Cross slide nut blueprint help

[3strucking]

I need to make a new cross slide nut and I have a print of it. I have no formal training so I want to see if I can get some help reading it. I understand most of the measurements but I need help. Which measurement is the bore and which is the thread spec? See attached image.

 

[Canus]

Your drawing has a mix of Metric and Imperial dimensions. Looks like Acme 8tpi with 10.325 mm minor diameter.

 

[Technical Ted]

My guess is it's a metric (import made) machine that uses imperial dials/lead screws so I agree that it is a mix of metric and imperial dimensions.

Ted

 

[Alexander McGilton]

Do you have the existing lead screw to the lathe, and do you intend to re-use it?
Either way it is going to be worn so you may well replace it. Duplicating or finding a T13.5-1/8" as it says in the fine print would be a challenge. Considering that the pitch diameter is not specified. You may well go up a size to 5/8-8 acme and make a corresponding nut.

 

[3strucking]

I have not taken the cross slide off the machine yet.

 

[sdelivery]

Your drawing shows a Left Hand Thread 1/2 inch 8 pitch ACME lead screw nut.
The angle is wrong to be a trapezoidal screw (metric)
3 foot Fully threaded peices are available from mcmaster carr but I don't know if they have a left hand bronze nut

 

[RJSakowski]

McMaster Carr has both the LH threaded rod and bronze nuts in 5/8-8 size. The nut has enough meat that it can be adapted to meet the drawing spec with the addition of a saddle shim. Definitely easier than trying to cut the internal thread. The thread fit is a class 2G which may have more backlash than you would want. You can use a split nut configuration to bias the thread and provide a better fit.

 

[Beckerkumm]

It was recommended to me to replace a cross slide screw with a precision screw rather than a rolled one. They are more expensive and generally more difficult to find. I'd be interested in thoughts although a DRO can mitigate the lack of precision. Dave

 

[3strucking]

On the top left drawing, what is the 1.5x15 measurement and T13.5x1/8?

 

[Technical Ted]

My interpretation is the 1.5x15 is a 1.5mm x 15 degree chamfer. The T13.5x1/8 is a 13.5mm (.531") diameter thread with a 1/8" lead which is 8 threads per inch. It must have either .125" or .250" dials depending on whether it reads off the radius or diameter. In metric, thread pitch is specified by the distance between threads. In imperial, we specify threads per inch. I've seen metric machines made this way in the past. Everything is metric expect for the pitch diameter which is imperial so they can have imperial reading dials.

If making both the screw and nut, you can pretty much, within reason of course, make the thread diameter whatever size you want. The important thing for a lead screw is the pitch (lead). Grind the tool to match an acme thread gauge for the desired pitch and match the nut with whatever diameter you select for the screw. I typically make the nut first and fit the screw to match for fit.

Ted