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Prepping for Rulon on a Pratt Whitney Model C

Mark999

Aluminum
Joined
Mar 29, 2018
Hello,

I'm probably overthinking this, but I want to be very sure before I set up the mill and cut the saddle slide ways for Rulon application. The machine is a 1941 Pratt Whitney Model C 14x54 toolroom lathe. The bed is scraped and now it's time to prep for Rulon to bring the apron up to its original position.

I have the apron lifted up into its nominal position by sweeping the feed reverse rod from the fixed tailstock end fixture. The top of the apron is level in both directions and a small amount of lash is present on the rack. Once the saddle is installed, I checked again the level in both directions and it checks out good; level across the cross slide and matches the bed in the long axis.

PW14x54Saddle.jpg

What I'm planning to do is machine down .057" and use .0625" Rulon with a .010 scraping allowance.

DSCF8015.jpg

Now the Vee way is the most worn and needs this amount cut away, but the flat way is not as bad. For consistency I was thinking of machining .057" off both so the same amount of Rulon would be left.

Thanks for your attention and if there is any info not provided let me know and I'll do my utmost. Is this the correct course of action?

Thanks,
Mark
 
I trust you're factoring in that .057 taken off perpendicular to the face of the V-way doesn't move it .057 in the vertical direction. A little trig required, but say so if it's not obvious.
 
You're right and I need to keep that straight. I want to remove .057" perpendicular to the face which is .081" in the Z direction on the mill. That way the Rulon (.0625+.005-.010=.057) will bring the height to the desired target.

This .057" is from a zero out in space that has already been worn away. I was thinking on touching off on a known worn area and call that -x from zero.

I really don't want to F this up. Thanks for the help.
 
Let me make sure I'm following.

Referencing your first photograph, I thought you had leveled the carriage and checked it perpendicular to the ways, THEN used feeler gauges to check clearance to the front and back side of the V-way, four places, and then the clearance to the flat way in back.

So on the left front you've got the number .047 which is the greatest wear you've found. It would be logical then that you could use .062" Rulon and take .057" off that face of the saddle V. Then to keep things even you'd take the same amount off the front side of the saddle V-way and go from there. Is that right so far?
 
Tri Star sells .047 Rulon 142. You have to figure the glue thickness. Usually we figure .003 to .005". I would also check to make sure the saddle ways are flat. You could also use Moglice too. They say .060" is best but they sometimes put on less.
 
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Let me make sure I'm following.

Referencing your first photograph, I thought you had leveled the carriage and checked it perpendicular to the ways, THEN used feeler gauges to check clearance to the front and back side of the V-way, four places, and then the clearance to the flat way in back.

So on the left front you've got the number .047 which is the greatest wear you've found. It would be logical then that you could use .062" Rulon and take .057" off that face of the saddle V. Then to keep things even you'd take the same amount off the front side of the saddle V-way and go from there. Is that right so far?


That is correct except I have not checked perpendicularity to the spindle, only referencing the apron in its nominal position. Tonight I can get some feeler gauges in the back to check this relationship with the bed.

Later when the Rulon gets scraped, I'll check its relationship with the spindle. Shooting for .0004" concavity.
 
That is correct except I have not checked perpendicularity to the spindle, only referencing the apron in its nominal position. Tonight I can get some feeler gauges in the back to check this relationship with the bed.

Later when the Rulon gets scraped, I'll check its relationship with the spindle. Shooting for .0004" concavity.

<edit> Relevant to the question of cross alignment

It just raised a question in my mind, looking at the clearances you find. In use, the carriage is pulled from the leadscrew or feedrod and resistance to movement is at the tool closer to the spindle centerline. Meaning the forces are skewed. That skewed force would tend to twist the carriage and put most of the wear on diagonally opposite points of the V-way, specifically the left outside and right inside. Since you're showing the most wear at the left inside surface it stood out as unexpected. Meaning, depending on your setup on the mill, you might take off too much in one place to scrape into alignment with the allowance you have on the Rulon.

I'm not asserting you're in any trouble, but it was just kind of a sniff test to see if all the facts smelled about right.
 
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