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Machine Stalls and Observations

Some observations with free time and aluminium

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woody123/05/2020 21:24:02
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Evening all, hope well and safe.

I had a few hours spare and made some observations which I think I should share. First, which is not a Big one, I found if I get the cheap brazed carbide tools to almost centre and shim the business end only increasing the rake they are much more willing.

Second, which is my main point is machine stalls. Regardless of the above (tool shimming). if I push depth of cut I get stalls. However the stalling of the machine only occurs at the end of the cut. I.e feeding toward the head stock I get a stall close to the chuck. Feeding away from the chuck I get a stall close to the tail end. The stock i was wasting I know too, 6082, 6069 bar and a piece of 50mm X 40mm tube (unknown) the tube was the worst offender.

I also found there is a very fine line between happy and stall territory. Any thoughts would be much appreciated, I am struggling to put a logical explanation on it.

Thanks,

Woody.

Neil Wyatt23/05/2020 21:42:03
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Try grinding some clearance on the front of the tools, you will need a green grit or diamond wheel.

Often the brazed on tips are parallel sided and not finish ground - increasing depth of cut makes them rub.

Neil

woody123/05/2020 22:09:59
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Will give it a go, however? How do I radius the nose. As an example, I grind up the so called finishing tool to a sharp point and then stone a radius. It doesn't really matter the tool as such. As soon as I radius then check with a straight edge the tool tip is always to far gone. I can grind, I fettled for 18 month solid, but the business end I just can't get right.

Thanks.

JasonB24/05/2020 06:55:01
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An idea of what machine you are using, what you call a "deep cut" what feed rate (hand or power? ), diameter of bars would help. Also is the motor stalling or just the chuck and the belt slipping.

Dave Halford24/05/2020 10:54:19
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Hi Woody,

As you've got an 'old un' like I started with (1915 vintage in my case) they tend to collect a lot of unsuitable carbide cutters that travel around with them. I found 2 that worked with the limited speed and power available, a 1/2" boring bar and a 1/2"straight finishing tool. Both need to be sharp pointed to work and I only used them for really hard stuff. With indexable tips 0.2mm radius is finishing and 0.8 is roughing.

I never tried them on alloy as HSS worked 10x better.

I assume when you feed to the chuck you start in the bar middle and like wise feeding to the tailstock? If so the bar is able to move away from the cutter at the start and can't at the end so the DOC increases and clunk, all stop.

Stalling carbide in steel is normally death to the tool cutting edge.

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