making chucks with a collar, to my knowledge. You need a chuck number 34-33C.
A refurbed one is on ebay right now: 190526601126
The JT33 is kind of small. The collar is not strictly necessary, but it helps.
05-02-2011, 07:24 AM #3
That threaded coller is specifically to retain the chuck for use in milling. Most likely your Craftsman was a rebranded Walker-Turner from your description. W-T also made a mill holder that screwed on in place of the chuck. For drilling you should be able to use the taper without retention. Just tap it into place with a hammer and block of wood or a mallet. Maker sure you have the collar threaded on first so you can use it to pop the chuck off if needed. Don't ever use an unretained JT33 for milling!
05-02-2011, 07:35 AM #4
I agree with ForestGnome, the collar helps with side forces that would normally shake a JT33 taper loose. I have one of these DPs (the commercial version, no less) and while I'd be fine with a drum sander on the thing, not sure I'd put a 1/2 inch 2 flute endmill and tear into 316 with it!
That DP is good for drilling metal, plastic, and wood, and for modest side-loads, as per drum sanding.
It's a nice unit. There is a tilt table accessory which I have (gloat gloat). It's downside is no geared table lift as per later models. I solved this using an HF trailer wheel crank lift, turned upside down.
05-02-2011, 08:16 AM #5
My Craftsman DP had the same sort of JT33 chuck on it as well ... a nasty cheap one with the retaining collar.
I replaced the original chuck with a plain JT33 Albrecht, and it stays on just fine. I suspect you have not knocked your chuck onto the taper well enough ... don't go crazy, but do knock it on smartly with a mallet and a protective block. Be sure your tapers are clean and dry first.
05-02-2011, 08:32 AM #6
Hey bosleyjr, thanks for the lift idea! I've been toying with the thought of making a rack and pinion setup for my W-T, but never had the time. It sure gets heavy with an x-y table on it.
05-02-2011, 08:33 AM #7
I have a Delta DP, 1990 vintage with a taper other than JT33 (I do have a Rockwell with JT33) and I was always having problems with the chuck staying on the taper. It got to the point that I would leave the DP with a wood block tight to the bottom of the chuck. I finally out some Loctite 638 retaining compound on the taper and it's held ever since.
05-02-2011, 08:57 AM #8
I bought a new a Craftsman drill press in 1963 (gold paint). It had the locking collar 33JT chuck system. In those days, King-Seeley made the high end drill presses for Sears. If the chuck is cleaned and driven onto the male taper, it is extremely difficult to remove. Much has been written about how to get them off. But Sears sold collet chucks for router bits, drum sanders and shaper arbors that also fit the spindle. The collar is certainly needed to keep those devices from falling off the spindle. But, just as important, the collar also acts as a puller when you want to remove the chuck to mount another device. I changed attachments a number of times while I had that drill press and the collar system worked flawlessly. Easy tool changes and the chuck never spun.
Delta Rockwell sold drill presses with the same locking collar and also sold the other devices, much like Sears.
I have a NOS Rohm 1/2" chuck with the 33JT and locking collar, so Jacobs was not the only maker of such chucks.
I ruined my first Albrecht chuck, a 1/2" with 33JT, by just wringing it onto the male taper. It spun off and wrecked the chuck bore and male taper the first time I tried to drill a large hole in steel. I learn from my mistakes, and never did that fool trick again.
05-02-2011, 09:27 AM #9
Supreme also made JT33 taper mount chucks with locking collars.
05-02-2011, 11:20 AM #10
JT33 is a relatively small taper, but it was meant for only smaller DP's.
Typical specs of older American made DP's with this taper mentioned 1/2" drill in mild steel as max capacity. How many times have you used a S&D reduced shank drill to make a larger hole in steel?
Oner solution to prevent the un-collared 33 taper chucks from falling off is to drill a through hole in the chuck and tap the spindle for a retaining screw. This would be similar to the way chucks on electric hand drills are secured with the center safety screw.
Besides using side thrust tooling in the chuck another cause of falling off is use of tapping heads that require a fair amount of pull to revere on tap retraction.
05-02-2011, 01:43 PM #11
Here's a pic of my WT with a new Rohm JT33 installed. The locking collar can be seen. I haven't tried any operation that would put a side load on it, and would be reluctant to try anything other than drum sanding.
As you can see, the collar adds quite a bit of extension to the spindle.
