PM935TV

I wrote that doc just for you.
:teacher:
Power feed on the Y and powered head positioning are what drove me to the 935 (I put power feed on the knee as well as X & Y). I could have come up with a way to do both on the RF-45, but didn't put in the time. In practice, I have found that power feed on the Y is mostly useful for squaring up ends of stock.

I have yet to reposition the ram on my 935 - unless you're boring out motor blocks or the like I don't see the value in it. I have found it much simpler to angle the material being drilled than to take the head out of tram and have to re-align it later.

Keep in mind the extra cost items. I spent alsmost as much on the VFD controls + 3 power feeders + 4-axis DRO + Power Drawbar as I did on the mill.

Putting a Power drawbar on the 833 would take some effort but is totally doable. I would make a mounting plate that attached to the two cap screws holding the motor, and mount the PDB on that:
screenshot_3066.jpg
 
If looking at the 833, I would just go with the 833TV, it will be much quieter than a gear head and you will have no issues with lower speeds for SS. You are much more likely to use the higher speeds, 1500 RPM is really slow for most work in aluminum and softer materials, or if you are using smaller end mills. Most of the time I am running my mill in the 2000-3200 range on aluminum, steel 600-1000 RPM with 1/2-3/4" end mills. The 833 is still a manageable size, but if you want to use 2 vises or a vise and a rotary table at the same time than a 42-50" table is much preferable. If you have the space than a full size knee would be my recommendation, a PTA to move unless you have a rolling base which I have on mine. Still takes 2 people to start it moving. Work envelop wise, the two most important dimensions that I find most limiting are the maximum distance spindle to table and Y travel, you also loose a bit on the Y travel with a DRO scale. I believe the 833TV has more Z height and slightly less Y travel than the 935. As far as axis drives, on either type of mill I would definitely recommend an X and Z drive.

Rigidity wise, mass does make a difference, but also the webbing and the geometry of the machine. They will all exhibit some flex, but beefier box sections go a long ways to increasing rigidity. I do not have any limitations on my full size mill which is around 2700 lbs.

A power drawbar makes life a lot easier with the R8 collet system, my last benchtop mill would not accommodate one so I mostly used and ER-32 collet system. A bit more tedious in particular if you switch out indicators, end mills, and drills for multiple operations.

Single phase motor you do not get the advantages of the VFD, and you have to deal with blown capacitors and the starter switch. If you do frequent on/off cycling of the motor than they will go much quicker. With a VFD you can power tap and also have quick reverse. If you plan to go with a knee and a VFD I recommend going with the standard belt version, as David mentioned the Reeves drives do wear out, but often after many years of use. If using a VFD with a Reeves drive, you want to use the Reeves drive to adjust the spindle speed so the belt wears evenly and also the sheaves. A VFD on these type of mills is pretty straight forward, and as Bill mentioned some people put them in the base or behind it. Example of a simple cabinet mounted on the head of a 935, I normally would do a custom panel but this was a bare bones system.

PM935 control pod.JPG
 
I have a 935 with a VFD and haven't run into any issues machining anything in the range of sizes that I work with, so have nothing negative to report. It was the largest unit that I could barely fit into the garage.
 
Thanks for all the replies.

My current mill is 124 pounds. The 833 is 880 pounds with the stand. That alone is a massive improvement.

The more I look at the 935 the more I like. I just noticed the 833 has no spindle brake. Yet another thing I know I'd like.
 
parshal said:
Thanks for all the replies.

My current mill is 124 pounds. The 833 is 880 pounds with the stand. That alone is a massive improvement.

The more I look at the 935 the more I like. I just noticed the 833 has no spindle brake. Yet another thing I know I'd like.
Click to expand...
I don't where you saw that. My 833 certainly has a spindle brake.
 
Thanks David! I did a search for 'brake' in the pdf manual and no hits. What page is that on?
 
Man, I guess I'm slow this morning. I see no mention of that on page 4 which is the Specs page. I'm looking at the latest version downloaded from the 833 product page.
 
I am very sorry I was looking at the 835S manual (which is what I have) not the 833.
No sure why anyone would want a bench mill rather than a similarly priced knee mill unless it is purely a space concern.
Please enlighten me.
 
The 833 is seven times heavier than my current mill, it has a similar table size and movements as the 935 and is $6k vs $8300. The cost, for me, isn't as much a factor as what I would use it for. The 833 is way more than what I have now and looks to cover everything I ever plan on doing. Of course, plans change.

Thanks my thinking right now.
 
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