A miserly Rack/n/Pinion build, Clarke CL430

Part one

Ok, so of those of you who have had the pleasure of knowing the Clarke CL430, one of the things that soon begins to bug pretty much everyone I've known with a CL430 is how slow it is to move, you dread having to move the table up and down between operations, once you're there it's fine but getting there soon gets the heart rate up and nobody likes to be worn out. (People should know the irony that one of the 20th centuries biggest promoters of exercise "life style" died of a heart attack).

So this lathe is just begging for a rack and pinion, well it got one, but it got it too late, and I suspect this was largely down in part on warco's effort to promote the lathe to serious metalmunchers, but getting hold of one of the WMT300/02 is as rare as hens teeth it seems.

So going down the best part of £800 for this monster you're feeling the urge to have a go yourself, but I think I walked before I could run, and underestimated just how much you need to consider before you can get this seriously going.

So step one has already been covered, we know we want a rack and pinion feed and we want it on a CL430, step two would be to survey the land, what are we dealing with, when it comes to fixing this thing on the machine.

So this is a glance at my machine as it sits today. I'm part way through building an aluminium chip tray as you can see. But it's also got a few other differences to the original, vital i'd say. I couldn't actually fit the rack and pinion on this because the tray blocks it's original position for the moment, the rack itself has been removed(and now I've lost it) but It's really simple enough to explain, I bought a straight length of 1mm pitch rack bar with a pinion from ebay and drilled 3 holes along the length, to which "fixing posts" were attached, the base of the posts needed to be angled because I figured I had the most room to play about on the base of the lathe, (so the rack was upside) and the cast face of the base is slightly off parallel by a few degrees. This ran the length of the base of the bed once it was fixed.

Down below you can see part of what formed the next problem, where the hell do you attach an apron to the lathe? I figured the easiest and strongest way to secure it would be to remove the cross slide, mark out drill and counter sink two M8 sunken socket screws into the apron, this was adequate because it meant that nothing in essence was truly damaged by my workings, and it could be removed if I I didn't want it anymore, my number one rule of modifications is don't do anything you can't undo to your equipment.

So now we come to the exciting bit, what I actually made this apron out of. I used a 1/2" piece of T6 aluminium plate, some myford gears I deprived from a potentially caring and loving myford user on an ebay auction that nobody seemed interested in. (got a full set of myford change wheels). and some silver steel bar.

And a close up of the workings.

So I hope the gear train is fairly self explanatory what happens, I took the handwheel from another machine spare I had. That sits on some bearings. The little block you can see to the left of the traverse handle is a brass bearing block, because my pre-prototype proved 1/2" of support for the pinion shaft wasn't enough.

To the far left you can see the disgrace of my build which was a kind of "wrench on" half nut that was truly awful to use. You can ignore that but there isn't a lot of space under there and things were getting dire at that point, the half nut is a slitting saw cut piece of a feed nut from Clarke spares, don't break too many of them as they are a little pricy.

Part Two

The legacy of all this amounted to bugger all in the end, I've never continued it, why? because in practice it was a bit of a dog in the surface finish department. I found one big problem may have been the gearing was a little too fast, it probably was traversing at about 34mm per revolution. I should note as well that once you remove the feed nut all this table has to hold onto in a cut is the saddle gib, so it's probably swinging from left to right in a very slight rocking motion with every movement.

So what have I learned! It needed more support, a front fixing plate is no match for a full casting which is what most aprons have, the feed nut on the original helps to keep the movement of the lathe linear or straight, it acts as a guidance to give you nice even movement rather than jerking around under load. SO big thing I would do second time is to replace the feed nut with a slide fitting bush, which mimics the form of the original feed nut. This will do wonders for it's ability i'd imagine.

You're probably all thinking at this point how on earth you'll ever get hold of a decent rack and pinion, gawd you're gonna have to run down to the engineering works and get on their case about some cooked up scheme you have. Guess what, you don't need one after all! in essence, you already have a perfectly good rack sitting right infront of you, introducing the wormwheel (courtesy of Wikipedia)!

So You think about it your lead screw can carry a gear (sometimes two one above and one underneath). And advance at the steady pace of 0.6 pitch (you will need a different gear to the one shown so that it's radiused or bows slightly towards the centre of the worm wheel). Ok, it's not a complete gimme, but it's a start and i'm thinking this could forgo a rack altogether, obviously, I've still got one somewhere so that's what I might do if I have the courage to have a go again, but why not take the hint of a lifetime from ol' mike and save yourself some pain/ndrilling to your machine.(Theres a leadscrew clutch on the CL430 so it wont start moving every time you switch it on, should be noted that using a wormwheel would make it difficult to/ or atleast roundabout fashion to install a cross feed mechanism, so in that case a rack would work better, IF you wanted that. I was ever so simply suggesting a different approach to the same problem that could be considered)

So there it is, my dirty secret. I'd ignore the half nut as an act of desperation but there could be some life yet if I gave it another go? Who knows?

