# Knee adjustment fix of my Bridgeport



## Bernd (Nov 25, 2008)

Now that the Bridgeport is all back together again I need to fix the knee adjustment shaft and crank. As you recall I stated that there was a fix that needed to be done. Since I'm not restoring the machine to original condition I made my own crank and fixed the shaft to make it work.

First a couple of pics to show what is wrong with the knee adjustment mechanism. Apparently during a move in it's career the handle and shaft got bent. Here's what it looked like when I got the machine.






You'll notice that the clutch mechanism it partly broken, but still useable.





Here's a side view. It is noticeably bent.





In order to get the clutch off you need to use the collar behind the clutch to jack off the clutch. But I can't do that because the shaft is bent and would not allow the clutch part to come off. What to do? Well, I broke the rest of the clutch with a hammer. But there still was a small shoulder to get the nut over. At least I was able to get at the screws that hold the collar in that holds the shaft in. You can see the broken parts of the clutch on top of the ways.





I finally got the shaft out. Now what? Well I need to remove the gear and bearing so I can put the shaft in the lathe and turn off the rest of the clutch.





The shaft would not fit through the hole in the spindle of the lathe so I had to set up the steady rest. Here I've turned off as much of the rest of the clutch part as I could. That threaded part with the hole in it unscrews but I still need to get past that bent part, so I cut it off with the hack saw.





Here is what's left after trimming the clutch and cutting off part of the shaft.





Here's a pic of all the parts that go into the shaft of the knee adjustment screw, plus the broken handle.





Here's a close look at what the clutch part looks like on the handle. Somebody had welded the two parts together. While I was using it during the tear down to move the machine into the basement I broke the handle. So I welded it back together. Unfortunately I grabbed the handle to move the machine and broke it again. I decided not to fix it this time.





Here's what I did to fix it so I can use the knee adjustment. I decided I was going to make a part that would fit over the shaft like the clutch part and then have a hex on one end so I could use an ordinary socket wrench. The first part was to turn the round part and cut the flats for the hex. I used a piece of hex stock with a 1/2" hole and two set screws as my hex mill fixture.





Clamp the hex in the vise and cut one flat. Then turn in the vise and cut next flat until all six flats are cut. Then measure and take a finish cut.





And hopefully you come out with a part looking like this.





Next I cut the part down so about 1" of hex stuck out. Then back in the lathe and the larger diameter had a hole bored into it to fit the shaft were the clutch as attached to. Some Loctite was added and the part placed on the shaft.





And here is the completed fix ready for use.

Next will be a set of new soft jaws for the vise and the DRO has a few digits that are not working. Other than that the mill is working fine. I'm quite happy with the machine.

A friend of mine offered to make a rotary phase converter for me for $35. I couldn't turn that down. So I guess the 7.5HP rotary I was going to make will be on the back burner for now.

Also now I'm going to work on some tooling for my machines. I've noticed that I lack sorely on some tooling to make parts.

If your wondering where all this started take a look here: http://www.homemodelenginemachinist.com/index.php?topic=3080.0

Regards,
Bernd


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## Lew Hartswick (Nov 25, 2008)

I think I like the hex better than the 9 tooth dog clutch. I'm sure it will jump out a lot less. 
But I would make a "real" crank instead of using a ratchet handle. 
  ...lew...


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## rake60 (Nov 25, 2008)

Looks Great Bernd!

I like the idea of the ratchet myself.
I feel like I have more control on the crank when pulling than pushing it.
With the ratchet every motion can be a pulling motion.

Well Done! 

Rick


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## dsquire (Nov 25, 2008)

Bernd

Damn smart way to mill a Hex. I learned something new again today that I can use.

cheers

Don


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## Bernd (Nov 25, 2008)

Lew Hartswick  said:
			
		

> I think I like the hex better than the 9 tooth dog clutch. I'm sure it will jump out a lot less.
> But I would make a "real" crank instead of using a ratchet handle.
> ...lew...



Real crank coming up later. This will have to do for now. Need to get the required parts to make the "real crank". Stay tuned

Bernd


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## Bernd (Nov 25, 2008)

dsquire  said:
			
		

> Bernd
> 
> Damn smart way to mill a Hex. I learned something new again today that I can use.
> 
> ...



Here's a few more tricks to add to this. Make the hole large enough and you can use a sleeve with a slot cut in it to sleeve down to smaller diameters. Also you can use a square jig for making square cuts. But, and this is a big but, make sure the hole in the center of the part. 

Perhaps a thread on making these jig's is in order.

Bernd


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## kvom (Nov 26, 2008)

Hex collet blocks are pretty inexpensive. I'm going that route. Your solution looks very practical, assuming you have some hex stock laying about. I'm surprised that the shaft didn't deflect with that much sticking out of the vise and no tailstock support.

The ratchet looks interesting, and I'd like to hear how it works in practice. I believe that for moving the table an amount that needs multiple turns the crank will be preferable. I just spent a session in the shop where I needed to switch between using R8 collets and a Jacobs chuck, and there was a lot of cranking each time.


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## Bernd (Nov 26, 2008)

kvom  said:
			
		

> Hex collet blocks are pretty inexpensive. I'm going that route. Your solution looks very practical, assuming you have some hex stock laying about. I'm surprised that the shaft didn't deflect with that much sticking out of the vise and no tailstock support.



The hex piece is about 2" long and has 2 1/4-20 set screws to hold on a 1/2" dia. bore. Also I took very light cuts with a very sharp roughing mill cutter. There was no chatter.
I've also made a few alunimum sleeves with a smaller dia. to fit the hex block for holding smaller dia. parts. Make sure you split the sleeve length wise. Another block I use is a square one so I can cut squares or wrench flats on a piece of round stock.



> The ratchet looks interesting, and I'd like to hear how it works in practice. I believe that for moving the table an amount that needs multiple turns the crank will be preferable. I just spent a session in the shop where I needed to switch between using R8 collets and a Jacobs chuck, and there was a lot of cranking each time.



Cranking the knee down goes fast since all you need to do is use one finger to swing the ratchet. Going up is another story. I plan on making a crank for it after getting my fingers wacked a few times by the ratchet. :
This Bridgeport came with quick change tooling, you can see that in the 10th pic down. I've also included a pic of the tooling below. The end mill is a 1/2" dia. spiral roughing mill 3.250" long. So not much cranking to change tooling.






Bernd


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## Lew Hartswick (Nov 26, 2008)

kvom  said:
			
		

> I just spent a session in the shop where I needed to switch between using R8 collets and a Jacobs chuck, and there was a lot of cranking each time.



Boy isn't that the truth. I have been doing some work that required : 1/4 mill cutter, #3 center drill,
 #7 twist drill, and a 1/4-20 tap. Which would have been multiple back and forth between collets and
chuck. SO! I made a #7 drill with a 1/2" shank and already have the tap holders with a 1/2" dia holder
(as Marv has shown) 
The op. went: 1/4 collet - mill cutter, #3center drill ( 1/4" dia) switch to 1/2 collet - #7 drill , tap holder
DONE. All with collets. In the future when I need a drill in the middle of an op that uses collets I'll make
another "adaptor" as required. 
  ...lew...


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