Project ... Myford M type lathe

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vtsteam:
Ah, Stuart thanks. I thought about heating it to soften, but forgot about the fact it could be done twice and hardened again. :loco:

Eugene:
Steve, boys, thanks for the input.

I'm not going to touch the existing tool holder, it is what it is, and I don't want to remove any authenticity if it can be avoided. It has some cyanide type case colours left that look quite nice. There are now eight blocks of EN 36 bludgeoned into shape that are waiting for me to finish them off (need to work out how to form HSS tools first) :scratch: so that should be enough.

Steve, I don't quite see the adjustable screw adding to tool post stiffness on the M type. The post is 1.25" dia. and cast integrally with the top slide, so basically bomb proof. An M 4 screw isn't going to add much, unless there is something I'm not seeing. As I said, all the eight new holders will have incremental adjustment via a screw anyway, and once the set is completed I'll have what will be virtually a QCT arrangement, but with the addition of ad lib indexing.

Thanks for the support lads, I'll be off air for a while beating a (insert derogative adjective of choice) Chinese made "Record" bench grinder into submission; it's got more wobbles than Dolly Parton drilling a concrete road.

Eug

vtsteam:
I have exactly the same setup Eugene -- same thickness toolpost, and believe me it does make a difference. The screw comes down and bears on the topslide toward the center of the lathe -- in other words, if it is 1/2" forward of the post, your post now acts like it is 1-3/4" thick instead of 1-1/4" and your effective tool overhang is also reduced by the same 1/2".

Chatter is a vibration due to flex in your whole tool support system. While it is unlikely you will bend a 1-1/4" post, is a different matter to harmonic deflection of the components which happens with relatively light forces. And parting off will really let you know the value of stiffness in a lathe's components. Up to you, of course.

Eugene:
Steve,

The harmonic thing makes sense, I see it now. Even with the new set up there is a certain point on an unsupported workpiece about 1 1/2" from the chuck jaws where I get a tiny bit of chatter; I'd put it down to harmonics without thinking any further. I hadn't given any consideration to where the adjustment screws will go relative to the tool end ..... I will now!

Thanks

Eug

vtsteam:
Eugene, the same thing can be had by putting a packing piece under the tool holder -- like a super thick washer -- the only problem is it needs to vary in height depending on the height of the cutting tool, or the tool itself can be shimmed in its holder -- however, the inconvenience of shimming is why multiple holders and the adjusting screws in the holders were invented in the first place

If you look at other styles of QCTP you'll notice the best of them use a BIG block of square steel as the toolpost -- usually with dovetail ways. This block has much greater cross sectional area than our round posts -- both because it is thicker, and because it is square. That whole block sits on the topslide. BIG footprint.

But if we properly arrange the adjustment screw on our style toolpost, it can act as if it has a much larger section, too

This was brought home to me the other day when I quickly adjusted my parting tool holder by sliding it up about an eighth of an inch on the post and tightening the holding bolt rather than using the adjusting screw -- bad idea! About 30 seconds into the cut I was seeing big problems and finally actual visible flex. Quickly retracting the tool before anything broke, I was like "What the he.....?"

It didn't take me too long to figure out that I should have bottomed out that screw. When I did, things returned to normal and I parted off without problems.

That's why I mentioned parting especially to you -- it was a pretty fresh subject!

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