Your disgruntled barfly

Michael Walters

Edited By Michael Walters on 06/12/2016 20:13:15

Hi Michael

on your first photo of your chip tray coul you not move your lathe foward so the tray could hinge down over front of the bench it would make life easier for emptying,just a thought from my over worked braincell.Regaurding wormscrew find an old ajustable spanner

Kevin

That sounds pretty awesome actually kevin, I never looked at it that way. Were getting fancy now. Maybe I can put a little cigar lighter on there while i'm at it? It's crazy, but it just might work!

And yes, an adjustable spanner is a very good example of a worm working on an everyday item.

Michael W

Impressive attempt Michael. Well worth trying and you deserved success. Thanks for explaining why it didn't work out; near misses are often far more educational than victories.

That built-in chess board appeals too. Every lathe should have one!

Dave

i get some weird crazy ideas i just look at things differant somethings work some dont,but isupose if we didnt think of crazy ideas a lot of things would have never been invente

ohh my braincell hurts now lol

kevin

Thanks Dave,

It was a big ask from the start, as i'm essentially trying to redesign a machine that was never meant to have one.

I'm sure some of the pricier hardinge lathes came with a gear operated chess machine that can outwit you quicker than it took to part off a 3" bar.

I just realized I made a bit of a slip on the syntax department again (my history teachers ghost would be raving at me). It should be near the top "I ran before I could walk". But just like history, you can't change it.

Michael W

On min my Myford, it has rack and pinion for fast moves, but I never use it for cutting. The fine self act feed uses the leadscrew, not the rack. Why don't you just motorise the leadscrew if winding is too hard?

chers for that.

Couple of points. Taig's / Peatols have the rack teeth pointing upwards. The pinion needs to mesh pretty closely with the rack - fantastic swarf trap that can jam it all up. The pinion is carried on an eccentric bush to adjust the mesh. If driven by a gear that could run in one too. On well made lathes the bearings for these shafts are fairly long compared with their bore. I'd suggest 1 1/2 diameters or more. They could stick out of a thin apron and often do on most lathes especially the one on the hand wheel - way more than 1 1/2 diameters giving plenty of clearance for hands.

I can hand feed my Boxford. The saddle moves about 1 1/4 " per rev of the 4 1/2" dia hand wheel. Never measured it before but suspect bigger lathes I have used move further and have much bigger hand wheels. The reason I can probably do it down to being told that I couldn't use power feed for a while during training. It's a 2 handed job just as using the other hand wheels are. One hand is needed to maintain the feed while the other one repositions and so on. I have seen video's of people doing one hand facing etc and find it odd that both me and a number of others found 2 hands is the best way especially if the slides are adjusted correctly. On the saddle the handle is for moving it and the rim is for the feed. I tried hand feeding a mini lathe - couldn't on this model as the wheel was too small or maybe the feed rate was too great. I intended to fit a larger diameter handle.

Myford have used a gear on the lead screw for moving the saddle about for a long long time on some of their lathes as have others. On the ML10's it also serves as a screw cutting indicator. Might be one source of a suitable gear. It's too course a feed for hand feeding really but the handle could be enlarged and the drive to it geared down.

It's possible to make a gear if a suitable tap can be found. Make the blank, gash it at the thread helix angle and then cut the tooth form with the tap as people who make worm wheels do. Info is about on the web. Depending on the size of the tap it might pay to hollow out the periphery of the blank to suit the tap as it will then have more contact area even if the tap is smaller. Flank angles may be a problem but the lead screw thread is likely to be acme or trapezoidal.so if the tap is the same style the flank angles will match. When rack feed replacement gears were made out of mild steel people would often case harden them  for increased strength and greater wear resistance. I used on made out of ordinary mild steel for a while without any problems on my Raglan. The original had broken teeth that had been replaced with a couple of filed to shape pins. Somebody probably used the feed as a slotting attachment.

If you want a crazy idea to think through make a new leadscrew nut and rotate that via a 90 degree helical drive. You'll just need some sort of mechanism to lock it when the nut is needed for screw cutting or feeding.

If you want to use a rack buying a used one of another lathe is probably the best option but it's best mounted on the side of the bed teeth down and ideally tucked under the bed rails to keep swarf off it. Not totally sure but epoxy putty or similar may be strong enough to clamp it down to and get it aligned to the bed. I would have thought that decent sized oblong pads of it would be ok and the fixing screws would keep it in place. It can be tapped just like other materials. If you do this your on your own but it might just work out with a bit more thought.

