Monarch 1944 12" CK

[extropic]

@rabler

Thanks for the explanation of design details.

I had not previously seen the retaining ring groove on the input shaft. I had wondered about the chamfer at the ID of the new special washer, but it all makes sense now. The circular cross section retaining rings (CCSRR) are news also. I had assumed the two retaining rings in the pully ID were conventional Waldes Truarc type snap rings. When I bump into interesting design details, like the CCSRRs, I wish I could have a conversation with the responsible designer to understand the rationale. I'm pretty sure that snap rings were available earlier than the '40s so there must be some reason the Monarch designers chose the CCSRRs. I wonder if the CCSRRs are intended to leave zero axial clearance. Maybe they were malleable enough to be upset, in place, to eliminate axial clearance. If I were boring out the pully ID, I'd cut grooves for modern snap rings rather than CCSRRs.

It took a fair amount of re-reading and viewing your pictures, but I think I understand the clutch system pretty well now. The pulley drives the friction disks through the two lugs so the pulley doesn't see any axial force from the pressure plate. Like you've said, there is no significant axial load on the pulley.

 

[Beckerkumm]

Have you been through the sticky on Practical machinist about the rebuild of the monarch 60/61 from Harry? I don't know how similar or different the machines are but the thread is very informative. I did not go through it in detail so I can't say if it will help. Dave

 

[rabler]

Thanks for the explanation of design details.

I had not previously seen the retaining ring groove on the input shaft. I had wondered about the chamfer at the ID of the new special washer, but it all makes sense now. The circular cross section retaining rings (CCSRR) are news also. I had assumed the two retaining rings in the pully ID were conventional Waldes Truarc type snap rings. When I bump into interesting design details, like the CCSRRs, I wish I could have a conversation with the responsible designer to understand the rationale. I'm pretty sure that snap rings were available earlier than the '40s so there must be some reason the Monarch designers chose the CCSRRs. I wonder if the CCSRRs are intended to leave zero axial clearance. Maybe they were malleable enough to be upset, in place, to eliminate axial clearance. If I were boring out the pully ID, I'd cut grooves for modern snap rings rather than CCSRRs.

Thanks for taking the time to go through this. Mechanical design is not my bailiwick, so I very much appreciate other eyeballs on it.
I've already ordered 68mm conventional snap rings for the pulley ID. I'll just have to grind a 2.65mm HSS grooving tool. I thought about trying to use snap rings instead of CCSRR's on the shaft too, but that would require regrooving the shaft, which I'd rather not pull out of the lathe.

I too wondered about the design. I believe Monarch sourced the assembly from Edgemont clutch, which is now Mecco Edgemont clutch. Maybe it was a WWII supply issue on snap rings?

 

[rabler]

Have you been through the sticky on Practical machinist about the rebuild of the monarch 60/61 from Harry? I don't know how similar or different the machines are but the thread is very informative. I did not go through it in detail so I can't say if it will help. Dave

I have looked through quite a bit of the PM Monarch forum, and corresponded off the forum with several members. Recutting the key slots on the perimeter of the clutch disc seems to be pretty common. Abom79 even has a video of doing that on his 40's Monarch. I started this current rebuild with doing that when I realized something was amiss with the bearings. I haven't seen anything on modifications for the bearings.

 

[rabler]

Fortunately the 12CK and the 612-2516 use the same D1-6 mount. I only have a 12" 3-jaw for the 612, I'll want to use a 4-jaw to dial in the pulley before boring that. Fortunately I can use the 4 jaw from the CK.

I've made some test cuts with the 612, but haven't used it for anything yet, so this will be an interesting first project for the 612, helping it's older cousin. I'm waiting for the bearings to come in.

 

[extropic]

Thanks for taking the time to go through this. Mechanical design is not my bailiwick, so I very much appreciate other eyeballs on it. >snip

If I don't pay attention I won't learn much. Worse yet, I might misunderstand.

