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New to me Hartford Mill
- Thread starter Susquatch
- Start date
Thanks @Brent H. I won't be using my machine enough to deplete the packed grease. I will probably wait a little before I order bearings though. It may turn out that I want the whole rebuild kit.
This is all getting a bit loosy goosy. The size of a 2hp motor with the appropriate frame is very limiting. Virtually all of them have shafts that are only 2.1 inches long. By the time I raise the motor with a 1/4" adapter plate and then take into account the correct placement of the pulley to align with the spindle pulley, (about 1/2 inches below the plate, I've lost 3/4 of an inch, which puts the Allen key lock on the pulley dangerously close to the end of the shaft.
So I'm looking at several alternatives:
1. I could drill and tap new Allen key holes in the first pulley instead of using the second pulley where they are now. Or maybe use 4 keys instead of 2.
2. I could make a two layer plate adapter to bring the motor back down to flush with the housing. But this might affect how much the motor can be swung to change belt locations.
3. I could offset the pulley a little. This would put some additional tension on the motor shaft, but I'm only thinking about an 1/8 of an inch or so. Just enough to get the Allen key away from the end of the motor shaft.
4. I could use 1/8 plate instead of 1/4 to buy an 1/8th back.
Just wondering what your thoughts are.
Extend the motor shaft?
The shaft probably already has a center hole. Drill and tap for a good size thread. Counterbore the first 0.250” or so to use as a register. Make a plug with threads, close tolerance shoulder and oversized OD (also with a center hole on the opposite side of the threaded spigot). Assemble with locktite (and a pin if you think it is necessary). Turn rotor between centers to machine off the excess material flush with the original shaft OD. Extend the keyway out through the extension. You can make the extension as long as you need. The load is on the OE portion, just the securing set screw is on the new part.
The shaft probably already has a center hole. Drill and tap for a good size thread. Counterbore the first 0.250” or so to use as a register. Make a plug with threads, close tolerance shoulder and oversized OD (also with a center hole on the opposite side of the threaded spigot). Assemble with locktite (and a pin if you think it is necessary). Turn rotor between centers to machine off the excess material flush with the original shaft OD. Extend the keyway out through the extension. You can make the extension as long as you need. The load is on the OE portion, just the securing set screw is on the new part.
I had been considering this idea in various forms and discounted it for two reasons. You bringing it up gives me a good reason to reconsider it.
The biggest concern I had was that the set screw would not really end up on the new part. It would probably end up on or too near the joint between the new and old part. The other concern was the idea of taking apart the motor and modifying the rotor. I confess that I am leery about doing that, but maybe I shouldn't be. Perhaps it's just another one of those things I need to do at least once in my life. I certainly see that others here on this forum have done it from time-to-time.
I had also thought about enlarging the pulley ID and press fitting a full length steel bushing into it. Basically, I'm not really worried about the motor shaft strength. It's the aluminium pulley that concerns me and then only the wobble wear it might experience installed on a short shaft. A steel bushing should resolve that concern.
Anyway, for now my hope is to find a way to recess the motor a bit to make more of the existing shaft available.
I've done a bunch of measurin and cypherin myself.
Assuming the belt plane of the two pulleys is parallel to the motor mounting surface, the top of the motor pulley should ideally be 11/16 below the top of the motor mounting surface because that's where the spindle pulley is. If the motor could be mounted on that surface like the old one was, then I would have 2" minus 11/16 = 1-5/16 of shaft in the pulley and the Allen keys end up at 5/16" from the end of the shaft. Plenty.
However, it can't be mounted flush because all the motors I have found have a diameter that is too small. With a 1/4" adapter plate between the motor and the top of the housing, I end up with 1-1/16" of shaft in the pulley and the two lock keys (which are in the second groove) end up just over 1/16" from the end of the shaft. NFG.
So, I am thinking I could buy 1/16th of an inch by offsetting the pulleys a smidge, and then buy another eighth of an inch on top of that by recessing the plate to get the motor an eighth of an inch closer to the mounting flange surface. I don't have the time or the desire to do a full blown stress analysis of such a plate but I think it's safe to assume that a steel version would be plenty strong enough at 1/8 inch especially since that's only in the center where the motor is and the motor will be attached to it in four places all with big washers to spread the load. I think it's also pretty safe because the vast majority of the load will be a torque load with very little bending load.
All told, that would get me 3/16 of an inch more shaft inside the pulley and a full quarter inch between the Allen key screws and the end of the shaft.
