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  • Jacobs Chuck Key

    Howdy fellas,

    Got myself a little issue here. I am looking for a key for a Jacobs 36b chuck 3/16-3/4 capacity. Problem I have here is that it takes a K4 key (according to jacobs) however the chuck I have was made in Hartford, Conn. I called Jacobs and they said they don't have a key and that I need to throw the chuck away and replace it with a new one. Apparantly, a K4 from other jacobs manufacturing facilites dont fit the 36b made in Hartford, Conn... Something about different tooling. Does anybody know of a source which may have a used key or something? Seeing that there seems to be some pretty good authorities on drills here, this seems like the proper place to ask for assistance.


  • #2
    Chuck Key Issue

    That's just insane.

    A K4 chuck key is a K4 no matter where it's made. Can you take a precise measurement of the 3 holes in the chuck and let me know? The current K4 Key works just fine with any of the 36 or 37 series chucks that I have ever come by. Unless the chuck really is bad, you best not throw out a chuck what will cost over $100 to replace. The K4 key has a pin that fits into 0.375 chuck body holes. A good serious tool dealer or an industrial supply house should have K4 keys in stock. There are some brand X keys that have the same pin and bevel gear that will work in the 36 series chuck. What mounting is your's? Are there any letters or just 36 on it? If you are in the USA as I assume, one way or another I'll help you get a key for your chuck. It is good otherwise?

    Just so you and others know Jacobs had (and I think still has) a factory over in England. The products are made to the same specs as the USA ones are.

    FYI: Hartford, Conn is their headquarters. The 36, 36B (5/8 or 3/4 thread), 36KD and 36PD all use a K4 key. You'll be fine unless you have some very wild chuck there which I really doubt you have. If the shank end of a nice new 3/8" twist drill, will fit into the chuck holes and the chuck itself says 36B on it then the K4 key will work. Please see the following links for some good info. The customer support agent just wants you to buy a new chuck.

    These are Adobe Actobat .PDF files. I suggest you right click them and save to your desktop or some folder on your hard drive. Once downloaded and opened, then try printing them for your records. There is good info here and you'll like to have both files handy. (General info on Professional chucks) (Keys and more - info)

    I hope this helps you out and that you can find the key OK. Places like McMaster Carr and MSC Industrial Supply and Travers Tools sell loads of chuck keys. Good luck and please post more.
    Last edited by Woussko; 12-14-2006, 10:59 PM.


    • #3
      thanks Woussko for the information,

      The chuck is in almost like new condition. I hate to throw it out, however I do sort of believe what the Jacobs tech rep told me. The K4 key I have is brand new and fits into the pilot hole correctly. The teeth make contact with the sleeve however here is where it doesn't work. Either the pitch, spacing, or depth is incorrect. I believe all the K4 keys have 12 teeth on them, so if the diameter of the key is the same, then would the pitch be the same? Not sure... I do know that if you fully insert it, you can't turn it due to a couple things. Seems like the teeth of the sleeve (outer edge) is wider then the spacing in the key so it interferes. you can see on the picture where the sleeve teeth have been "damaged" by an improper key. Also, it seems that the inside edge teeth of the chuck bottom out in the key itself. Pictures don't show this, but it is like key depth is incorrect on the inside edge. Oh, the chuck mount is 5/8-16..

      I can provide more pictures (or high res) if that would help.

      Funny.. When talking about this chuck key dillema, the Jacobs rep asked me if it had Hartford Conn stamped on it.. As soo as I said "yup" he was like.. "sorry, can't help" I guess there comes a point in time when you have to stop supporting legacy products...

      Thanks for any additional information.
      Attached Files
      Last edited by Lamakocklee; 12-15-2006, 03:58 PM.


      • #4
        lamakocklee,did jacobs give you a specific reason why the k4 would not work?now this chuck is a pretty large chuck,if it takes the k4 but anyway i have 2 boxes full of used keys at work,i will go through them.i will let you no if i come up with anything monday evening after work.snap a couple more pics so i can get a better look.

        A fishing pole is the best cordless tool!


        • #5

          When I asked Jacobs about this, the guy on the line said that the Hartford plant had a different tooling setup. When they closed the plant, all associated tooling was no longer used in production. He went on to say that there the chuck itself has marks to indicate what plant it came from.. i.e. Hartford Conn. , however the keys itself don't have any marks therefore it is impossible to tell unless you physically have it in front of you. I will get some detailed pics up of the key and chuck I have.

