Machining ballscrews

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WJH
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Machining ballscrews

Post by WJH »

I ordered a 6” 3 jaw chuck from Shars. Has two piece jaws. Both ball screws have also come in the mail. The smaller one for the crosslide is already machined for something.


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John Hasler
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Re: Machining ballscrews

Post by John Hasler »

Steve writes:
> but this is only good for gripping at the face...

I think I can do better than that (if I ever get around to it).
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Harold_V
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Re: Machining ballscrews

Post by Harold_V »

John Hasler wrote: Mon Apr 02, 2018 5:54 pm Steve writes:
> but this is only good for gripping at the face...

I think I can do better than that (if I ever get around to it).
keep in mind, the jaws must be capable of applying pressure over their entire length. If you can't fasten the soft portion in such a way that it won't, they won't serve you very well, as applied forces (like the intended cut) will spread the soft jaws at the outer end. Makes them relatively useless if that happens, and can be the source of scrapped work.

It's important, when machining soft jaws to fit a part, that you restrain the jaws in a fashion that emulates how they'll see the part when it is inserted. You want the finished jaws to bear equally along their entire length.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
WJH
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Machining ballscrews

Post by WJH »

So, this is a good time to mention an idea I had. What if I took my 6” 3 jaw chuck and made custom soft jaws to grip a 10” diameter locomotive driver casting? I’d make them thick enough to not flex.


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Harold_V
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Re: Machining ballscrews

Post by Harold_V »

That's precisely how soft jaws can and should be used. And, if the item you will grip is fragile, you make the jaws wider, so you distribute clamping force over a larger area. They can approach 360° of contact, allowing only enough clearance for the jaws to open and close. Extremely thin walled objects can be held perfectly safely, without damage or distortion if care is applied. And do keep in mind, the profile you machine in the jaws is, of necessity, the same size as the item you grip. If you vary much, the scroll sees the jaws from a different perspective and you risk losing concentricity. That also means that all parts should share the same dimension on which they are chucked.

If you haven't done so, I strongly recommend you check the Resource Library. I've posted on the use of soft jaws and have provided some guidelines that will help you use them correctly. If you don't follow "the rules" (not my rules, but the rules that lead to success), you may not enjoy the degree of success that is available.

Soft jaws are not restricted to holding round objects. If you wish, you can profile jaws on a mill (the jaws are installed in the chuck and restrained by gripping a round piece), then the profile is milled in the jaws at the desired location. Irregular parts can be chucked rapidly, with repeatability, making what could be a less than easy job way, way easy. Same rule as above, though. Dimensions should be held closely. That's one of the (huge) benefits of learning to machine to nominal dimensions, leaving tolerance to bail you out when you miss one. I call it good workmanship. Some folks call it a waste of time and money. I don't agree.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
WJH
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Re: Machining ballscrews

Post by WJH »

Harold_V wrote:That's precisely how soft jaws can and should be used. And, if the item you will grip is fragile, you make the jaws wider, so you distribute clamping force over a larger area. They can approach 360° of contact, allowing only enough clearance for the jaws to open and close. Extremely thin walled objects can be held perfectly safely, without damage or distortion if care is applied. And do keep in mind, the profile you machine in the jaws is, of necessity, the same size as the item you grip. If you vary much, the scroll sees the jaws from a different perspective and you risk losing concentricity. That also means that all parts should share the same dimension on which they are chucked.

If you haven't done so, I strongly recommend you check the Resource Library. I've posted on the use of soft jaws and have provided some guidelines that will help you use them correctly. If you don't follow "the rules" (not my rules, but the rules that lead to success), you may not enjoy the degree of success that is available.

Soft jaws are not restricted to holding round objects. If you wish, you can profile jaws on a mill (the jaws are installed in the chuck and restrained by gripping a round piece), then the profile is milled in the jaws at the desired location. Irregular parts can be chucked rapidly, with repeatability, making what could be a less than easy job way, way easy. Same rule as above, though. Dimensions should be held closely. That's one of the (huge) benefits of learning to machine to nominal dimensions, leaving tolerance to bail you out when you miss one. I call it good workmanship. Some folks call it a waste of time and money. I don't agree.

H
I’ll check it out. I strive to do things the correct way, it’s as if I take pride in my work.


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RSG
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Re: Machining ballscrews

Post by RSG »

Harold_V wrote: Tue Apr 03, 2018 12:07 am I call it good workmanship. Some folks call it a waste of time and money. I don't agree.

H
I strongly agree Harold. I have three chucks dedicated to soft jaws for various operations. There is no such thing as time lost when it comes to accuracy and quality in my shop while using them!
Vision is not seeing things as they are, but as they will be.
SteveM
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Re: Machining ballscrews

Post by SteveM »

WJH wrote: Mon Apr 02, 2018 5:46 pmI ordered a 6” 3 jaw chuck from Shars. Has two piece jaws.
I have several sets of used soft jaws that still have some life left in them, if you want to try them out cheap.They fit American standard tongue and groove chucks with 1.5" hole spacing.

The post where I was selling those is no longer in the for sale section, so I will have to dig them out and see what I have.
RSG wrote: Tue Apr 03, 2018 8:55 am I strongly agree Harold. I have three chucks dedicated to soft jaws for various operations. There is no such thing as time lost when it comes to accuracy and quality in my shop while using them!
I have four 3-jaw chucks, two with the inside jaws, one with the outside jaws and one with soft jaws. Chucks with just the outside jaws sell for cheap, so get one and you'll never have to un-scroll and -re-scroll your jaws again.

I have three 4-jaw chucks one with (you guess it) the jaws facing in, one with the jaws facing out and one with two in and two out, for rectangular work.

I can't remember the last time I swapped jaws.

Steve
RSG
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Re: Machining ballscrews

Post by RSG »

Agreed Steve, I'm up to 7 chucks now! LOL
Vision is not seeing things as they are, but as they will be.
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