Centec2 knee adjustment

[sean logieParticipant @seanlogie69385]

I'm looking to come up with some sort of Knee adjustment for my Centec2 horizontal mill .Centecs own is just too fiddly and time consuming . Any of you clever chaps have any ideas ,preferably I'd like to make it rather than buy .I have a couple of ideas using a old acme threaded bar and nut of an old trailer jockie wheel .The bit I can't figure (probably over thinking it) is how to put it into practice . There's not a lot of room to put something like this in place .

Sean

[sean logieParticipant @seanlogie69385]

[NigeParticipant @nige81730]

I dont know the centec but it looks as if the bed height is adjusted with those two adjusters bearing on that lug on the left? Could you use your acme threaded bar centrally under the bed in some sort of jack configuration and bearing on the base of the bed somewhere up between those two webs?

[Martin CargillParticipant @martincargill50290]

It might be worth trying to find an old style wind up car jack and using that under the table (assuming that there is space between the webs that you can see in the photo). I'm thinking of an old style one with a gear driven "crown wheel" acing on an acme screw, not one of the modern cantilever type.

[Martin CargillParticipant @martincargill50290]

One like this Loads on ebay – search for "screw car jack"

Edited By Martin Cargill on 03/09/2017 21:29:12

[Roderick JenkinsParticipant @roderickjenkins93242]

Hi Sean,

This is the table raising arrangement on my Sharp MkII milling machine.

Under the gaiter there is a 10 tpi 1/2" ACME screw that moves with the table and projects through the mill base. I don't know for sure what happens inside the gear box but I suspect it is like Martin's jack. One rotation of the handwheel raises the table 1/10".

HTH,

Rod

[sean logieParticipant @seanlogie69385]

Thanks guys ,I’ll be put the adjuster between the webbs on the knee .

Sean

[not done it yetParticipant @notdoneityet]

Sean,

Have you checked out the superb 'swap list' by Gary (binswood) on the yahoo forum? Your need is ease of operation and positional precision – as you are only in horizontal mode (with no easily adjusted quill in vertical mode).

I have no idea of the actual 'micro' adjustment on your machine but it is much harder to raise the table on my 2B compared to my Raglan.

[JourneymanParticipant @journeyman]

Sean, there seems to be a bit missing! The photo in the manual shows a handle at the rear for raising lowering the knee, the bits at the side look to be adjustable stops.

The later model 2A had a screw under the knee if you can find a spare it might fit on the 2.

John

[peak4Participant @peak4]

Posted by not done it yet on 04/09/2017 08:31:12:

Sean,

Have you checked out the superb 'swap list' by Gary (binswood) on the yahoo forum?

NDIY, just been unsuccessfully looking for the above list, could you give me a pointer as to where I might find it please?

Sean, my thoughts would be along the lines of the jack, cut down suitably, as much of the work would already be done for you in terms of castings etc.

It's very similar in principal to the design of the mechanism on the 2B I have. I could find you the diagram if it helps.  looks like the cross section diagram is in the manual linked to above.

The original bellows that protected the screw from swarf desintigrated on mine allowing the thrust bearing to get damaged by the ingress of metal chips.

My replacement bellows came from an old shock absorber sleeve, very similar to the corrugated rubber sleeves used on motorcycle from forks.

Edited By peak4 on 04/09/2017 10:16:01

[sean logieParticipant @seanlogie69385]

I’m toying with the idea of a fixed mounting with a tapered roller bearing which the end of the acme threaded bar will be fixed ,the nut will be secured to the plate the mill is mounted to . I’ll be fitting a 8″ dial wheel the other end of the rod . That’s the theory for now . The stew jack is a good idea only if I can find a small enough one to fit .

Sean

[Old ElanParticipant @oldelan]

Sean, try this URL. https://groups.yahoo.com/neo/groups/centec_milling_machines/info

John has shown a 2A of course. The 2 has some kind of ratcheting system AFAIK. It's the 2B that has the screw under the knee.

Edited By Old Elan on 04/09/2017 10:46:31

[Paul White 3Participant @paulwhite3]

Sean. I think this is what you are looking for. I made this from bits that were to hand , a bevel gear and screw made 1/2" square thread. Connecting the top of the thread to the knee I found difficult and propose drilling through both webs and inserting a cross support.

I am sure you know but the stops in your photo are upside down.

regards Paul.

