Jet 20" Drill Press Repair Question

[Brian Kent]

Jet JDP-20MF.

This used drill press has made beautiful holes but has some vibration in the head. I thought it needed new belts. But today I changed to a slower speed and found the problem. The pulley assembly attached to the motor has a huge amount of wobble. The pulley assembly is held to the shaft with a socket set screw. I loosened it but could not easily move the pulley assembly off.

I would appreciate guidance on trouble-shooting this. The parts are listed here: http://www.misgroupinc.com/partfiles/m_354170.pdf (pg17).

I guess my first question is about leverage to get the pulley assembly off to check and see if the motor shaft itself is straight and to see if there are bearings I can replace. Do I need to get a gear puller?

Thanks in advance.

Brian Kent

[Myk Rian]

Did you look for a set screw under the first one?

[Brian Kent]

Did you look for a set screw under the first one?

As in two set screws on the one pulley?

[Bruce Page]

As in two set screws on the one pulley?

Brian, sometimes there will be a two setscrews in the same hole. The second one is installed to lock the first.

[Brian Kent]

OK, I got the pulley off.

First, the motor shaft runs true. Whew!

I see two possible problems. First, there is a deep scratch with a burr on the shaft. It is barely visible in these photos as a diagonal line on the right side of the shaft. Second, I have questions about the key. The blow up diagram of parts shows the key as a rectangle with rounded ends. This one shows a lot of wear, has a slope on one end. The key shows two separate places where the set screw has dug in.

I assume I should turn on the motor and rest a file on the shaft to get rid of the burr. Is this key OK?

Thanks. Brian

[Brian Kent]

With the burr removed from the shaft, the pulley - just resting in place - runs true.

Now I am not sure how to overcome gravity to hold that key in place and to keep it from sliding too far on the slope in the groove on the shaft. It fits loose so it will not just hold itself in place.

edit: And as I look at the parts diagram, I don't think there is supposed to be a slope in that slot on the shaft. If there is no slope, it would hold the key in place.

Sorry if I am using the wrong terms for these parts.

[Jerry Bruette]

I'm guessing that at one time the key either fell out or was taken out and the set screw was tightened into the key way. That could explain the deep scratch/gouge on the motor shaft. It's also possible that the motor has been replaced. The pictures are a little blury but the keyway in the pictures doesn't look like the type that would take a key that is rounded on one or both ends.

Does the keyway get shallower closer to the motor end bell? If it does you wouldn't need to round either end of your key. I would probably put a new key in if the old one shows any wear.

If you'd like to file the motor shaft do it very carefully and not under power. You'd run the risk of tapering the shaft or having the file get caught in the keyway and possiby you'd have pictures to show us of your new injury.

I'd also find a way to measure the inside diamater of the sheave to make sure it's not over size or egg shaped.

Jerry

[Brian Kent]

If the sheave is the pulley, the inside diameter is 61/64"
The shaft is also 61/64" using the same gauge.

The key slot in the pulley is 28/64" wide. The key is 25/64" wide. 3/64" of play.

I went to measure the key slot in the motor shaft and found another big problem. The slot is completely misshapen, I assume because of an undersized key rattling around in there for years. I hope these photos show it. I apologize for my cell phone camera quality.

I am now looking for a fix I can live with that does not include replacing the shaft. It is the original Jet 1.5 hp motor.

[ray hampton]

the keyway in the motor shaft and the key are made to fit snug so that the key will stay in place while the pulley are installed, if the fit between the keyways and the key are not close then the key and the keyways will get damaged when you start and stop the motor time after time, If the key got a slope on one end of the key, will you install the key before the pulley or after the pulley are install ?

[Jerry Bruette]

Brian,

You have what's known as a wallowed out keyway. The absolute best way to fix it would be to replace the motor, I know that's an expensive choice you'd rather not make. You could try a product called Loctite 660. It's made for repairing worn shafts and wallowed out keyways. I've never used any myself but the factory rep from Henkel...Loctite's parent company... assured us that it would work at the training seminar we had about two weeks ago.

If you try it be sure to clean the shaft good, use the reccommended primer and follow the directions closely. The Loctite products I have used are very good, but like I said I have no personal experience with 660.

Jerry

[Cary Falk]

Do you have access to a welder? I would either try to fill in the space and from with files or a dremel. You could also tack the key in place and clean it up wit a dremel. You really can't make it worse at this point. Epoxy cam to mind to fil the gap but I don't think it will hold up.

[ray hampton]

If the sheave is the pulley, the inside diameter is 61/64"
The shaft is also 61/64" using the same gauge.

The key slot in the pulley is 28/64" wide. The key is 25/64" wide. 3/64" of play.

I went to measure the key slot in the motor shaft and found another big problem. The slot is completely misshapen, I assume because of an undersized key rattling around in there for years. I hope these photos show it. I apologize for my cell phone camera quality.

I am now looking for a fix I can live with that does not include replacing the shaft. It is the original Jet 1.5 hp motor.

You can fix this keyway [motor shaft and pulley keyway] BUT IT WILL REQUIRE a lot of filing or scraping to renew the grooves and maybe file a blank of metal to make the key, if the grooves are even [motor and pulley] then either buy or make a new key,3/64 are close to 0.045 and in my opinion TOO MUCH free play

[Brian Kent]

Do you have access to a welder? I would either try to fill in the space and from with files or a dremel. You could also tack the key in place and clean it up wit a dremel. You really can't make it worse at this point. Epoxy cam to mind to fil the gap but I don't think it will hold up.

I can buy or make a key the width of the keyway in the pulley and square the whole keyway in the shaft. Then make another piece to fit the remaining area. If it is a good mechanical fit, the epoxy or JB weld may hold it in position long enough to install the pulleys. I am not too confident in my ability to do that cleanly, but as you said, I can't make it much worse.

How much is it to replace the motor?
Since I don't have the bucks today, I will try a fix and see how it works.

[Brian Kent]

Brian,

You have what's known as a wallowed out keyway. The absolute best way to fix it would be to replace the motor, I know that's an expensive choice you'd rather not make. You could try a product called Loctite 660. It's made for repairing worn shafts and wallowed out keyways. I've never used any myself but the factory rep from Henkel...Loctite's parent company... assured us that it would work at the training seminar we had about two weeks ago.

If you try it be sure to clean the shaft good, use the reccommended primer and follow the directions closely. The Loctite products I have used are very good, but like I said I have no personal experience with 660.

Jerry

This looks more reasonable to attempt, along with a key that fits the pulley better.

[Brian Kent]

Just a random thought…

When you stop to measure the thickness of a hot piece of metal while grinding, don't use plastic calipers.

That's all.