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14x40 lathe power feed improvement

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petertha

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#1
Well it has been a long, long haul getting my lathe operational, dating back to original issue posted ~May-2017.
http://www.hobby-machinist.com/threads/source-metric-keyed-shaft-to-replace-bent-one.58851/

But I’m happy to report it’s been running for a couple weeks now & (knock on wood) seems to be silky smooth. Maybe even better than it ever ran but I don’t want to jinx it. So here is the story highlights in case you run into similar issues with a similar lathe.

The problem started under power feeding. Nothing excessive, 0.025-.035” DOC in steel. My clutch started clicking, then complained louder, then finally disengaged altogether with the dramatic clatter. I removed the clutch springs & balls, stretched them a bit, no improvement. By hand I could feel the power feed bar was binding so something was amiss in the apron. I was very fortunate to meet another fellow 3 hours north of me who owns same lathe different name & he helped me through the initial disassembly when he was in town which was a new experience for me. Thanks John!

After teardown & apron removed I saw the worm gear had worn away at the cast iron C bracket that retains it. Rather disturbing because this machine has seen relatively light duty up until a few years ago. Fortunately the hardened steel worm gear was not damaged. FYI there is an excellent 12-part Keith Fenner YouTube series called Lets Look Under The Old Girls Apron where he rebuilds a distant Taiwan 14x40 cousin of my lathe & he had this same issue. Newer lathes look to have a different layout & improvement. I milled a nice flat in the bracket correcting the wear & John turned me a bronze spacer ring from a Princess Auto bronze bushing that acted as a glorified thrust washer.

After reassembly it was slightly better but clutch still disengaged. Bummer! If I rotated the PF rod by hand it turned ¾ turn free then frictioned up. But this is also where the worm uses up its backlash & starts to engage & pull so the problem could be elsewhere. This began the journey of WTF 10 possible things that might cause friction anywhere in the system. I removed the carriage top & cleaned up the <cough> ‘scraping’ so it slid better on the ways. I checked all the carriage gears & shafts, they run smooth on the bench. I fiddled with the alignment of the C bracket because it’s a loosey-goosey bolt-on design that can rub on the shaft with the bolt pattern tolerance. I removed the helix gear & its shaft from the apron. Gear was worn but hard to know if sufficiently bad. Every time I made an attempted fix or adjustment I had to re-assemble the lathe to see if it worked.

Finally I had the overdue thought to just check the PF rod runout itself by putting it back in the lathe supported by the clutch cup & tailstock bearing block. Then DTI mapping down the rod length. Sure enough it was bent, max 0.080” at about 1/3 length from headstock. Predominantly in the same plane as the keyway slot. I’ve heard that the shaft can stress relieve itself over time on the keyway, or maybe it got distorted when the bracket wore? Or maybe it was not true to begin with & the wear aggravated it?

My options were straighten or replace, so I pursued both simultaneously. I could find a similar (19mm OD x 5mm keyway) from Chinese lathe which would need to be modified, about $200 & couple months delivery. I wasn’t too concerned about the tailstock end turndown mod. But the thing you come to realize about Asian iron is they do some bizarre things when it comes to drilling roll pins in these rotating parts. Like off center & at ‘hand drill’ angles. So matching that off-geometry to other parts like clutch cup wasn’t too appealing. Enter Modern Tool who went out of their way to source me parts from Taiwan including new helix gear (which engages worm) & some other spares. Unfortunately my shaft was no longer available. New shafts are very expensive. Milling an IMP (7/8”) shaft keyway is do-able, but I was told it would probably warp more than what I had.

So I took my PF rod to a local driveline place where they do that kind of straightening press work. Unfortunately it just wasn’t getting done, so after 4 months of patient waiting I took it back. I then contacted Keith Fenner. He has a lot of talents but shaft straightening is his forte. Plus he is a super nice guy. I shipped it down & he had done within a week within 0.005”. I’ll attach a link where I’m now semi-famous (inside joke). BIG THANKS & LEGITIMATE PLUG TO KEITH!!!!!!

Now with a perfectly straight shaft this baby is finally going together! Not so fast. Again, better but not still not right. WTF. More email exchanges with John. What could be different? I started to get the sense by elimination maybe it always was a bit out of alignment but basically ran despite itself. The driveline will overcome a certain amount of resistance by brute force. I noticed the bracket holes were oversize but shiny on one side (read bowing the bar into submission). There is also no datum, pins or contact registry of apron to carriage, just 2 bolts holding the apron on. That carries the bracket & worm along for the ride. Another potential misalignment?

So I decided to replace the C-bracket & make 2 independent steel blocks, each with longer bronze bushings. This allowed me to float the blocks into position using the rod to dictate concentricity. I made them undersize so that I could shim the blocks to however they fit on apron & match the bolt pattern. The bronze gives me longer sleeve area & also have bushing boss material on either side of worm. This is desirable because when you power feed carriage in either direction or PF cross slide, the worm thrusts to opposite sides & contacts this.