          Thanks for taking the time to look for some keys. I appreciate it. Chances are that the key that will fit it will be in somebodys garage tucked away in a corner long forgotten..



          • #6

            All I can say is that I have both newer Jacobs 36, 36B-3/4 and 36KD chucks here and a 40 year old 37PD. My K4 keys fit them all just fine. Now here is an idea that might work. Accupro and Rohm both make up 3/4" chucks and their keys are slightly different from Jacobs. Also some time back there were Supreme chucks made somewhere in the USA. Chic works in a power tool repair shop and I bet he may have just the key you need. I do remember that Accupro keys have metric size pilot pins and different gear teeth so one of their keys just might work. The same for Rohm only they normally have the same size holes as current Jacobs, but not always. It would be sort of a guessing game, but my bet is that if you had one each from Accupro, Jacobs and Rohm that one of them would work for your needs. If worse comes to worse, look on Ebay for a replacement chuck. Sometimes you can find NOS (new condition old stock) for far less than brand new. Does the chuck itself say K4 anywhere on it? One final idea would be to try the + shaped chuck keys that have 4 ends on them. You might get lucky and maybe one from over in China would just happen to work. I wish that I had your actual chuck here so I could see and measure it up. Do you have more than just the one K4 key? You might try another. There is a tiny chance your key has defective machining. If all else fails, you could use 2 pair of big Channellock pliers, but I really hate that way to loosen and tighten a chuck. Do keep in mind that the new 36BA-5/8 is not a cheap chuck. Does your's fit on a drill with reversing? The new ones are not drilled and countersunk for the retaining screw. That is something that a good repair - machine shop can take care of. The hole needs match up with the head on the screw. On non reversing drills this is not an issue. Please post more. Chic and I would somehow find a way to save you some $$$.

            MSC Industrial Supply has loads of chuck keys. They are pretty good about returns of things that are in perfect condition. I'm thinking you might get several different chuck keys for 3/4 (0.800 in Jacobs) chucks and one just might work well. I would wait on Chic and I'll take a look around my stuff too. I remember having a big T shape oddball chuck key that comes close but doesn't fit any of my chucks. Maybe it's just the one you need. If I find it and it looks close to a K4, I would be happy to just send it your way. I bet you're right about the back corner of a garage idea. It's funny that my really old Jacobs chucks (several) have never caused this problem for me, but then none are exactly like your's. Please do post more pics and also tell some about what the chuck is being used on/for.


            • #7
              Here are some links for chuck keys that may be helpful to you. I can't be 100% sure any will fit, but one might. I would use this as a sort of last resort.




              And finally why I can't stand the idea of your having to replace the chuck with a new one. McMaster Carr wants $168.92 plus shipping and MSC Industrial Supply wants $187.48 plus shipping. They come in a cute little box with K4 key included. This is for a new Jacobs 36B 5/8 I personally would look for a mint condition used one with key included. That's only if you just can't get a key that fits your's.
              Last edited by Woussko; 12-16-2006, 01:55 AM.


              • #8
                I think I went a bit wild, but here is what I think some valuable info. I have a few friends that like me happen to like older hand and power tools so I made a few calls and also took another look at what I have here. I personally happen to have 3 new Jacobs K4 chuck keys of which 2 are in a little drawer waiting for use later on and one is in current service. I have a Rohm 1/4-13/16 capacity chuck with a #3 Jacobs Taper mount, a Jacobs 37PD 1/4-13/16 chuck with pin drive in addition to being a #3JT mount and a brand new 36B5/8 which is rated 0.18 - 0.80 inches and has a 5/8-16 thread mount but is not drilled and counter sinked (how it ships) for a retaining screw. I guess Jacobs figures we can do that ourselves if needed. A friend has an old Jacobs 36 chuck with straight #3 Jacobs taper mount. Anyway the older Jacobs #36 which is rated 0.180 - 0.800 and my old #37PD both say Hartford, Conn on them. All of our chucks work just fine with the newer K4 keys. I wonder if maybe by some wild happening your chuck key is defective. Do you have easy access to another one? If not, I guess you might just buy one somewhere and hope it works. If you have any good power tool repair shops or industrial supply houses in your area, try to take the chuck or the tool with chuck there and see if they have any luck. I should add that a K4 key fits nice in my older Rohm chuck too. They aren't exactly the same, but they come very close. The Rohm key seems a pretty good fit in all of my big Jacobs chucks too. When it comes to chucks made in ROC or China, many of them are made to metric standards. Then Jacobs keys just don't fit them. I have yet to see any drill chucks with metric threads, but I bet such are made and out in the field.

