QC Toolholders

[mahgnia]

Just finished a small project, making 4 more toolholders for my homegrown lathe QCTP (http://metalworkforums.com/f65/t121056-project/page-44#post1603045).

I found an old rusted piece of 1" steel plate, cut it up in the bandsaw and then cleaned up the faces with a blunt(!) fly cutter in the X2 mill attachment to make the toolholder blanks.
Milled the dovetails and the toolbit slots in the X2 mill attachment, 2 off 8mm and 2 off 12mm.
When doing the 12mm slots I decided to see how much the modifications to the X2 (http://metalworkforums.com/f65/t198398-x2-mill-mods-upgrade) had improved rigidity and power, and so I used a 12mm slot drill and cut the full width to the 12mm depth in one pass. I was surprised that the mill did the cut without any problems with power, and only minor vibration.

Pictures below of the toolholder blanks after milling and drilling/tapping, and completed ready for use.
364113364112

Andrew.

[bob ward]

I like the idea of moving the height adjuster from its usual position in the centre of the holder, I can see that being useful sometimes.

[mahgnia]

I like the idea of moving the height adjuster from its usual position in the centre of the holder, I can see that being useful sometimes.


Bob,

There are advantages and disadvantages - the advantages are that the toolholder can be narrower to bring the tool closer to the toolpost for rigidity, and also the piston on this type of toolpost is pushing against solid metal for better clamping.
The main disadvantage is that if the toolholder is not a very close fit on the dovetail you need to wiggle the toolholder a bit while you tighten up the clamp to ensure that the dovetail is not skewed slightly in the toolpost. Also, the front dovetail could be slightly weakened, and if the toolholder moves on the dovetail the adjuster takes more of the downward cutting forces. However, it hasn't caused me any issues yet.

Andrew.

[Pete F]

Nice job Andrew. I too thought the idea of moving the height adjuster was a good one.

Yes the piston style of toolpost are a lot more forgiving in terms of tolerances, as the piston pushes the dovetail away from the toolpost. I'd heard that style was less rigid than the wedge style, but didn't properly understand why until I made my own. With the wedge style the wedge pulls the holders back the other way toward the toolpost, and both the wedge and the flats of the dovetail will lock up at the same time. At least that's the ideal and of course that makes them very sensitive to dimension. They will still lock if the flats don't touch at the same time as the wedge locks, but won't be as rigid. It's something to keep in mind for anybody making this type of holder.