That led me to realize the brass helix gear that engages the worm & drives the carriage also has to be exactly centered to the worm gear. The gear is kind of a saddle profile so if it’s displaced in or out just a bit, the teeth engagement will bind up. So measured it out & made a shim washer to ensure it stayed aligned.

Everyone still awake? :) Now it’s Dec & re-assembly again (I’m getting good at this). New clutch springs, new PT bushing blocks, new brass helix gear, and new alignment. After some careful power traversing & monitoring… It seems happy-happy now. After a couple hours rotating I could still see my rod bluing slowly rubbing off indicating the bushings are sliding nicely & doing their job. The clutch set screws are now set much more conservative than ever which indicates to me the feed power is using its energy traversing vs. overcoming binding & friction.

I’ll bang some pictures to hopefully make sense of this novel. Aside from the headache factor, at least this has taught me a lot more about my lathe.
 

petertha

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#5
Initial condition of my worm gear, brass helix gear & C bracket
 

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petertha

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#6
My original fix idea: bronze spacer washer just running free.
PF rod run-out checking in the lathe supported in clutch cup & tailstock bearing without carriage influence
 

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petertha

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#7
Sketches of original bracket/washer mod & my new block/bushing proposed fix
 

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petertha

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#8
New blocks with integral bronze bushings & shims
Testing helix gear tracking & spacer shim washer to center
 

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petertha

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#9
Forgot the pics of top slide underbelly. Bit of a Hmmm... moment actually. If this is what the 'better' Taiwan machines look like, I'd hate to see a rough lathe. The crisp, shiny, induction hardened & ground V rails & flats you see on the topside bed looks over-the-top inconsistent with what actually slides on top of it. Maybe that's the just the way they all are & I was expecting something nicer. I don't think I could use the word 'scraped' with a straight face. The pattern looked way to course for oil frosting.

I blued the surface & carefully blocked off some high points with a fine stone & oil and de-burred the edges. I didn't want to get carried away here so it was 0.0000 type cleanup. I did a before & after pull test with a fishing scale & can say for sure I improved it. But its very subjective. It takes more starting force & drag force with something like WD-40 film on it just as a baseline reference. As soon as you put thicker way oil on, it still requires a bit of 'un-sticking force' but then glides like a curling stone. So that was never a significant hold up issue, but it made me feel better to look in there. I did have chips & sh*t in behind the V wipers. I'm going to come up with a better solution here using a thick felt wiper vs. just the plastic slider (Fenner style).

The underside bed gib clamps (or whatever they are called) are just rough sticks of cast iron. They were ground reasonably flat but again, zero basic chamfering or deburring. I set them up gapped with feeler gauges. There is a fine line between sticking & sliding so required some set screw diddling.
 

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Dabbler

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#10
Nice clean up on your machine. I'm glad you've gotten it all back together again!
 

ddickey

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#11
What kind of lathe is that Peter?
 

middle.road

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#12
If you can post some picts of the lathe I'd appreciate it.
I have a feeling looking through your other posts that it might be a close relative of my CT1440G.
You picts & dwgs above really helped me understand the operation of clutch.
Now that I'm finally using the lathe regularly, tiny oddities are cropping up and I've got this uneasy
feeling after reading your posts that I might be face with a preventative maintenance teardown.
Going to start watching Keith's series, thanks for noting that.
 

petertha

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#13
Its a King model CT-1440G, built 1997-04. King still exists in eastern Canada (they were quite unresponsive attempting to source me parts). Mine was bought through a local distributer at that time, Modern Tool here in Calgary. Their main business is big boy industrial machines, but they carried this model for some time. My buddy from Edmonton has a 14x40, same CT1440G designation, different name. We compared parts manuals & they are identical. I guess that was the era where lathes & mills were available under different paint schemes & stickers but from same (Taiwan at that time) factory. I've heard that that particular factory no longer exists, but Modern was able to scrounge a few remaining parts.
 

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petertha

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#14
Nice clean up on your machine. I'm glad you've gotten it all back together again!
Thanks Dabbler. I haven't forgotten about shop tour. I had to get this monkey off my back & now Xmas...yadayada. Lets make it happen in the new year!
 

middle.road

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#15
yep, yep, they're twins looks like. Thanks.
Going to start digging through your posts.

1514311801254.png
 

petertha

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#16
I should mention some details about the bushing blocks. The main reason for the notches where the cap screws enter is so that you can get in there with a hex wrench. Once the apron is assembled, its a very tight & awkward space to tighten the bolts I used an allen key with slightly shortened foot. You cant really get a wrench up in there.

