Deckel FP2 X axis issue

efleming · May 7, 2016

Spent some quality time today on a machining project using my 1964 FP2. After a few hours of machining with everything working well, I stopped the mill to change tooling. Upon moving the X axis hand wheel, the table was no longer moving yet the wheel was moving freely and the screw is turning fine. It was about mid table when it stopped working. Milling operations were very light and nothing odd occurred. No binding or stress. Looking at drawings in the manual, it does not appear to have a shear pin that could have failed. Any thoughts before I pull it all a part? Looks like I have to make a tool to get the left side bearing seat unscrewed.

Best regards,

Eric

Danny VanVoorn · May 7, 2016

My first thought is the nut and or screw are badly worn and one or the other finally stripped the threads off of it completely. Question; was there a lot of backlash in that axis to begin with?
Dan

efleming · May 7, 2016

Backlash was very tight and within specifications. It went from working perfectly to not working between tooling changes. Very odd to me.

Plusminus · May 8, 2016

Could it be the nut has come loose? Can't think of anything else.

Greetings,

Peter

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AlfaGTA · May 9, 2016

Two potential sources of your trouble...Although not sure why this would happen "instantly" between tool changes.

The thrust bearing and adjusting nut have backed off and now you have lots of end float on the screw.....It rotates and is moving, just not the "X" slide.

Or as Peter suggests the lead screw nut itself has backed off. The lead screw nut is held in position by a threaded ring nut....Needs a tool really to tighten that nut properly....

Here is my solution to the wrench. Must have the ability to pass over the screw....Hence the cutout design.

Could also be as Danny suggests being stripped on the bronze lead screw nut, but this is less likely if the backlash was minimal before the problem cropped up.

Cheers Ross

efleming · May 9, 2016

Thanks for the suggestions guys. Just before heading out to work this morning I used drill bits to figure out the size of pin needed to make the tool to remove the threaded nut. 4MM is what I came up with. While doing this I noticed the threading nut spun and was loose. I plan on purchasing hardened 4MM dowel pins in the next few days and making a proper wrench for tightening.

So if I am to understand correctly, by having the threaded nut loose, the lead screw nut is now spinning along with the lead screw itself thus keeping the table from moving. Correct? I would have thought that as long as the threaded nut is still holding the lead screw nut from coming out of it's seat that there would still be some sort of lockup for the nut to keep from spinning. Is it held from spinning simply by pressure from the threaded nut?

I'm going to tear it all apart in the next few evenings to inspect and learn more about it. I really appreciate all the comments.

Best regards,

Eric

Danny VanVoorn · May 9, 2016

efleming said:
Thanks for the suggestions guys. Just before heading out to work this morning I used drill bits to figure out the size of pin needed to make the tool to remove the threaded nut. 4MM is what I came up with. While doing this I noticed the threading nut spun and was loose. I plan on purchasing hardened 4MM dowel pins in the next few days and making a proper wrench for tightening.

So if I am to understand correctly, by having the threaded nut loose, the lead screw nut is now spinning along with the lead screw itself thus keeping the table from moving. Correct? I would have thought that as long as the threaded nut is still holding the lead screw nut from coming out of it's seat that there would still be some sort of lockup for the nut to keep from spinning. Is it held from spinning simply by pressure from the threaded nut?

I'm going to tear it all apart in the next few evenings to inspect and learn more about it. I really appreciate all the comments.

Best regards,

Eric

If the nut retainer came loose and that is the only problem then you got off easy! One thing that is important on a FP1 is the location of the lubrication groove or hole; I would definitely look at the instructions for a FP2 on removing the screw for cleaning before doing that job. On the FP1 they want the groove or hole in the nut installed in the (down) 6 o'clock position so the oil flows in to it.
Dan

AlfaGTA · May 9, 2016

Don't believe there is any lube hole or groove to align on the FP2 lead screw nut. ......
There are no keys of dowels...held fast by compression from the retaining ring nut against a shoulder in the housing. You just need to tighten the retaining ring nut and carry on.

Cheers Ross

efleming · May 9, 2016

AlfaGTA said:
Don't believe there is any lube hole or groove to align on the FP2 lead screw nut. ......
There are no keys of dowels...held fast by compression from the retaining ring nut against a shoulder in the housing. You just need to tighten the retaining ring nut and carry on.

Cheers Ross

That is good news. Time to make a wrench. Thank you.

Best regards,

Eric

Danny VanVoorn · May 9, 2016

AlfaGTA said:
Don't believe there is any lube hole or groove to align on the FP2 lead screw nut. ......
There are no keys of dowels...held fast by compression from the retaining ring nut against a shoulder in the housing. You just need to tighten the retaining ring nut and carry on.

Cheers Ross

I can't speak for all but I have a brand new screw and nut sold to me as for an FP2. The nut on that one definitely has a lube hole in the side with a groove to get oil to it?
Dan

AlfaGTA · May 10, 2016

Danny:
You are most likely correct on the oil feed hole, having an example tells best.....Been eons since i made a replacement for my home FP2. Looked for the one i replaced last evening and no luck. I am sure i have it,
but who knows where it is now....

If the nut has a groove running around the OD of the nut , that connects with the feed drilling then i stay with my first advice at just tightening the ring nut to secure the lead screw nut.
Would bet that the groove is there to feed oil no matter how the lead screw nut was clocked.....

Cheers Ross

ballen · May 10, 2016

Hi Ross, Hi Eric,

AlfaGTA said:
Don't believe there is any lube hole or groove to align on the FP2 lead screw nut. ......
There are no keys of dowels...held fast by compression from the retaining ring nut against a shoulder in the housing. You just need to tighten the retaining ring nut and carry on.

I can confirm what Ross has written (specifically for Eric's machine, not in general!) because my FP2 is very close in its manufacture number to Erics (within a few weeks or months off the production line). The X-axis lead screw nut on my machine has no oil drain hole, no groove or alignment spline or anything. Held in purely by compression, exactly as Ross says. I am certain that Eric's machine is the same.

Cheers,
Bruce

Danny VanVoorn · May 10, 2016

Well, apparently we have confirmation that all FP2 X axis lead screws and nuts are identical and no changes were ever made in the design throughout their history? No changes ever in their lubrication systems?
Actually all I'm trying to do is put information out there that could make a difference so I don't have to hear pleas for sympathy later.
Dan

AlfaGTA · May 11, 2016

Danny:
Point taken, and i agree.
Cheers Ross

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