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Power cross feed on Myford Super 7

Cross feed jammed

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Dusty07/12/2018 13:21:21
453 forum posts
8 photos

Any ideas guys, my power cross feed has jammed. I used it yesterday without problem, I have just been into the workshop and faced off a piece of material by hand when lo and behold my power cross feed kicks in. I stop the lathe and find that the knob for power x feed is in and I am unable to move the cross slide. Has anyone ever had this problem and what are the probable causes. I would like some idea before stripping the apron from the lathe.

JohnF07/12/2018 14:48:44
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695 forum posts
72 photos

Never had the problem but just a thought depending on the cross slide position if you remove the compound slide you should be able to see the transfer gear , other than that it’s a strip down

John Haine07/12/2018 15:35:12
2184 forum posts
122 photos

I had precisely this problem a few years back, happened intermittently. I can't remember what I did to un-jam it, probably had to remove the feedscrew with its nut and bracket and the drive pinion comes off with it. Then you can jiggle things to release the clutch I think.F and feed levers and you should be back in business. I hope this helps.

Shortly after that I converted to CNC, problem will not recurr!

steamdave07/12/2018 16:22:10
387 forum posts
31 photos

Has it jammed because you have wound the cross slide out too far and the lead screw has become disengaged and you can't wind it back in?

If so, you can restore normal operations by trying to wind in the cross slide and at the same time winding the leadscrew handle forwards and backwards maybe half a turn each way. It may well take several attempts, but it will eventually go.

Dave
The Emerald Isle

Edited By steamdave on 07/12/2018 16:22:55

ega07/12/2018 17:41:26
951 forum posts
82 photos
Posted by steamdave on 07/12/2018 16:22:10:

Has it jammed because you have wound the cross slide out too far and the lead screw has become disengaged and you can't wind it back in?

If so, you can restore normal operations by trying to wind in the cross slide and at the same time winding the leadscrew handle forwards and backwards maybe half a turn each way. It may well take several attempts, but it will eventually go.

Dave
The Emerald Isle

Edited By steamdave on 07/12/2018 16:22:55

This sounds like the problem suffered by GHT; the answer, no doubt similar to yours, is in his book.

Dusty07/12/2018 18:34:07
453 forum posts
8 photos

It appears that on the drive gear for the cross feed there is a plate secured to it with three countersunk socket screws, one of these had come undone and was sticking out by 2mm. I was unable to find any other problems and can only presume that the csk screw was the culprit. I have almost got the lathe back together again and will see if I have solved the problem in the morning. It is amazing the amount of rubbish that had accumulated in the saddle and apron despite regular cleaning. I think I will try it out before making final adjustments.

Chris Trice07/12/2018 21:14:26
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1034 forum posts
2 photos

Mine now has a mechanical stop incorporated into the mount for the DRO that stops the cross slide being withdrawn to just before the point where the power cross feed gear disengages but before that, I simply scribed a straight line on the side of the cross slide and the top surface of the saddle in a convenient spot so that when the two lines met, I was one turn away from it disengaging. You can do the same on the topslide too.

Dusty08/12/2018 09:24:17
453 forum posts
8 photos

I must add that my cross slide was not withdrawn that far it was in fact approx only 40mm withdrawn so that was not the problem. I will report back later on my results, that is after I have taken SWMBO shopping.

John Haine08/12/2018 10:15:46
2184 forum posts
122 photos

Dusty, when you reassemble it may be a good idea to apply the alignment technique I described in case it wasn't (just) that screw.

Dusty08/12/2018 15:46:26
453 forum posts
8 photos

All is well, I have re- assembled the apron and carriage, a bit of a faff as I did not remove the leadscrew. Tried and tested works perfectly. I am at a loss to explain why the loose screw had the effect it did, but I can find no other cause.

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