Centec 2B - New arrival and Q&A

P.S.

https://www.chronos.ltd.uk/product/2mt-drill-chuck-arbor-tapped-3-8-bsw-jt6-taper/

Thanks all - I guess that big locking nut for the half-nut / rack feed handle must be 3/8" BSF then?

Did my first horizontal milling in anger today and it went quite well. Not getting a super smooth finish on vertical milling yet (3/8" 4-flute endmill on brass rod) but lots of things to tweak. I'm starting from the beginning all over again.

One thing that is definitely jumping out at me is planning the order of operations - switching from drill to mill and back to drill again is quite a time sink!

Also, after trying to eyeball the centre of a piece of square bar with scribe marks and a needle-point wiggler and failing three times in a row to find the actual centre, I may be starting to understand the push towards a DRO ...

I assume so, it is on my 2A, can't remember a W/W thread being used apart from the drawbars. Measure it to find out for sure:

https://www.ring-plug-thread-gages.com/PDChart/BSF-thread-data.html

Brass, TBH can't remember milling any. When cutting brass on the lathe the tool doesn't have back rake, it may be grabbing and needs to be sharp.

You could try one of these to be going on with.
Dearer options such as Starrett etc. are available too, if you have money burning a hole in your pocket.
https://www.arceurotrade.co.uk/catalogue/results.aspx?search=centre+finder

For the Mk3 VH there is a small grub screw, just behind the quill lock handle, that pokes into a slot that limits the quill vertical movement. The nut on the front of the VH does nothing on my VH.

Peak4/Bill, I'm using the wiggler with a 1/4" ball head. Are these cylindrical finders better? In the meantime, should I be paying attention to it stop oscillating as my zero, or when it deflects?

Realistically I think I may have just fallen foul of expecting 1/4" square rod to actually be 0.250" .

I managed to nip up the bolt on the front of the vert head, it just seemed to be leaking oil through the loose bolt hole without it. Any ideas on what oil should go in it?

All the best!

I'm a bit jealous of the fun William is having learning with his new toys! You can't say the process isn't interesting, but like magic tricks, finding out how it's done is an anti-climax, and then the task is just business as usual. Don't worry, next stage is making things accurately from someone else's plan, and beyond that is developing your own designs. There's always more to learn, and 3D CAD fills hours when the workshop is too hot or too cold.

Putting a DRO on a milling machine is a no-brainer, at least on the table. DRO transforms the machine, for example by eliminating the need to carry backlash correction and to carry 'how many turns' in your head. If a DRO is affordable, get one straight away.

With a DRO I rarely use anything other than a cylindrical edge finder and a needle wiggler on my mill. Cylindrical edge finders are easier to use than other types. I use it to locate a reference from two edges, and then work from that with the DRO. (Checking it often against other references.)

More often than not my needle wiggler is a dressmakers pin (a large pin with a plastic ball on the blunt end) and a blob of plasticine rather than the manufactured item. It's mostly used with a loupe to locate crossed lines or a centre-pop when no edge reference is available.

The accuracy of metal stock varies. Black Mild-steel is crudely untrustworthy. Bright mild-steel is much better, but varies between different strips, so check it. Not unusual for round rod to be a Reuleaux polygon (like a 50p coin) rather than truly circular. And I have some ¼" square rod that's actually a parallelogram. Ground stock is best for off the shelf accuracy, but expensive. Though Bright MIld Steel is usually 'good enough', a common first operation when milling is to start by cutting a reference surface rather than trust stock straight out of the box: if it doesn't have a reliable surface, cut one!

Dave

I fitted a 3-axis DRO to my 2B and then added a DRO scale for the quill, which is surprisingly useful. As per SOD, I use an edge finder and work from an edge or a centre point (easy to find with a DRO). All my drawings are dimensioned accordingly - I never have use scribe lines or a centre-punch.

New millers first mistake, not measuring the stock

2nd mistake not remembering that different to a lathe bright steel unlike black can be full of stresses and a freshly milled surface can turn into a banana after a decent cut if not balanced by a similar cut on the opposing side.

