Hello everyone, my name is Kent and welcome back to my workshop.
This is a Tormach TTS tool holder.
It fits a special collet that draws the holder to the nose of the mill spindle, creating
a reproducible tool length offset, and eliminating the need to touch off after a tool change.
By accurately measuring and storing the tool length to a lookup table, we can recall the
tool length offset during a tool change.
To measure tool length, a small surface plate is offered, with a hole that receives the
holder's shank.
However, we can do better.
Today we'll drill a TTS shank size hole into a decent size granite surface plate.
We'll then look at how to perform a tool length offset measurement and enter and use those values
in LinuxCNC.
This is the surface plate that Tormach sells to measure tool length using a height gauge.
Unfortunately, the size is so small that many height gauges will be poorly supported.
A larger surface plate has many more uses than the specialized TTS surface plate, but
larger surfaces plates don't normally have a hole drilled to receive the TTS tool shank.
Today, we'll drill that hole.
To drill the hole, we'll use a 20mm diamond core drill, and this one has a 70mm depth
capacity.
Heat is a killer of tools and the diamond core drill is no different.
To reduce heat generation, we reduce the speed of the drill press to 200 RPM.
The surface plate is heavy and the drill press table must be capable of supporting the weight.
Before starting, verify that the drill is square in both axes with respect to the surface
plate.
This surface plate has ledges, and I want to drill nearest the internal edge of ledge,
to provide the greatest strength while minimizing the drilling depth.
To help find the correct location, we use a template.
To help cool the core drill, minimize dust, and provide some lubrication, water will be
used.
To retain the water, a barrier of plumber's putty is used.
More water is better because the water quickly becomes a slurry.
Use only light pressure.
The drilling will be slow, but going slow will also increase the chance of success.
I occasionally backed out the drill to help water reach the tip of the drill.
At this point, it felt like progress was no longer being made.
The water, now a slurry, and core drill were only slightly warm.
Turns out, the drilled core had snapped off, and plugged the drill.
Perhaps backing off the drill caused this to occur.
Clearing the drill requires pushing the plug out, which is not necessarily easy.
It may be better to drill some amount and then carefully break and remove the core.
If your core drill plugs, try to remove the drill without moving the surface plate to
avoid needing to realign the hole with the core drill.
It was very satisfying to see the slurry drain away.
The total time to drill through the 45mm ledge was roughly 15 minutes.
Next, we clean the surface plate and then will look at how to perform tool length measurements.
We'll use a height gauge to measure the tool length after first zeroing the height gauge
to the surface of the surface plate.
However, the height gauge wheel has some amount of leverage and it's easy to lift the height
gauge while zeroing.
I like to verify that I've properly zeroed the height gauge by comparing to a gage block.
At 3 inches, the height gauge should clear the gage block.
At the smallest amount less, there should be interference between the height gauge and
gauge block.
A similar strategy is used to measure the tool.
First bring the height gauge down to the tool, to the smallest distance while still maintaining
clearance.
Measuring all points of the tool in case one is longer than the others.
Then, to verify that measurement, any additional decrease should create an interference.
By chance or design, this tool has a very convenient length.
Since, under normal conditions, tool lengths should not change, we can store lengths to
a lookup table.
This is the tool table in LinuxCNC.
We add a new tool to our library, numbered 6, with a measured length of 2.500 inches,
a diameter of 1.50 inches or 38mm, and a meaningful description.
After entering the information, select SaveFile to save the tool table.
Then select ReRead to load the saved tool table and verify the new tool is present.
And finally select ReLoadTable to update the in-memory tool table.
The tool table is referenced by g-code when selecting and changing the tool and when doing
tool height compensation.
After the selecting our height probe, and loading it's length offset, we touch off on
the stock height.
The probe's length was measured with the plunger depressed to the probe's zero point.
After finding the stock's height relative to the probe's length, we can switch tools
to the face mill we just measured and not need to touch off again.
The TTS tool holders use the spindle nose as a common reference datum.
Ideally, the skimming cut at height 0.000 should not remove any material, but the raw
extrusion will never be perfectly flat, and so perhaps a thou was removed from the high
side.
To further test the face mill we can take a bit more material off.
This required approximately 750W and thus the limit of the 1HP spindle.
And finally we perform a slower finish pass.
The face mill replaces a fly cutter to address concerns of safety and the long term effects
of an impossible to balance fly cutter.
I'll still use the fly cutter, just less frequently.
The face mill leaves a nice finish.
I was pretty hesitant to drill my surface plate but I didn't like the dedicated small
TTS surface plate.
It took a while to find a source for a deep enough diamond core drill.
Other than plugging the core drill once, drilling the surface plate was uneventful on a drill
press.
Keep the drill cool with water, use slow RPM with light pressure, and all should be fine.
I would be reluctant to do this with a hand held drill, but perhaps it would work if using
a guide, which could be as simple as a wooden block, with a 20mm hole, clamped to the surface
plate. Thank you for watching.
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