Bridgeport Clone, Vari-speed Head Woe

[Eddyde]

Today, while continuing the setup and contemplating the CNC conversion of my new mill, I decided to check the full range of all the axises. X 29.75", Y 12.25"... Then I turned the stop all the way south on the Z, pulled the quill lever, smooth all the way down Just about 5.25" of travel. Then I pushed the quill back and about halfway up CA-CHUNK dead stop! I moved the lever down-up again and again, it would not go past the same point, it was a solid metal to metal stop. I tried to engage and disengage the down-feed, no luck. I started to freak a bit thinking I somehow broke a tooth on the pinion gear or worse the rack on the quill! I never disassembled a B'port head or clone there of before, so it took me about two hours to get the quill out everything looked fine, not a chip or mark to be found. so I look up into the bore and see a "C" shaped cylinder wedged up near the top. I got it out and figured its the chip guard that covers the slot opening behind the depth adjuster... It must have come loose and jammed the quill. The way I see it working, It sits in a wider section, at the top of the bore, it has two tabs that catch under the heads of two screws 180 deg. apart in the top of the quill, when the quill is all the way up it slides inside the piece, when the quill is pulled down the tabs travel in two grooves milled in the side of the quill until they contact the screws then the quill pulls the piece down to cover the slot in the head. I guess the quill traveled too far down and bent the tabs on the piece straight then on the return, the screws hit the bottom of the taps preventing the quill from sliding inside and pushing it up till it hit the top of the bore. Okay problem solved, but not really because I could not figure a way to reassemble it without taking the top of the head apart... Well I didn't have the time to do that so just I put it back together without the piece.
So My questions to all you Variable -Speed Head Gurus:
1. Is the a way to install it without taking the upper head apart? (I know the answer but hope still prevails)?
2. How bad is it if I just leave the piece out?
3. Has this ever happened to anyone else?
4. is there a way to prevent it from happening again?

I greatly appricheate any help

Thanks

Eddy

 

[JimDawson]

I don't think so. The good news is that I have two torn down heads in my shop right now so I'll take a look and see if I can figure out a way to do it with out a complete tear down. I think you can split the cases just above the head without taking anything else apart. It will be tonight before I can get back to you on this one. I vaguely remember fixing this from the bottom without a complete tear down about 35 years ago.

It really needs to be in there, keeps the chips out of the spindle bearings.

 

[Eddyde]

Thanks Jim, As always you come though with the support!
I saw the pictures on alloy's post, looks like a good score. I guess tearing it down is not that bad, after all. I should probably do it anyway as even though the mill is NOS, its almost 29 years old. I'll get a new belt, clean & check everything out. I also figure I might find a place to stick the "encoder" for the Machtach. Till then, I'll be sure to keep the quill up and the dirt out, as much as possible.

 

[JimDawson]

I think that if you bend the tabs back, and kind of spring the sleeve into it's recess, then there is enough clearance to slide the quill back in and it should work. Pretty sure that's how I did it many years ago. More recently, I've always had the head torn down. Not really much of a job to take one apart.

Pulling the vari-drive motor can be a bit of a PITA, the pulley wants to close. Find a piece of 1 1/2 inch pipe, cut it about 1.500 long, then cut it in half lengthwise. Weld a small chain link or washer on it so you can hook it to get it out. Use this to keep the pulley halves open after you have pulled the belt tight. Now you don't have to try to fight with a block of wood and a prybar.

If you want to disassemble part of the head, then you can split it here. 3 nuts holding it. Just pulls right off. This allows access to the felt retainer on top of the quill.



Please post pictures if you decide to mount your tach pickup. I'm interested!

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[Eddyde]

Jim, Thanks again for all your help!
That might work, I'll give it a try if I don't just tear down the whole head. I probably will it's just that it will eat up a day of precious mill time... As I only get up to the shop on weekends and not even every weekend I wanna be makin' Chips instead!

The pulley tool is a great idea too, I will definitely make one. I'll post a thread of the Machtach install, for sure!

Best,

Eddy