Torque required for a small mill power feed

Fizzy,

If you visit

**LINK**

you will find a description of a mill feed conversion of the type you require. I believe the "Mike" whose site it is, is an occasional contributor to MEW and also a member on here. I bought an identical motor off eBay for less than a tenner ages ago to copy his project for my Amadeal XJ-12 mill (now sold) but never got around to it. I also bought all the other electrical parts, too. If you would like them, drop me a PM and you can have them for the cost of the postage.

John

Looks like the motor he is using has something like a 30:1 gearbox so max return speed would only be 6" /min but on the flip side the motor will be spinneing quite fast at cutting speeds.

My attempts to convert a CMD10 micromill (X1) have ended up with a Nema 23 stepper which provides around 1.2 Nm. Or a pull of 12KG at one cm radius if my maths is correct.

This works and cuts just fine provided that the machine is set up nicely. Too stiff and it will struggle.

Iain

Jason,

You are right. Rapid return it ain't, but there is a dog clutch of sorts and the leadscrew retains a handle on the other end, so a bit of rapid arm-twiddling soon sorts that problem. It is, after all, the cutting direction that is important.

John

This cropped up some time ago. I want a power lift on the head of my miller and I doubt if a stepper will do it. A 24v wiper motor and some gearing might but it's likely to be overloaded. For short periods I don't care much about that.

I did look around for a power feed and my conclusion was that a fairly powerful 75mm Nema23 stepper is the cheapest option providing that the max current draw is under 3amps because of the cost of cheap drivers. This looks to be a cheaper option than a new wiper motor especially in 24v.

Personally because of the design of a DW miller I don't want the motor body or mounting sticking up above the table so would add some gearing maybe via a toothed belt drive but butch plastic gears looked to be attractive. I currently have no idea what mod would be needed on those. While it's not a good idea to use other manufacturers data it looks like some steppers will produce their rated torque up to a maybe a couple of hundred rpm so there is plenty of scope for gearing down to get even more torque.

I set my slides fairly stiff and if I did a power feed would do a that's sure to drive it rather than worrying too much about sums and detail.. I can get an around 3" dia gear on the end of the lead screw so I will just find out how fast the stepper will go and gear as much as possible.

Yes I do know that a nema 23 wouldn't stick up above the table attached directly but gears can be used to more or less insure it will work.

John

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The simple tubular ones for fishing tend to be fairly accurate and reasonably priced. I do fish at times and have a couple. If buying do think about the range you might need. Too high will just spoil the accuracy of very low readings.

I mostly use them for checking fishing line breaking strain and also to see which knots work best with various types.

And still get broke at times. The stated breaking strain is usually way out not even accounting for knots.

John

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Edited By Ajohnw on 19/08/2016 14:03:25

Yes, he is a very helpful fellow. And a wizard of sorts if you'd heard the legends to be true!

Michael W

There are some interesting golf cart and mobility scooter motors on Ebay. Those seem to have plenty of torque.

About a year ago I bought a small window motor (Peugot 205) with integrated worm and gear for this purpose but it probably won't be man enough to make cuts, although I don't take heavy cuts anyway on the WM-16.

Ed.

There's a risk of overthinking this. Although I like to do some ballpark calculations when designing things, it's fairly well understood that a fairly typical window winder works fine on mill-drill table feeds.

The nice thing about simple brushed motors (apart from the fact they are simple and easy to drive) is that the torque increases as they bog down, unlike a stepper that suddenly skips steps.

Measure the stall torque of a (geared down) window winder motor with the full (14V) applied and ask yourself if you think this would be insufficient for the sort of side load your typical mill drill will impose on the tool, even allowing for friction in the slides. Unless you plan to use your table as a press tool, it's not really going to require a massive motor.

... and if you're thinking of using a drill motor as someone suggested, you can try it out before you remove it from the drill. Put a socket in the drill chuck and connect to the handwheel nut. Then you can try it under actual working (and cutting) conditions.

About twenty years ago I made myself power table feed to my Naerok 350 mill using a car window up/down motor. I made a dog clutch and used some small gear from an old phot copier. Using components from discarded washing machine speed board I made speed control, also fitted a double pole change over switch so that I have forward and reverse and a push button so that I fast traverse. For a power supply you can use a battery charger or make your own. The unit fits on the end of the table and is level with table. In the beginning I used to keep feeling the motor and it hardly got warm. Its still working OK and does a good job. Not all windscreen wiper motors are designed to work in both directions, up/down are so chose carefully.John

If you can get an old Lucas wiper motor (British car from 1950s/70s), these motors have wound fields rather than permanent magnets, they are fairly rugged, and will stand 100% over voltage/24V. I use one as my feed motor at 18V, it gets quite warm to touch after 1/2 an hour.

Ian S C

Looks like window winder motors can be obtained on ebay for £10 or less. It looks like they all use further gearing past that built into the motor. Some have masses of connections. I would be inclined to find one with just 2 pins if anyone wants to try it.

In these safety concious days I doubt if breakers allow people to remove items from cars themselves. Pity as then it might be possible to get all of the external gears.

To be honest though having used wind up by handle windows I would wonder if they are powerful enough for how my DW is usually set up.

John

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I have built this exactly to spec albeit with a 2 amp power supply. The motor isnt able to turn the lead screw by a country mile. Everything is as free and easy as possible but it will require a lot more torque to tuen over. Project abandoned!

Fizzy can you confirm what "this" is as there have been several options suggested

http://www.active-robots.com/motors-wheels/dc-motors/12vdc-motors

John have you tried any of those? Based on the torque figures I gave earlier they all look rather weak with the exception of the 139:1 ratio but that would be so slow the tool would just be rubbing.

Hello,

On a simple automatic feed for my BF20 milling machine using a stepper motor, please, see my post dated 10/04/2011 13:09:23 ***HERE*** .
And my album ***HERE*** .

Dias Costa

JasonB,

I sent fizzy all the bits I bought to make a feed system, but never used. I assume that "this" is Mike Cox's design. I don't understand why it works perfectly OK on Mike's X1 mill but not at all on fizzy's X2. They don't look too dissimilar to me, judging by the photos and specification on the Arc web site. The motor I sent is exactly the same as the one Mike Cox used.

John