Lathe Cross Slide Problem

[PixMan]

Any progress, Ed? Just curious, no push.

[EdK]

(05-27-2014, 08:06 PM)PixMan Wrote: Any progress, Ed? Just curious, no push.

Unfortunately no. Since they were forecasting rain for Monday, I had that day reserved for working on the lathe but my sister called me on Sunday evening inviting me over to a barbeque on Monday. I assumed it would be cancelled because of the weather but the rain held off until the evening so I didn't get to work on the lathe at all. I've been thinking about what's the best way to measure for the center of the nut height to make sure it's in line with the lead screw height and so far I haven't come up with a good method. I'll post a question about it once I get started. That probably won't happen until next weekend since this week looks to be booked with other tasks needing to get done first.

Ed

[PixMan]

I'm confused about that, Ed, because you had given me a dimension of 0.926" from the flat bottom of the nut to the thread center line. That's exactly what I made it. I assumed you had already figured out the dimension when you put it on the print.

[EdK]

(05-28-2014, 07:10 PM)PixMan Wrote: I'm confused about that, Ed, because you had given me a dimension of 0.926" from the flat bottom of the nut to the thread center line. That's exactly what I made it. I assumed you had already figured out the dimension when you put it on the print.

Ken,

I think in one of my posts I stated I had added about .020" to the dimension so I could tweak the height by either skimming or shimming. I'm not that skilled in these types of measurements so I thought it best to add a bit to the dimension for tweaking after I figured out how to make the measurement accurately. I'll figure it out. I just need to take the time to think it through.

Thanks Ken.

Ed

[Mayhem]

So Ed, am I reading this correctly and the post above roughly translates to:

"How do I measure the centre of the nut height relative to the bottom of my cross-slide?"

[EdK]

(05-29-2014, 09:48 AM)Mayhem Wrote: So Ed, am I reading this correctly and the post above roughly translates to:

"How do I measure the centre of the nut height relative to the bottom of my cross-slide?"

Close but not quite. Well, maybe it is right in a roundabout way. I need to measure from the center of the leadscrew mount to the top of the cross slide. The bottom of the cross slide is a raw cast iron surface and no good for taking measurements off of. I'm better at drawings than at words so I'll draw up how I think I need to go about measuring it and you guys and let me know if I'm going down the wrong path.

Ed

[EdK]

See attached sketch. I think this is what I need to do to get the measurement for the lead screw nut dimension. I need to get the measurement for dimension ?1 and then get the center of the lead screw nut, dimension ?2, to that same dimension.

Ed

   

[PixMan]

You need a few more dimensions. You had shown a photo of the underside of the cross slide, and I believe you had milled a rectangular landing spot where you will fasten the nut.

What is the thickness between the top of the cross slide and the surface you milled? Add that thickness to the 0.926" that I made the nut, and you have the "?2" dimension to compare to "?1".

[EdK]

(05-29-2014, 07:32 PM)PixMan Wrote: You need a few more dimensions. You had shown a photo of the underside of the cross slide, and I believe you had milled a rectangular landing spot where you will fasten the nut.

What is the thickness between the top of the cross slide and the surface you milled? Add that thickness to the 0.926" that I made the nut, and you have the "?2" dimension to compare to "?1".

Ah yes, good point Ken. Hmmm, it seems one would need a deep throat micrometer to get that dimension. I don't have such a tool.

OK, rethinking this, I think I can use a depth micrometer to get that ?2 dimension.

Now I just need to figure out how to get the ?1 dimension to compare to the ?2 dimension.

This is the main reason I created this forum. So dummies like me can get answers to basic questions without being ridiculed.

Thanks guys. I'll figure this out with your help.

Ed

[PixMan]

Do you have a depth micrometer that would span the dovetail on the bottom? if not, use a parallel (bar) of a known dimension and measure down to the bottom of the pocket you milled (and subtract the thickness of the parallel if you used one.) Measure with a micrometer or height gage the overall height of the cross slide top. Subtract, you got the thickness. You need that anyhow to get the right length of engagement on mounting screws.

Add thickness found to the .926" existing thread center line. Now you have the starting "?2" dimension.

Now measure the depth from top of cross slide to existing lead screw (top of it), add 1/2 the screw's diameter and you have "?1" dimension.

What is the difference between the two center line lengths? Mill down or shim up as required.