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Emco Compact 5 Modifications

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Graham Meek15/05/2022 11:16:37
473 forum posts
300 photos

After deciding to downsize my workshop in January, the need to get the Compact 5 (C5) up to a standard I was comfortable with became a priority. The use of my larger machines would be of benefit while they were still here.

Having had the luxury of the Screwcutting Clutch on the Maximat Super 11 it was something I was not happy to do without. The C5 had always been tempting me to do this mod, so during my recuperation in February I set about designing the attachment.

gboxbody john slater.jpg

The above view shows the Mk1, and it also shows you really need to be in the workshop more. The reason being I had forgotten to allow for the dis-engagement of the Leadscrew. This being a necessary requirement on the C5, other wise in Manual mode the operator has to turn the banjo gears as well.

gearbox components.jpg

This need to retain the C5 disengagement Knob meant the Operating lever would need to move from the chosen site where the knob was to in front of the headstock. Thankfully during the need to do a complete redesign of the main body it was possible to have both controls in the one place.

compact 5 main body 1.jpg

compact 5 main body 2.jpg

The keen eyed amongst you will notice the main body is now in two halves, or parts. Again had I have been a more frequent visitor to my workshop at the time, I would have noticed the Bracket welded to the inside of the Headstock cover, which takes the cover locking screw.

compact 5 screwcutting clutch.jpg

Had it been possible to retract the leadscrew with drive key attached through the bearing in the lathe bed, then the original design would still have worked. Unfortunately the key stands proud of the shaft and this cannot happen. Thus there was nothing to do but start again with two halves, and yes this was after I had machined the main body in one. Of course I could have cut the bracket off, but that is not how Graham operates.

dog clutch assembly.jpg

The redesign also threw up another problem, in that the Dog Clutch, because of the split line needed to sit higher in the upper part of the main body. Unfortunately this brought the dog clutch selector into conflict with the drive belts when changing to the lowest Mandrel speed. This was eventually overcome by machining a flat on the selector similar to the flank on a camshaft. An eccentric balance weight is yet to be made and fitted to the outer end of the selector shaft.

A new bearing assembly was also made for the Leadscrew handwheel which has some Radial ball bearings in. The housing was extended towards the Headstock to provide the anchor point for the outer Trip Rod support. The ball bearings will eliminate wear to the leadscrew end face and give better repeatability when screwcutting.

While I have used this lathe for screwcutting in the past, it was a rather hair raising experience. This attachment now completely eliminates the heart stopping moment as the tool approaches the chuck jaws.

I will in due course go on to describe other attachments for the C5, two of which get the benefit of the screwcutting clutch. I hope you have enjoyed my rather long winded post.



Edited By Graham Meek on 15/05/2022 11:20:55

Kiwi Bloke16/05/2022 06:55:10
666 forum posts
1 photos

Hi Gray. Inspired and inspiring! When I saw your post announcing your intention to down-size, and to concentrate on the Compact 5, I was tempted to ask facetiously whether we would be seeing a full screw-cutting gearbox, with leadscrew single dog clutch for it. I didn't because downsizing decisions are too often the result of adverse circumstances, and I certainly didn't wish to be insensitive. However, it seems you're well on the way to elevating this machine from near-toy level to Serious Machine status, so perhaps the question is now part-answered... I'm sure we're all going to be fascinated by developments.

It seems to me that the Compact 5 has serious design defects, predisposing it to problems resulting from wear, that warrant attention, perhaps before embarking on complicated enhancements - well, that's true of my machine, at least. Have you any interest in re-engineering the cross-slide feed 'nut', which, on earlier machines, is cut directly into the saddle, and is neither adjustable nor replaceable? Also, will we see leadscrew half-nuts and saddle handwheel feed, as (IIRC) hinted at in a previous post?

Edited By Kiwi Bloke on 16/05/2022 06:57:43

Joseph Noci 116/05/2022 07:19:18
1081 forum posts
1309 photos

Very nice work as usual Graham. I was not aware of your trials and do wish you well.

Difficult to lose the Super-11...I trust you will always have a place for the FB-2 though..

From the machining marks on the Clutch upper body it seems the process was carried out under CNC control? As usual, a complex piece done well! Keen to see it come together.


Graham Meek16/05/2022 11:02:07
473 forum posts
300 photos

Hi Kiwi Bloke,

Thanks for your kind comments, there were times when I nearly abandoned the whole idea. Thankfully things are now on the up and life goes on.

I'd like to take the opportunity to mention that I don't think a lot of people realise the cross-section of the C5 Bed ways are identical to the Unimat 3/4. I recently posted on here, about the restoration of a Unimat 3 that was given to me. It was a bit of a basket case and was fitted with a large induction motor all suspended off the headstock.

Despite the obvious abuse to this machine in it's life, there was zero wear on the bed ways. The Tailstock and Cross-slide assembly were worn but the wear was nothing like I was expecting.

Fortunately Emco saw the light with my C5 as this one comes with an adjustable / replaceable cross feed nut. The Leadscrew nut also benefits from a backlash adjustable feed nut. The trip-rod bracket is anchored off this adjustment screw.

Thus I think given my intended use for these two machines I don't see wear being a problem.

I did draw-out such an apron attachment some while ago, but as yet I have not got around to making it.emco compact 5 handwheel conversion p1.jpg

emco compact 5 handwheel conversion p2.jpg

Whether I ever will, is another story, I might if I get the chance to obtain another C5.



