Bronze Cross feed nut....ain't eating !!

[rafe]

Rafe,

I don't own an SB and ............. Same principle should apply to the compound.


Robert D,

Thanks for the information Robert, I am thinking of taking some of the play out and calling it good ....Before the nut stripped I had a little over a full turn of backlash
that is about as extreme as it gets before failure, and fail it did ....so with a new nut and screw It should be a drastic improvement and I am thinking I may put a thin spring washer to the right of the gear on the shaft (see shaft on blue box)...another sleeve goes over the shaft and mates with that flat surface,and the play shows up there when the dial is tight and on the dial when that area is tight, I don't see what that could harm I'll shoot for .005 play

 

[wa5cab]

Rafe,

I assume that by spring washer you mean Belleville washer. That will work and if the washer load rating is adequate will reduce the end float of the cross feed screw to zero. At least while not turning or facing. However... first, and a minor objection, it is always going to increase the effort (torque) required to turn the crank. And second, if you put the washer against the right side of the gear everything else will be OK while turning and while facing from outside toward center. But while boring or facing from center out, the cutter reaction force will be against the washer trying to flatten it more. And the actual "Y" (front to back) position of the cutter may not be where you think it is. So a spring washer might not be a good idea.

Robert D.

 

[rafe]

Hi Robert,I think the Belleville is a cone that's not what I meant, I was thinking of the bent type?? I am a little confused on the actual consequence of that gap and the effect it will have on the crossfeed screw and the crossfeed nut. I am trying to visualize it
and can't quite get it ...I have put the shaft together and may post a photo of that. Although you have got me thinking that it might be better to make a brass washer to close it down some, rather than put any force in there.

PS I re-read your earlier post and to clarify what I'm saying is, I don't think the gap I'm talking about will cause backlash on the dial, just a gap there (End play) or if pushed straight in will cause the gap to be next to gear, however I think it will play a part in wearing out the nut and should be minimized ....Regards

 

[wa5cab]

Rafe,

OK. I'm not sure but those may be called wave washers. In any case, the results would be the same.

Backlash in the cross feed screw is an aggravation perhaps but even if you reduce the feed screw end float to zero you still in setting the cutter position have to compensate for the nut to screw clearance by always approaching the dial setting in the proper direction. For turning and OD to ID facing, this is clockwise. For boring, it is CCW.

Robert D.

 

[rafe]

Well, it's back together and it works like a dream thanks to Jayhawk machine tool on E-bay for the fast shipping on the nut and mcmaster carr for the acme rod .......super fast shipping and all the advice on here. I don't foresee any problems on the crossfeed for a while and this will make threading a little quicker .....

 

[rafe]

Still going strong .....can't believe it's been over a year ....seems like yesterday

 

[projectnut]

MSC sells left hand acme threaded 1/2" x 10 tpi rod. It comes in different levels of precision. The real precise rod gets expensive. You only move the cross slide a small amount when finish turning a shaft to an accurate diameter,so I doubt you need real precision rod.

For the feed screw of a milling machine's table,it would be different. You might move the table a considerable number of inches to accurately drill holes.

They also sell steel nuts for the rod. Steel isn't the best answer,but for a home shop,I don't think you'd wear out the threads any time soon. Keep it oiled. The RPM on the cross slide is never anywhere near fast. It is the best way to get by cheap.

McMaster-Carr also sells different grades of left hand thread Acme threaded 1/2" x 10 tpi rod and left hand threaded Acme nuts. The highest grade aren't cheap, but the are high quality. Like the OP I waited just a little too long before replacing the rod and nut on my Seneca Falls lathe. I was able to buy the rod and a generic nut and make the necessary modifications on the mill.