Spindle mount advice please

With the new high speed spindle on its way I need to make a mount for it. On the Fadal mill the part of its spindle housing that protrudes below the head has a cylindrical part that is 5 inches diameter by 2.5 inches long. I want to make a clamp that will fit this. The clamp will have another hole bored for the new high speed spindle (HSS). The centerlines of these holes are 6.25 apart. This allows the HSS to be clamped near its nose and for the side of the HSS to clear the head of the mill. The holes to be bored in the clamp are 5.0" and 3.0" diameter and there will be 2.25 inches of material between the holes. The outside dimensions of the clamp will be 2 inches larger than the bore holes, which means there will be 1 inch thick material surrounding the holes. I will mill the outside of the clamp so that there will be two flat surfaces that will be tangent to the rounded ends of the clamp so that the clamp will be sorta teardrop shaped. The mount will be 2.5 inches thick. I plan to use two 3/8 cap screws for clamping each spindle. The mount will be split in two places for clamping. These splits will be parallel with the long axis of the mount. I have though of other ways to split the mount but don't know if they are any better. The mount could be split between the holes and then only two screws would be needed for clamping as the screws would draw both holes tighter at the same time. I could also put the splits at right angles to the long axis of the clamp. This would leave more meat for threads but would also make the tightening screws for the big hole hard to get at because they would face toward the back of the mill. I would like to use Dura-Bar as the material but don't know yet where to get a piece that's 7 by 12.25 x 2.5 thick. I could use

6061 but I don't know if it would tend to ring and cause unwanted vibrations, which would lead to poor finishes and broken tools. Suggestions are welcome. Thanks, Eric
Reply to
etpm
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It seems unlikely that 6061 would ring in that application. The sections are too thick for it to transmit significant vibration, IMO, unless the vibration input is quite large. If it's large, your high-speed spindle probably just threw a bearing.

More troublesome could be the high rate of thermal expansion for aluminum clamped around steel. If it heats up, it *might* reduce the clamping force. But I doubt that, too. You'll probably have enough compression on it when you screw it tight that you'd never notice any loosening in normal operation.

Reply to
Ed Huntress

I regularly buy Dura-bar from these folks:

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Download the stock list on that page and I'm sure you'll find something close. Keep in mind they'll slice thin pieces off the end of large rectangles and trim the long dimensions to size. I've had slices as thin as 1.25 cut from 14 x 25 bars, then trimmed to 10 x 18 or so.

They also work with American Griniding in Chicago if you want the stock Blanchard or surface ground to thickness. I find the prices very reasonable.

Reply to
Ned Simmons

On Friday, May 6, 2016 at 12:51:34 PM UTC-4, snipped-for-privacy@whidbey.com wrote: I could use

My thoughts are worth what you paid for them. In other words I do not have a clue. But if I had the stock on hand, I would machine the mount out of aluminum. And if it is not good as is, I would mill some grooves in it and fill them with load. Maybe pouring it in and then tamping it with a punch so it is a real tight fit. Or filling the grooves with bits of granite an d epoxy.

Dan

Reply to
dcaster

Zamac aluminum/zinc alloy , not sure which one would work best . Has similar damping properties to CI . Not sure if it's commercially available but a hobby caster could alloy and pour a blank for you . If the pattern is right there would be very little waste .

Reply to
Terry Coombs

Terry - what's CI?

Hul

Terry Coombs wrote:

Reply to
Hul Tytus

Cast Iron

Reply to
Terry Coombs

Here's what I made many years ago to mount a Westwind air bearing spindle to a Bridgeport. I machined the two plates at the same time, bolted together, so there'd be no possibility of them having a different dimension between the two holes. I bored the holes to final size with a boring bar.

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Jon

Reply to
Jon Elson

Thanks Ned, I filled out their online quote form last night. Eric

Reply to
etpm

I hadn't thought about the thick section preventing ringing. That's why I asked for advice here. Thanks Ed. Eric

Reply to
etpm

So filling the slots with load will dampen vibrations? So I should lead the slots with load? If I go that route I could just fill the slots with lead shot. Thanks for the suggestion Dan. Eric.

Reply to
etpm

Doesn't Zamac tend to cold flow when under lots of pressure? Eric

Reply to
etpm

Well they use lead for dead blow hammers. So I think it would work. They also make machine bases out of weldments filled with granite chips and epoxy.

Ed ought to be able to provide more information. I just read a lot, but have no experience on this.

Dan

Reply to
dcaster

I should emphasize that it depends a lot on energy input relative to the mass that you're concerned about.

There is an old machine tool story about a lathe company -- Reed Prentice, I think -- that hired a new engineer to re-design their headstock. He designed it with a thicker CI section...and it transmitted vibration like hell. The old design apparently managed to absorb the energy and, through internal friction, turn it into heat.

But you're dealing with such small displacements and low energy that I think the thicker section would do the opposite of that lathe. The mass relative to the vibrating force is very high, and those are the situations in which the old belief that thicker sections are more resistant to transmitting vibration applies.

I think.

Reply to
Ed Huntress

Greetings Jon, I wondered about using a two piece mount like yours because I have some 1 inch 6061 plate I could use for the job. How good is the finish when milling? Since the Fadal spindle housing is for sure way more rigid than a Bridgepot mill quill if your setup works well then I should be able to get away a similar mounting system. Thanks, Eric

Reply to
etpm

It sounds like it wouldn't do much in this application. Lead is a great vibration damper and its mass also helps, but I really don't think that Eirc is going to have a vibration problem with this job.

Reply to
Ed Huntress

I'd bet that the young engineer also used a better grade of cast iron, and so got less internal damping.

Joe Gwinn

Reply to
Joe Gwinn

This is the mount I used for a 65mm spindle on my KMB1.

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Its been a while since I used it, but I don't recall any partcular problems with tram or alignment. Obvisouly less of an issue if just doing engraving. I also did 3D milling with it with loads upto about 0.15HP.

Change the setup to not have a home switch for Z. Change range of Z (above done with alternate setup (.xml) file)

Lower quill. Manually set absolute zero (machine position) Install mount on quill and spindle in mount. (this part is a little fiddley to hold it all together at first)

Run job.

Reply to
Bob La Londe

That is why I encouraged him to make an adapter out of aluminum. With a fall back position if he was not happy with the vibration.

Dan

Reply to
dcaster

CI = Cast Iron

Reply to
CatfishJohn

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