Centec 2B Mill

[jason evansParticipant @jasonevans10206]

hi all

looking at getting a mill for the garage, and a centec 2b mill has come up near to me. it needs a refurb externally and not sure yet how it runs. it has a vertical head included and power feed on the bed. also has coolant pump on the base.

are these any good for general/light work, can spares be easily sourced.

any help much appreciated.

jay.

[jason evansParticipant @jasonevans10206]

[Mike Palmer 1Participant @mikepalmer1]

Jay

Grab it before anyone else sees it, Centec’s are excellent mills for ME’s I have had two of them. Really solid and well engineered, a raising block for the vertical head is a useful addition, if it doesn’t come with one you can make one on the mill.

If you need more convincing Cheery Hind made all her wonderful models on a Centec, there are currently three versions on eBay.

Mike

[Michael GilliganParticipant @michaelgilligan61133]

Jay,

If you haven't been there already, look at: **LINK**

http://www.lathes.co.uk/centec/

Mike Palmer seems to have summed-up nicely.

MichaelG.

[not done it yetParticipant @notdoneityet]

Two Centecs sold on epay this last week.

2A with riser block, Mklll head and power feed and a 2B with Mklll head but prolly no overarm.

Both made over £900. A Mklll head made around £600 recently (on epay).

I'm a member of a small model engineering society – only about 20 members – and there are three of us with Centecs.

Riser bock is more important for the 2A, but handy if you have the head room. Power feed is a definite bonus.

Mklll heads (with quill) are much more sought after than the Mks l and ll.

Go for it. Spares? Make your own for most wearing items? They have been around for decades and can still be put back to original spec, I expect. In good order they are, IMO, far better value than any chinese equivalent (there are probably none, as these are perfectly at home for both horizontal and vertical milling) for most hobbyists.

[jason evansParticipant @jasonevans10206]

thanks guys. going to take a look later, will keep you updated.

atb

jay

[Phil PParticipant @philp]

I agree with everyting above, I too have had two Centecs, a 2A and a 2B and they were super little machines.

prior to me upsizing to a larger machine I actually grafted a spare Bridgeport vertical head onto the 2B at one point.

Phil

[Stephen BensonParticipant @stephenbenson75261]

The half nut put me off seems to be quite difficult part to reproduce, also the z axis was very odd on some versions

[not done it yetParticipant @notdoneityet]

The half nuts, I believe, can be done away with, if they fail and cannot be sourced/repaired, and a full manual lead screw nut installed. Those half nuts are only to allow for fast traverse of the long travel and, as hobbyists, we are not usually in that much of a hurry….?

[jason evansParticipant @jasonevans10206]

Popped down and had a look today. Very impressed with it, everything works as it should, travel felt good in all axis.

It has the horizontal arbor and the mk3 quill vertical head. Powerfeed all good and with gearset, and built in suds pump. It is 3 phase so will have to look into that, but have put a deposit on it so its mine ☺

Thanks all for your imput, now need to reshuffle the garage about.

[jason evansParticipant @jasonevans10206]

could anyone give advise on converting this to 240v, really don't know much about electrics.

I believe the table motor is 415v too.

thanks

jay

[duncan webster 1Participant @duncanwebster1]

If it's the one with the motor in the cabinet underneath, stick with 3 phase. Mine had single phase motor which made the cabinet drum like mad, the motor is actually boted to the cabinet, not a good design feature. Eventually fitted 3 phase motor and vfd, but I'm not sure you can drive 2 motors off a vfd, so you might be better with a phase converter, or better but more expensive 2 vfds.

The motor mounting is extremely inaccessible, you finish up flat on your back with your head inside the cabinet, so it might be an idea to sort it out before you install the machine proper on top of it, when you can get the cabinet up on a bench.

[not done it yetParticipant @notdoneityet]

Be aware that the power feed will almost certainly be 415V, while the usual replacement 3 phase motor to power the spindle, would be 220V for use on a single phase supply.

415V VFDs are rather more costly than 220V versions for any given size. Mine, I think has a 415V inverter for the power feed and now has a VFD driving the 3 phase 220V spindle motor.