                Have any of you ever seen the huge Jacobs K5 chuck key? It's for special super size chucks such as the 20N a super duty ball bearing chuck rated 3/8 - 1 inch and has a #5JT mount. The key is a T style with 7/16" pilot pin. This big boy cost some big $$$ so I really doubt any of us will be wanting one of them.

                I think I'm going to shut up and hope that Chic comes up with a good solution. If necessary do keep your eyes and ears open as now and then there are brand new unused or mint condition used 36B5/8 chucks for sale. I have seen a few over the past few months on Ebay going for $25-50. I know there's always the trust issue, but I doubt too many people with such a chuck are just in it for the money and are selling salvaged junk or are out to rip off people.

                Special note: My Jacobs 37PD is about 40 years old and is still in use today. The Rohm is about 15-20 years old and has only had light use so far. Both are quality industrial chucks. In an earlier post, I mentioned Supreme chucks. Some said Ridgid Supreme and some just Supreme. I hope sometime to obtain more info about them.
                Last edited by Woussko; 12-16-2006, 02:01 AM.


                • #9
                  Dang Woussko ,

                  I really appreciate you taking the time to type out all that information. I don't even know where to begin. That was sure a lot of usefull information. Unfortunately, I don't own any other chucks this large or any other keys. I can try to locate another chuck key around where I live to try it out, or do what you suggested and buy some from a retailer that will have no issue with me returning it if it doesn't fit. For some reason, I can't swallow having to spend almost $200 for something that is just going to be a project for me. I am going to mount this on a 1663-20 to spin the driveshaft of the lower unit of my old outboard motor (testing purposes, water pump seal).

                  That is strange how my chuck will not work with the key. I have attached some more pics of my key and chuck (has hole in it) for you to compare with yours. There are a few keys floating around on ebay, however I can't tell what will fit or not. Let me know if yours looks different. I am really curious as to what exactly is different. I see that on the MSC website, you can get a key that is not made by jacobs. I wonder if those would work.. Most likely, if I can't find an older key, a "will fit" key made by somebody other that Jacobs might be my best bet. I think on the McMaster Carr website, there are keys with Rohm equivelant numbers. I wonder who makes those? Yeah, last resort is pliers or a wrench but actually, the key I have now, if i pull it out of the pilot a little, will turn the sleeve ever so slightly before binding up. I understand trying to find a key for an oddball Asian import may be difficult, but this is an American made chuck made by a company who still makes chucks.

                  Again I appreciate the help and knowledge you and chic and anybody else can provide.

                  Attached Files


                  • #10
                    Here are some additional pictures of the chuck and key if anybody is interested. I didn't want to add too many attachments, so here are some links.



                    • #11
                      I have been through this stuff myself. I really am thinking that maybe all you really need is another Jacobs K4 key and that maybe something is messed up with the one you have. As for your idea of installing it on a Milwaukee 1663 drill that's going to be wild but it sure can be done. I might add that the 1663 is one nice 1/2" rated spade handle drill and especially with the electronic speed control. Please don't overload it. What size shaft do you need to rotate? If a 5/8" chuck would work, those don't cost near as much as a 3/4" one. This is just in case you can't find a key that works. Anyway, I really would try another K4 key and let's hope this one does work. I have some other old timer chucks and have never had the kind of trouble you seem to be having unless the key was either defective (it happens now and then) or it was worn out. Is your chuck drilled and counter sunk for the retaining screw? If you'll only need to run the drill in the forward direction then you can forget the screw. I will add that to remove the chuck later on and to remove the current chuck, get a good 3/8" long arm L shape hex key such as ALLEN or EKLIND which are USA made. Tighten the jaws on the short arm and then strike the long arm with either a rawhide or hardwood hammer or a block of wood. Never strike tools with a steel hammer. They can and do bust and you end up hurt. Please do not use the chuck key as a chuck remover tool. That's a good way to mess up the holes in the chuck body and also bust or bend the pilot pin on the key. Good luck with your project and please post updates. Now I'm off to see your pictures.


