Machining Between Centres

[Keith MorrissParticipant @keithmorriss26344]

I am a new member of this website and still not sure how it works, but here goes for my first question.

 

I have a small lathe which goes under many guises but basically it is a Sieg C1 micro lathe.  It is 250 mm between centres but yet I have no idea how you can actually turn between centres on this machine.  To get the morse 2 centre in the headstock spindle you have to remove the chuck and backplate but then cannot get either the backplate or a faceplate on to be able to turn a lathe carrier to turn the work for machining as there is not a comercially made item to fit to the spindle to turn the work.

 

Has anyone got one of these machines and has manged to turn between centres and how have they done this?

[Keith MorrissParticipant @keithmorriss26344]

[John OlsenParticipant @johnolsen79199]

I’m not familar with these particular machines, but normally you should be able to fit a faceplate (or driving plate) and still put a centre in the spindle hole. There should be a hole in the middle of the plate large enough to accomodate the centre. What happens next depends on the style of the faceplate and the drive dog. Some dogs have a bent tail that engages with a slot in the faceplate. Some dogs have a straight tail, and you need to bolt a stud onto the faceplate/drive plate at a suitable location to engage with the tail. The idea is for the connection to not be too rigid, since it is the centre that is supposed to determine the location, not the dog. It is quite common to wire the dog to the driving stud, especially if you are going to cut screw threads, since you don’t want the job to rotate part of a turn independently from the drive plate.

 

If it is meant for a driving plate, it will probably have slots right through to accomodate a dog with a bent tail. If it is meant for a faceplate it may have t slots.

 

Back in the day when you bought a lathe all you would get, unless you paid extra, was two centres, a driving plate, and a drive dog.  That was how the Unimat 3 came when I bought mine nearly thirty years ago, although I bought plenty of extras too. I have seen people criticise the aluminium “faceplate” that came with the Unimat, this is a bit unfair since it was only ever intended as a drive plate. The actual faceplate was an extra, it is a solid cast iron item with four t slots.

 

Turning between centres is a very useful thing to do for parts that need to be machined all over and need to be concentric, like spindles.

 

regards

John

[StackerjackParticipant @stackerjack]

Normal procedure is to remove the chuck/faceplate, fit the centre into the Morse Taper hole in the spindle, then refit the faceplate. The hole in the centre of the faceplate allows access to the centre, while the slots/holes allow a carrier to be fitted, which drives the work.

If you do a lot of this sort of work, a catchplate may be used instead of a faceplate, which is usually much smaller diameter, and has a slot on one edge, into which the tang of the carrier fits.

Hope this helps,

Jack

[Keith MorrissParticipant @keithmorriss26344]

Thank you for replying to my question Jack but the problem that I have is that the hole in the faceplate is smaller than the centre used in the spindle or the backplate.  If I were to open the hole I would then not be able to refit the backplate or the faceplate as the screws that fit it to the spindle would be machined out making them un-usable.  This should have been stated when I wrote the question but didn’t, apologies.

 

As stated in my question there is not a commercially made catchplate available and I wondered if anyone had made something that worked.

 

Many thanks though for your email.

 

Keith Morriss

[JonParticipant @jon]

Not familiar with that machine but would be entirely surprised if it was not a very east task to remove the tailstock or at very least slide it back almost off the bed to install the MT2 centre.

 

If thats the case i take it you cannot drill with tailstock and chuck?

[Gordon AParticipant @gordona]

Hi Keith,

 

Would it be possible to use the flange that the chuck bolts to as the drive after removing the chuck?

If you secured a short bolt into one of the holes in the drive flange that  holds the chuck; putting a nut on either side of the flange to secure the bolt, could you not then use that as the drive pin for the carrier?

Sorry, but I am not familiar with your lathe, but one of my neighbours has a similar but larger far eastern machine, and this is how he overcomes the problem.

 

 Gordon.

