Centec 2B - New arrival and Q&A

Good evening gents,

Courtesy of Steve at Landylift (stellar service and will have no objections to using him again) I have taken delivery of my first ever milling machine, a Centec 2B.

It came with a horizontal arm and arbor support, a fabricated riser block and Mk. III quill head, as well as a 3" Abwood vice, two dozen horizontal milling cutters of various kinds and a couple of T-nuts.

It's fitted with a VFD and separate control box for run/jog, reversing direction and start/stop.

I have tried a little milling using the vertical head, a fairly high speed and a four toothed endmill and it was an absolute success.

I can't seem to move the vertical head ontop of the riser block even with the nuts slackened off, it seems to be held fast. Before I do anything stupid, is there a common cause for this?

I decided I wanted to also try horizontal milling, so I slid the riser block forward to act as a support arm (having to disconnect the vertical head belt since I couldn't slide the vertical head backwards to keep it in line). I fitted the arbor, with a cutter and the arbor support and noticed - there are keyways on the spacers, keyways on the cutters, but no key or keyway on the arbor. Once I hit any resistance in the cutting process, the cutter stopped while the arbor kept spinning. Am I missing something??

What is the purpose of the nut on the front of the vertical head? It seems to just spin in place on my one.

Thanks for the advice re: collet chucks, I have a Clarkson Autolock collect chuck and a series of imperial collets, and imperial cutters from Tracy Tools. Annoyingly, some of them only seem to thread partway on to the collets, not sure if I can do anything about that?

Anyway, thank you all for the help and advice - I'm having a blast already!

Some people intend the the whole riser to move forward so the dovetails with the head on are not expected to move so may have no clearance.

Keyways, you buy cutters intended for all mills including 5hp monsters so they all have keyways just in case. Neither the 2, 2A nor 2B arbors have a keyway.

Tighten the arbor nut properly ( only when the arbor support is in place) and the cutter won't slip.

No idea.

It won't be a Clarkson issue, I've got 70+ named cutters and they all fit in my Vertex Osborne clone.

My arbor for the Omnimill has a keyway, never use it. As Dave says just horse up the nut. Less chance of doing some spectacular damage without a key if it all goes wrong. I have never knowingly had a cutter slip without a key. Word of warning though - don't try any ambitious climb milling with a slab cutter - unless you want to test your work holding to the limit / see how past you can project the job across the shed!

Paul.

Thank you both, I wondered if I was going mad on that one!

For tightening (both the horizontal arbor and the clarkson chuck), is there an obvious way to lock the spindle(s) other than putting it into low gear and hoping?

I meant to say that the top of the riser block has a dovetail on the full length, so I would have expected it to move somewhere - but it doesn't budge in either direction when the angled bolts are slackened.

Hi William,

I can't seem to move the vertical head ontop of the riser block even with the nuts slackened off, it seems to be held fast. Before I do anything stupid, is there a common cause for this?

The drive belt will stop the whole thing from sliding and the belt adjuster may well prevent the head sliding on the riser block keyway. There is only one position for the vertical head when in use.

Both other posters have good points to bear in mind.

It takes up a lot of space, doesn’t it? Mine needs even more as it has a power feed drive on the end of the table - another ~6”.

You will need the motor reverse when you change between vertical and horizontal milling. My VFD defaults to the same setting each time the power is switched off - something to rememer if yours is the same.🙂

I have a control box hanging off with a fwd/reverse toggle so that's OK!

I inadvertently left the fixing bolts for the vert head slightly slack while milling, it caught slightly and must have unstuck some hardened oil or something, as the head now moves OK.

I don't do much horizontal milling, as the V head is a bit heavy for me to go removing at the moment, post Covid.
I believe it's normal to use the arbor without a key, particularly with slitting saws to save them shattering if you get a bite.
Don't forget, you need to reverse the motor for horizontal milling, compared to vertical, otherwise the arbor lock nut will tend to undo.
The original panel on mine had a big toggle switch for reversing the main spindle motor, but I didn't appreciate why originally. (sorry I missed NDIY's comment on reversing)
I now use it for reversing the single phase table feed motor, and have the main three phase motor reversible via the inverter.

The vertical head should lock with a big spanner on a couple of flats on the bottom of the spindle.
The horizontal, from what I remember, doesn't have a lock, but really the only thing you need to lock it for, is the drawbar, which only need a light tightening to seat the morse taper.

My horizontal arbor has spanner flats, from what I remember, though it's in the workshop, and tea smells like it's almost ready.

Bill

Edited By peak4 on 26/07/2021 22:42:18

Now I'm getting worried, do not tighten the drawbars more than finger tight + 1/8 turn on a spanner.

To secure cutters in the horizontal arbor there may be a tommy bar hole (which mine have) near the taper.

You do not need to be a gorilla to do up the Clarkson either it is not an ER collet.

Yep, I forgot of course the flats are there for tightening. Time for me to get a 1" spanner!

I tightened the horizontal arbor down and had another go and all was well - up until the point that the cap on the end of the arbor brushed against the inside of the arm support, and being reverse threaded proceeded to unscrew itself, which was quite a bum-clenching moment. I think there's meant to be a bearing that would fit in the arm support to gap it properly, I'll have to look through my bag of bits.

Is there a commonly available equivalent to 'Shell Vitrea 41' oil and 'Alvania 3' grease? There's a good amount of lubrication already but I don't want to do too much while risking it.

