# Colchester MK1.5 13x36



## Big Bob (Dec 24, 2012)

My original manual says height from top of top slide to center line of lathe is 1-7/8 inches. My square tool post cuts a little high (Enco... not the sales internet guys).  Best I can measure is 1.74 to 1.75 inches. Used 0.001 height gage and tenths micrometers on around half inch bar sticking out 3 inches from chuck and less than 0.001 TIR. Trying to eyeball to mark on tail stock for center is 'iffy' to a few thou. Anyone have experience measuring center on lathe or with the square tool post. The toolpost appears to have up to 0.009 height difference from the bottom of the cylinder that goes on the top of the top slide. Bob


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## Tony Wells (Dec 25, 2012)

Not quite sure I am following, but can't you use the height gage to measure from the bottom of the 4-way to the top of the rod and subtract half the measured rod diameter? Or to get to the top of the slide, same thing....top of the rod to the top of the slide and subtract half the rod diameter? Or am I missing something?


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## Big Bob (Dec 26, 2012)

I used height gage & half rod diameter. I get diffrent heights same tool on bottom of slot in which tool sits for each of the 4 positions up to about 0.009 inches.  This also varies with different times I install the post with different values at the 4 positions. 
I took the tool post apart. From base of cylinder to its top ( on which the square holder rests on several spring loaded balls in the cylinder), I measure a height difference around it go 0.0055 in. 
  I suspect problem is that previous owner machined cylinder base not perpendicular to it's center. 
  Looks like I should true up in lathe ( Colchester MK1.5 Colchester ) and take couple thousandths off high side; and build up thou or so on low side (eg Rocklinizer etc deopsiter).
  There appears to be up to 0.003 variation in square holder's base to where tool sits, but cylinder locates in a cylindrical bore, which I have not yet measured. Perhaps a 123 block to hold it. Will try soon.
 I am concerned with varying readings, possible measurement error, etc, I may adjust and wind up cutting too much under lathe center.
 How much allowance is really required for being on lathe center with turning , boring cutters?
 ps I do have Phase II QCTP,but want also to use the square tool post.


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## Big Bob (Dec 27, 2012)

Yes, that is what I meant.  I already carefully stoned the compound slide with fine arkansas stone for burrs before assembly of tool post. Did same for bottom of tool post.
You gave me good things to check. I'll work on it some more. Thanks.
Bob


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