Power knee?

[sdelivery]

I want to power the knee on my BP with 12 inch travel knee and a 48 inch table.
I would like to know what you guys are using, the frequency of use and the longevity of use.
I don't do much small machine stuff so I don't really know.
I have a scale on my knee and I really appreciate that but I am done with cranking and really don't want to do the drill routine.
I guess the question is more what is strong enough to lift that knee with tooling and part weight over and over.
I definitely can't have a spinning handle.
I have a servo 140, a servo 150 and a AL500.
Looking at ratings and recommendations the 140 is recommended but does it last?
The customers I go to generally go through them like water and have them laying around in some state.
I looked at the searches on the subject here but everything was approx. 5 yrs. Ago or older
and believe I would like fresher information.
Thanks

 

[FOMOGO]

I put a 500 inlb, $130 Vevor off ebay on my Bridgeport over a year ago. Has worked just fine, and sure beats the hell out of hand cranking. Bought a second to put on my larger Acra mill. Make sure your knee gib adjustment is good and not binding anywhere in it's travel. Mike

 

[markba633csi]

Measure the force needed to crank it- an old-fashioned beam type torque wrench would be ideal for that
Then you'll know how many foot-pounds it takes and go from there
I'm guessing about 1/6 Horsepower thru a reduction gear would do it
Depends on the weight on the table and how fast you want it to move
The faster you want it to move the more horsepower it will take with a given gear reduction

 

[Eddyde]

Maybe install some gas springs to help reduce the weight of the knee and reduce the torque needed to lift it. Probably reduce ware and tear on the gears and screw as well.

 

[tailstock4]

I use Servo power feeds on two vertical mills I have now. The 200 type is on the knee as per Servo’s recommendation – especially on the larger mill. Through the years I’ve mostly run Servo, but I have had an Align power feed which worked fine. The biggest difference between Servo and any of the others I’ve tried is that Servo is a little smoother throughout its operating range and seems to have a little more torque at really slow speeds.

One thing that makes Servo more expensive is the need for a special hardware mounting package for each mounting situation. You can save a little money if you make your own. It isn’t too hard.

Here are pictures of the mills with the power feeds. By the way, I don't think you'll regret putting one on the knee whatever size mill you have.

 

[OTmachine]

Maybe install some gas springs to help reduce the weight of the knee and reduce the torque needed to lift it. Probably reduce ware and tear on the gears and screw as well.

Or possibly a window sash type system using a cable and weight.
Could also use hydraulic cylinders with one being weighted to mimic a sash system.

Something like this is what I am referring to: https://phelpscompany.com/weight-pulley-systems.html

 

[Winegrower]

By the way, I don't think you'll regret putting one on the knee whatever size mill you have.

Agree, this has been one of the better accessories on my Bridgeport. I adjust the knee position much more than I did when I hand cranked it.

In my experience, any of these power feeds have the ability to handle the knee weight, but I have not put the maximum load weight on the table, and probably never will.

 

[sdelivery]

I use Servo power feeds on two vertical mills I have now. The 200 type is on the knee as per Servo’s recommendation – especially on the larger mill. Through the years I’ve mostly run Servo, but I have had an Align power feed which worked fine. The biggest difference between Servo and any of the others I’ve tried is that Servo is a little smoother throughout its operating range and seems to have a little more torque at really slow speeds.

One thing that makes Servo more expensive is the need for a special hardware mounting package for each mounting situation. You can save a little money if you make your own. It isn’t too hard.

Here are pictures of the mills with the power feeds. By the way, I don't think you'll regret putting one on the knee whatever size mill you have.

View attachment 469982 View attachment 469983 View attachment 469984

I like the wheel vs crank handle.

 

[OTmachine]

I like the wheel vs crank handle.

That ^^^, is a good idea! I really do not like the crank on my Rockwell 21-100 and a 10” handwheel would be much nicer. I will have to mock one up from plastic that I have on hand to see what I like. And if I do it good enough, may just leave it.

 

[BGHansen]

Kudos for patience and diligence. I bought my BP on 9/16/2017. It had a 2-axis DRO built into the CNC setup; first thing I bought was a single-axis DRO for the knee. The instructions for that required MULTIPLE full-travel ups and downs to tram the scale; 16" of travel at 0.100" per turn! I bought a Z-axis power feed from All Industrial Tool supply for around $350 and installed it by 10/13/2017. The BEST money I've spent in my shop! Mine is an Asong unit rated at 150 ft. lbs. Been using it for 6 years with no issues.

Bruce


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