Hi Joe,

As mentioned above things are on the mend now, so I am doing OK thanks. The C5 project has been a God send really, if a lot of very hard work given the timescale I set myself.

Unfortunately the FB2 is going as well. While it will be hard to see both of them go, it has to be done sometime. Better to do it while I am able to. The machines will make someone else happy and I hope they get as much enjoyment out of them as I have had. I am really looking forward to using the smaller machines, I started out with a Unimat SL 64 years ago.

As regards the CNC, sorry appearances can often deceive. Everything was done by first principles and the trusty Emco Rotary table. Total machining time was just over two days.



Graham Meek17/05/2022 09:21:01
473 forum posts
300 photos

One thing I did forget to mention is that the gears were made using the Emco Compact 5 Dividing attachment and are all 1 MOD.



Jouke van der Veen17/05/2022 14:38:18
174 forum posts
17 photos

Dear Graham,

Your design of the Emco C5 looks for me an interesting extension for the lathe.

What I not yet fully understand is the working of the engagement/dis-engagement mechanism.

Another (remaining) question is if the handwheel could be placed to the right hand side of the saddle so that the latter can move closer to the headstock.



Graham Meek18/05/2022 10:22:33
473 forum posts
300 photos

Dear Jouke,

Stops on the trip rod running along the front of the machine can be set to any desired thread length, with-in the limitations of the machine. The trip rod moves to the left or right depending on the operating lever position. Which dictates whether the the thread is a RH or LH. Moving the operating lever to the right means the trip rod moves to the left and visa versa.

The operating lever works the banana shaped plate, at one end of this is the trip rod and at the other is the dog clutch selector. Thus any movement of the trip rod directly affects the dog clutch selector.

As the carriage moves along the bed during screwcutting it makes contact with the stop, 2.5 mm later the dog clutch is disengaged. Moving the operating lever in the opposite direction, after withdrawing the tool, returns the carriage to the start position.

As there is only one tooth on the dog clutch it can only pick up the drive at one pitch intervals.

Regarding the hand wheel position, this end was chosen so as to utilise the existing leadscrew nut fixing position and to retain the original operating force position on the carriage.

In my experience there is always a dead space at the headstock end of the bed due to the chucks, faceplate and catch plate attached to the mandrel. I therefore did not consider there would be much loss of travel. However in this instance I may be wrong.

I hope these notes help,




I have just completed a new topslide feedscrew using the above attachment, I hope to post a photograph soon. Which is for the next phase of the mods, a Retracting Topslide.

Jouke van der Veen18/05/2022 20:07:57
174 forum posts
17 photos

Dear Graham,

Thank you for your extensive information. I have to study this.

Concerning the engagement/dis-engagement mechanism there could be some misunderstanding.

I meant the design of the engagement of the saddle to the leadscrew in combination with the handwheel (not for the screwcutting at the left end of the leadscrew, which I have to study).

I have now a complete Emco C5 with an adjustsble cross feed nut and an extra bed with saddle + crossslide without adjustment. The latter is used as cross table for the Emco C5 milling column. I had some ideas to replace the non-adjustable nut but I am also (slowly) working on a motor driven cross slide. In this case a cross feed screw is fixated in the saddle and a stepper motor with a hollow shaft attached to the front of the cross slide is running on the screw. The hollow motor shaft should then contain an adjustable nut rotating on the steady cross feed screw. Alignment of the steady screw and cross slide/motor movement is a major issue. I hope this description is clear.

I am interested in improvement of my Emco C5 but I hesitate to make irreversible changes (in other words: damage) to original Emco parts.



Graham Meek19/05/2022 10:06:14
473 forum posts
300 photos

Dear Jouke,

The leadscrew engagement on the Handwheel conversion is carried out by the lever on the left-hand side of the carriage. This lifts a cylindrical half nut via an eccentric into engagement with the leadscrew. The cylindrical half nut is keyed to stop it rotating so alignment with the leadscrew is always assured. (One half nut has been used on numerous occasions in the past by various lathe manufacturers).

While your C5 powered cross feed sounds an elegant design. I think if I were trying to do this I would start with a C5 CNC cross slide and carriage assembly. These regularly come up on the Internet for sale. I think this would be an easier starting point. A plus point is these parts are, I believe, made from Cast Iron.

With regards to my design modifications. I pride myself in that I do not modify the existing machines in any way. I always make use of existing tapped holes for attachment points. No existing Emco part was modified in this recent design and my C5 could be put back to standard in a matter of minutes.



Graham Meek20/05/2022 16:47:32
473 forum posts
300 photos

Work has ground to a halt on these projects for a short while. I need to spend time getting the larger machines out of the workshop.

As a taste of what is coming I have enclosed one of John Slater's 3D views of the Retracting Topslide attachment.

c5 retract john slater.jpg

Since John has made this drawing I have moved the Operating handle to the other side of the unit. That way it does not foul the Tailstock.



Graham Meek28/05/2022 10:27:14
473 forum posts
300 photos

Despite the workshop being in mess due to the larger machines going. I have had a chance to make the new Topslide Feed screw and the Main Body for the Retracting Topslide.

compact 5 retracting topslide feedscrew.jpg

This was machined on the C5 from a long old 10 mm bolt. I find this material machines well and screw cutting is a pleasure. As was using the Screw cutting clutch on the C5. Of course it would have been quicker with the retracting topslide.

main body.jpg

The Main Body was machined on the new Proxxon Mill and after locating all the holes by co-ordinates the bores were finished on the C5 using the 4 Jaw chuck.



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