Yet another DIY table feed thread

J

jmarkwolf

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I’m intrigued with the idea of making my own x-axis table feed for my new-to-me Bridgeport.

I know I have the “right” to banish the thought but I apparently don’t have the “ability”, to borrow a phrase from Ron White the comedian.

I can’t justify the $600 or more to buy a good one, and from various accounts on the web, I am skeptical that a $275 one is worth owning.

I’ve scoured the web and seen the Youtube videos of numerous projects, some are pretty clever and others…, but all of these seem to refer to motors that were “on hand”. I don’t have any motors “on hand”.

The windshield wiper type motors seem to be “biased” to run in only one direction efficiently, electric seat motors might be a good choice but they aren’t designed to run continuous duty, DC gear motors and other various types might be a good choice but I’m afraid I’d have to buy a several to find a good candidate, which may end up costing a significant percentage of the cost of simply buying a “store bought” table power feed unit.

Finding one with the suitable combination of desirable speed, RPM, and voltage complicates the matter.

So far, I’m thinking timing-belt coupling with a dog clutch for engagement/disengagment, and an axial DC gear motor, 150 lb-in, 150-200RPM, 12-24VDC is the best choice for my application.

Can anyone recommend a specific make, model and economical source of such a motor?
 
Such motors are found in cordless drills. Look for dead units - bad batteries. Most drills are tossed when the batteries die and then I have no problems scavenging what I need.
alabamaed36046
Ed Shelton
 
alabamaed36046 said:
Such motors are found in cordless drills. Look for dead units - bad batteries. Most drills are tossed when the batteries die and then I have no problems scavenging what I need.
alabamaed36046
Ed Shelton
Click to expand...
Just as Ed said , myself its batteries, but I saved my 12Vt ones and soldered jumpers to a 12vt car batt.
Even better to find a two speed reversable drill. But wouldnt you need some kind of dog clutch?
can see it will work for x feed. Chain drive, belt drive? Take the trigger out replace with a varible
radio shack pot? On and off toggle switch all in a shop built box? 12vt batt & trickle charger? Dont
mind me, just thinking out loud again, cause im thinking of the same thing only, I do have all axis
power feeds, my case its the knee. From the simplest to boring a vehicle engine, oh it lowers easy
comming up, 15 turns I gotta sit down and I may have 100 more turns to go. So I try and think how
much HP does my two arms have to raise the knee? Engineering nightmare. Counter weights no,
thinking of air assist ram? feasable. Enough air (happy spot) then crank with one finger up or use
small drill. And then, there are air motors? So far I favor air piston something not attached, to be
put away, foot controled. Remember assisted power steering. So many avenues. Ill get back.
 
alabamaed36046 said:
Such motors are found in cordless drills. Look for dead units - bad batteries. Most drills are tossed when the batteries die and then I have no problems scavenging what I need.
alabamaed36046
Ed Shelton
Click to expand...


And most any of them can be run on 12v, that you can get from an old PC power supply. Most will already have speed control and revers build in, just butcher/modify as needed. (this is my plan as well)
 
some of the battery drills have an elaborate trigger switch built in. did you ever hear the hi pitched whine when you barely pull the trigger ? I have no idea what it is doing that but as an example, the 18v dewalt tools that are vari speed use a $50 plus trigger. and some of their cute little motors have replacement brush assemblys that are cheap. I too am thinking that direction.
 
I had thought about buying and sacrificing the larger Harbor Freight 19V battery powered hand drill for $50.

Should have the torque, don't know about the rpm, and it probably won't have a conventient mounting flange.
 
Fascinating thread, as I want (badly) to put a power X-feed on my mill, but keep going in circles looking for a motor that will work. The idea of a cordless drill is integrating, just a bit of a "mounting nightmare", as I have no idea if the "entire" motor assembly comes out of the drill, or if I need to keep some plastic case parts intact?

Have looked around at some DC motors, but even when they state the torque I have no idea if its enough or not. I KNOW a cordless drill will work, as I have used mine at times, so maybe I should research the torque of the cordless drills to see what range I KNOW will work. Going to keep an eye on this thread, as any ideas will sure help me figure out what to do
 
Thats a nice set up :) will have to look around as those wiper motors are a lot bigger than the ones I see at Princess auto (which look way too small). Guess I will start digging for motors again, as last time I went looking I got hung up looking at stepper motors, but they sure were not cheap. I think first I need to find a way of figuring out what the minimum torque I need is to move the table (as I have them stiff to cut out any vibration)
 
Easiest way to figure out how much torque you need, is with a simple fish scale. Hook it to the handle of the axis in question, and slowly pull at 90deg to the handle (perpendicular to the tangent of the circular path of the handle...) and see what it takes to GET it moving. It usually takes more to get it moving, than to keep it moving. just don't yank the scale, and get the largest number

Then take this number, probably in oz, or lbs, and multiply it by the distance from where you pulled, to the center of the handle. E.g. the handle on my lathe is 4" from the center of the leadscrew. My granddads fish scale pulls 1lb, to get it moving. This tells me that the amount of torque that I need to drive that shaft is 4 inch pounds. Since motors are usually spec'ed in either oz-in of ft-lbs, a conversion is required. To convert to ft lbs, we would divide by 12, as we already have the correct force unit. If we wanted to convert to oz-in, we would multiply by 16. That gives us either 1/3 ft/lbs, or 64 in/oz.

This will tell you how much torque you need to move that axis. Now all you have to do is figure out how fast you want to move the axis, and you can figure out the horsepower required to do so!

Good Luck!

-Cody
 
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