# Grizzly G0704 - quill drop



## camcl3 (Jul 22, 2020)

This has probably been covered...after an hour of searching this forum I decided to ask.  I have a Grizzly G0704 that is new (less than an hour of use) and I noticed the quill dropping up to .005 when milling.  It only seems to do this when it is removing a lot of material.  Anyone else experience this?  Any help would be appreciated.  Thanks in advance


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## Mitch Alsup (Jul 22, 2020)

Too  much information--not.

Is the milling-bit in there sufficiently tight?
Is the spindle retraction spring set to pull up enough?
Did you bother to lock the spindle so it can't move?
How are you using to hold the milling-bit?
What size is the milling bit?
What RPMs are you running?
What material are you milling?
Is any lubrication being used?
How deep is the cut?
How fast is the feed?

The only times my G0730 did stuff like this was when the collet nut was not sufficiently tight.


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## camcl3 (Jul 22, 2020)

Mitch Alsup said:


> Too  much information--not.
> 
> Is the milling-bit in there sufficiently tight?
> Is the spindle retraction spring set to pull up enough?
> ...




Thanks Mitch - view below

Is the milling-bit in there sufficiently tight? _Yes, I tighten it snug but read not to overtighten_
Is the spindle retraction spring set to pull up enough?  _Have not adjusted the spindle retraction spring so maybe I should take a look - any insight would be great _
Did you bother to lock the spindle so it can't move?  _I lock the Z first, then lock the quill feed to engage the fine feed, then after making adjustment with the fine feed - I lock the quill lock lever.  I try to only drop the quill a minimal amount so that I don't lose rigidity_
How are you using to hold the milling-bit?  _3/4" R8_ 
What size is the milling bit? _1" End Mill_
What RPMs are you running?  _Does it all RPMS_
What material are you milling? _Brass _
Is any lubrication being used? _Yes, CRC cutting oil_
How deep is the cut? _Starts .005" and will drop down up to .010".  It doesn't do it when I only take off .002 or so...just when it is making a little more aggressive cut_
How fast is the feed?  _Usually does this at all feeds when I'm removing anything more than .002"...but not always._

Thanks again,
Cam


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## RJSakowski (Jul 22, 2020)

Tool pullout is a fairly common occurrence on Tormach mills with automatic tool changers, the primary reason not locking the tool tightly enough.   I suspect that it is your problem as well.  I tighten my collet mounted tools to well past snug.  

A 1" end mill is large for your mill.  Are you using a collet or an end mil holder?  The helix on the end mill tends to pull the tool out of its mounting.  An end mill holder and an Weldon shank end mill is less prone to pullout


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## camcl3 (Jul 22, 2020)

RJSakowski said:


> Tool pullout is a fairly common occurrence on Tormach mills with automatic tool changers, the primary reason not locking the tool tightly enough.   I suspect that it is your problem as well.  I tighten my collet mounted tools to well past snug.
> 
> A 1" end mill is large for your mill.  Are you using a collet or an end mil holder?  The helix on the end mill tends to pull the tool out of its mounting.  An end mill holder and an Weldon shank end mill is less prone to pullout



Thanks for the reply.  Sorry, I left this out - it's actually an indexable end mill and I'm using an R8 collet but I can get an end mill holder.  I was thinking after I posted that I have tried it both ways very very tight and then not as tight but still tight if that makes sense. 

I have the DRO on the front of the machine that comes with the 704 and then I also have the 3 axis DRO, my model is actually the 759 which is just the 704 with the DRO.  Anyhow, the front DRO shows the .005" +/- drop and I wonder if it would show that if the tool was pulling out?

Thanks again


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## Mitch Alsup (Jul 22, 2020)

camcl3 said:


> Thanks for the reply.  Sorry, I left this out - it's actually an indexable end mill



That is called a shell mill. Are you sure the indexable inserts are positive rake? Brass is picky like this.



> and I'm using an R8 collet but I can get an end mill holder.



You are using a (from above) 3/4" R8 collet directly in the spindle holding a 1" shell mill.



> I was thinking after I posted that I have tried it both ways very very tight and then not as tight but still tight if that makes sense.



Did you remove all traces of oil on the inside of the R8 collet and shank of the shell mill before tightening? (lacquer thinner)



> I have the DRO on the front of the machine that comes with the 704 and then I also have the 3 axis DRO, my model is actually the 759 which is just the 704 with the DRO.  Anyhow, the front DRO shows the .005" +/- drop and I wonder if it would show that if the tool was pulling out?



Does the cut look like the shell mill is dropping into the work?
Does it look like it drops and then holds steads or doe it look like it continues to drop as the cut goes along?

