Saturday, February 5, 2011

Simple Tramming Tool - Part 2

I found some time in the morning of the 3rd day of the Lunar New Year while my wife was preparing for her friends' visit to our place.  Started only wanted to drill the 8mm hole on the beam of the indicator holder, leaving the steel shank till later date.  But I persisted on after we sent off our guests and stop just in time for my showflat duty at 3.30pm.  The shank was turned down to slightly below 8mm, at 7.995mm.  Tested the fit - the best I can achieve (frankly, I've not done any of such and therefore, nothing to compare with...).

The 3/8" steel rod which is to be the shank was cut from a long piece I happened to have in my stash.  The Proxxon mitre saw was used to cut it to its approximate length and faced off in the lathe to about 80mm long.  The 2 ends were centre drilled so that I can turn the steel rod between centres.   I initially opted for the revolving centre at the tailstock end, but the diameter of the part holding the bearing prevented the tool to reach the end of the steel rod.  The dead centre was used instead. Despite that, I've to turn the tool at an angle to reach the tailstock end of the steel rod.  As I'm unable to reach the headstock end because of the cross slide getting in the way (QCTP was fastened to the slot further away from the headstock to reach the tailstock end), my plan was to turn down half the length of the rod and flip the stock around for the other half.

The cut was made with 0.1mm each pass (0.2mm removed in diameter).  After each pass, I would measure the diameter at each end of the cut to square up the lathe.  From a taper measuring a difference of 0.09mm at cut length of about 40mm on the first half, I managed to bring that down to 0.03mm.  Couldn't seem to lower this figure anymore than that.

After both halves were done, I tested it on the beam that will be holding the 2 indicators.  It fits with a slight twist.

2 options are now available for me to complete this; 1) drill and tap M5 at one end of the steel rod and fasten the shank to the beam using a M5 cap screw, 2) loctite them together.  I'm likely to go with option 1 as the beam to hold the indicators wasn't well made.  Once the mill is squared up, I'll make a replacement with more accurate hole placement.
Some pics as always...

Drilling the 6mm through hole after centre drilling.
The 8mm hole is drilled to a depth of 10mm leaving about 5mm in the stock for the cap screw.
The 2 holes are not very concentric.  Wonder if I would have problem later...
The unknown steel of about 3/8" in diameter and slightly more than 3" in length.

Testing for fit. A slight twist bottoms the shank.  Good stuff!

Flipping the rod around to turn the other side.

Turning operation done!  Not too bad a surface finish.

This is how the tool will look like. 

I didn't take any pic with the indicators mounted.  Will do that when I tram the mill.  Hope to get back to the z axis mod real soon.

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