Bridgeport Mill - How do you know what speed to run the new(er) table feed?

[CCWKen]

My new-to-mill mill came with the old 12-speed mechanical table feed. As long as I run the 3-ph motor at 60hz, I'm assured the feed is as listed on label. However, these speeds are nowhere near some of the feed speeds I'm getting with calculations. Some are calling for 20-40+ipm but my feed tops out at just under 10ipm. How did they do it "in the old days"?

How does one know what table feed speed you're getting with the newer feeds when all you have is a dial pointing to some single digit numbers? Are you guys running index runs to determine relative speeds or just guessing?

[rkepler]

Lay a ruler on the table, hang something from the head to point to it and run for a predetermined time. If you get 3 inches travel in 6 seconds that's 30 ipm. Once you have numbers for most of the positions you can interpolate between them. Run enough jobs and you'll start running the feed by saying "that chip looks about right" after setting the cutter RPM (I still use an old Morse tools booklet for that).

[RichR]

... How does one know what table feed speed you're getting with the newer feeds when all you have is a dial pointing to some single digit numbers?

If the leadscrew for the table is 10TPI and you attach a tachometer to it, it will read 10 times higher than the IPMs, so 300RPM=30IPM. Maybe
look into one of those low cost digital tachs on Ebay or someplace else.

[3 Phase Lightbulb]

Can you post of picture of this table feed device? Are you saying the table feed is powered by it's own 3ph motor, or somehow powered by the mill's 3ph motor?

[J Tiers]

Can you post of picture of this table feed device? Are you saying the table feed is powered by it's own 3ph motor, or somehow powered by the mill's 3ph motor?

I think he means one of the (presumably) DC PWM all in one drive units, that just has a dial numbered maybe 1 to 10 on it.

And the answer is essentially that since the maker made no calibration, that's your job. It might slow a bit under load, but if you time it as mentioned above, you can put your own dial calibrations on the thing.

[3 Phase Lightbulb]

If it's the old bridgeport table feed I'm thinking of, it's huge with a transmission, emergency brakes, back-up buzzer, seat belts, etc..

EDIT: is it one of these?

[tomato coupe]

My new-to-mill mill came with the old 12-speed mechanical table feed. As long as I run the 3-ph motor at 60hz, I'm assured the feed is as listed on label. However, these speeds are nowhere near some of the feed speeds I'm getting with calculations. Some are calling for 20-40+ipm but my feed tops out at just under 10ipm.

I don't think 40 ipm is a realistic feed rate (while cutting) to use on a Bridgeport. 10 ipm sounds like a reasonable maximum.

How did they do it "in the old days"?

Bigger, more rigid machines.

[Arcane]

I don't think 40 ipm is a realistic feed rate (while cutting) to use on a Bridgeport. 10 ipm sounds like a reasonable maximum.



Bigger, more rigid machines.

Depends on what you are cutting.

I've milled that composite board stuff and plain jane wood with a small 3 insert facemill and with a HHS 3/4" endmill both turning at at top rpm and my table feed maxed out. It worked very well.

[3 Phase Lightbulb]

You can do 20IPM all day long on a bridgeport with a roughing endmill in alum.

EDIT: Here is a nice video showing you what 20IPM looks like.. Here he's cutting rolled steel with a 3 flute 1/2" carbide endmill. I didn't catch how much he is chewing off each pass, but like I said, 20IPM all day long for lots of operations and quite often much faster

[CCWKen]

If it's the old bridgeport table feed I'm thinking of, it's huge with a transmission, emergency brakes, back-up buzzer, seat belts, etc..

EDIT: is it one of these?

Yep, that's it. It doesn't have air conditioning though. Have to run it on its own VFD. It works but it's going to need some new gears. When I took the side H/L shifter plate off to clean it out, I found 4-5 gears that are very worn. Especially the top three gears. Just wondering if it's worth getting a modern feed and dealing with the conversion.

[3 Phase Lightbulb]

Yep, that's it. It doesn't have air conditioning though. Have to run it on its own VFD. It works but it's going to need some new gears. When I took the side H/L shifter plate off to clean it out, I found 4-5 gears that are very worn. Especially the top three gears. Just wondering if it's worth getting a modern feed and dealing with the conversion.

From a practical standpoint, I'd say keep it if it works good. If it only goes up to 10IPM then that's fine. I've seen them before but never used them but since they are 3PH bridgeport power feeds I'm sure it's better quality than any of the import power feeds you would replace it with (assuming the worn gears just cause some noise and don't affect performance/finish surfaces, etc.) If you can find a new gear set then I'd definitely rebuild it.

[Illinoyance]

Some DRO's indicate the feed rate. My AccuRite does.

Those describing measuring distance and time are correct. On the smaller power feeds like Servo the speed under load will be a bit lower than measured at no load.

[tomato coupe]

Depends on what you are cutting.

I've milled that composite board stuff and plain jane wood with a small 3 insert facemill and with a HHS 3/4" endmill both turning at at top rpm and my table feed maxed out. It worked very well.

I assumed the OP was referring to metalworking, not woodworking.

[lakeside53]

I don't think 40 ipm is a realistic feed rate (while cutting) to use on a Bridgeport. 10 ipm sounds like a reasonable maximum.



Bigger, more rigid machines.

I cut aluminium (heavy cuts) all the time at 40-50 ipm on a BP. No issues. I can go up to 100 ipm, but...

Even with many steels 20 IPM isn't unreasonable. All depends on your chip load and DOC. I can even max out 3hp in steel now and then.

Oh.. with razor sharp "modern" carbide and high spindle speeds of course.

[CCWKen]

I assumed the OP was referring to metalworking, not woodworking.

Then explain the 10ipm for steel and 50 and 100ipm for aluminum. (Using a fly cutter.)