# G0704 Issues



## Chatterking (Feb 9, 2020)

I have a G0704 Mini Mill that I came across at for what I felt was a really good price.
It was purchased new 12/15. The original buyer never used it. It was still brand new.
His wife came down with medical issues right after he bought it so he never had time to do anything with it.
He was moving into a Senior center so it had to go.
So while I wasn't looking for a mill the price was too good to pass up plus it came with a free Delta 14" Bandsaw.
I have since sold the bandsaw but still have the mill.

I have had several issues in the first couple of months of using it.
1st the spindle runs very hot. So hot that its uncomfortable to touch it.
After running awhile it refuses to start. Let it sit overnight and cool down and it'll start again.
I was running it in high range at the time. Since then I've been running in low only and that seems to help.
The spindle still runs warm but no where near as hot.

The 2nd thing that happened is while running in high the intermediate gear set seized tight with the shifting fork.
Seems that the selector knob was rotated slightly past the high detent and this forced the fork against the gear set and cause exssive friction.
New gear set and all is well.
Be fore warned about running this thing in high with the knob not in the detent.

3rd thing is the plastic gear that meshes with the motor got stripped in a couple of spots.
Turns out the mounting of the motor plate thru the 6 shcs was not very accurate.
When the shcs are tightened up they put the motors gear and the plastic gear in a poor place as far as the mesh between the two.
I actually stripped the gear myself by checking the torque of the mill while it was running.
I put my hand around the spindle and squeezed slightly. That little bit of resistance was enough to strip the gear.
Another new gear and opening up of the holes on the mounting plate allowing the motor plate and motor to move around solved this.
I could then push the motor tight against the plastic gear so that there was a better meshing going on.

My current issue is after trying to power tap a 5/16-18 hole in aluminum the mill wouldn't start.
It pops the GFI breaker on the outlet.
SO after doing a couple of checks to find where the issue is it starts again.
Now I can't find where the issue is.
I'm in the middle of project that I'd like to get done so I don't want to poke the bear.
I'm just going to limp the thing thru then I'll doing some more checking.
Right now I'm wondering about the forward/reverse switch. 

What my biggest question is about the kicking out and refusing to start after it gets warm/hot.

The spindle running hot, is this normal? I've run lots of "real" mills and never seen a spindle run hot.
I can turn the spindle by hand but I would say I'd expect it to turn easier than it does.
Especially since this is such a small mill.

If I could get the running hot and occasional no start issue cured I might start warming up to this thing.
Right now, I'm not at all impressed by this thing.
I like the small size and being 120v is nicer and makes things easier than having to have 220.
The travels are OK but the Z is limited at 2".
Everything is a little on the crude side but I guess thats to be expected.

Any tips help on my issues and concerns?


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## markba633csi (Feb 9, 2020)

The plastic gears are certainly a weak point on those, as you've discovered.  Some folks convert them to belt drive- there used to be a person (Ebay?) who sold adapter kits for that
You could replace the spindle bearings with better quality ones if you have access to a press.  Most likely the factory uses the cheapest parts they can including bearings.


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## stupoty (Feb 9, 2020)

Spindle sounds like there is too much pre-load on it. maybe back it off a little.

Stu

edit, 

There is a bit on running in the mill , maybe it wasn't run in as it was so new ?

------------------>

The spindle break-in procedure distributes lubri-cation throughout the bearings to reduce the risk of early bearing failure if there are any "dry" spots  or areas where lubrication has settled in the bear-ings. You must complete this procedure beforeplacing operational loads on the spindle for the first time when the machine is new or if it has been sitting idle for longer than 6 months.Always start the spindle break-in at the lowest speed to minimize wear if there are dry spots. Allow the spindle to run long enough to warm up and distribute the bearing grease, then incremen-tally increase spindle speeds and repeat this pro-cess at each speed until reaching the maximum spindle speed. Following the break-in procedure in this progressive manner helps minimize any potential wear that could occur before lubrication is fully distributed 

<---------------------------------

from the manual 
http://cdn1.grizzly.com/manuals/g0704_m.pdf


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## mikey (Feb 9, 2020)

I agree - sounds like preload is too high. It is also very likely that your mill uses the cheapest bearings that will fit in there. If you install decent bearings and preload them properly I bet that would solve the heat issue.


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## Chatterking (Feb 10, 2020)

Think the tight bearings are overloading out the electrics at some point when things get too hot?

Next time it kicks out the electrics I'll see if I can turn the spindle by hand and if its any tighter than normal.


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## fitterman1 (Feb 13, 2020)

Hi fellas, reading through this thread I seem to think that excessive preload is actually loading up the motor to the point that any more work like tapping or milling is just gonna send that breaker into spasms.
Chatterking, you're gonna have to do some dismantling and see how loaded up that spindle is by testing it by hand turning, should spin easily with some "felt" friction and smoothly with no gritty sensation when turning. and there should definitely be no endfloat and wobble.
And run the motor under no load, completely disconnected from the geartrain.
Listen for bearing noises from both spindle and motor.
As mentioned already, get rid of the gears and go belt drive and you will help eliminate chatter.


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## Chatterking (Feb 17, 2020)

fitterman1 said:


> As mentioned already, get rid of the gears and go belt drive and you will help eliminate chatter.



Trouble with this it eliminates only 1 of the what 6-8 gears?
Cost to eliminate 1 gear vs the cost of the one gear?

Cause of my gear failure was poor assembly gear mesh.

If my gear fails again after a couple of months I'll think about it.
If it doesn't fail for a couple of years I'll just buy another gear.


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## jjtgrinder (Feb 19, 2020)

Since that machine has been sitting up for quite a while, I would go through it completely and clean it.  I recently bought a new Sieg X2D LMS 4962 machine, I installed the belt drive conversion kit on it and I am very happy. It runs relatively quiet and has plenty of power.
I completely with agree with Fitterman1’s (and the others)


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## kd4gij (Feb 19, 2020)

First, You can put it in neutral , Halfway between high and low it should free spin. The cooling on these mills suck, If I am doing a lot of heavy milling I take the cover off the motor. it makes a big difference. A good mod is to cut the fins out of the top of the motor cover and mount a muffin fan like out of a computer power supply on top of it. The motor is protected by a thermal cutout. it resets once it cools down. And a 5/8-18 tap is a bit much for these in stock form.









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## Chatterking (Feb 21, 2020)

In neutral it turns, but ts far from "spinning freely".


5/16-18, not 5/8 tap.

And I have pulled the cover off the motor.

Was doing some work on the beast yesterday and it seems like the variable speed control knob is schetchy. When I turned down the speed it tripped the breaker again. Reset the breaker and all was good again.


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## sru_tx (Feb 21, 2020)

I just went through my 0704. The plastic gear that connects the intermediate shaft to the motor stripped. The bottom bearing of the quill/spindle would run fairly hot. Not sure if they're related. 

I replaced the gearing with a timing belt but continued using the intermediate shaft. I have a thread up on that. With a lathe it's an easy fix for not much more than replacing the plastic gear and no mods to the motor mounting.

While I was working on it I decided to address the hot bearings. Pulled the quill and changed the preload via the top collar. I found I needed to give the quill a quick tap of a hammer to "unload" the bearing and reseat it.  Now it turns easier by hand and runs way cooler.


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