If you were to lift after the start of the cut AND then go back to the same depth, does the DRO read the same as before you started the first cut? (Trying to isolate holder issues from readout issues)

Have you tried with a smaller (real) end mill? instead of a shell mill?


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## camcl3 (Jul 22, 2020)

Yes, they have positive rake.  Correct - I am using a 3/4" R8 collet directly in the spindle. I can see it digging into the work as it moves along and hear it.  The dro shows it continuing to go deeper as it cuts.  It's not all at once.  I haven't tried a real end mill I don't have a use for one at this point.  I will make sure the inside of the collet is clean of all oil.  I did clean it when I got it but will check again.  I will also try to lift after I cut and go back and see the depth.  Thanks


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## Nutfarmer (Jul 22, 2020)

If the DRO  shows it dropping the collet isn't what's slipping ,it's the quill or maybe the head. What ever the DRO  is measuring would be where to check. While the collet slipping is the most common reason. Check the quill lock and make sure that's not the source of your problem.


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## camcl3 (Jul 23, 2020)

Nutfarmer said:


> If the DRO  shows it dropping the collet isn't what's slipping ,it's the quill or maybe the head. What ever the DRO  is measuring would be where to check. While the collet slipping is the most common reason. Check the quill lock and make sure that's not the source of your problem.



Thanks, it is only the quill dro that shows it dropping.  The 3 axis dro doesn't show a drop.  That is what makes me think it is the quill and not the head but I'm clearly a beginner and trying to learn so take that with a grain of salt.  I am locking the quill but will see if I can get it tighter and see what happens.  Thanks again


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## hman (Jul 23, 2020)

OK ... from everything you've said, it definitely sounds like it's the quill itself that's moving.  The DRO evidence is a real convincer. 

I looked at the mill on Grizzly's website and checked through the manual.  It looks like the quill locking lever (236) is a bit flimsy - can't tell from the diagram, but it looks like it might be M8 or something about that size.  Then there's the brass pin (237) on the end.  Possibly inserted into a hole in the end of the screw.  I'd try removing the lever and pin, and checking to see if the pin is loose in the screw.  It might also be the case that the pin is a bit too long for the hole in the screw.  If so, the pin could pivot at its "inner" end, allowing the quill to move up and down. 

If the quill lock is indeed the problem, a fix might involve shortening the pin's shank slightly, re-making the pin so it fits more closely in the screw, or maybe even drilling and tapping the mill head for a beefier screw.

PS - I gotta politely disagree with RJ regarding mill pullout, at least in this case.  If you were side milling or taking a much deeper cut, mill pullout would definitely be a consideration.  But if you're having a problem at 0.005" or 0.010" DOC, the downward force on the mill would be miniscule.


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## camcl3 (Jul 24, 2020)

hman said:


> OK ... from everything you've said, it definitely sounds like it's the quill itself that's moving.  The DRO evidence is a real convincer.
> 
> I looked at the mill on Grizzly's website and checked through the manual.  It looks like the quill locking lever (236) is a bit flimsy - can't tell from the diagram, but it looks like it might be M8 or something about that size.  Then there's the brass pin (237) on the end.  Possibly inserted into a hole in the end of the screw.  I'd try removing the lever and pin, and checking to see if the pin is loose in the screw.  It might also be the case that the pin is a bit too long for the hole in the screw.  If so, the pin could pivot at its "inner" end, allowing the quill to move up and down.
> 
> ...



Thanks Hman!  I may remove the lever (from 236) and wrench tighten with more torque to see if that makes a difference.  I've contacted Grizzly Customer Service and am eager to see what they say after they look into it.  The machine only has a couple hours of use so I'm a little concerned that this is an issue already.  I really appreciate you taking the time to look into this!


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## macardoso (Jul 24, 2020)

I have a G0704. The quill lock lever is garbage. All it does is apply a bit of side force to the quill to keep it in place. 

I replaced mine with a brass tipped cap screw. Then I can get an allen wrench on it to really crank it down.

Also the G0704 is pretty small compared to most machines, just be reasonable what size tool and cut you are using. I find it likes 1/4" tools in steel and 3/8" in aluminum (working the tools hard). You can use bigger tools but the cutting forces go up and you really don't end up removing material any faster than the smaller tool could do.


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## markba633csi (Jul 24, 2020)

I would think a 1" cutting tool is too big for that size machine with it's limited ridgidity and power.  I would stay with smaller sizes.
Also, brass is a "tenacious" metal and very grabby.  Be sure to use eye protection; the tiny chips spray everywhere.
-Mark


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