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Holding a parting blade

I got a small parting blade in Vancouver last week: It has a 'V' cross-section with the top 0.057" and the bottom 0.048". It is 5/16" wide. The question is: How do you hold it to work? I assume that the 'V' should be vertical to provide clearance on both sides but to mount it like that requires some tricky arrangements. I tried to look for a holder that would do that but could not find one.

I can see how having the 'V' tilted so that one side of the 'V' is vertical would be easier to do but would it work right? I understand now why the 'T' shaped tools are easier to deal with.

I would like to use the blade in a rear tool post on the Taig which brings up another issue: If you try to grind a top rake on the blade and clip the point even slightly the point is going to be *above* the center and I cannot see how this can be corrected by shims as in a front tool post.

None of the literature available to me nor the web searches have helped so far.

Reply to
Michael Koblic
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Not to invent the wheel, but I bought a parting tool that works with carbide inserts and has a flat blade that is easy to mount. Spoiled now and would never go back. Carbide insert parting tools are very nice.

Reply to
Tim

They make holders for these tapered parting blades. The one I bought from Grizzly (P/N H5904) handles a 0.75" high blade, but I'm sure other sizes are available.

The slot into which the blade sits is angled just a bit so that the V will sit (nearly) vertical, giving similar side clearances in a cut. It probably doesn't have to be exactly straight, just close.

Mine is designed for a front tool post, so it'll center up with the work easily with a few shims. I'm sure the rear tool post type must be different, and may have to be built to suit your particular configuration. But then, its not unusual to spend as much time building jigs and tools as one spends making the final product.

Reply to
Paul Hovnanian P.E.

The slot into which it mounts should have a tilted side equal to half the included angle of the blade.

Without that -- you can put a thin strip of shim stock ((0.057 -

0.048)/2) or 0.0045" thick near the bottom to set the angle. Make the width of the stock less than 1/4 the height of the blade, and round off to the nearest lower thousandth, so go for 0.004" shim stock. 5/16 divided by 4 is 0.0781", so aim for about 1/16" wide by at least as long as the slot in the holder. A bit longer will let you fold the ends over to keep it from sliding as you slide the blade to adjust stick-out.

Since the Taig does not have a reverse switch, and it has a rather small threaded spindle to make running in reverse somewhat dangerous, you want to run forward and cut on the bottom side of the blade, not the top, so I guess that it is a bottom rake. :-)

Make the holder to provide an automatic rake without having to grind, just as the quick-change holders for the Aloris toolposts and clones have. Ideally, you want to make a way to slide the holder up and down the post to set the tip height for different degrees of blade extension and then lock it firmly. A dovetail on the post and a gib on the holder might work well.

Does the above help any? Not everything is on the web. :-) Get in the habit of thinking of ways to overcome your problems and you will have to ask fewer questions over time -- and will be able to answer some of the questions of others.

Good Luck, DoN.

Reply to
DoN. Nichols

That's what I was afraid of.

I believe the correct term is "top rake on the bottom" :-) If you cut truly with the bottom of the blade you would be cutting with the narrow part of the 'V'. Unless, perhaps, in Australia...

Oh yes. I have some other thoughts, too. They are too Rube Goldbergish to describe here. If they work I shall photograph and post.

Not everything is on the web. :-) Get

I tried that the other day. The result was something I call "the wheel"...

Reply to
Michael Koblic

It is not that bad.

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Well ... I'm referring to "the bottom" as defined by gravity, not by the manufacturer's intended orientation. :-) Of course you cut with the wider part, and the narrower provides relief.

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If they work -- that is what matters.

Enjoy, DoN.

Reply to
DoN. Nichols

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