On the vices and joys of machine tool reconditioning...

[ttrikalin]

And this is my interpretation of Dean's indicator stand...

See the instructions here: http://www.deansphotographica.com/machining/projects/indicatorstand/indicatorstand.html

[steamer]

Didn't know about that site....seems very informative!

Dave


....not Deans Site....the scraping site.

[steamer]

Tom

I am looking at your compound base, and noticed the difference in mark up between the compound and the master....it's subtle...but

if you look at the mark up with the compound as the master, on the left side near the dial end of the part, you will see some burrs....these are not present in the mark up with the master.....at least I don't see them

Do a thorough deburr with a stone that will get into the mouth of the dovetail, and mark it up again using both the master and the compound, it should print the same.

My compound base was worn near the front and on the sides near the pivot.   Remember that the master covers the pivot area, while the compound slide does not.

Looking good buddy!   More importantly, YOUR THINKING!.....It's a real mind game isn't it?

Dave 

[ths]

It is such a mind game isn't it? I love this thread, great work, great advice, and what a machine you'll have in the end. Hugh.

[ttrikalin]

It is such a mind game isn't it? I love this thread, great work, great advice, and what a machine you'll have in the end. Hugh.

Yep it is a head scratcher...

Well, I thought about it on the way back from work tonight and I have a theory...

Assume that
1. The template, i.e., the two basal bearing surfaces of the compound slide are flat and on the same plane
2. The master is a plane (flat).

Then the following geometry can explain the markings. I will show the photographs and how they square with this theory.

[ttrikalin]

This is the marking of the side with the points (A) and (B) using the template (compound slide). Only a thin strip marks, suggesting that it is on the correct longitudinal plane. It is not as wide as the template base, because the template base marks the inner part, near the dovetail (see the wipeout pattern in the third photo)



The marking of the same side using the master (prism). Note that a big flat surface marks, suggesting that the surface is on a plane (is flat). 



This is the wipeout pattern of the template (compound slide). In the photo the top sliding surface touches on the area marked (A) and (B) in the schematic.

[ttrikalin]

This is the side with (C) and (D) in the schematic. Shown is the markup using the template. It marks more in the front (left side in the photograph), which is in (C). An explanation is that (D) curves slightly down -- shown in the schematic 2 posts above as an exaggerated curving.



This is the marking with the master (prism). Effectively this side of the swivel base (side C-D) is crowned, and the prism has been applied to the side marked (D). Thus it marks mostly near the right side in the photo (D) but not near (C).



Note that when marking with the template, the intensity of the blue marks is higher at (C-left); when I marked with the master prism, it marked more at (D-right), because I happened to orient the master prism on that side.

Finally, note the wipe pattern in the swivel base -- the template. In the photo you should be looking at the lower bearing surface. It has been wiped in its width but on the right side, which corresponds to (C). Its left side corresponds to (D) and it is relatively less wiped because of the curving of the surface near (D).

[ttrikalin]

I think that I will repeat the markup after checking the flatness of the master as per Dave's comments yesterday, and see if I get the same story with careful markups.

Before scraping too much, I will do additional tests, by measuring height on the surface plate using the tenths indicator. However for this I first have to check the parallelness of the swivel base, on which the swivel rests:

[steamer]

If you find any burrs then I can only conclude your theory is correct.  I'm glad you are cross checking your mark ups.
Dave

[steamer]

Tom
A situation that can arise while scraping a dovetail is the top of the blade hits the angled part of the dovetail before you finish the cut into the mouth of the dovetail and it leaves a burr.  Just be on the lookout.

Dave

[ttrikalin]

Today I made thermally insulated handles for the master prism... There are 4, made of blue delrin.



Closeup of the side ones, which are permanent... The derlin sleeve fits over a 1/4' aluminium rod piece which has been locktited in the master. The derlin has been JB-Welded on the aluminium handle; I did rough up the rod with the corner of a file to give the epoxy something to bite on.

[ttrikalin]

The back ones are counter sunk and tapped for an 8-32 screw. They are removable



and all these are done on the brass bed Sherline...

[ttrikalin]

Tomorrow morning I was planning on flushing the transmission fluid -- but I may check the master and the repeat marking up of the compound base, and make some measurements on the surface plates instead. I am not in the mood for tranny flushing (what mood would that be?)

[steamer]

Nicer handles than mine Tom!   I don't have any!....

If you get a good mark up in the morning after it's been left alone for a while, you'll be in good shape.


Dave

[ttrikalin]

OK, a month later i found 5 hours of undisturbed shop time... and I progressed bit with the scraping and checking of the surface alignment...
Here is how it looks... we are at the edges of my metrology instruments... most of which are crappy...

Cross-slide:
First, as shown in a previous post, the lower surface marks well, fully, and the slides are coplanar (based on the marking).

So I am checking the upper surface in various points A-G; I use similar sheets for other surfaces.



Because the upper bearing surface marks well (previous posts), I use a gage block to get the (relative) average height at various spots like this:

Here is measuring the average, and the measurements. They are in agreement, with a tenths indicator, rounding to the closer tenth.