Mill head, rebuild.

[Mcdavis86]

I have a mill head like this stripped bare on my bench right now. Here are some points of wear to inspect...

First, the 2 variable pulley halves that slide up/down (the other halves are fixed). There's one on the motor shaft and another on the spindle pulley hub. The common (very) wear points for these pulley halves are the shaft keys which are made of brass or even plastic and get chewed up by the steel shafts. The other are the oil-less bushings inside the pulley bore they slide up/down on which can be a PTFE impregnated metal shell or even a plastic bushing. These simply wear out and your pulleys get all sloppy and wobbly.

Second, the spindle pulley hub and the spindle gear hub. These mesh together when you shift the mill into high speed range. As you shift into high speed range what's happening is the shift lever is raising the spindle gear hub up, into the spindle pulley hub. Each hub has wedge shaped teeth that mesh together so the closer they come together the tighter they mesh until there's no slop at all. These teeth wear and on most heads there's an adjustment to tighten them as they wear. Eventually they wear to the point that the hub teeth bottom out in each other then it's game over and time for new hubs.

It could be other things like bearings, but the above two wear issues are far more common so I'd start by inspecting those first. If they require repair (they are wear parts that need replacing at some point, like belts) I wouldn't let it slide or other parts of the head will begin to self destruct.

That was my concern, I can deal with it now but I fear it will eventually “grenade” and cost me even more money, I’ve always worked places with nice tight machines, this is the first mill I’ve ever owned myself. I really wanted a Lagun because I’ve always preferred them(slightly) to a Bridgeport because they seemed a little more substantial and rigid, I do have a little buyers remorse now though seeing how much cheaper and available Bridgeport parts are. Can I inspect/replace these from the top or do you have to take out spindle?

 

[coolidge]

That was my concern, I can deal with it now but I fear it will eventually “grenade” and cost me even more money, I’ve always worked places with nice tight machines, this is the first mill I’ve ever owned myself. I really wanted a Lagun because I’ve always preferred them(slightly) to a Bridgeport because they seemed a little more substantial and rigid, I do have a little buyers remorse now though seeing how much cheaper and available Bridgeport parts are. Can I inspect/replace these from the top or do you have to take out spindle?

You do not have to remove the spindle at all. The whole top of the head comes apart without removing the spindle. The only part that even touches the spindle is the spindle gear hub and that just slides off. You will remove the upper aluminum head housing, motor obviously.

This is what's inside on my mill, the variable speed pulley, that shiny shaft is the spindle pulley hub by the way. To the lower left is the timing belt pulley and belt. Lower right is t he brake handle. Underneath the bottom half of the variable speed pulley is the break shoes, it's like an old style car brake drum.



Spindle pulley hub, lower half of the pulley and this aluminum assembly which holds the brake shoes and spindle pulley hub bearing.



Here's the spindle pulley hub and pulley after a soak in evaporust, they cleaned up excellent.



Here's what's under the pulley, the 'bull gear' e.g. low speed range. We can finally see the spindle, it still doesn't need to come out. Just grab the big gear it slides off with a yank. See those beveled teeth at the base of the gear, that's the top of the spindle gear hub.



Here you have it half the head disassembled!!

True, the internet is flooded with Bridgeport parts but hold off on buyers remorse, first check out Misumi USA. This is a supplier in the US that seems to have a lot of parts in stock for Japan/Taiwan machines. https://us.misumi-ec.com/ They also have extremely detailed CAD drawings and dimensions of things for matching up parts to the ones on your machine.

This is what I have ordered from Misumi so far -

1. 6 machine leveling bolts and lock nuts. Nobody carries those monsters for my machine but Misumi had them in stock both in black oxide and nickel plated. They are not only large and have a fine thread, the bolts are hollow with a radiused tip to fit the socket in the leveling pads. A real odd duck.

2. The oil-less bushings for both variable speed pulleys, mine are different sizes motor vs spindle pulley hub. Note, when they build these machines they mill a slot in these bushings slightly larger than the machine keys the pulley slides up/down on so I'll have to mill that 9 mm slot in the replacement bushings I ordered and that's fine.

3. All manner of metric machine key sizes and lengths and styles wow! I ordered a bunch from them.

4. While I purchased all the replacement snap rings from McMaster-Carr, it was Misumi who had the CAD drawings, dimensions and most importantly the industry part numbers to search on. I simply did a search on Misumi for the snap ring designated in my machine manual's exploded parts view and presto there it was on Misumi's site. Misumi's CAD gave me all the dimensions, thickness, diameter etc. so I could match them up on McMaster-Carr which was less expensive. Misumi likes to sell those in bulk.

For other parts I was able to buy brand new bearings for the entire head, all 11 of them ugh! NSK Japan and most were quite reasonable price wise. There are 2-3 major bearing sellers on ebay. One of them had the oversized super precision and rather expensive P4 (ABEC 7) angular contact bearings for the spindle. Those were the ones I was worried about given the machine is 28 years old. So sourcing bearings was not an issue.

Finding the belts was easy, both the main VS belt and the timing belt.

I also found new brake shoes on ebay. There are quite a few styles but not infinite. I just had to measure my old ones (which honestly are still in great shape) and match them up.

The one part I could not source was the two hubs, because mine are oversized vs the knee mills. I now have 2 backup plans if mine wear out, they are still tight but I don't have much wear left on them.

TIGHT?? Wow I worked on my quill this evening. Someone had over tightened the quill lock at some point and smushed up a bit of metal. You didn't notice it working the quill with the quill handle given the leverage, but you could feel it bind when sliding the quill in by hand. I knocked it off with some 2000 grit, then polished the spot with 3000 and 5000 grit. Now she's like butter. BUT dang those are some close tight tolerances. I had neglected to oil one area when I was testing, man it got tight, real tight. Oiled it back up and back to butter.

 

[pontiac428]

That was my concern, I can deal with it now but I fear it will eventually “grenade” and cost me even more money, I’ve always worked places with nice tight machines, this is the first mill I’ve ever owned myself. I really wanted a Lagun because I’ve always preferred them(slightly) to a Bridgeport because they seemed a little more substantial and rigid, I do have a little buyers remorse now though seeing how much cheaper and available Bridgeport parts are. Can I inspect/replace these from the top or do you have to take out spindle?

Have you had a chance to really warm it up, run some spindle oil and back gear grease in, cycle through the speeds to dress the belt and condition the Reeves cones? The noise might go away on it's own once you've run it back in. Just sharing my experience, friend. My Lagun sat for years in a facilities shop at a closed down school and made head noise for the first hour or so due to loss of lubrication. After exercising it with plenty of oil, flushing the back gear with oil to clear the old grease, and pumping in fresh while running the head through its range, everything has been peachy keen for over 4 years of use.