My Table traverse for Chinese mill.

[BaronJ]

Hi Guys,

Since my Chinese mill does not have a motorised table traverse and I don,t fancy paying the rather exorbitant prices that are wanted for them I have looked at a lot of designs on the web and decided to have a go at building one.
Also its a pain, in more ways than one, standing there winding the table back and forth.

So I thought that I would see if I could design and build one from scratch. With this in mind I decided to have a trawl around my local scrapyards for something suitable to use and came across a car windscreen wiper motor.

I found this one from a wrecked Nissan Micra. Being lazy, I grabbed this one because it was very easy to get it off the chassis bulkhead. Four hex head bolts and it fell out. The power connections were a very convenient plug and socket attached to the back of the gearbox.

At this point I didn't know what condition it was in, only that it was quite clean with only a little rust on the motor case where the paint had flaked off.

When I chose it I didn't realise that it was a two speed motor, but on testing it, it soon became obvious. It also had wipe home switch built into the gearbox which confused me at first.

Anyway it runs quietly in either direction at both speed settings. Though I'm informed that these wiper motors don't like being run backwards so that is something to remember.

The photographs show the motor after I had removed the wiring and connections from the back of the gearbox. Though you can't see it, I drilled out the rivets holding the gearbox together and stripped it down. The grease inside was more like wax than grease. So I cleaned it all out and re-lubricated the shaft, gearwheel and pinion. The gear shaft runs in a phosphor bronze sleeve.

I threaded the holes where I drilled out the rivets 4BA and made a new gasket to go between the two halves of the case. The original gasket was a line of what looked like hot melt glue. I had to double the gasket material thickness so that the gearbox cover plate didn't bind the gearwheel. I used 4BA countersunk head screws to fasten the coverplate.

Part of the reason for stripping the gearbox down was so that I could get at the switch mechanism inside and remove it. It also removed half of the wires that went into the harness socket that was mounted on there. So now there are only three wires to worry about. Common, high speed and low speed.

One of the photographs shows the plate that the motor was secured to the car bulkhead with. The nut on the end of the shaft is M8 and the splines secured the wiper driving arm.

 

[purpleknif]

I just gutted a 12 volt drill and use a $25 PWM speed controller on mine. Works great. Gobs of torque and a ready made clutch for safety.

 

[BaronJ]

Well it works a treat !!!

 

[chucketn]

Does it run in reverse as easily as forward?

Chuck

 

[gus]

Hi Baron,
Please post working Video. I have one of these DC motors. Are your using a clutch too?

Power Table slide is number 1 on my hit list. Sick and tired of hand cranking.:rant:

 

[BaronJ]

Does it run in reverse as easily as forward?

Chuck

Hi Chuck,

Yes ! The motor always runs in one direction, these wiper motors don't like being run in reverse. The lever moves a tumbler gear, so you have both directions and a neutral position where the drive is disconnected from the table. This makes hand traversing very easy.

I'm also examining the potential to include a mechanical limiting mechanism.

 

[BaronJ]

Hi Baron,
Please post working Video. I have one of these DC motors. Are your using a clutch too?

Power Table slide is number 1 on my hit list. Sick and tired of hand cranking.:rant:

Hi Gus,

I don't have any equipment to record video. Sorry !

However a forward, neutral and reverse is obtained simply by moving the lever up and down. The secret is in the use of tumbler gears, as shown below.



Ignore the dimensions on the drawing they are wrong ! In any case unless you used exactly the same gear sizes that I used they would need to be changed anyway.



Here you can see how I did it. I machined the wiper motor gearbox housing so that I could press fit a brass bush to support the collar for the tumbler gears.
The gears have 6 mm spindles. These are simply press fitted into the plastic collar. The plastic is of the type that is self lubricating.



This drawing does not have the correct measurements but gives an Idea of the layout.
See next post for correct drawing.

 

[BaronJ]

This should be the corrected drawing. Having posted the original which was wrong and then re-posted the original instead of this one ! Shall we say third time lucky...

 

[BaronJ]

Some more photographs.

 

[gus]

Hi Baron,

Thanks for the fotos and drawings. Been cracking my head on neutral,forward & reverse.

 

[BaronJ]

Hi Baron,

Thanks for the fotos and drawings. Been cracking my head on neutral,forward & reverse.

Hi Gus,

Absolutely dead simple.

The tumbler rotates to put one or the other small gears into mesh with the big one or neither. Note that all three small gears are constantly in mesh ! The small one, to one of the two same size ones, and the two same size ones to each other.

 

[BaronJ]

I got another windscreen wiper motor today. Similar to the other one but the opposite hand and only single speed.

 

[BaronJ]

Seems I got it wrong ! This motor is dual speed. It uses the case as one terminal. The two wires give high and low speeds when connected to the positive supply.

I've started stripping and cleaning the gearbox and removing the connector from the gearbox cover plate. I've drilled out the rivets and tapped the holes M4, made a gasket and used hex cap screws to secure the cover plate back onto the gearbox housing.

 

[BaronJ]

Hi Guys,

This is what I've done so far:-



I removed the two wires going to the motor from the connector block prior to drilling out the rivets attaching the gearbox cover plate to the housing.





The motor and gearbox on this wiper motor are not only half an inch shorter than the other but the drive comes out of the other side. Unfortunately if I mount this one the same way as the first table drive the motor body will be above the top of the mill table. It really needs to go below so that it doesn't get in the way when machining something that exceeds the end of the table.



