I suspect you probably need to scrape the dovetails too.
Both sides of the saddle, but only the underside of the table opposite the gib.
If it’s anything like my Herbert, I needed to then make a new thicker gib strip as well.
Personally I’m no expert in this stuff, having only ever scraped in one machine in my life, during the first lockdown.
In the end, it came out to a couple of tenths over 8″ by the time I’d done, so not perfect, but as good as I was going to get.
I didn’t start photographing anything, until after I’d done the underside of the table, but there’s a record in my Flickr album HERE or on Facebook HERE.
Most of the photos are really trying to illustrate how I learned to set up for the measurements.

I did make an angled flat plate out of a lump of cast iron, to the same 55° as the dovetails.
Seen being used here for a slightly different purpose

And the setup for measuring parallelism of the dovetails, albeit on the knee here, rather than the table

I’ve a feeling these images might go missing again, as after submitting, they were viewable, but I couldn’t click on them to show as a larger photo.
Right click & open in new tab came up with 404 error image not found.

I’ll try inserting again one last time

Getting brassed off with this now. 🙁

Bill

Well the table is quite easy to evaluate since it has the flat ways directly on the bottom. You can do it with a decent sized surface plate. Mine was convex on the underside slightly (about a thou high in the middle as I recall with the plate up-turned) so I had to scrape it from the middle outwards after filing off the wear ridges. Once you have the flat ways straight you can cobble up a simple gauge to check the dovetail spacing but you must make those bottom ways flat first.

If I was going to get serious abut gibs and flatness I would look at using a laser which can be used to inspect across the entire surface

Unfortunately your last image has gone awol, like several of mine, and the youtube link doesn’t work for me.
That’s the same sort of method I was using to check for wear on mine, but I also tried with a micrometer and two round bars just to confirm, repeating for several different diameters; Initially I used two round bars on one side and a long parallel, with a third round bar on the other, still measuring across with a micrometer, just to make sure the dovetail was straight as well as parallel if you see what I mean.
i.e. to ensure it’s not a perfect banana shape.

You have the opposite profiles to me, the dovetail section on your saddle, is under the table on mine.
I guess the same method still applies; I scraped the table top flat, though far from pretty cosmetically.
I then scraped the front of the table, vertical and flat.
That way, I could stand the table on the front edge on the surface plate, and use a similar sliding clock to make sure the dovetail internal profile is flat.

You could then use a stack of blocks & feeler gauges etc to ensure the other rear dovetail is flat and parallel to the front.
One thing that does spring to mind, is have you blued the dovetails to each other on the saddle  and the underside of the table?

As an exaggerated example, lets say you have 55° dovetails, but because of differential wear one end is 54° and the other 56°, the centre line with a clock will still show straight and parallel.
A similar issue on the opposing part might cause a tightening at the end, whilst being loose in the centre.

Just a thought of something different to measure.

Bill

The last photo with the DTI will show whether the dovetail is parallel to the front of the table, but not necessarily show any high spots, other than along the line travelled by the stylus.
I made a couple of straight edges with a bevel; the one with the cream painted end is 55° and scraped flat; it was a slice of cast iron off a bus bar clamp/fishplate about 12″ long.
Even if it’s not exactly 55°, it doesn’t matter, as it was also used on the mating dovetail, which was further blued to this one.
This happens to be the column, but the overall principle remains

I’m not claiming to be any expert here, it’s just how I went about the task

See also for a close up

Bill

On 17 January 2024 at 20:07 Steve355 Said:

…………….

if anyone has any thoughts on the piano wire shims ?

Is there any wear/flattening on them.
The only thoughts I have, since you confirmed there isn’t a removable dovetail.

Completely unrelated, and someone had lost them in the T slots, hence finding some loose after unloading.
If there is any flattening, did someone drop them into the oil grooves, to compensate for wear on one last job before they sold the machine.
No reason for them to be related to the gib, unless it was to push it downwards.

Bill

Bill’s comment made me think – I’ve seen wires used to ‘space’ a gib strip to stop it’s toe dragging along in the gutter at the bottom of the dovetail, (and/or it’s head riding in the angle at the top) – if this makes sense..

..a bodge alternative to ‘pinning’ them so that contact remains central to the shears and they are prevented from slipping or being forced up or down under screw pressure..

On 17 January 2024 at 20:32 peak4 Said:

On 17 January 2024 at 20:07 Steve355 Said:

…………….

if anyone has any thoughts on the piano wire shims ?

Is there any wear/flattening on them.
The only thoughts I have, since you confirmed there isn’t a removable dovetail.

Completely unrelated, and someone had lost them in the T slots, hence finding some loose after unloading.
If there is any flattening, did someone drop them into the oil grooves, to compensate for wear on one last job before they sold the machine.
No reason for them to be related to the gib, unless it was to push it downwards.

Bill

Coming late to this one … with a wild guess that might prompt some thought:

Vincent motorcycles [and others, I presume] used wires inside drilled oil-passages, as a very effective way of tweaking the cross-sectional area and thus the flow.

Is there a possibility that these wires serve a similar purpose ?

MichaelG.

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Edit: __ even managed to find an illustration after all these years !

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