Once the shimming was all worked out & final assembly time, the blocks were attached just lightly bolted in position. The PF rod was threaded through, apron moved far left to headstock end so it would see the maximum influence of the clutch cup for rod positioning and not apply any bending to the rod itself. Now I snugged the RHS bolts. Move the carriage right just enough & repeat for LHS bolts. If everything is centered proper, it should be frictionless rod rotation with carriage at any position on lathe just turning by hand. Assuming you have a 'Fenner straight' rod :)

The 2 blocks vs. C gives a bit more control over an integrated C casting relative to bolt pattern which you have to live by
 
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johnnyc14

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#17
Yeah it looks just like my CanTek brand machine. Glad you got yours running Dan. I'm planning the same power feed improvements as Peter made on his.

i-9svKNgW-L.jpg
 

middle.road

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#18
Yeah it looks just like my CanTek brand machine. Glad you got yours running Dan. I'm planning the same power feed improvements as Peter made on his.
And, the Manual you passed on to me a couple of years ago has come in so incredibly handy!
I still haven't got the 'Klunk' in Low Gear fixed. -hehe
I wish those threads of ours hadn't been lost in the conversion. A lot of really good information in them.

I'm dreading if my PF goes out...
 
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johnnyc14

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#19
I didn't know that happened Dan. All the pictures I posted before spring 2017 disappeared when Photobucket tired to blackmail their customers and I switched photo hosting to Smugmug. All the projects I posted before that were gutted of all the pics. If you need pics of anything I'd be happy to re-post them.
 

petertha

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#20
Something I forgot to do but worth considering if the apron is dismantled again. My apron gears are greased as opposed to sealed oil bath like newer lathes. So its basically an exposed open hole on the bottom. Although its positioned closer to the operator away from where swarf builds up under the lathe bed, I did find some cutting chips up in there when I cleaned out factory mung grease. This new grease runs very smooth but I feel its also softer & stickier so might cling & hold chips. Anyway, I made a simple cover template but forgot to tap some holes while it was off. This kind of idea might be applicable with a bead of sealer & oil bath if you went that route.
 

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petertha

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#21
I didn't elaborate on this aspect much, but maybe worth mentioning with a pic. Yet another potential fitting tweak you might encounter. The brass gear that engages the steel worm gear is mounted on a shaft with a key. The steel worm gear drives the brass gear which drives the internal carriage gear train to traverse the carriage. That's the power feed mode.

The brass gear can only go on one way. It has a depression on the outboard side for a washer & cap screw. But what I had not appreciated until I chased down my particular misalignment issue step by step is that the brass gear can actually be set improperly. I assumed it should butt up against the shaft shoulder (and I suspect that's how its supposed to be). But for whatever reason, probably related to my apron not being positioned correctly on the carriage top (but nothing I can do about it) its possible to have a perfectly concentric PF rod running within correctly set up bushing block, but if this brass gear is off center even a slight amount, that will make for binding. Because the gear has kind of a saddle profile, any in/out deviation really aggravates this misalignment. Hope this makes sense. Anyway, that's why I ended up having to make a brass shim washer between the apron casting & brass gear to establish this distance because if I tightened the gear end cap fully, the gear slid it down the key & was out of alignment.

Now whether I'm correcting 'factory' issues or this is an inherent design thing, I can only guess.
 

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middle.road

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#22
I was looking at my today and oiled the devil out of it and noticed that there's 'rub' marks on the PF shaft in the sweet spot since I really started using the lathe.
I'm in denial/ignore mode now. Have to cross my fingers and get through the next few weeks. Just picked up some more side-work this evening.
I'm going to have to go through your posts in detail and figure it out from there. And figure out when to fix the Low gear klunking.
 

petertha

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#23
Its hard to speculate. From what I've now seen, I think there was a significant amount of final hand fitting work when it comes to these machines, at least this particular model/era. Don't get me wrong, its great value & quite accurate. But some corners cut that could have made a good machine much better.

Here are some interesting pics I forgot to post but maybe another clue. See how it has no wear on the apron side of hole, you can still see original drilling & even overspray paint. But its rubbed shiny on outboard side of hole? That tells the same story of how my blocks wanted to be shimmed to run concentric once the straight rod was installed as the datum. The ‘extra’ shim thickness came about because I mimicked the hole center dimensions of the original C-bracket bore & it was wrong to begin with. The question is when did this occur, slowly over time or aggravated by when the gear issue occurred.
 

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cd_edwards

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#24
knew I'd seen some others pics of this. . Where did you find the new springs? seems I need one to replace the roll pin someone installed in place of one of the springs..
 

petertha

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#25
I got lucky & Modern Tool in Calgary was able to source me some parts from factory in Taiwan including the springs. I don't have other lathe brands to compare but my hunch is they may be generically similar to others if that helps.
 

middle.road

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#26
knew I'd seen some others pics of this. . Where did you find the new springs? seems I need one to replace the roll pin someone installed in place of one of the springs..
Mine were made of rather heavy wire, diameter was a tad smaller than 1/4" about 3/4" long. Rather crudely made. Ends were just cutoff, not ground.
I did have a hunk of the same type in my parts drawer, but didn't bother to make proper new ones.
I've got pictures somewhere - but of course can't find them at the moment...

My gears looked decent during the tear down to fix the half-nut a few ago.
Wish I had remembered this thread so that I could have modded it while I had it tore down.
1531353097108.png
 

petertha

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middle.road

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