How To Measure The Diameter Of A Spindle Taper?

Hello everyone, a follow up on my progress. I followed a procedure that Ken (4gsr) suggested. I put a dial indicator on my adapter plate and the run out was very small. I then put the dial indicator on the chuck and the run out was very high .005 - .010" So I took the chuck off of the lathe and un-bolted the adapter. The chuck has multiple bolt holes on the rear mount. When I drilled my adapter I used three of those holes for mounting.

I the ran a series of tests, I rotated the adapter plate one hole at a time, for mounting on the chuck. Mounted the chuck and ran a run out test. I then repeated the steps moving the adapter one hole at a time. By doing this I was able to reduce the run-out to .0035.

I have not got to the taper test yet, as I tried some other things first. I wanted to rough in my tail stock adjustment so that when I turned the relief cuts on the test bar, I could use the tailstock to hold the bar stock.

I adjusted the tail stock and made some test cuts between centers, both with aluminum and cold rolled steel, I wanted to see if between centers taper could be adjusted out.

I was able to remove the taper after adjusting the tailstock. The finish on the turned aluminum had a very nice finish. The finish on the cold rolled steel was very rough and had areas where the dimension appears to change, like indentations in the cut.

I when through and re-adjusted the cross slide and compound slide gibs. I also tightened the QCTP holder and tool holder and repeated the tests.

Still the same results with the cold rolled steel.

Note: My lathe is a 12 x 36" Clausing 6316 lathe. When I purchased the lathe it came with an AXA QCTP holder. I have some 3/8" carbide turning tool holders TAR.

I put a dial indicator on the tip of the carbide insert and then with both hands I tried to rock the tool holder. I was able to move the tool holder easily .0005"

This is with my bear hands, I can imagine the amount of force that is applied to the tool holder when cutting steel.

So my question at this point is? Is my tool holder tool small for my lathe? Should I upgrade to a BXA QCTP holder? Should I upgrade to 1/2" tool holders?

Or is there something I can do to remove the flex in the tool holder?

Thanks All

Joe
 
The Flex you are seeing is from the carriage, cross slide, compound, not the tool post.

I would suggest upgrading to a BXA later as some date in the future. Upgrading is not going to reduce the .0005" movement you are seeing.

Ken
 
Ken, How can I remove the flex in the carriage components.? I am assuming that this is what is causing my poor finish on the steel bar?

Thanks

Joe
 
Joe, what kind of steel are you cutting? If it is 1018 then getting a nice finish is going to be tough.
 
Joe Pitz said:
....... I am assuming that this is what is causing my poor finish on the steel bar?

Thanks

Joe
Click to expand...

That has nothing to do with poor finish. As Mikey said "what is the material that is being cut?". And you have to look at tool geometry too.
A 1018-1026 grade of material is tough to get a good finish just from a typical insert type cutting tool. For someone very new at this, you need to get you a piece of HSS and grind a cutting edge that has a higher than normal back rake angle. In fact a high shear type cutting edge is what you need for finishing to get a nice finish on low carbon steel next to polishing with emery. In fact, I use emery to finish the surface with at times when I'm having troubles getting a good finish. And I've been doing this for many years, too!

Going back to flexture in the tool post. I bet if you measured it on my half worn out lathe, that number would be closer to .005". And it don't stop me from getting good finishes on the stuff that I do.

Ken
 
Thanks Mikey and Ken, Since I am a total newbie, I really have no base line to go against. So it is good that you guys are providing me some good info in order to establish a
base line of expected results. The steel is Home Depot stock, El Cheapo in order to do some testing, more than likely 1018, as it looks real grainy.

I will pick up some more steel and try again. Yes I have been reading Mikey's HSS tool grinding articles and practicing, but wanted to get the lathe in order for turning.

Looks like I am almost ready, I have to make the test bar that Tony indicated and test for run out. Then I can continue my tool grinding exercises.

So much to do and so little time, my 8 hour a day job keeps on getting in the way of having fun. :)

Joe
 
Joe, you don't need a BXA on that lathe; the AXA is fine on a 12" lathe. If you use the right tools in the right way your tool post is plenty rigid enough.

You mentioned you're using a TAR inserted tip tool. I've not used this geometry but I looked it up and it appears to be a negative rake tool. Negative rake tools work great with a rigid set up but cutting forces are much higher than positive rake tooling. The nose radius of the insert has a big impact on tool performance and this is especially true with negative rake tooling. What is the nose radius on your insert? If it is larger than 1/32" you are going to have some challenges in harder steels, including crappy 1018. The bottom line is that your lathe will work much better with positive rake tooling and even better with HSS tools.

I'm not sure what the steel from Home Depot is but there is a good chance it is 1018. Ken is right - use HSS on this steel.

When you do the 2-collar test it is more important to have a piece that will have minimal deflection. You do not need steel for this; Aluminum works fine. It does have to be stout so use something in the 1-1/2" OD range. If I were you I would grind a sharp HSS tool for your test; it will cut with minimal deflection. Carbide tools are not meant to take very light cuts like those used for a 2-collar test.
 
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