[Paul White 3Participant @paulwhite3]

this should have been in above posting

[sean logieParticipant @seanlogie69385]

Thanks Paul. That was the way they were ….. I think lol

Sean

[Dave HalfordParticipant @davehalford22513]

Posted by peak4 on 04/09/2017 10:13:13:

Posted by not done it yet on 04/09/2017 08:31:12:

Sean,

Have you checked out the superb 'swap list' by Gary (binswood) on the yahoo forum?

NDIY, just been unsuccessfully looking for the above list, could you give me a pointer as to where I might find it please?

Sean

theres one in the files section, centec parts swapping pdf, it's not by Gary , but …………….

A lot of the screw jacks need to protrude below the base plate, mine sticks out 2 inches or so so not much use if you have a drawer beneath the mill.

[not done it yetParticipant @notdoneityet]

It's not by Gary , but …………….

Oops, sorry – it's by some bloke by the name of Dave Halford! Any relation to you? My mistake, apols as most of the good stuff on that site is from Gary.

A good write up, all the same.

Of course, I don't need it as I am lucky enough to have a 2B. Apparently some on that site (well, one at least) think the 2 is not worth modifying… but I don't agree with that sort of piffle – they are a very good and solid design with plenty of extra opportunity, when fitted with a vertical head.

It's def worth blanking off part of any draw underneath, for the operational improvement gain, I am sure.

[Dave HalfordParticipant @davehalford22513]

Thanks, to be fair you are the first to mention it, good, bad or indifferent :O)

I've turned whats left of my 2 into a mini surface grinder simply by plonking a half horse bench grinder into the top dovetails. It's come in handy once already.

[peak4Participant @peak4]

Sean, have you seen this on ebay??

**LINK**

Might save a lot of work if you can come up with the cash.

Bill

[sean logieParticipant @seanlogie69385]

Yes I’ve seen that thanks Bill . I quite like the challenge of trying to make my own ,it’ll be a tag agricultural but I think it’ll serve my needs . New caravan is eating into my worship funds anyways 😁…. got to keep er indoors happy I’m sure I’m not the only one on here who gets… “more stuff for your shed ” .

[sean logieParticipant @seanlogie69385]

It's a bit agricultural but it works a treat ,some more fine tuning to be done .

 

Not sure why the photos is on it's side …

Edited By sean logie on 09/09/2017 18:20:37

Edited By Neil Wyatt on 09/09/2017 19:27:26

[RainbowsParticipant @rainbows]

Bonjour

Going to resurrect this thread for a basically identical issue – except the knee casting of my Centec 2 has extra iron between the two webs seen on Sean's machine. Good for rigidity, bad for having a clear space to stick a leadscrew and gearbox and handle and so on in. I'm missing the original handle but otherwise the rack and pinion still functions.

Thinking about working within the limits of the existing set up I don't like that 1) the stop screws aren't graduated 2) if you have to move the knee further than the travel of the screw you have to move the entire stop, thus losing your measurement, 3) if you let go of the lever and the position stop / gib lock isn't tight then the knee will fall down

1) -> replace the screws with micrometer barrels, though I do wonder about the durability of them. Doing repeat cutting passes would get boring fast with no way to switch between precise adjustment and rapid approximate cuts as on a leadscrew dial.

2) -> replace the screws with extra long micrometer barrels? This one I haven't properly worked out yet.

3) -> A mystery to fix. Counterbalancing the knee with a gas spring would help. A switch attached to the handle which actuates a form of lock/clamp would be nice but I can't yet think of a mechanism

If anyone has ideas or has solved this on their own Centec then I'd like to hear them.

Also if anyone has a centec handle for sale I'd be interested, trying to work out that taper and cut a square hole is possible but maybe a bit tedious.

[Dave HalfordParticipant @davehalford22513]

There no reason you can't bolt a jack system on the outside of the knee. Finding something with a micrometer dial built in is the hard part. Though a DRO would get you out of that one, then old screw bottle jack would serve.

Some systems I've seen involve the thread going through the base of the mill and whatever it's stood on. A bottle jack avoids that issue.

[Peter Howell 1Participant @peterhowell1]

Hi. I'm fairly new to the forum so I missed the original posts. I have a Centec 2 that I aquired several years ago with the aim of restoring.

The knee adustment on mine is by a pinon operating on a rack inside the knee, This is attached to a shaft that passes right through the head stock and terminates in a taper onto which a handle fits. This all looks original.

It would be quite easy to fit a graduated hand wheel in place of the handle. But I do have the much sort after quill feed vertical head.

[Dave HalfordParticipant @davehalford22513]

If you both search for sold centec on ebay you'll see a couple of modded Centec 2's and an amusing price for a Mk3 vertical head thats still for sale can't think why

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