It seems there's a drawbar for the horizontal arbor, but just some threaded rod for the vertical, so I'm using that for now but will keep it gentle until I can fabricate a proper one.

On a related now I'll need to do some drilling soon, and would love to do it on the mill. I'm a bit confused though. I can find almost no drill chuck arbors with drawbars at all, let alone the specific one I required - (JT6 to MT2 with a 3/8" thread).

Am I over-thinking it that I will need a drawbar for the drill chuck? So many are sold as tanged and I find it hard to believe that all of those are used on a lathe only?

That said I have found one 2MT drill chuck arbor with a 3/8" drawbar thread and that's a B18 taper. It seems only import tools use this and I'd prefer to avoid that if possible - but the drawbar and drill chuck would set me back only about £25.

Drawbars aren't normally needed for drilling because cutting with a drill forces the taper tighter, hence less likely to slip. So tight, a tang is needed to eject them.

Milling applies sideways and reverse forces to the cutter that tend to loosen a plain taper, causing poor finish due to movement, or the taper dropping out entirely. For the same reason, drill-chucks shouldn't be used to hold milling cutters - they are designed to grip up-down, and perform badly when the cutter moves sideways.

A drawbar pulls the taper home good and hard and is almost immune to sideways forces and vibration. Don't overtighten them though, especially if a cold taper is inserted into a hot socket and done up by Mr Gorilla. They can be a real pig to unstick.

On the subject of unsticking, loosen the drawbar a turn or two then tap it sharply with a brass hammer. (I whack mine with an ordinary steel hammer via an aluminium block. The softer metal prevents damage to the drawbar.) Under no circumstance pound on the drawbar - a fast light crack to break the stiction, rather than several slow heavy thumps that will mangle the threads and do other damage.

Dave

Edited By SillyOldDuffer on 27/07/2021 12:59:30

If you have the stub on the end of the arbor then pull the support forward till the nut misses it, the drawbar stops end float, the bearing provides horizontal support only (clue is in the name.)

It seems there's a drawbar for the horizontal arbor, but just some threaded rod for the vertical, so I'm using that for now but will keep it gentle until I can fabricate a proper one. Pardon??? Just keep it gentle

You do not need a drawbar for a drill chuck, my mk2 VH takes a tang with no bother.

William,

Don’t over-think things too much! If a 10mm length of threaded rod will suffice, just use that as needed and get a 10mm threaded one (Arc sells one for £5.20 plus delivery). I have 10mm, 3/8” and 5/16” drawbars, some which simply stay with the tool (definitely the smallest chuck with the 5/16’ thread). Mine are complicated by some bits needing to be used on the other mill (or even in the lathe). I made all the imperial drawbar nuts from the same length of hex so they fit the same spanner. Metric are double-nutted.

I have a row of screws, in a board on the wall, and hang the tools up by the drawbar nut. Some screws get used, some don’t. The 10mm drawbars get most use and my Clarkson is not often put into service these days.

Next time I take the ER32 chuck off my Raglan, I will be fitting an ER16 and get a third nut for the set (that way I can just swap cutters and nuts rather than separate the cutter, then collet, from the nut for each change). I expect, at some point I might pick up a few extra collets in the most used sizes, giving more options when changing cutters.

One of the first things I made on my mill was a pair of wedges for removing Morse Taper tooling. Saves ‘bumping’ with a soft faced mallet - just loosen the drawbar a bit and prise off the taper with the wedges.

I find it's easier to use a draw bar arbor for my drill chucks in the mills as it's easier to eject them and release the taper than faff about with a wedge through the quill. Plus no risk of dropping the chuck on the table when the taper lets go.

Righto - good to know - when I said 'take it gentle', I meant with removing the tools with a (brass faced) mallet via the threaded rod drawbar, as opposed to just twisting a self-ejecting one. I'll look into some wedges - like a pry bar?

Thank you for the tips re: tanged vs threaded arbors. If I could find a compatible JT6 taper MT2 arbor with a 3/8" drawbar thread I would. I'll keep an eye out for one, but good to know I can do without.

Don't you have captive drawbars?

I have one for the horizontal, but not the vertical. For now I'm using a bit of threaded rod and I'll look to turn up a captive drawbar at my earliest convenience.

Nice looking Mill William.

One thing I am struggling with, is the resettable dial on the X-axis. It shares a design with the Y-axis - the outermost ring is a locking nut - twisted one way it pushes against the handwheel and the dial, locking it in place. Twisted one way it pulls inward, allowing the dial to spin freely.

This works fine on the Y-axis, but on the X-axis, the outermost ring just spins in place, so I can't lock the dial and am unable to move the table a set amount, as the dial will drift out of sync with the handwheel.

I wonder if the thread has been stripped, as the ring is halfway pushed out, not enough width to lock the dial, but a gap between it and an adjacent spacer. If I nip up the handle fully with an additional washer it can locks the ring, but the rest of the assembly still rotates.

Is there something obvious I'm missing? I've compared both sets of dials and they seem identical.

Clearly, spare parts are a no-go for this mill, so if possible I'd like to repair rather than replace with something else. In the meantime, I was thinking of using some brass shim to make the dial rigid and not resettable.

Edited By William Ayerst on 30/07/2021 13:15:41

I would just get the Arc Euro MT to J6 and make a drawbar from M10 threaded rod. I have mm whit and UNC in two sizes of drawbars for mine as if I see tooling at a good price a Drawbar is cheaper than some other tooling.

Steve Larner