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View Full Version : Bridgeport worm gear cradle broken. What does it do?



jh628
09-10-2012, 05:17 PM
I am in the middle of stripping down and cleaning up an old Bridgeport and have found my first expensive broken part:

http://i.imgur.com/1zpj9l.jpg

I can see that it mates with the power down feed transmission part (shift sleeve?), but I do not see any wear marks on either the worm gear cradle or on the aluminum surface of the shift sleeve. The worm gear cradle costs around $200, so I am wondering if it may be worth it to try and salvage the one I have with a repair of some kind. I just need to get a better idea of what the broken piece does. Can anyone offer an explanation?

macona
09-10-2012, 05:25 PM
It engages the worm gear against the spindle for the power feed. If you dont need power feed dont worry about it.

Dr Stan
09-10-2012, 05:46 PM
It engages the worm gear against the spindle for the power feed. If you dont need power feed dont worry about it.

Only if you do not plan to use a boring head. If it were me, while its torn down, I'd try to repair the cradle by brazing it back together. I do not recommend welding with nickle rod in this case as you'd probably create more problems than you would solve.

You could also search around for a replacement on EBay, Lost Creek, and other suppliers of used BP parts.

Another possibility would be to buy a piece of Durabar and carve out a new one.

Before you braze it, bake it at 350 degrees F to drive out any oil/grease. Just make sure SWMBO is not home. :o

lane
09-10-2012, 09:10 PM
Search Bridgeport parts on E-Bay they come up and go cheap.here is one.
http://www.ebay.com/itm/BRIDGEPORT-MILL-PART-MILLING-MACHINE-WORM-GEAR-CRADLE-USED-WITH-PARTS-/160858094416?pt=LH_DefaultDomain_0&hash=item2573e3bb50

sophijo
09-10-2012, 09:36 PM
That broken area is sorta a "weak" design. I've done it! I brazed mine and it's working well. Welding crystalizes the cast iron. Check out Keith and Turnwright Machine works, on you tube to see how it's done.

Forrest Addy
09-11-2012, 05:24 AM
That should be repairable and possibly need no machining afterwards if the fracture is clean and no fragments are missing. Fit the fractures together to see if they "key" or "mesh" together. If they do clean the castings thoroughly, bead blast the fractures to remove surface carbon, and immediately after apply silver brazing flux. Assemble the broken pieces together wiring them or bracing them in accurate position.

I prefer Harris 56 silver brazing alloy. You can get a blister pak of silver and flux kit from your local welding supply

Silver braze takes about 15 minutes. Longer if you have to track down a bead blaster. There are vids on YouTube. You will know when you did a good job because the little silver test blob you apply suddenly disappears and silver winks at you from around the fracture. Be careful of cleanliness, fluxing, and heat. Screw up on any one item and the repair will most likely fail.

If the repair succeeds, you will most likely be able to use the cast iron part soon as the flux is removed (boiling water) and the mating parts test assembled. If fit doesn't happen right away a little fitting or clean up may be required. Pre-braze alignment is all important.

Dr Stan
09-11-2012, 10:23 AM
I prefer Harris 56 silver brazing alloy. You can get a blister pak of silver and flux kit from your local welding supply

Forest is correct. Silver brazing would be better than regular brazing for this repair.

John Stevenson
09-11-2012, 01:36 PM
This would be an ideal part to have made using a 3D printer.
Advantages are quick, cheap and by carefully selecting the correct grade of porous plastic you could make it 50 times better than the original Bridgeport unit.

A.K. Boomer
09-11-2012, 05:54 PM
If a 3dD printer would work then do it ---- not everyone wants to move 8 tons of dead beaver around in their shop to get the same job done....

Richard King
09-11-2012, 06:18 PM
I have had good luck buying Bridgeport parts from this company.

http://hqtinc.com/quillhousingassembly.aspx?page=2