Motor issue with Mill/Lathe Combo.. Ideas?

[Keyblazer]

I bought a mid 80's Shoptask 1720 Lathe/Mill combo.
In the process of refurbishment for a few home projects...



Works great, but there seems to be an issue with the motor when I change the belts to get the faster speeds.

The motor spins up, reaches about 70/80% of its max, and then begins to "Dither", and falter. It does not happen when a lower gear or no load is on the motor.

If I leave it running like this, it pops the breaker.
I changed the power outlet to one on a different breaker, and it still does the same.
I just went thru the motor, and all the bearings, and electrical connections. All looks fine, although I found one wire going to the motor that looked overheated.

Motor ID plate says: 3/4hp 110v/60hz 12A 1650rpm Capacitor start.
Built 86-12.


Looked at the fitted Capacitor, it says 110V 300mfd... also Chinese, but the manufacture date is 81-6... so looks like a replacement.



Any thoughts or input would be most helpful!

 

[larry_g]

Sounds to me like a CF (centrifugal) switch problem. At loe power do you hear the CF switch click when shutting down? When you have a problem do you hear the switch click when shutting down? The CF switch electrically connects the start cap to the start windings to get the motor started and then opens when the motor is mostly up to speed. I suspect that under load, high speed setting, the motor is not getting up to a fast enough speed to open the CF switch. The switch may be dirty, worn, or some thing else that has raised the dropout RPM, or it may be fine and the motor is just not up to the load.

lg
no neat sig line

 

[Keyblazer]

Thanks!
I will go check, but I do know it makes a click when slowing down... just not sure it does it all the time.

Here is a pic of that area of the motor... the contacts looked fine with no obvious burning...

 

[gungatim]

I have a similar machine different color but basically the same.

had the same issue. mine was barely if ever used. turned on find on low speed but high speed stalled out, and stalled if you put your hand on it even.

problem was the grease in the spindle had hardened up. had to completely tear it apart and clean all the hard cosmoline off and properly lube it. been fine ever since.

you may have the same issue...

btw, I got rid of the chuck and got a set of proper collets off amazon and makes milling 80% lowers super easy...

 

[Keyblazer]

You are correct.
When the motor is under load, and does not reach its target rpm, and it does not make the "Click".
It does if its on the lower gear setting or no load is applied and the motor reaches its target rpm, it does.
I also notice that the "Motor Feed Conduit" that takes the power from the on/off switch to the motor gets hot real quick if I leave it in this dither condition.

Can you give me an idea on what to check?

 

[Keyblazer]

Gungatim,
On the "Home Machine Shop Forum", I have documented the resto.
I pulled the spindle and bearings and cleaned and regreased them.
It was in good shape, but I did it anyway. Now the bearings are clean, but I think a tiny bit tighter than before.
How did you set your bearing preload?

Before...


After...

 

[larry_g]

Thanks!
I will go check, but I do know it makes a click when slowing down... just not sure it does it all the time.

Here is a pic of that area of the motor... the contacts looked fine with no obvious burning...

I was speaking less of the contacts but more of the Mechanical part of the switch. It has to work freely and smoothly. In the picture looks good and is working at lower loads so it is probably ok. Now on to the grease, Most high speed rotating bearings like this use oil. Does this machine have any oil reservoir in the headstock that would allow oil to work? Does the manual say anything about lubricating?

lg
no neat sig line

 

[Keyblazer]

Thanks for the response and input Larry!

I am not an electrical guy, so struggle with this stuff beyond the obvious.

Later, I will pull the endbell off again and look more closely at the switch and centrifugal unit, to see if I can see any issues.

It was suggested on my resto thread, that the issue might be the capacitor, but I have no idea if that is plausible or how I test it.
I did find an online basic test of a capacitor by making sure it was discharged, then using an old analog ohm meter. It said that the capacitor would register a reading then drop to zero... mine did exactly that.
I do have a buddy of mine hunting down a replacement regardless.

On my resto thread, they also suggested that old grease might be the issue...
Some of the bearings looked fine and some looked full of old junk, so I redid all of them in the main spindle, and will get to the milling head soon.
Here was one behind the upper pulley spindle.....


Here was the rear spindle bearing, and it was ok..


After cleanup, the bearings and cups looked fine.
Rear bearing, and front bearing.



Finding a Manual for a Shoptask 1720 was impossible.
Someone spotted an identical machine for sale, and it had the model number "HQ400" and that got me there.