Her you can see the M4 hex socket cap screws that I used to re-fasten the gearbox cover plate to the housing. You can see the new gasket that I made to replace the original glue line gasket. This cover plate is also the support for the worm wheel which bears against it. The worm wheel and its shaft are under slight pressure so there is no end float what so ever in the output shaft.



I wrote the wiring details on the label so that I would know which one did what. This motor is also dual speed ! It uses the motor body as the common connection to it.




I've already selected the gears that I am going to use for this version from the laser printer gearbox that I was given. I have two of the black ones shown in the bottom picture.

More to come.

 

[BaronJ]

Hi Guys,

Made some more progress today. I need a plate to mount the motor.



So sorting through the scrap box I came across this piece of 3 mm thick hard aluminium plate.



After marking it out for the spindle hole and the three mounting screw holes, I needed to make a hole big enough to clear the gear that I am going to put on the motor shaft. In this case 35 mm diameter.



Not having a hole cutter or a drill this big, I used this carbide router bit. I've used these cheap router bits several times in both aluminium and mild steel with very good results. I used neat cutting oil as lubrication and around 350 rpm, feeding by hand as I would a drill bit. The only downside with doing this is that you get a substantial harridge on the back side of the cut.



The harridge is easy enough to remove with a sharp wood chisel but it tends to scratch the anodising off the surface.



I also used a small router bit to make the countersinks in the three mounting screw holes. Again using neat cutting oil.

Next step is to mount the drive gear to the motor and check for clearances. Because this wiper motor has a shorter shaft its sits much closer to the mill table end.

More Later:

 

[BaronJ]

Hi Guys,

Got some more done on the MK2 version.


This is the pair of gears chosen from the laser printer gearbox to be the tumbler gears. I turned off the long sleeves so that the gears were the same either side, then it doesn't matter which way up the are fitted. I put circlip grooves 1 mm wide 1 mm down from the end of the shafts in order to retain the gears.



The white gear is the one that will get driven by the two black ones.
The plastic plate will be used in the completed unit. The shaft supporting the white gear is a dummy just used for setting the tumbler gears in the right place. The dummy shaft is 10 mm in diameter the same as the mill table leadcrew end. The tumbler gears shafts are 6 mm diameter just pressed into holes drilled into the plastic.



This is the white gear shown in the previous picture along with the mounting bush and retaining ring. It's yet to have the keyway machined into it. The fastening screws are M3 countersunk.



This is the gear mounted on its bush. The countersinks have not been done at this point although the holes have been de-burred.



This gear, part of a duplex one has been turned down so that its thickness is only as wide as the teeth. I machined both sides and drilled it to have an 8 mm bore which has a taper machined into it on the other side to fit the motor gearbox shaft. The taper can just be seen in the picture. This gear will drive one or the other of the tumbler gears.



Its shown here just placed on the motor gearbox shaft. When its tightened down the splines will grip the bore and stop it slipping.



As can be seen there is not very much clearance between the gear and motor mounting plate. This is because this motor has a much shorter output shaft. When I did a trial assembly there was only one millimetre clearance between this plate and the top of the tumbler spindles.



This photograph shows the arrangement on the lathe that I used for slotting the 4 mm wide keyway into the bush for the gear. The red handled screwdriver is a 2 mm Allen hex driver being used to adjust the depth of the cutter bit. The cutter bit is a 60 mm long square HSS tool bit with the end ground to an edge. I made the hand slotter after having cut the keyways in the mill gears by traversing the lathe saddle back and forth.



And the finished slotted bush. Surprisingly it was harder to cut in the brass than it was cutting steel. Someone suggested that what I thought was brass was probably bronze. Which might account for the difficulty !



Here it is trial fitted onto the mill table leadscrew. It fits securely without any slop. I'm quite pleased with it.

More Later: Thanks for looking.

 

[robcas631]

Great job Baron!

 

[BaronJ]

Hi Rob,

Thankyou ! Your encouragement is much appreciated.

This version the MK2, is a little more complex than the MK1. I hadn't expected the size of the gears to make so much difference in controlling the tumbler mechanism.

More to come.

Thanks:

 

[crankshafter]

Hi Baron,
Please post working Video. I have one of these DC motors. Are your using a clutch too?

Power Table slide is number 1 on my hit list. Sick and tired of hand cranking.:rant:

Hi Gus.
I made a powerfeed for my mill-drill, i used 42V(I was runing it on 24v, plenty speed ) feedmotor out of a old wirewelder. Directly on the feedscrew with a dogclutch between. Used a PWM and potmeter to adjust the feed. Easy and simple. AND works like charm.woohoo1 No fiddling with gears and :redface2:*bang*
Reg.
CS

 

[gus]

Hi Gus.
I made a powerfeed for my mill-drill, i used 42V(I was runing it on 24v, plenty speed ) feedmotor out of a old wirewelder. Directly on the feedscrew with a dogclutch between. Used a PWM and potmeter to adjust the feed. Easy and simple. AND works like charm.woohoo1 No fiddling with gears and :redface2:*bang*
Reg.
CS

Planning to DIY Mill table Power Feed. Bought a MIT aka made in Taiwan 30 years ago for the Bridgeport Mill in the plant. With the factorty shutdown,same went to the Rag& Boneman. MIT Power feed cost me US$1000.

With the mini mill there are times when long pieces are milled. I can fall asleep milling long pieces with ten-------20 repeat cuts.:rant:

I have the speed controllers and motors from Ebay. After the Nemett-Lynx is up and spinning ,it will be mill upgrading.

Not been gear cutting after the last mitre gears for the Rupnow H&M Engine.
Some upgrading required for the DIY gear cutting equipment.