I'll prolly rough cut the adapter plate with a cutting torch and then recess it for the motor on my lathe.
The alternative is to drill and tap new Allen key holes in the first groove of the pulley.
I may do both or as mentioned earlier, perhaps even use 4 Allen keys on the one 4-groove pulley.
Think I have a nice motor coming. It's a "damaged in shipment" Nidec 230V 3ph VFD rated motor that they said tested ok at half price. So it's basicly new with some cosmetic damage. It has a 1000:1 turn down ratio and its in a 145T frame. I can return it if it doesn't work so I said ship it! Basically a no-brainer for me.
I also found a small 12x12 piece of 1/2" plate at my local farm supply shop that I can use as a motor mount adapter. I'll rough cut it to size using my cutting torch and then clean it up with an angle grinder. Then I'll mount it on my lathe and recess it to 3/16" or so where the motor sits so the motor is recessed into the plate. I have it on really good authority that 1/4" will work. The 3/16 is just a small safety margin to make sure that the pulley set screws are solidly engaged on the motor shaft.
Next step - replace the back gear bearings.
I also found a small 12x12 piece of 1/2" plate at my local farm supply shop that I can use as a motor mount adapter. I'll rough cut it to size using my cutting torch and then clean it up with an angle grinder. Then I'll mount it on my lathe and recess it to 3/16" or so where the motor sits so the motor is recessed into the plate. I have it on really good authority that 1/4" will work. The 3/16 is just a small safety margin to make sure that the pulley set screws are solidly engaged on the motor shaft.
Next step - replace the back gear bearings.
Question - is there anything special about the grease that H&W sells for packing the bull gear area?
Can they / will they ship it across the border?
I have a bunch of different types of grease here on the farm already. I buy it by the case. Some of my farm neighbours buy grease by the barrel. Anyway, if I can use some of what I already have, it will save me some hassle.
Can they / will they ship it across the border?
I have a bunch of different types of grease here on the farm already. I buy it by the case. Some of my farm neighbours buy grease by the barrel. Anyway, if I can use some of what I already have, it will save me some hassle.
OK, kind of what I hoped you would say. I'm thinking a high temp wheel bearing grease would be overkill but might work just fine.
Yesterday I cranked the tables on both mills to the far right and had a good look at the leadscrews. The Bridgeport is visibly worn in the middle VS the ends. Yet I was surprised to discover that I could only measure about 10 thou difference - not very reliably so though because I found it quite hard to measure the wear on a slightly sloped tooth with any precision or repeatability using a tubing mic or a caliper.
The Hartford appears to have no visible or measureable wear at all. Frankly, it looks and measures unused - but I know that is not possible. It makes me wonder if the screws have been replaced......
Recall that the backlash as observed on the handcranks was in the range of 90 thou on the Bridgeport and 15 on the Hartford.
If it turns out that I keep the Bridgeport, would you replace the leadscrews?
It's likely that I will never use a power feed. I have a cheap one on my mill/drill but other than an initial evaluation, I never use it. But never say never.
Just watched the H&W videos on rebuilding a step pulley Bridgeport again. Seems I might be kidding myself just trying to repair the back gear slop. Prolly better off doing the whole thing while I'm in there cuz it looks like it all has to come apart to get at the bottom bearing. Not really happy about that but it is what it is. If so, I'll prolly order the whole rebuild kit. At this rate it could become a winter project...... Too bad because I can almost smell it working as the motor gets closer to delivery.
Another dumb question. Having watched Barry using his big arbor press I'm getting a little paranoid about installing bushings and bearings. I don't have a press like that nor am I likely to get one. However, I do have a big 30 ton Hydraulic press. I'd never feel the 30 ton till after the housing was totally crushed, but I bet I could feel the bearing/bushing bottoming out on a 2 ton unit.
What do you guys think about putting a 2 or 3 ton high lift bottle jack into my 30 ton press to install bearings and bushings with?
What do you guys think about putting a 2 or 3 ton high lift bottle jack into my 30 ton press to install bearings and bushings with?
Dabbler
ersatz engineer
great idea!
Thanks for the endorsement. I'll do it!
Another dumb question: I was watching Barry's rebuild videos and caught him saying that the grease pack is all about looking after users who forget to oil. Up until then I had thought it was oem. But I confess that I have hated all that grease ever since I first saw it.
As a farmer I see old hard grease all the time. If you don't keep the grease flowing by shooting in new grease every so often, dirt collects on the grease, it hardens, and then it becomes a nightmare. I'd much rather oil as required.
Am I crazy?