PM1236 setup quesiton and pics of my first cuts

[Ray C]

On that one measurement, did you mean 0.0015 or 0.00015?

Anyhow, it seems like you're on the right track but, some pictures of what you're doing would help us know for sure...


Ray

 

[Morgan RedHawk]

I dunno Marco, I just cant decide between the white skirt and the white boots...If I were to wear both together, I might look silly...

Ray, that was 0.00015 (zero point triple zero one five)...which is why I did it twice.
Here are the readings and calculations if you want to check my math:

	Tailstock Collar	Headstock Collar
Collar diameter	1.9742	1.9725
1/2 collar diameter	0.9871	0.98625
High reading	0.0115	0.0075
Low reading	0.0040	0.0060
Average	0.00775	0.00675
Corrected Avg (Avg - 1/2 collar dia)	-0.97935	-0.9795

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the difference between the corrected averages is 0.00015 which is why I was surprised and figured I must have done something wrong and did the measurements and calculations again, coming up with the same final result.

For reference, when I first machined the bar and made the collars I used the steady rest to face and center drill. Next I put the bar on the live center without disturbing the end in the chuck. I machined the bar and collar locations and then removed the tailstock. Next, I set the machine to the slowest speed and the finest feed. I machined the collars down without moving the cross slide until I was getting a cut all the way around both (I have some runout issues to deal with, but that will be for another day). It took quite a few passes of 0.002" each until I was getting a steady "shhhhhhhhhhhhhhhhhhh" on both collars. Once I was sure the tool was contacting the entire circumference of both collars, I started the test cuts. According to the RDM instructions, if you suspect the diameter of the bar does not have a consistent diameter, you are supposed to correct it. I figured the tailstock was out of alignment, so I checked the diameters of both collars with a mic, and figured them into my calculations. The first time I calculated it, I used the proper significant figures for the accuracy of my measuring tools, and came up with an difference of 0.000. That is why I decided to read between the lines (on the indicator) to see what I got.

I will take some pics tomorrow and upload them so yall can see my setup.

 

[Ray C]

I dunno Marco, I just cant decide between the white skirt and the white boots...If I were to wear both together, I might look silly...

Ray, that was 0.00015 (zero point triple zero one five)...which is why I did it twice.
Here are the readings and calculations if you want to check my math:

	Tailstock Collar	Headstock Collar
Collar diameter	1.9742	1.9725
1/2 collar diameter	0.9871	0.98625
High reading	0.0115	0.0075
Low reading	0.0040	0.0060
Average	0.00775	0.00675
Corrected Avg (Avg - 1/2 collar dia)	-0.97935	-0.9795

<tbody>
</tbody>

the difference between the corrected averages is 0.00015 which is why I was surprised and figured I must have done something wrong and did the measurements and calculations again, coming up with the same final result.

For reference, when I first machined the bar and made the collars I used the steady rest to face and center drill. Next I put the bar on the live center without disturbing the end in the chuck. I machined the bar and collar locations and then removed the tailstock. Next, I set the machine to the slowest speed and the finest feed. I machined the collars down without moving the cross slide until I was getting a cut all the way around both (I have some runout issues to deal with, but that will be for another day). It took quite a few passes of 0.002" each until I was getting a steady "shhhhhhhhhhhhhhhhhhh" on both collars. Once I was sure the tool was contacting the entire circumference of both collars, I started the test cuts. According to the RDM instructions, if you suspect the diameter of the bar does not have a consistent diameter, you are supposed to correct it. I figured the tailstock was out of alignment, so I checked the diameters of both collars with a mic, and figured them into my calculations. The first time I calculated it, I used the proper significant figures for the accuracy of my measuring tools, and came up with an difference of 0.000. That is why I decided to read between the lines (on the indicator) to see what I got.

I will take some pics tomorrow and upload them so yall can see my setup.

You must have spent all darn day messing with that... Good, that's what it takes.

Those are pretty good numbers -but the proof is in the pudding. You'll get very close to knowing how it cuts when you do the stand-alone 2 collar test -and even that has it's frailties because nobody in their right mind will ever do a production cut that way. It is a good test though. Spin a shaft between centers (once the TS is adjusted properly) and THEN you will know. -Don't worry, it will be fine and you'll get good results. Just make sure you use a shaft big enough in diameter so it doesn't flex under cutting pressure.

Here's a secret... For 99.9% of anything you do, you won't need a shaft any better than +/- 1/2 thou over 12". The "only" times you need to worry about tenths is if you're cutting a bearing bed on a shaft -and that is rarely ever longer than 1.25".

Do the job right but don't get obsessive about "perfection" because that gets in the way of actually finishing something. It's all about error-stack up.

Ray