I need to get a holder for 5/8" tool (indexable cutoff blade). My QCTP is AXA series and I use a number of 100-series tool-holders, but they only accept 1/2" high toolbit. The 200 - holders accepts 5/8 , but will they fit my QCTP (will dovetail match) ?
I can always make me own, but $15 a holder, I'd rather buy it.
No -- it will not. The dovetail is both wider and taller for the BXA/Series-200 toolposts and tool holders. The Phase-II toolposts and holders come with drawings giving the dimensions for all of the sizes, not just the one which you own. Study those drawings. (Have you thrown them away instead of saving them?)
What size of lathe do you have? You might want to consider switching to BXA/Series-200 totally. That is what I use on my 12x24" Clausing.
You might be able to make one, but there remains the question of whether it could be adjusted to have the tool tip at the proper height. Are your tool holders adjusted near to bottoming on the compound? If so, the only choice is to thin the material below the tool shank, which will produce a weaker tool holder. This could be done by milling the slot wider in an existing holder -- but the holders tend to at least be case hardened, so you may have to burn out a milling cutter to accomplish what you want.
You don't say whether or not, if you have a AXA parting blade holder style/type # 7, or 250-107. This # 7 holder has a slot that is angled, not horizontal like the common lathe cutting tool holders. The blade height capacity is listed as 1/2", but the slot measures .560".
If you already have the AXA # 7 holder, you could possibly modify the indexable parting blade and/or the holder to fit the parts together. Maybe remove some height from the bottom of the blade, and some from the holder. This approach will affect the insert top rake angle. The idea of modifying the insert blade might not be appealing, since it's probably an expensive piece of tooling.
You'll probably need a different type of holder specifically for the insert blade, if the indexable blade manufacturer recommends that the blade be mounted horizontally (no pitch/angle).
The location of the set screws on a common tool holder might require you need to fabricate a second part to accomodate the insert blade, so the larger slot in the BXA holder may not be optimal, even though the indexable blade will fit in it. The slot in a common AXA holder is approximately .550"h x .450"d.
Another possible solution might be to fabricate a holder for the indexable blade that can then be mounted into a common holder.
Any of the above modification/fabrication suggestions would be likely to result in less than perfect results, since parting operations are greatly affected by rigidity. Making a custom holder could produce the best results, and save you the trouble of making one later.
As DoN suggested, the fit of the indexable blade tip in relation to the lathe spindle's center height will determine if you'll be able to, or how, you'll need to mount it.
I would swear that I wouldn't have thrown away anything that important, but I sure don't have those drawings. I have made a couple of different size holders by measuring the ones I had, but it sure would be nice to have "real" drawings. Do you know of anyplace where I can get them? (AXA, piston type, at least).