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This month we will be installing the X&Y Axis lead screw nuts on a Bridgeport Series I milling machine. If you would like to watch the instructional video, please scroll down past the detailed guide.
1. We start on the left side of the table. The first step in this procedure is to remove the Hex Jam Nut, Ball Crank Handle, Dial Lock Nut, Dial and the Dial Holder. Once they are off remove the End Cap.
2. Once your are done on the left side move to the right side and complete the same procedure. If you have a power feed unit on this side you will need to remove it but the end goal is to remove everything connected to the X-Axis Leadscrew.
3. Now return to the left side and under the table you will see the Feed Nut Retention Screw and the Washer Head Screw. Using a long screwdriver remove the Washer Head Screw first then the Feed Nut Retention Screw (It may be hard to get out).
4. Now you can remove the X-Axis Lead Screw and Nut in one piece. They may not come out easy and you may need to tap them out from the right side using a Soft Blow Hammer
5. Once you have the Lead Screw and Nut out clean the Lead Screw and inspect the brass nut for any lubrication line holes. If you see a lube line hole duplicate the position of the hole on the new nut. Also shine a flashlight down to the nut to make sure the keyway is still intact. If it is not you will need to remove the Feed Nut Bracket and you will need to watch the Table/Saddle/Knee Disassembly video for instructions.
6. Install the new 2 piece Nut onto the cleaned Lead Screw by threading each half onto the screw. Once you have the nuts threaded to near the same position they were when removed bring the two halves of the nuts together and then back them off to where the keyway lines up (it should be slightly under .200″). At this point we are ready for reinstallation.
7. slide the Lead Screw and Nut back into the Feed Nut Bracket. You will have to make sure you keep both halves of the nuts lined up with the Keyway for proper fit. Once they are in go to the right side and pull the Leadscrew towards you to make sure the Nut is bottoming out.
8. You can now install the new Feed Nut Retaining Screw and Washer Head Screw into the Feed Nut Bracket. You can put a small amount of tension on the Retaining Screw but final adjustment with be done after the end caps are reinstalled.
9. Reinstall the End Caps and all the other components on the left side first and then the right side. Once everything is reinstalled you can adjust the backlash in the Nuts. You can watch our Backlash Adjustment video for instructions on this procedure.
10. The Y Axis disassembly is exactly the same as the left side of the table so follow step 1 of these instructions. If the Screw does not slide out you can reinstall the Ball Crank Handle and Hex Jam Nut to assist in giving you the force need to pull them out.
11. Look for any needed lube lines to be drilled in the new Nuts prior to reinstallation. Clean the screw and reinstall with the new Cross Feed Nut using the same procedure as steps 5 to 9 above.
12. If you have a missing Key you will have to remove the Feed Nut Bracket from the machine which will require the remove of the table. These steps can be seen in our Table/Saddle/Knee Disassembly video. If you can’t see the pin in the Feed Nut Bracket use a sander or grinder on the surface to smooth it to the point you can see the Key Pin
Use a small punch to remove the Key Pin from the Feed Nut Bracket.
Line the hole in the Key with the hole in the Feed Nut Bracket and insert the new Key Pin. If the pin is loose you may need to use locktite or epoxy to hold it in place. If the pin is slightly too long you can grind or cut it off if you would like (Feed Nut Brackets had slight size differences over the years).