                      • #12
                        After seeing the pictures I have two suggestions for you. 1. Get a new genuine Jacobs K4 key and be sure it says Jacobs on the key. 2. Get a little fine steel wire brush that would be able like a tooth brush for shark's teeth. It looks like there is some crud in the chuck gear ring. Try to scrub it nice and clean. Even an old tooth brush might work, but a wire one with very fine steel wires will really work. They are very handy to have around anyway. Check good auto parts places and.or good hardware stores. To me in your new pictures which are good ones, it looks to me like the chuck key is a bit less than perfect condition. I have a feeling that a new key and cleaning the ring gear will have things working much better for you. The last resort is another chuck. Since I think (may be wrong) that all you really need is the 5/8-16 threaded mount and something larger than 1/2" capacity (please state diameter of what you want to rotate) that there may well be several other choices for you other than the big $$$ one. In a worse case since you only need this a day or two, call a few tool rental yards. I bet one of them may have a big 3/4" spade handle drill they can rent you. They are out there but you may have to hunt some. They won't have the nice speed control like your 1663 has. I own one and love that drill and bet you do too. I also happen to have an old timer 1850-1 big bad 3/4" spade handle drill that will rip my arms off if I'm not very careful with it. The 1854-1 is the like the son of the 1850-1.

                        By the way for fun guys, here are some pics of my old beast drill. The name plate is all messed up, but as best as I've been able so far using older Milwaukee parts lists, it seems to be a mid 60s - early 70s tool. This is the drill with the old 37PD Jacobs chuck with Hartford, Conn on it and my K4 keys work fine in it now that the chuck has been cleaned up and soaked in light oil and then allowed to drip for a week to let the excess out of it. Messy LOL
                        Attached Files


                        • #13
                          lama,tuesday i will send you some used keys in the mail,send me a pm of your address,in the mean time do me a favor,if you have a vise,flip the chuck upsidedown and let the collar of the chuck sit on the vise jaws,and with a soft hammer tap it a few times.the collar should move down a bit then see if the key will go into the pilot all the way.i had to do this a few times and this fixed the problem i had incountered with some bad chucks.
                          A fishing pole is the best cordless tool!


                          • #14

                            Good thinking about the collar being out of position. That would sure mess him up. Also, Thanks for your offer to send him some keys. I have a feeling soon his problems will be gone as long as he doesn't work his Milwaukee 1663 like a 1854.

                            Below are some good technical support documents from Jacobs about keyed drill chucks. I think all of us would do well to download and print them. The second one shows what Chic is refering to in regard to the collar sleeve.

                   (Chuck removal and installation)

                   (Basic repairing of keyed chucks)

                   (Accessories for keyed chucks)

                   (General info on the Jacobs product line. A good starting place)

                            Here are pictures of what I would like for Lama to clean (ring gear) and a little wire brush like I would try using. Any good stiff little brush should help. Look for the arrow that I added to Lama's picture. The ring gear needs to be kept nice and clean.

                            Lama, Please keep us updated on your progress.
                            Attached Files
                            Last edited by Woussko; 12-17-2006, 05:39 AM.


                            • #15
                              Wow you guys are incredible.

                              Woussko, The size of the shaft is exactly 5/8". Problem is, it has splines so I have to add a sleeve on it so that it can grip without damaging the splines. I don't plan on working it too hard. Long enough to see if the water pump seal is leaking. Hopefully gear oil won't surface. By the way, nice drill. Funny. Hopefully some day my tools will be "collectors" items and will be sought after. I will clean up the gear ring as indicated by your picture and tap it as chic suggested. By the way.. Good pdf links on chuck.

                              Chic. I really appreciate your offer to send me some keys. I'll PM you my mailing address. Also, whadda I owe you for the keys? Also, it did not occur to me that the coller could be incorrectly seated. Is there a limit as to how far it will move or can it be "adjusted" to allow for the correct backlash (if it applies)?

                              thanks guys lkl
                              Last edited by Lamakocklee; 12-18-2006, 08:42 PM.