Spindle issues 833TV

[mike96]

I am putting this in a seperate thread than the CNC conversion as it technicaly has nothing to do with the CNC conversion itself. Now that I have the CNC conversion done I have a couple of other issues that need attention (issues I find as I use the mill). I did ask these questions over on the PM FB page as well, so I figured I would check in with you guys also to see what you think. bascly I am having a couple of issues with the spindle on my PM833.

The first is spindle nose heat. Is is common to have to take the spindle apart and repack/retorque the bearings when new? I ran the mill for about 45 minutes at speeds varying from about 60 RPM all the way up to max RPM in 5 minute increments before putting a load on the spindle and the nose/tool holder didn't get very hot. Now that I have put a load on the mill and cut some parts she gets pretty toasty after about 10 minutes of use. I cant hold the spindle for more than a second or two before I have to let go HOT...

Second question I am using TTS style tool holders in the mill, But the collet does not go all the way up into the spindle. It is not an issue that I have seen else where on FB group or anywhere else as of yet so I am not sure what is going on, but it appears that the taper in the nose of the spindle isn't cut deep enough to let the collet go all the way in. The set screw as been adjusted and it isnt the draw bar it pulls the collet in just fine. The collet appears to registers agents the nose fully around the taper and holds the tools just fine, it is just that the collet sticks out about 3/16 inch below the nose and the TTS holders don't register agents the nose as they should. Does anyone else's collets look like they hang down lower than they should?

Thanks

 

[buzzfab]

This is not the first time I have heard about the overheating bearings in this model. I have not run my spindle yet as my conversion is still ongoing but you are the 3rd person I know of with this issue. Here are the other 2.

Dr.DFlo on youtube had this problem, he talks about it and replaces the bearings/seals in this video here

also user TCandee on his forum talks about his spindle overheating and having to swap out the bearings is this thread

https://forum.drdflo.com/t/cnc-milling-machine/44/23

Eric

 

[3Dogs]

I have heard of issues with the cylindrical part of the spindle not being machined correctly, so the R8 taper collets won’t seat all the way:

Post PM-833T Spindle Bore Runout

I decided to check the runout after boring out the upper part of the R8 spindle. The Morse taper arbor PM supplied had at most two ten-thousands runout. (See attached video) A 1/2" end mill shaft in the Interstate collet had about one thousands runout. I clamped a 1X2 board in the vise...

www.hobby-machinist.com

Also, there is a long thread about the PM-928 with the wrong taper machined into the spindle. Hopefully, it’s not that...

 

[RJSakowski]

Second question I am using TTS style tool holders in the mill, But the collet does not go all the way up into the spindle. It is not an issue that I have seen else where on FB group or anywhere else as of yet so I am not sure what is going on, but it appears that the taper in the nose of the spindle isn't cut deep enough to let the collet go all the way in. The set screw as been adjusted and it isnt the draw bar it pulls the collet in just fine. The collet appears to registers agents the nose fully around the taper and holds the tools just fine, it is just that the collet sticks out about 3/16 inch below the nose and the TTS holders don't register agents the nose as they should. Does anyone else's collets look like they hang down lower than they should?

Thanks

I run the TTS tooling system on my Tormach 770 and on my RF30 clone. For the TTS tooling to function correctly,te tool holder must seat on the face of the spindle. My Tormach R8 collet sits flush in the spindle socket. The Lyndex collet on my RF30 clone sits about .030" proud of the spindle face. I modified the collet to do so. 3/`6" stickout is excessive. The question is what is out of normal practice, the socket or the collet? (there is no published standard for R8 tooling) It appears that common convention is that the maximum diameter of the R8 collet is 1.250". The socket should be similar at its maximum diameter.

You can check with multiple collet. If they all stick out, the spindle is likely out of spec.

 

[j-becker]

That seems odd. on my 833TV the Tormach collet ends up about flush with the spindle nose. The holders then reference against the spindle nose.

 

[mike96]

Got a few replies on the FB post along with a photo of a Tormach collet vs China made collet. There is a notable difference in the length of the taper on the end of the china collet. I am gonna order an actual TTS collet this week (like I should have done in the first place, I am old enough to know better by now), that should fix that issue. I will let you guys know when it gets in.

 

[mike96]

OK. Got a couple of e-mails back from PM on the spindle. According to their tech guy Mike, it is normal for the spindle to run hot at higher RPMs, No definition of what Higher RPMs are to, so perhaps I am running the spindle too fast but then what is the point of having a mill capable of 3000+ RPM if I cant use those speeds... As for the torque spec on the spindle bearing nut so I can take it apart and re grease the bearings, there is none. it is only tightened enough to take out axial play in the bearing. Other than that the only other advice I got is to use Isoflex spindle grease and not to use too much of it... So we will see. Starting to think maybe another brand mill would have been a good choice. I mean PM sells a mill that uses the same bearings as the 833 in the spindle and turns at over 2000 RPM more than this one, but if I cant run this mill at the speed it is capable of then whats the point... Sorry if I am sounding like I am venting now but this is going to frustrate me.

 

[mksj]

It is pretty common that spindle bearing need to be replaced for CNC operation, the mill was purchased as a manual mill which normally would see intermittent high speed use. I previously had a gear head 3 speed desk top type of mill rated for 3000 RPM, and at anything sustained (more than 10-15 minutes) over 2500 RPM the spindle would get too hot to touch for more than 1-2 seconds. Was actually scary hot, and I am sure it accelerated the loss off the bearing grease. If you plan to do CNC on a mill not designed as such, than it is just one of those upgrades one needs to do. Seems like even the Tormach has issues with the spindle bearings lasting, everything is to a price point for the type of expected use it is being sold for.

 

[3Dogs]

You might want to check out this thread:

Spindle cutting in and out

So this evening I was running some aluminum nothing aggressive on my pm727v converted to cnc with spindle control via kbsi240d board and acorn . After about 30 minutes into the run I noticed the rpms fluctuating just enough to hear i kept running and about 5 mins after hearing the rpm change the...

www.hobby-machinist.com

 

[StevSmar]

at anything sustained (more than 10-15 minutes) over 2500 RPM the spindle would get too hot to touch

When I was running in my PM-1224-T lathe I ran it through all the speeds to break them in. I was surprised at how hot the spindle was after running it at maximum speed… I doubt that would happen under normal use since a lathe is very much intermittent duty.