Meddings M4 Mk3 strip and rebuild

[Bob McDougallParticipant @bobmcdougall63250]

Picked up this sold as seen Meddings drill, plate says M4 , anyone know how this differs from the M4F ? .Turning the chuck in low speed the motor spun but in high speed it skipped. Aslo return spring was not working. Tapped the chuck out, MT2, Laid it down , loosened the head pinch bolt and tapped back and the head twisted off. I didn' t like the idea of lifting it off vertically even with two. shelf and table slid off nicely after some wd40 love. all in the van.

The gearbox input pulley was really tight, a single grub screw held it on the shaft. It was a straight pull with the three leg puller but needed some heat and underside pressure. In hindsight I should have left it with Kroil penetrating oil on for 24 hrs. The puller was at the limit of its reach and had to stack M6 nuts onto the shaft end to fully release the pulley. Cracked the pulley lip but it came off in the end.

The gearbox cover , six bolts, the dome cover was missing one, inner and outer circlips on both shafts removed and the cover lifted on 1" blocks. The gear changer was holding it in and it wasn't clear how to seperate. Knocked the input shaft through the bearing in the end and lifted the cover with the output shaft and Tufnol gears still attached. leaving the input shaft in the head. The bottom bearing had lifted from its seat and this shaft now lifted easily away from the gear sellector arm.

As mentioned in many other threads the high speed gear was stripped.

The three leg puller feet were too thick to get under the output shaft bearing so had to fabricate some angle iron and clamps . I was planning on replacing the bearings or I would have maybe cut a washer in half to let the bars only contact the bearing hub . The bench vice just absorbed all the hammer blows so the concrete floor and oak blocks gave a very solid base and moved up to gentle taps with the big hammer.

An M10 bolt with a nut was used to drop the output shaft out of the cover bearing.

were going to need a bigger boat.

Gentle taps with more mass feels more like a proper press than trying to whack it with a 1/2 lb.

All apart and pondering about the gear, DP16 20PA 56T delrin, measures 13mm thick but 12mm plate is more common so Ive bought a 100x100x12mm block and a no2 gear cutter and will have a go at gear cutting.

[Bob McDougallParticipant @bobmcdougall63250]

Stripped gear, snapped spring and a loose grub screw

[Mike PooleParticipant @mikepoole82104]

The M4 series seem to come in a few models, MB4 was a bench top version, MF4/RC was a floor standing model with round column and MF4/FS is floor standing with a foot switch stop, this has a different base to incorporate the stop switch. A rise and fall table was an option but is a different table to incorporate the rack drive mechanism. The M4 may be a head from a multi head drilling station. I have some leaflets and parts list if you are interested message me with an email to send them to and I will send you a scanned PDF copy. The original gears were made of Tufnol and ones like yours are all too common, they are rather pricey from Meddings so cutting your own makes good sense, it might be worth cutting a spare or two while you are set up.

Mike

[Bob McDougallParticipant @bobmcdougall63250]

Thanks Mike , interested to see any literature related to this machine, Foot switch , useful when theres swarf flying roung the chuck and you cant reach the off.

I sold a boxford union to buy a downham jig borer , but i miss the full pillar so much . so now i;ll cut a new gear on the downham for the meddings.

some more pics, and a grub screw that jammed the quill arm cover.

the return spring was snapped it had a very tight outside holding pin , the housing was held in with a 2.5 mm grub screw.

The spring was in two pieces, too much snapped away to try and fold a new end. I will buy this from Meddings, its made for the exact weight of this quill. interesting cover, It fits really well. . no ratchet as I saw in some other models. . The cable clamps unscrew.

took the nut off and the arm cover didnt come off, this should lift straight off. a grubscrew inside was jamming it.

So I tried to tap the shaft out

The arm hub came loose after alot of tapping both ways, The grub screw on the collar had come loose and jammed into the hub unner, this photo has it turned in about two turns as i wanted to know how far out it was. I was so convinced the shaft was stuck I put a nut on the thread and applied more force. the effect was probably to snap the 5.96mm pin. not tapered.

