Mounting HSS in a CNC lathe

Not personally but I've clamped HSS in a vise and turned a pin to repair a lathe with. A mill may be more friendly for measuring deflection as well.

It's a lathe tool, which in 99% of cases is set on centre height by adding packing slips, and that's all there is to it, ...............if once at centre height you have vacant space of top of the tool - pack that as well.

To make life easier use a simple tool height gauge.

I have used hss for production machining of Teflon on CNC turning centers. We had an assortment of spacers and shims to adjust center height. Right angled spacers are nice because they space the tool so it is centered under the clamping screws too.

Your question is not clear ?What size tool bit are you using,1/8 ,3/8 what? Most cnc lathes have a 1 inch cutting height. Just buy a 1 inch square cobalt high speed steel tool bit. If it is smaller than 1 inch, just put correct spacers under and over and along side of your tool bit.Or maybe consider this. old school engine lathes had a lantern style toolpost with ARMSTRONG STYLE tool holders. These ARMSTRONG style tool holders came in many sizes ,and might be adaptable to your cnc lathe.Edwin Dirnbeck

Limy Sami said:

It's a lathe tool, which in 99% of cases is set on centre height by adding packing slips, and that's all there is to it, ...............if once at centre height you have vacant space of top of the tool - pack that as well.

To make life easier use a simple tool height gauge.

Click to expand...

What he said plus three more:

1) Do not grind the TOP of the HSS at all.

Whyso?

- desire for consistency most of all. You need to try to duplicate the "insertable" tooling environment.
-- far faster touch-up grind, sharpening, honing
-- greater "mileage" out of the blank, same tasking
--- less material "gone" if the front and side need re-shaped for a new task

So how to get back-rake?

2) DO use

- sloped holder, and/or wedges not shims. Consistency was the ORIGINAL selling-point fo Armstrong/Williams forged holders for "lantern" (and not-only) tool posts and was derived from built-in slope. So the blank (locally forged HCS initially..) could be set, used to do work, removed, sharpened, replaced, SLID up to gage (see L-S comment) .

No need of altering the clamping of the holder & rocker-angle or wedge-height of the toolpost itself.

Roll forward. Hardinge and others made lots of tool blocks with the slant built-in, some with screw-adust for the wedges. Whole block could be swapped without altering setting. See also 4-Ways with sloped sides, not level ones, in-built, and even some with swivels to select the angle. See eBay etc. find a photo now and then with Go Ogle for "images" if you don't have any of these under-roof

- and, "Oh, BTW?" not all tasking even NEEDS back-rake.

Next..

3) So how to control chip curl or break?

Same as some turret lathe tooling.

- Separate chip-breaker clamped with the cutter, but on TOP of it, the shape, angle(s), and set-back from cutting edge all "in the plan" for the material and tasking. No grinding of the top of the blank involved

- Another example the combined clamp/chip-breaker, early generations of flat-blank carbides, usually neg-rake.

Get this "right", no top-grind, your slanted holder provides for better consistency faster sharpening, lower labour cost, lower SKILL level OF the labour in a production environment, not "home shop hobbyist". There's less reliance on the "artistry" of (s)he who grinds the tool in-house.

A volume-production factory NEEDED that. We got it. And LONG before "CNC".

Even the ability to operate with ta da . HSS "inserted" tooling, pre-Carbides and still, yet, today. See-also mills and hor-bores far, far more than lathes. More edges at work.. and it was kinda HANDY if they were all on the same song-sheet, working as a "team"!



Otherwise?

It is the skill of the set-up guy and grinder hand you will be "testing".
Not the metallurgy of the blank.

Nothing new here. Not by - wot? A hundred years, already?

Carbide-era didn't "invent" fixed toolholding for "inserts". All they did was improve upon it. CNC-era need it to be "better than ever it HAD been".

Or wudda been stalled.. spindles idle, operator hovering.. every time a tool chipped or wore beyond useful.. back to being at the mercy of that scarce-labour setup & grind "Magician-Wizard" to make his rounds.

car2 said:

You picked an "everyday object" with a whole lot of variables that will affect "stress" (I assume you are referring to stress somewhere on the shank of the tool measured with strain-gauges or such)

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The criteria was to load an object in two or more methods, like bending + torsion or bending + axial, then do hand calculations, FEA, and physical testing with strain gages. Fortunately, students are allowed assumptions which will make our life easier. We had to research similar studies and a lot of published work goes well beyond the scope of this class.

BROTHERFRANK said:

I have used hss for production machining of Teflon on CNC turning centers. We had an assortment of spacers and shims to adjust center height. Right angled spacers are nice because they space the tool so it is centered under the clamping screws too.

Click to expand...

This was what I imagined the case would be. I hadn't though about angled spacers to center it under the clamping screws. That will probably be the most economic solution.