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Monarch Ser.60 Gearbox Removal Illustrated

MichaelP

Titanium
Joined
Dec 7, 2008
Location
IL/WI border
I had a major oil leak from the gearbox of my Monarch Ser.60 lathe (13”, no Power Rapid Traverse) and, finally, became ready to find the source and fix it. Before starting, I met with Mike (Draglineguy) who shared with me his experience in removing the gearbox of his Monarch. His help was invaluable and saved me many hours of guessing. As a result, the actual gearbox removal took less than two hours.

I would like to share with you the step-by-step instructions and provide photos of the process.

I used Monarch Series 61 Parts Catalog and will provide part references/page # for those parts that are in the catalog (not all of them are). Note that the Ser.60 Parts Catalogs are worthless and only show a few parts, so don’t waste your money on them. Get the Ser.61 parts catalog instead.


Let’s begin.


1. Completely remove the oil plug from the gearbox oil sump (J56, p.20) and drain the oil.


2. Remove the round lid and gasket (H103,104, p.18) covering the cross shaft located in the lower right corner on the face of the gearbox. Remove a snap ring from the end of the shaft, if present. On the back of the lathe disconnect the cross shaft from the articulated arm (watch the key!) and pull the shaft away toward the back of the lathe.
 

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Here is how the front end of the cross shaft looks. Note the keyway crossing the snap ring groove. The key remains inside the gearbox, so you'll have to orient the shaft correctly during re-assembly. It's worth mentioning that the cross shaft is re-inserted AFTER the gearbox is put back in its place.
 

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3. Disconnect the right (tailstock) side rod support (Q65, p.34) by removing two Allen screws.
 

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4. Remove three taper pins to disconnect the Control Rod (Q26, p.34), Feed Rod (Q28, p.34) and Leadscrew Reverse Rod (P86, p.32) and release the ends of the rods by pushing them to the right (the right side rod support can slide to the right).
 

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Remove four Allen screws attaching the Leadscrew Bearing Housing (J84, p.20) to the gearbox. Leave the Leadscrew connected to the Bearing Housing. Lock the half nut and slowly rotate the apron hand wheel clockwise. This will help releasing the Leadscrew with the Bearing Housing attached.
 

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5. Remove the lower headstock front cover (D33, p.10) where the Speed Plate (D30, p.10) is positioned. This will reveal a pair of Allen screws holding the upper portion of the gearbox.

Then, using a large straight screwdriver, remove two cover screws found in the lower portion of the gearbox on the front. The cover screws hide two deeply located Allen screws that hold the lower portion of the gearbox. Remove those four upper and lower Allen screws.

NOTE: For some reason PM doesn't allow me to put the pictures here in the right sequence. Probably, due to the file naming. But I'm sure you'll figure everything out.
 

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6. Remove the End Gear Cover (A1, p.4) and End Guard Cover (A14, p.4) located on the left side of the headstock and gearbox. This will expose the end gears and the left end of the spindle. Remove the front oil splash plate.
 

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7. Remove the bevel gear (P79, p.32) from the Index Sector (P80, p.32) located between the spindle speed arms (E10, E12, E32, E34, p.12) on the face of the gearbox. This is a part of the Leadscrew Reversing mechanism.

The bevel gear is held by a taper pin, in addition to a set screw. Without removing the arms, the taper pin can be removed toward the left if the Index Sector is rotated all the way clockwise (just lift the Detent Plunger (P83, p.32) and push the Sector all the way to the right).

Note that this rightmost (clockwise) position of the Index Sector (when the Detent Plunger is in the leftmost notch of the Sector) corresponds to the reverse rotation of the leadscrew. It means that the Reverse Rod Lever (P57, p.32) is in its top position (fully lifted). It will be important when you reassemble everything back.

During reassembly, I’d suggest to move the Index Sector all the way clockwise, re-attach the Leadscrew Reverse Rod to the gearbox, then lift its lever and in this position re-attach the bevel gear with its taper pin and set screw. See two photos in post #15 below.
 

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8. At this point the gearbox can be removed by sliding it forward.
 

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P.S. In my case, the leak was from the screw holes in the gearbox bottom cover (J3, p.20). The three larger screw holes for Cam Plate (K21, p.22) attachment to the bottom cover were deeply counter bored, and the thin remaining lips simply broke off.

In addition to the cover plate repair, I replaced its gaskets (the original gaskets were 1/64” thick, I used 1/32” thick ones with a gasket sealer). I also replaced two oil seals: one (H98, p.18) on the back of the gearbox where the cross shaft enters it, and another one at the Control Rod entrance (J69, p.20). Those seals are located below the oil level, so their replacement was quite important. Those two seals are identical: originally, Garlock 141 (current Garlock Part # 21158-0141). I used easier to obtain and less expensive substitutes, CR Seals 7512 and 7513 bought from a local Motion Industries shop. The only difference between 7512 and 7513 is that 7513 has an extra dust lip, so I used it for the Control Rod.

I decided not to proceed with replacement of other gaskets and oil seals. First of all, they didn’t show any leaks, and I didn’t want to get into possible problems trying to take the rest of the gearbox apart. Besides, all other oil seals are above the oil level anyway: one is on the Leadscrew (J83, p.20), and, possibly, one more on the Feed Rod (based on an assembly drawing sent to me by Monarch. See also M46, p.26).
 

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I did some additional work too. I added 3/32" and 5/32" Teflon packing strings from Home Depot into the glands of the speed arm shafts and Index Sector shaft. All of those are located on the front of the headstock, so I needed to take off the Upper Front Cover (D34, p.10) to remove the speed lever arms (E10, E12, E32, E34, p.12), Detent Plunger assembly and the Index Sector. All those glands were leaking (headstock oil), and the additional packing solved the issue.

If you want to do it too, I’d suggest you to set the highest spindle speed and note the position of the arms (E10, E12, E32, E34, p.12). I also made witness marks on the arms and their shafts. It helps when you re-attach the arms. After the arms are re-attached, you will need to adjust the screws holding them against their collars (E11, E13, E33, E35, p.12), so that the rubberized stops don’t interfere with the full arm travel/gear engagement. To achieve this, switch an arm into either the lowest or highest speed position. Your choice between the highest and lowest speed must be based on whether one of the stops interferes with the arm. Choose the position where the arm is fully engaged the gearing yet remains some distance away from the stop. Now adjust the screws to make the arm just touching the nearest stop. Move the arm from one extreme position to the opposite one to confirm that either of the stops doesn’t interfere with full arm travel. At this point tighten the jam nuts on the screws. Repeat for all four arms.
 

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And here are two photos illustrating re-assembly notes in my post #10 above.
 

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Finally, I'm showing some misc. photos of the gearbox in case somebody needs it.
 

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I'd like to add that before replacing the gearbox, you should make sure that the small hole in the base of the lathe that drains oil spills from under the gearbox is not plugged. It's located in the area where the nose of the pliers points. Some "clever" machinists plug the hole if they see oil leaking from it. :)

That's all, folks!
 

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Hello Michael :)

I don't own a Monarch lathe, but hats off to you for providing such an in depth, and thorough treatise on your gearbox removal. Your narrative, combined with your pics, was concise, organized, and "short and sweet". I am very impressed... :)

Brian
 
Michael
I am doing some similar work on my gearbox and would like to know what you did to fix the counter bored holes that broke out on the bottom cover.
 








 
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