There is a guy is Sweden that has a great site on the HQ 400, a CNC conversion and had the manual too.
Here...
http://www.privatech.se/HQ400_eng.html

Manual says grease too, but no spec, so I used wheelbearing grease.

 

[wyliesdiesels]

The conduit is getting hot and the breaker trips because its pulling too much current. The motor may be getting hot to. Larger motors would have integral overload protection. Becareful not to cook the windings. If the breaker isnt tripping when it gets hot u may want to change the 20a breaker to a 15a.

This is indictive of obviously either too much load on it(u dont have any) or too much resistance(bad grease)....

Im an electrician not a machine guy, so i cant help specifically with the lathe

 

[matt_i]

I would have used an ISO 220 oil on your spindle bearings for a short time to troubleshoot. The standard #2 NLGI grease is very very thick for a spindle. A better alternative is Kluber. Or down to something like a #0 NLGI rating.

 

[Keyblazer]

The grease I used is called "Light Duty", so I thought I would just run the darn thing in the lower speed and see if it beds in a little.


I needed a test piece, so off I went...
Using the lowest speed, which was fine.
Started with a offcut of 6061.




Replacement tension Knob for my Bandsaw, that was plastic and broken...



Running in the lower speed, it worked fine, and no issues with breaker or overheating...

 

[gungatim]

Gungatim,
On the "Home Machine Shop Forum", I have documented the resto.
I pulled the spindle and bearings and cleaned and regreased them.
It was in good shape, but I did it anyway. Now the bearings are clean, but I think a tiny bit tighter than before.
How did you set your bearing preload?QUOTE]

I didn't set preload, just followed the procedure in the spindle rebuild document in the yahoo group "3_in_1_Lathe_Mill_Drill" in the files section. put it back together the same as it came apart...

if you are not a member I can send you the pdf, but it looks like you don't really need it. there is a lot of good info there if you join, of course yahoo groups **** in terms of format, but you don't get bashed like a lot of the other machining forums if you are a backyard hack like me...

 

[Keyblazer]

Just found and joined the group, thanks Gungatim.
I could only find a milling head spindle revamp pdf, not the main lathe spindle.

 

[gungatim]

Just found and joined the group, thanks Gungatim.
I could only find a milling head spindle revamp pdf, not the main lathe spindle.

that's the one I used, I did the milling head, not the lathe head. I couldn't get the chuck off the lathe head to get it apart to clean and lube, it is held on with some recessed screws I can't get to unfortunately...Wanted it off and out of the way to have more space for the mill...

 

[My Old Tools]

The cheap Chinese motor was barely adequate when new. Now it doesn't have enough power to get up to speed in top gear. It may have already lost a winding. The easy fix is to replace it with a 1HP US made motor of the same RPM.

 

[Keyblazer]

Yup, it doesn't take much of a stretch to figure out its 30 years old and probably toast.

Maybe a DC treadmill motor makes sense...

 

[alfredeneuman]

Maybe a DC treadmill motor makes sense...

Not at all.
You'd be trying to mount a DC motor on a machine that had an AC motor on it.
You'd need to add the DC drive in addition to the motor. There would be extensive rewiring involved.
And even then there's the possibility that it would not perform.

I think My Old Tools had the best option> "The easy fix is to replace it with a 1HP US made motor of the same RPM."

 

[txvwnut]

I've got a Shoptask Eldorado Bridge mill that both the motors have gone **** up, and I'm converting it to three phase and running a VFD. The reason for the VFD is I should end up with a variable speed setup instead of having to change belts all the time.

 

[Falcon67]

Not at all.
You'd be trying to mount a DC motor on a machine that had an AC motor on it.
You'd need to add the DC drive in addition to the motor. There would be extensive rewiring involved.
And even then there's the possibility that it would not perform.

I think My Old Tools had the best option> "The easy fix is to replace it with a 1HP US made motor of the same RPM."

Check the Yahoo groups for the smaller lathes - the treadmill motor mod is a very popular upgrade, especially to the 9x20 lathes. Lots of links to surplus motors and notes on PWM controllers for them. Completely variable speed, lots of torque.

 

[My Old Tools]

3 phase with a VFD is a viable option as well.

 

[alfredeneuman]

Check the Yahoo groups

I'll take your word for it. I don't use Yahoo anything if I don't have to.
I'll retract my previous statement

 

[Keyblazer]

btw, I got rid of the chuck and got a set of proper collets off amazon and makes milling 80% lowers super easy...