William, Re the chrome dome nut leaking. it doesn't seem to do much other than retaining the stop pin behind it; mine leaked too, so I added either a fibre or a copper washer underneath it.
Re lubrication, none of the documentation I've managed to find specifies what to use in the V head, so I'm just using the same as the main gearbox i.e. Shell Vitrea 41 equivalent. essentially a plain ISO 100 oil
See Tony's site
http://www.lathes.co.uk/faq/page19.html

Yes you're correct, the ¼" stock probably isn't either ¼" or square.

For the most part, I've not found much difference in use between the ball ended or cylindrical edge finders, so I just use the 0.2" one, as it's a simple one turn of the graduated handle to allow for ½ the diameter to show the edge. (It would be a pain using a metric one on an imperial machine, or vice versa.)
It is worth wiping a stone over the stock material before using an edge finder, to remove any burrs, which might mislead.

Bill

Edited By peak4 on 02/08/2021 12:24:07

Any edge finder can be perfectly still (not oscillating) at any time - whether touching or in free air. A wiggler should be stationary when touching a tiny spotted mark but a cylindrical edge finder must have gone just beyond the non-oscillating stage to be sure of the correct point. Clearly no (well minimum) error at all if finding both edges (of a parallel part) to determine the centre between those two sides.

Setting your origin (zero, zero) to a selected square corner of a part should work for most instances. DROs are far superior than making backlash adjustments🙂 .

I would think that you've overfilled the quill if there's a leak around the dome nut. The quill is the oil reservoir, or have I miss-understood it or all these years? .

For a good finish on brass,use a flycutter .

The boss attached to the front nut on mine stops the vertical movement of the quill before the grub screw (dog point on mine) gets to the bottom of the milled alignment groove. About 1mm clearance to the bottom of the groove, maybe someone has re-worked it during its' life, but the quill and casting base line up (at the moment anyway as I am going to put a DRO on that ).

I’ve not milled brass with my Centec. I would likely try horizontal with a slab mill for a very flat surface. No risk of tramming issues and only a single finishing pass for the whole surface. William has no need to remove the VH to change to horizontal, so very easy to swap modes.

William,

Don’t overlook the horizontal MT option for drilling horizontal holes. Can be useful at times… don’t always need the overhead support for using that drive.

I'd not considered a slab cutter but that does make alot of sense. My widest horizontal cutter is 5/8" - other than a 1" bore is there anything I should be considering with regard to teeth/etc. on a cutter like this?

I tried to cut a piece of aluminium flat using a horizontal cutter and ended up with a tiny groove on the outside edge of the cut. I don't know if this was because the overarm was sagging and causing the arbor and cutter to sit at an angle, or something else. The VH was on the front of the overarm/spacer so next time I'll try pushing that back along the dovetail.

That nut on the front of the VH had oil leaking out of it like crazy, so I used an aircraft screwdriver to hold the stud on the inside and tighten it up on the outside.

Turns out the disc on my wiggler is only nominal 0.100" - actually 0.1185" - that would have been annoying! I grabbed a M&W 0.500" edge finder too - not because I think I need it, but more because it will fit in the clarkson chuck and is roughly the same height as a mill - rather than having to crank the table down 3-4" and then back up again!

Edited By William Ayerst on 03/08/2021 08:53:51

Do everything up tight, and then tighten some more, and ensure the cutter is well supported. Make sure the work is firmly held; I've had a slab mill lift work out of a Kurt vice. Spindle speed the same as any other cutter of the same diameter. Feeds based on number of teeth and number of thou per tooth. I usually start at 4 thou per tooth. From a practical viewpoint I suspect the lack of arbor keyway and lack of power will be the limiting factors. A slab mill can remove serious amounts of metal; this is pussyfooting as the mill didn't even notice as the cut started:

Andrew

Can't beat Andrew ................ but I can offer photos of my 2Aminus as it was then (minus a gearbox) with a 2 belt drive facing the top and bottom of it's own raising block.

Note that the nut does not touch the bearing and it's only a 2 thou cut.