[jason evansParticipant @jasonevans10206]

thanks. I think I will go with two vfd's. can anyone recommend a good model to get, as there seems to be quite a choice.

thanks

jay

[Jim GuthrieParticipant @jimguthrie82658]

If you are going to change the power drive motor, consider making it reversible. On my Centec 2A, the previous owner had changed the Centec supplied single direction motor with a reversible one and it does give more flexibility when used as a vertical mill.

Jim.

[Gary WoodingParticipant @garywooding25363]

I've had my 2B for about 12 years. It has the original 415v 3ph motors and came with a rotary converter that I found clumsy and noisy. I removed both motors, split the star points so the windings could be connected as delta, and fitted two Mitsubishi 220v VFDs. The VFDs are mounted just below the suds tray. See my ALBUM

The VFDs are controlled by the little control box mounted on the power drive motor, as shown in the photos. It gives instant direction and speed control and I didn't have to buy new motors.

[jason evansParticipant @jasonevans10206]

thanks. so are both the original motors dual voltage?

[Gary WoodingParticipant @garywooding25363]

No, both motors were originally 415v wired as STAR. I opened them up, and for each one, located the the star point, split it, and extended the wires to the connection block where they could be connected in DELTA. This made each motor 220v and could be driven, at no loss in power, from 220v VFDs. Because I've split the star points, the motors are now dual voltage.

[jason evansParticipant @jasonevans10206]

ah ok cheers. I have asked the seller and has replied that the main motor is dual, but the table motor is not.

is it a difficult process to change a motor from star to delta?

atb

jay

[duncan webster 1Participant @duncanwebster1]

It's not for the faint hearted. You have to dismantle the motor, find the star point where the three windings come together, cut the joint off, attach 3 tails and bring them out to where you can connect it up as delta. The purists would have it that you should braze the 3 new joints as motor winding can get quite hot, but I used soft solder and it worked OK. Then you need to make sure it's all properly insulated before you put it all back together

As this is a fairly small motor you might be able to get a dual voltage replacement fairly cheaply, or even a DC brushed motor, for which a controller would be cheaper.

[John RuddParticipant @johnrudd16576]

Posted by duncan webster on 14/01/2017 12:48:32:

It's not for the faint hearted. You have to dismantle the motor, find the star point where the three windings come together. …..

The purists would have it that you should braze the 3 new joints as motor winding can get quite hot, but I used soft solder and it worked ok…

I would counter the argument that soft solder is more than suitable….if the windings are getting that hot then you're in trouble…..

[duncan webster 1Participant @duncanwebster1]

Well I did say purists. This was motor maufacturer's advice, but I soft soldered mine

[John RuddParticipant @johnrudd16576]

Duncan,

I didnt mean to contradict..

Sorry, what I meant to say was that soft soldering would be appropriate….silver soldering is not required….

Soft solder gas a melting point of approx 188 Celsius….motors with a class F insulation have an allowable temp of 155 and that includes an allowance for hot spots….so even if the hot spot occurred at the soldered point the joint would probably be ok, but weakened….even of running a motor at those sort of temps ought to ring alarm bells….You would smell it…..running hot…..

[jason evansParticipant @jasonevans10206]

Thanks guys. Sounds like quite a job. I do like the idea of having feed in both directions, has anyone actually found a replacement motor for the table.

[Gary WoodingParticipant @garywooding25363]

If you intend to modify or replace the table motor you will, of course, have to remove the existing motor. This is fairly straightforward and involves unbolting the gearbox from the table. Unfortunately, to remove the gearbox you have to remove the lead-screw from the driven gear, and this involves undoing the two lock-nuts shown in the new photos in my Centec album. As you undo these lock-nuts, the lead-screw is gradually pushed out of the gearbox BUT there is a rather well hidden Woodruff key that keys the lead-screw to the main gear, and this must be aligned with the slot in the bearing (shown in the album) otherwise the lock-nuts jam the key against the bearing and the whole thing locks up tight. The lead-screw is not attached to the worm-wheel, it simply acts as an axle.

I can't remember if the lead-screw has to be completely removed from the table (I did it in 2005), but that's the easy part: getting the lead-screw out of the gearbox is the tricky bit. Once the lead-screw is out of the gearbox it's a simple matter to remove the worm-wheel which then allows access to the screws attaching the motor.

Edited By Gary Wooding on 15/01/2017 11:26:32

Edited By Gary Wooding on 15/01/2017 11:27:48

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