# South Bend 9 tool height measurement



## ericc (Jan 15, 2019)

Hi.  Most of the time I just estimate tool height, but for sweeping a taper, it is important to be pretty close to center.  At least within 0.01" is desirable.  I have one of those screw thread center height gauges for my other lathe, but the idea doesn't work so well after I swapped my tool holder for a large, squat quick change design.  There is very little flat area on the top of the compound to measure from.  A lip turned at the top of the gauge cannot approach the top of the cutting tool.  There are modified square designs which are a little more useful, but at some orientations, the tool holder almost completely obscures the top of the compound,  There seems to be no other decent place to measure from.  I tried dropping a plate over the ways, suported by the top Vee's.  The two are not at equal height, so the plate slopes, as verified by sweeping an indicator connected to the cross slide.  I noticed a video by Halligan bridging the two legs of the carriage with a bar, but this does not look level either.  It also seems kind of odd, since the top of the carriage is not flat.  Many of the import lathes have flat ways, so it is easy to measure these.  Would it be appropriate to use a bar with one or two feet on it, so it will register off the flats, or are these not really guaranteed either?  Or, get a bar with two little feet on it to contact the flags.  I'm not even sure if these are the same height.  Another way is to cut a plate with a flat on one end, and a vee notch for the other, and only catch the inside Vee way.  One would have to make this plate in a somewhat trial and error way, since there is little online documentation.  Does anyone have some good practice/designs?


----------



## Superburban (Jan 15, 2019)

I'm not sure how accurate you get, but I generally set the height, by lining up with the point of a dead center slipped into the tail stock.

When doing a facing operation cutting inwards, you can then see how far you are off from the center, as you approach the center. Low, you will see a little nib left on top of the tool point, high you will see it below the tool top.


----------



## ericc (Jan 16, 2019)

The only times I've had trouble with tool height were while parting (tailstock dead center method is adequate) and indicating tapers.  I have found that indicating tapers is pretty challenging, and have traced my error to the indicator tip being off center.  Of course, if you want to try and fit a few times, you can zero in, but it should be possible to nail it on the first try.

I just went to the shop to try the Halligan method (from Youtube).  The rounded feet on the carriage are sloped in both directions, and is nowhere near parallel with the cross slide ways.  Putting a parallel across these and indicating gives about 10 thousandths per inch slope.


----------



## jcp (Jan 17, 2019)

I used Joe Pi's method for my SB 9.


----------



## ericc (Jan 17, 2019)

Looks good. I'll see if I have the right size bar to get in there.


----------



## Dinosaur Engineer (Jan 21, 2019)

A quick way of getting tool setting height is to chuck a dowel pin and centre accurately. Then measure the height from the top of the dowel pin to the tool support area and then deduct half the dowel pin dia. The measurement may be done with height gauge , caliper or with gauge blocks and D.T.I. Once you have the measurement it makes sense to make a tool height block to this size.


----------



## ericc (Feb 17, 2019)

The problem with the South Bend lathe is that it doesn't have that nice flat way in the correct place like Joe Pie's. If you just place a bar across the vee ways, it won't be level. Level means that you can sweep an indicator in the toolpost with the cross slide and the reading will be constant. This means that you can put a height gauge or square and be at the same height regardless of extent.

This requires a bar with a vee cut and a flat groove with the correct depth. I tried searching all over the Internet for the dimensions, but all I could find was that the vee is 90 degrees. I measured the height to be about .280" but this is not quite correct, since the top is worn, and it would have to be done with pins. Instead, one can simply estimate and cut an approximate depth vee. As long as it is not full depth, it will work. Also it must be deep enough that the bar will slope downwards from the flat to the vee. Then, just cut the flat until the bar is level. Note that there is also a mathematical way to get this in one try, but it is really hard. Any takers? Anyway, the solution converges quickly. For example, if the bar slopes .016", cut it to .015" and it will be quite close.

Here is the finished bar.


----------



## ericc (Feb 17, 2019)

Hmmm. Had some trouble uploading.


----------



## SLK001 (Feb 17, 2019)

There is a scribe mark on the tailstock spindle put on by the factory at axis centerline.  Unless your TS is grossly worn, use that.


----------