 Whoops to get the correct helix angle from a tap the size needs to match the leadscrew. Silly me trying to solve some one else's problems. In my case where I use the tap for a worm wheel it does match. You could make one yourself, hardened silver steel. It wont need many teeth as it will only contact the worm gear over a short distance. They can be gashed and relieved with a hand file leaving a very small "flat" at the cutting edge or milled like that.

John

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Edited By Ajohnw on 07/12/2016 10:57:18

Could you motorise the lead screw with a redundant electric drill and make it a power feed, but retain the hand wheel for a more sensitive feed ?
BobH

I don't know why I don't just motorize it, I have knowledge of using and making small circuits and making reversing switches but I just wonder if it would stand the test of time like a mechanical feed system would.

I did think about using a drill once but the leadscrew nut is 19mm, and the drill chuck is 10mm, so it wouldn't work without a socket attachment.

Michael W

No problem, my pleasure as always. I honestly didn't think people would want to hear about my screw ups!

Michael W

but it sets thoughts going and gives good starting point for ideas.

Thanks for your thoughts John,

I'm sure having seen a lot of lathes you can tell a lot of my ideas are based in myford's designs, precisely because it's a very straightforward system for the same class of lathes. It was too hard to break down the thought process mechanically from a bigger lathe.

I think a new apron could be redesigned using either black steel/or cast bars of iron. It definitely lacks a certain amount of durability and iron seems to make all the mechanisms more stable and smoother to run on, from it's great heftiness. I've changed from aluminium pulleys on my lathe to cast iron and the difference in noise is startling!

It was like as though I was just about getting there with the project and I fell at the final hurdles when it was almost workable! Writing about it certainly does encourage me to rethink it. The gearing just needed to be that much little slower, 15-20mm per revolution would've been fine. And a little more stability around the fixings could've gone a long way to making a clear path to success.

I definitely agree about the rack needing to be upside down too, you're always fighting the offset force of the thing (and the swarf annoyance) otherwise. I would also consider making a pinion mesh that was truly adjustable too rather than totally fixed.

Using a worm wheel you could also create a crossfeed mechanism if you coupled it to a bevel gear drive, without needing to slot the entire lead screw which would be a nerve racking milling operation. Needing to keep a slot parallel over 430mm is a little dodgy, least to say it might all go kaput and you could wreck your leadscrew!

Michael W

I think I would go to the myford gear running along the leadscrew idea but can't remember if this lathe has a clasp nut for screw cutting.

The method is used on the ML10 and Speed 10. It's cheap and nasty really and probably not up to industrial use. A number of similar old lathes used the same idea and I am sure I have seen examples on ebay where some one has added a geared drive to them. It's just carried on a plate attached to the apron. It could be beefed up some what by increasing the bearing surfaces by matching the "thread" in the gear to the leadscrew but I think there are pcd problems if the gear is made too thick. Screw cutting indicators usually use a much larger cutter diameter than the leadscrew's. You would need to look into this. I'm not sure but well cut worm wheels that I have seen made this way have a chamfered rim and top tooth width of about 1/3 or the diameter of the worm maybe even down to a 1/4. There is probably some info in milling books.

Your feed rate problem is easy to fix - this one might be a bit extreme.

**LINK**

but do bring the handle out from the machine via a very long bearing. Cast iron hand wheels crop up sometimes up to about 5" dia but tend to be expensive. I think that the S7 ones are a bit on the small size really but those are about. The bearing aspect just needs to be a length of bar plus suitable hole fastened to your saddle plate. I'd have thought 1/2 al would be ok for an apron providing that the "forces" aren't too far apart from each other. They wont be in terms of the saddle drive. The final gear that drives the one on the leadscrew also need s decent bearing length. I mentioned 1 1/2 dia lone but unless there was good reason I'd up it to 2 or even more. It helps with rigidity as there must be some clearance so the length of the bearing sets the degree of rock. Suppose you could use a drive fit in a pair of ball races if space is a problem. It might be on one of the drive gears but is unlikely to be on the one on the end of the hand wheel..

John

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Indeed, when you think about it a backplate casting would make a very good piece of stock to make a decent sized handwheel out of.

Michael W

hi michael

if you want to use your drill there are some adaptors that fit the chuck and the square end for the socket i have put a photo in my album wont let me put it here hope this may help you

kevin forgot to say they usualy come in a set of 3 1/4  3/6  1/2"

Edited By kevin beevers on 08/12/2016 15:28:20

Easy to make adaptors to suit drill. Get a bit of square bar to suit the socket and turn a round end to suit the drill chuck. Just now made one to quick wind a jack. Any steel will do as it's not getting much torque or work.