[adyParticipant @ady]

A bit weird…but if the 2mt centre is too “big” to let the faceplate back on I would fit the centre and turn the outer diameter down until the faceplate does fit over it.

 

The headstock end is just a fixed hardpoint anyway, since it revolves at the speed of the driven work.

[JasonBModerator @jasonb]

Easy option is to leave the 3 jaw in place, put in a bit of scrap round bar, say 3/8″ dia, set your topslide to 30degrees and turn a point onto the bar. Do not remove the bar until the job is finished so you should have centre drilled your work prior to this.

 

You can now fit a lathe dog with a cranked leg onto teh work and the crank will engage with teh side of one of teh chuck jaws to drive the work, other end is supported with a tailstock centre, preferably a live one but it will reduce the length of work you can fit between cts.

 

One other advantage of this method is the head ctr will be perfectly true unlike a MT ctr in a poorly aligned head.

 

As Gordon says a nut and bolt through a flange bolt hole also works, done it many times

 

Jason

[Ian S CParticipant @iansc]

Jason, you beat me to it, I,v been off looking at Google on the subject, the method suggested may not leave much room to work on a little lathe like this, but its good for short stuff.  I think from what I see, after you take off the chuck, put a bolt in one of the holes in the mounting flange, there’s no need to put the face plate on.   If you made a drive dog with a tail bent at the radius of the mounting hole, you would not need the bolt.  A live center in the tail stock is well worth either buying, or even making your own, no plans needed, just some thought, and some scrap metal, and two ball races of suitable size, not very big for a no 1 MT center.  Ian S C

[NJHParticipant @njh]

Hi All

I’m a bit confused here.

The Seig  C1 spec gives the headstock taper as No 2 MT but the bore as 10mm.

Now a No. 2 MT  socket is 0.7″ ( = 17.78mm) at the wide end so I don’t see how it can be No 2 MT ?  ( No 0 MT though is 9.04mm so maybe??)

Now the headstock centre should be soft, fitted in position, and trued as Jason says. Once this has been done a small centre punch dot in the centre and another adjacent to it on the nose of the mandrel will allow accurate fitting in the future. In the absence of the correct centre that will fit through the faceplate I think Jason’s scheme is fine.

Keith welcome to the world of problem solving – it’s a great hobby!

 

Regards

 

Norman 

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Keith, is it not possible to make a simple drive plate out of, say a disc of 6mm plate and fix it where your face plate goes with a hole big enough for the centre and a hole at suitable distance for the drive dog pin. After all it doesn’t have to run true like the faceplate.  Like Ady says you can always turn the centre, to accomadate any fixing screws.

 

Regards Nick.

Edited By Nicholas Farr on 03/01/2011 12:20:25

Edited By Nicholas Farr on 03/01/2011 12:20:56

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Nornan, Should be easy enough, my Hobbymat only has a bore of no more than 11mm, but that has a 2MT in the headstock..

 

Regards Nick.

Edited By Nicholas Farr on 03/01/2011 12:19:12

[JasonBModerator @jasonb]

As Ian says it looks like the flange holes are threaded so just a stud or bolt with a lock nut will drive the dog around and allow you to use a MT center, this would be born out by the fact ARC sell a straight driving dog for the C1.

 

Jason

[Keith MorrissParticipant @keithmorriss26344]

Many thanks for the suggestion guys.  For those of you not famalier with this model lathe you can find it on the net by looking into Arc Euro Trade, Axminster Power Tools, Chester UK and Machine Mart, it is either the Seig C1, by Arc and Axminster or The Cobra

 by Chester and CL250 by Machine Mart.  All may have variouse specs but I can assure you that the headstock is #2 Morse although the bore is stated between 9.5 and 10 mm.  My machine is just over 10.5 mm bore so you can’t go by the suppliers details as they do vary somewhat.  Neither the backplate or faceplate will accept the morse taper centre specified and have thought about a couple of the suggestions such as turning the centre down so it will fit through the bore of the backplate, incidently the backplate has a 15 mm hole and as stated by Norman the centre is too large to fit through this hole.  If a suitable catchplate had been designed for this machine then you could turn 250 mm between centre as stated by the manufacturer.  For quick work then yes I could turn a piece of scrap in the chuck.