What did you buy?

 

[Falcon67]

I'll take your word for it. I don't use Yahoo anything if I don't have to.
I'll retract my previous statement

Well, just so you know there is a ton of know-how stored there. 4x6 saw group, 9x20 lathe group, 12x36 group, etc, etc. Don't skip over useful info just because the name on the door is kinda ratty now.

 

[RAYJAY]

another shop task owner here picked mine up used very little for $850 with stand did mod it a little so far with the chip pan, and want to change out the euro style tool post for a AXA tool post, i do have the original manual for this machine if anyone needs it, there is no support for this machine from the manufacture,

 

[txvwnut]

another shop task owner here, there is no support for this machine from the manufacture,

And never has been. Bought mine new got less than 50 hours on it when the first motor died.

 

[Keyblazer]

Is the a 3 in 1 thread here?
If not, sound like we need a dedicated one!

 

[RAYJAY]

And never has been. Bought mine new got less than 50 hours on it when the first motor died.

they are a good little lathe / mill once you get them dialed in. its just when you call them its like your bothering them, and not calling for free info just wanted to buy a couple of upgrades they have listed, mainly the compound rest axa tool holder for right now, later i do want to make a bridge mill out of the one i have


Bolton tools is making the same 3 in one that shop task did

http://boltontool.com/Lathes/lathe-mill-drill-combo

 

[RAYJAY]

Is the a 3 in 1 thread here?
If not, sound like we need a dedicated one!

having A 3 in 1 here is like being a HF addict...... lol


i personally just do not have the space to dedicate to a full size lathe and mill

 

[Falcon67]

Here are 3 in1 links

http://www.hobby-machinist.com/forums/smithy-shopmaster-grizzly-other-3-in-1-machines.206/

http://www.chaski.org/homemachinist/viewforum.php?f=27

Edit - also
https://groups.yahoo.com/neo/groups/3_in_1_Lathe_Mill_Drill/info

And from there
http://forums.delphiforums.com/n/ma...&nav=start&prettyurl=/Shoptask&gid=2090517769

 

[txvwnut]

Is the a 3 in 1 thread here?
If not, sound like we need a dedicated one!

I started with a 3 in 1 setup due to I needed a mill and a lathe and had a limited budget. I started with a Smithy 1200xl and it was a great little machine with the exception of the Morse taper quill. MT tooling is kinda hard to find and expensive when you do find what you need.

I had inquired about the Shoptask unit after I bought the Smithy as that's when I found out about them. They sent me a flyer in the mail some years later with a pre-buy discount on the bridge mill. I bought the Shoptask unit and sold the Smithy. I should just kept the Smithy as JT(the owner of Shoptask) pretty much lied in the sale flyer and I did not get everything I was supposed to with the pre-buy of this yellow piece of ****.

Fast forward a few years and I got a deal on an early Enco knee mill off c-list, so that is what does all the milling work now. I took the mill head off of the Shoptask and now I have a crappy lathe instead of a crappy 3 in 1.

 

[gungatim]

What did you buy?

This set:
https://www.amazon.com/gp/product/B00R13WQQA/?tag=atomicindus08-20

I had to buy a piece of threaded rod 3/8-16 to make a longer drawbar to tighten it up as the stock one for the drill chuck ends up a bit short. they work well with endmills and don't slip out like the drill chuck, plus you gain several extra inches of height.

MT2, 7PC SET 1/8-1/2" x 16THS
• Drawbar End Threads: MT2: 3/8" - 16
• Morse taper: external
• 1/8-1/2" x 16THSMade of high grade tool steel. MT2, 7PC SET

 

[gungatim]

The cheap Chinese motor was barely adequate when new. Now it doesn't have enough power to get up to speed in top gear. It may have already lost a winding. The easy fix is to replace it with a 1HP US made motor of the same RPM.

when I first got mine and had the power issue with the motor, I read a lot of people had the same problem. also the motor being enclosed in the column for the mill part supposedly contributes to the motor overheating. there are several who swapped out the motors, and/or opened the column for more cooling. That is what I expected to have to do, but apparently I got lucky and got a good one. seems it's about 50/50 on the motor quality. pretty much the same as the HF/import drill presses, some have no trouble, others the motor loses its magic smoke after just a few hours of use...

I bought a few cheap digital calipers from HF to make the DRO mod but haven't gotten around to it yet.