 

[rabler]

I'm waiting for bearings to arrive. Feeling dead in the water. I did get the 612 back to a basic running shape. I guess I could go true up the backplate for the 6-jaw auction find that will go onto the 612. I had been working on another project with the CK, a rotary stand for the mill tools. I think I'm hitting my limit of open projects. Still have trenches and a front porch to work on, although rain yesterday means everything needs another day to dry out to work outdoors.

 

[rabler]

Progress on the CK clutch repair. Got the driven pulley turned out on both sides for the bearings. Turned a conventional spring retaining ring groove in it. But turns out one of the "features" of the original wire/round cross section retaining rings is they take minimal ID clearance. The modern retaining rings wouldn't clear on the shoulder on the headstock side, so I used one of the original retaining rings there.

This was an challenge in using a lathe in another building, about a 1/4 mile away from my shop, so I had to run back and forth several times for odds and ends as that building isn't stocked for machining. The 612 doesn't have a DRO either. That will have to change! Also a couple more things went on the long term to-do/repair list for the 612. There is a definite bad spot on the cross slide leadscrew. And the rapid traverse apron shaft needs new bronze bushings, it is a bit noisy. My contactor on the RPC is also buzzing badly. I think it is just a cheap contactor, easy enough to replace.

In the first picture you can see the two areas turned out for the two slighly larger 2.677 (68mm) OD vs orignal single 2.625 OD bearings. The central groove is a grease distribution ring, which is no longer needed as I used sealed bearings. They may only last 10 years of hobby usage, I can deal with that.

Next step is to make the retaining washer for this pulley.

 

[rabler]

Well, )&*^%.

I was over at the barns this morning for the usual morning chores, and then went into the garage there to make the retaining washer. Got a piece of 1018 round chucked up and dialed in to something around .005". Had the 4-jaw on from turning the pulley above, wasn't worth pulling it off and putting the three jaw on for this. Plan was to turn the OD down from 2.25 to 1.800", so getting it dead on wasn't necessary.

Wanted to bore the center out first, so chucked up small drill bit, fired up the RPC and started up the lathe. Lathe was set on 285 RPM. Figure for a 1/4" bit I'd like around 800RPM. Went to shift the headstock. This Monarch 612 lathe has a novel headstock, there is a large round dial with 18 positions, and two good sized levers above the dial. The left lever is to select between "Run" and "Shift". The right lever is "Hi, Neutral, Low". Each of the dail's 18 positions has two speeds marked, one for Hi and one for Low. I'd thrown the right lever into neutral when indicating in the piece of stock, and back into high. I tried to pull the left lever into the shift position, which is required to rotate the dial, and it wouldn't budge. Argh



This lathe is a bit different in that the shifting has some hydraulic assistance, and you therefore can't shift with it not running. I suspected the hydraulic/lubrication pump, and sure enough the dripping from the headstock sight glass was abysmally slow to non-existant. I loosened the line out of the pump and sure enough it leaked oil when I fired it up. So I've got something plugged up somewhere. Possibly just a filter? It was quite cold last night so that may be related, I left the heat cranked up in that building to see if that resolves it. Obviously a full tear down of the lube system would be prudent, just wanted to limp along and get the the other lathe back on it's feet. Three inoperative lathes, and no working lathes, is a bit disconcerting. Obviously there are advantages to owning new machines, less trouble prone but not foolproof either.

Editted to add: Well, I ran back over to pick up the manual for the 612, and after heating that garage for a while, it shifted fine, oil flowing nicely in the sight glass. Still feel that a good overhaul of the lube system is in order. But I should now hopefully have the last of the parts I need to fix the CK.

Don't mind my grumbling.

 

[rabler]

Success, the CK clutch is back to running. Bearings run nicely. Still a bit of ringing from the clutch when it is disengaged, but with the way the clutch plate floats in there I'm not sure how it could be totally eliminated. Anyhow, the collection of obnoxious and distressing noises from there are gone. I'll button things up tomorrow, covers and guards need to be re-installed, but it is once again functional. Big sigh of relief, not having a working lathe is not a good feeling.