 

Once again many thanks for the suggesti0ns guys, much appreciated.

 

Keith

[Ian S CParticipant @iansc]

You don’t need a catch plate, the flange on the mandrel is the catch plat  the holes in the catch plate are unthreaded.  Ian S C

[Keith MorrissParticipant @keithmorriss26344]

Ian,

The flange that you mention is actually the backplate for fitting the chucks and not a flange, this backplate though is attached to a flange on the spindle but it is only about 30mm in diameter.  The backplate is attached to this by 3x4mm socket screws and has a bore of 15mm just like the faceplate so the centre will not fit through this either.  The easiest way is to turn the centre down and allow the centre to fit through the backplate or faceplate as suggested by Ady.  I also could make a catchplate as suggested by Nick, maybe there’s a project in here somewhere.  I guess this little machine is not as popular as I thought, despite its size there are a lot of accessories for it and I have got quite a few but have not yet got the benefit from them due to other commitments.  If there is anyone out there that has got one of these machines and you have worked through this issue, please let me know.

> >

Regards

Keith

[JasonBModerator @jasonb]

You may have some luck on this Yahoo group

 

http://groups.yahoo.com/group/C1minilathe/

 

J

[Keith MorrissParticipant @keithmorriss26344]

Hi Jason

Tried this website as suggested, but it would not let me in even though it accepted all my details and then asking me to verify I.D. and that’s when it locked me out.  I have tried this website before but then I could not get on it, still waiting to hear from the administrator to see why I can’t log in.

 

Keith

[JasonBModerator @jasonb]

Other option would be to contact ARC who sell the C1 and ask what they suggest, I thought that Ketan may have seen this post as he is a member.

 

J

[AndyPParticipant @andyp13730]

Keith,

 

I have a C1 although mine is the Chester Cobra variant, smashing little machine for it’s price. I haven’t had the need to turn between centres so can’t offer a solution to our problem. All the suggestions so far are valid and turning down a standard soft MT2 centre does seem to be the easiest although unless you shorten it significantly it still leaves a lot sticking out of the spindle.

Looking at the backplate and the flange on the spindle I think it would be just possible to make a faceplate that would accept the full MT2 taper although there wouldn’t be much meat left around the holes for the mounting bolts.

 

While googling for the MT spec I came across an old thread on here concerning a MT 1.5 spindle on a Toyo lathe which rang some bells, perhaps this points to some of the ancestors of this machine as there is some resemblance.

 

Cheers,

Andy

[John OlsenParticipant @johnolsen79199]

If the need is for a MT2 centre that has a smaller than normal nose so that it can stick out through the faceplate, I would suggest looking for a MT2 shank with a plain end…these are sold by the usual suppliers. The  non taper end is a plain parallel section, and is unhardened. (Don’t get a taper one meant for a drill chuck by mistake.)  So you can fit it in the taper on the lathe, turn it down to the diameter and length you want, then turn a 60 degree centre on it. You can also mark both it and the spindle so that you alwyas put it in the same way. That gives you the advantage of a nice ground and hardened taper part, saving you a lot of work. It does not matter that the centre is not hardened, since the live centre does not need to be, and it allows you to correct it later if the tip gets spoilt. Last time I used one of these tapers was to cut a screw thread on it to mount a home made boring head, so you can see that the material is quite OK to machine.

 

regards

John

[adyParticipant @ady]

Is the tailstock adjustable on your unit?

 

It’s not something which occurred to me, but the intention may be to make it impossible to turn between centres because there’s no adjustment.

 

The newer arceuro units do have an adjustable tailstock.

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