The inside of the M4 arm cover with a slot for the pin in the drive shaft, the collar grub screw i believe had jammed into this .

tapped the remaing pin out . the collar with the loose grub screw was for pinching the x asis of the

Humble Pie, driving the shaft into the collar had pushed up metal on the shaft, tiny file, and it comes apart

The pin should be in one piece the collar looks like a modern finish coating, maybe its non origional.

Setup on the Downham jig borerwith a 12DP cutter doing 41 teeth on a 91mm disc. a test of the setup. arduino.

The stepper was on a button to increment teeth, the first timei turned the mill motor on the indexer just ran constantly. added some filtering and cut 41 teeth overlapped the first and last and very happy.

[Bob McDougallParticipant @bobmcdougall63250]

Motor test, connections were for 415V 3phase, star, for my 240V 3Ph needed to swap the pins, the lable says "mesh" rather than delta, The three phases were connected to UVW. Earth to a recess in the case far left.

for 240V inverter the three phases are connectrd back to UVW, no connection to N, Earth to case. Always check earth continuity from chuck to earth pin on the plug. Or just earth the machine and always use 30mA RCD breakers. when changing motor contacts , lie it down so slipped parts dont fall inside.

New gear, In the lathe I first bored the 25.0mm hole in the acetal square 12mm blank. then from a 25mm x 11mm bossand then a 12mm thread. in hindsight I should have drilled and tapped. bandsawed the corners off the blank square and took to 92.0 mm on the hub. then turned the rear shaft to 11mm to fit in the ER20 indexing colletThe cutter was £23 on ebay , 56 teeth, less than 50p a tooth, felt blunt but its cutting plastic, …, the burrs were awful, not sure if I was going too fast, . but it cut.

Well heres a use of my 4th axis from my homemade cnc. made it for carving names on wood pens, made two ,

The 12:70 reduction with the large stepper holds the word very rigidly, I bought a new stepper driver with more microstepping but the 1/32 worked fine. I had code on the arduino to index by 1/56 every time I pressed a button. I turned it all on and the stepper just continually rotated. EMC !!! dont you love it. so Hard 470 ohm pullups and 1uF caps on the input pins solved that. all calculations were in floats and it indexed very well. Its plastic.

How many tines did you cut the gear, the first cut wasnt deep enough, or the second, the third was about right. luckily to re-cut is fairly easy to line up the cut teeth with the cutter. the important thing is not to move the cutter. in the Z or X between attempts. so i got a really ugly looking gear with loads of swarf attached I had to remove off with a scalpel.

Keep your balls in. , this shaft will need supporting from underside when re-fitting the gearbox cover, tiewrap on the detent sprung 3.1mm balls, i lost one . i heard it hit something about 2m away. 30 seconds with a magnet and i knew I would never see it again. so one is now 3.0mm. Slide the gear assembly onto this anc cut the tie wrap out . it worked .

line the holes up with the springs, it is possible to get it 90 degrees off. 50% of the time. To fit the gearbox cover I put a wooden ~1" spar across between the back and a slot in the quill bore to hold the end of the input shaft up,

Fitted the head , had to stand on 4 " blocks, and Im 6ft2, no quill or motor or feed. Maybe

Damage to the quill feed , i had seen this and this photo is two weeks old but re-assembling it bit into the quill,and caused a tight spot , the tooth was pushed over , no cracking, soft against the hardened quill, , I needle filed it down and it feels great.

Finally to make it run… Attached the motor and… the pulleys are different heights. by one . I know I took the front pulley off but it looks to me its the motor pulley thats too high. But I will be calm and let kroil do its work, , it runs.

excited. the high speed gear is a little tighter on one side than the other but…

This has been a pleasure of a project and I hope it helps others repairing similar machines. I bought the return spring from Meddings and it arrived next day with fitting instructions.

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