05-02-2011, 06:09 PM #12
I don't get this......
What is it about the collar that adds so much extension to the spindle? With Jacobs and Supreme chucks the collar doesn't add any appreciable length to the spindle, maybe 1/2" or so at most where the threads are. Yours seems to be unusually long for a chuck. Is that a keyless chuck?
05-02-2011, 06:48 PM #13
05-02-2011, 11:19 PM #14
You have a shaft with the outboard (chuck end) bearing on it. This sticks out about 1.25 inches I guess (I'm in a hotel room, not my shop). A ~1/2 inch collar with OD threads on one end fits onto the shaft, and is pinned in place. The chuck has a shoulder with a retaining ring that holds the ID thread collar on. This is a weak point, BTW. So the collar on the shaft adds about a half inch, and the shoulder requires some space. So the shaft is maybe 3/4 inch longer than it needs to be.
I've used an Albrecht keyless chuck on this machine. Either I didn't clean the taper well, or the id or od taper is nicked, or I didn't install it tightly, or the chuck is too damn heavy, but the image of that chuck spinning through the air with a 3/16 bit in it (at about 3500 rpm? I think) got my attention.
ForestGnome, glad you liked the pic of my table adjuster. Got the idea on this forum, IIRC.
05-03-2011, 01:18 AM #15
05-03-2011, 01:22 AM #16
7000 rpm is quite a spin on a Craftsman drill press. My WT tops out at 5000, and I'm looking to slow it down. . . .
05-03-2011, 01:39 AM #17
Thanks for all the great information everyone. Here's a picture of the drill press after I restored her. It has a lid that covers the pulleys on top also, but I haven't finished cleaning that part up yet (and I've never really been a big fan of how it attaches anyway).
You can see one of the chucks I bought off ebay on there now. I did tap it on with a block of wood, but when I spun up the end mill and tried to mill .005 off a 316 SS nut, that's all she wrote. A stupid move on my part - live and learn.
I'm going to search around for a heavy duty chuck with a locking collar maybe. The one I have (the original one) is actually in pretty decent shape. I cleaned it up and it's okay. I just wasn't sure if the JT33 should hold the chuck on its own or not.
As you can see in the photo, I've also got a nice little X/Y table there (made by Mastercraft Engineering - model # 500). I don't have the original hold down ears, but the table itself is in great shape (couldn't pass it up for $70). I still need to lap the slides on the X/Y table and clean it up a bit (and adjust the gibs, etc.), but overall it's in excellent shape. It also spins, which is nice, so I can sort of use it as a dividing head of sorts in a pinch.
For brass and aluminum, I think it will work okay as far as doing some limited milling. Ultimately, I think I'm going to try to pickup a used Clausing 8520 or 8530 for milling anything serious though. I also have a small Taig lathe, which has a milling attachment, but obviously that's very limited in terms of milling too much.
Thanks again for all the info on the chuck and taper. I really appreciate it.
05-03-2011, 01:44 AM #18
My vise took most of the abuse (and the end mill also). I tried to sharpen the end mill on the grinder, but not a whole lot of luck with that. It's a two flute end mill.
05-03-2011, 02:04 AM #19
In looking over some of the chucks on ebay, I see a lot of them appear to have a collar that pinches down. I'm not sure if that will provide enough clamping force against the JT33 taper for milling purposes or if I should stick to something which actually threads on like the OEM Craftsman design I have now.
I was actually thinking about turning something out on the lathe that screws down into the little collarless chuck I have here now. Like 4 cap screws that hold a threaded collar onto the top of the chuck and then I can thread the chuck up onto the threaded collar on the drill press maybe.
05-03-2011, 02:54 AM #20
I just went out and re-installed the original chuck. Here's a photo.
I tightened up the locking collar a bit more than I had previously. I put the end of a drill bit into the holes on the collar and this gave pretty good leverage. I also stuck a rod in the hole on the pulley up top - then turned in opposite directions. That pulled the chuck up nice and tight.
I chucked up a precision SS rod and then stuck a dial indicator on it. Looks like TIR is about .004", that should be okay for drilling I think. There's a certain amount of play between the shaft that goes up and down (which carries the spindle) and the casting of the drill press itself. I can take some of it up by squeezing down with the locking lever (the one which locks the shaft relative to the casting of the drill press). I realize it's not going to be as accurate as a milling machine or something. I think .004" is probably not too bad for your average drill press out there.