K&T 2CH/205CH guys -- is there an easy way to get the Y-axis screw out?

Hi guys,

I have a healthy bend in the Y-axis screw of my early '60's 205CH (same as 2CH?). I'd like to pull the screw and straighten it. Is there an "easy" way to get it out and then back in again without doing a major teardown?

Thanks, and regards.

Mike

Bump . . .

Hi Mike,

I'll give you a bump for now -- it is late and I am tired enough that I might not make sense . . . more tomorrow or the next day.

I presume by "Y" you mean the saddle feed along the knee -- what K&T call the "cross feed screw". I have my 2CH apart including the lead-screw. It has been long enough since I took it apart that I would like to take a good look at it before I get you mixed up.

Archie

Hi Archie,

Yes, the crossfeed. The end 4" or so has the bend.

Regards.

Mike

Maybe, maybe not . . .

Mike,

Does the bent portion of the screw need to go through the nut? (& will it go through?) While you might be able to remove the capscrews that are holding the cross-feed nut, but there is also a dowel pin that will not let it move much.

So that we are all on the same page, here is a piece clipped out of my 2CH parts manual (I do not know if a 205CH is identical):



Part #56 (cross feed bearing clutch brg carrier) holds the two opposed tapered roller bearings that take the cross feed screw's axial thrust. I have not yet removed this carrier from my mill's feed distribution box -- the removable portion of the front of the knee. From the illustration. I think you can remove the screw by removing the bearing carrier. The main problem is that there are so many things stacked on the screw's shaft that could fall out of alignment -- I think it would be difficult to put the screw back in place. In transmission work these sorts of situations often occur and a dummy shaft is used to keep the parts in alignment while the real item is out of place. This dummy tool would only have a few features that were necessary -- the minor diameter of the splines and the ID of the bearings. The dummy would push the screw out from the rear and during re-assembly, the screw would push the dummy out -- some "english" probably being required to get everything to fall into place. (Most of the dummy's features should be chamfered to make this easier.)

Having theorized, I must say that this is not something I would recommend unless one was a K&T mechanic and expected to have to do this more than once. Even if the procedure would work with a straight screw, I am concerned that the bent screw might make things tough.

Have you considered doing at least a partial straightening before disassembly? Do you have an idea how the shaft got bent?

I seem to be raising more questions than I am answering . . .

Archie

Hi Archie,

Thanks for the scan. I think I'm going to try an in-situ fix to at least restore smooth motion to the end of the travel. The end of the screw is fairly out in the open, so I'm going to make up a jig to get around it and put some force on it.

How did it get bent? The crossfeed trips on my machine are all janked up. Not sure how much of that is from some meathead beating on the trip block at some point, getting it either out of position or out of action. Either way, the crossfeed doesn't trip out prior to the saddle interfering with something. I forgot about that while doing a cut, and waited for the stop to trip out the feed, which it didn't. Being at the end of its travel and having its entire length in free space, the screw got cocked and then bent before the feed clutch disengaged.

All this seems to be complicated by the mono-lever box my machine has on it, which apparently reduces both the saddle and table travels. Sort of wish that wasn't on there now, as it requires some special dogs to get it to do its thing, which the machine didn't arrive with, so I can't use it.

Regards.

Mike

Direct approach . . .

Mike,

I would definitely try the in-situ approach -- you may not be able to make it perfect, but you certainly should be able to improve it. With some tooling to allow you to control the amount of force and location of where force and support is applied you should be able to approach straightness without overshooting or adding bends.

Good luck,

Archie

Remove the CF handwheel and the knee crank handle, remove the directional shifters, remove the CF dial assembly and maybe the knee dial, remove part #81, and you may have to remove a few other parts. Remount the handwheel and clutch assembly, lock the saddle, and turn the screw out. You'll know if you're going in the right direction. The bearings and the rest of the stuff on the screw will stay in the knee; some of the pieces may move, or drop, out of position making reassembly a bit difficult. This is not hard to do. Once you get in there you'll see what you need to do.
Part #56 is going to have to be removed also. IIRC, it should come out when you start removing the screw, if you can't get it out prior.

You will most likely have to make a new screw. I tried to straighten a bent screw with no luck several years ago, but I din't use heat. I do believe they are heat treated.
Harry