# PM935TV



## parshal (Feb 15, 2020)

I'm thinking of getting a larger mill than my LMS benchtop.  I want more table size and, mostly, travel.  I want VFD, power x-axis and a DRO.  

My 1340GT is 3-phase and I installed Mark's VFD.  I see the 935 can be ordered with single or 3-phase, both with a VFD.  Is there an advantage to one over the other?  Should I get 3-phase and put on my own VFD?  I'd really rather not spend the time doing that if I can help it.

Thoughts for those that have done this?


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## wrmiller (Feb 15, 2020)

This is just my opinion/reasoning:

I already had a 1340GT lathe, and wanted to upgrade to a knee mill. I went with the 935TS 3-phase, and bought the VFD from Matt at the same time.

I chose the stepped head mill because I didn't want the complexity and expense of rebuilding a Reeves drive sometime down the road, and I knew from experience that belt-driven heads are much quieter, smoother, and simpler contrivances.

I have one of Mark's control setups on my 1340, but I went ahead and did the mill myself as it is much simpler than the lathe setup. Basically it was a control box, some switches, and a pot.

Matt gave me the idea of mounting the VFD inside the mill base on the inside of the inspection plate. Keeps it from getting chips and whatnot on it.


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## davidpbest (Feb 15, 2020)

I have some views to share on this, but first I’d like to know if you have any experience at all using a J-head mill, and if you do, how much time on one and which knee mill you have used.


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## parshal (Feb 15, 2020)

I've never used a knee mill myself.  I've watched a couple in use years ago.  I have a simple LMS Sieg-type mill now.

Basically, I want more stability than one on a bench and I want to take bigger cuts and have a larger table. I hate pecking at things with this little mill.

Bill, that's interesting.  I've not gotten that far into this yet to figure out potential future headaches.  

It's good to hear a VFD install is simpler for the lathe.  I really don't want to go building a box and all the other stuff for it like I did for the lathe.  It's not that it's difficult but those hours need to be used doing other stuff this spring/summer.


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## wrmiller (Feb 15, 2020)

parshal said:


> I've never used a knee mill myself.  I've watched a couple in use years ago.  I have a simple LMS Sieg-type mill now.
> 
> Basically, I want more stability than one on a bench and I want to take bigger cuts and have a larger table. I hate pecking at things with this little mill.
> 
> ...



What do you mean by 'bigger cuts'? 

Prior to my 935 I had a 9x40 bed/bench mill that I could bury a 5/8" rougher end mill in chrome molly and I don't think the mill even knew it was chewing on something. Blue/black chips and burned up the cutter though. Stout mill. I won't do that with my 935. It may handle it, or it may not. I honestly don't know. But I didn't buy this mill to do serious metal hogging. I mostly build pistols and make hobby stuff. I have 1/2" roughers (coarse and fine) that I use when making fixtures and whatnot. For most of my 'smithing I use 3/8" and smaller end mills.

The main reason I 'upgraded' from my 9x40 to the 935 was to get the knee and a articulating head assy that I could easily set angles and tram.


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## parshal (Feb 15, 2020)

I think I'm limited in my cuts due to the less than rigid bench.  I could build a stronger bench but I'd still be limited in my table size.  I need more X axis travel.  Setting angles would be wonderful as well.

I don't build pistols but do my own rifles.  For starters, I want to have enough table to mill the barrel channel.  But, in the end, I just want something bigger.


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## davidpbest (Feb 16, 2020)

Before you make a decision, don't discount the larger more advanced benchtop mills with their factory supplied base.   READ the attached before you decide on a PM-935.   If you'd like more information, let me know.


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## wrmiller (Feb 16, 2020)

parshal said:


> I think I'm limited in my cuts due to the less than rigid bench.  I could build a stronger bench but I'd still be limited in my table size.  I need more X axis travel.  Setting angles would be wonderful as well.
> 
> I don't build pistols but do my own rifles.  For starters, I want to have enough table to mill the barrel channel.  But, in the end, I just want something bigger.



Over the years I've found that gunsmithing isn't hard on machines. There is no 'hogging' massive amounts of material in gunsmithing. IMO accuracy and the ability/flexability to do different setups is more important. For me, the knee and articulating head makes a night-and-day difference. Is my 935 as rigid as my old CO 9x40? No. But for what I do, it's rigid enough. YMMV. 

I've built pistols on a LMS mill. And on a tiny Sherline. That is not something I'd recommend to most people though.

If I were doing more rifle than pistol work, I'd want a longer table. Something like a 949TV maybe? Just a suggestion.


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## parshal (Feb 16, 2020)

Keep the info coming. I do not not have my mind made up on any particular machine. 

Here’s what I have now so you can see how much more I need. I want the size to complement the 1340GT. 

 https://littlemachineshop.com/products/product_view.php?ProductID=3990

I’m sure I can build a stouter bench.


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## wrmiller (Feb 16, 2020)

parshal said:


> Keep the info coming. I do not not have my mind made up on any particular machine.
> 
> Here’s what I have now so you can see how much more I need. I want the size to complement the 1340GT.
> 
> ...



I had that mill. I even put a DroPros DRO on it. 

The difference between that and a 935 is night and day, even though I consider the 935 a 'light duty mill'. But then I consider my 1340GT to be a 'light duty lathe' also. 

OK, so knowing what I know now:

If space and/or money were a constraint and I needed to go with a bench mill, I'd buy the 833TV. Small, decent weight/rigidity, and Taiwan quality. Put a good DRO on it, and a power feed on both the Z and X axis

If I had the space for a small footprint knee mill, the 935 is still my choice. It's work envelope compliments the 1340GT nicely IMO.

Funds and space permitting, I'd go for the 949 Taiwan mill. I'd consider this the largest mill that would 'complement' the work envelope of the 1340GT. But that's just my opinion. Especially if I was doing long-gun work like fluting barrels and whatnot.


Just daydreaming here, but if I had the space and funds I'd have Matt's 10x54TS mill, his 14x40TL lathe, and a Sharp 1118H lathe to work on the small stuff. Not to make massive cuts, but to get the increased work envelope, stability and accuracy.

Let us know what you decide to get!


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## parshal (Feb 16, 2020)

I looked at the 949 first.  It's 1000 lbs heavier.  I'd never be able to move it around if I needed to do that.  

I don't expect to be fluting barrels but, if I could, I probably would try it.

Looking at the 833 the table and quill travel is very close to the 935.  The 833 is overall taller at 88" while the 935 is 81".  833 is about 500 lbs. lighter without the stand.  It looks like you can't get a Y axis power feed on the 833 which I would find useful. 

Other than not having a Y power feed the 833 covers all my bases.  I would believe it would be a massive step up over the mill I have now.  But, I have the space to go larger and the cost savings isn't dramatic enough for a one-time purchase. I know I can move the 833 with the forks on my tractor bucket.  Those may be at their limit with the 935.

I do cut aluminum but cut a lot of stainless as well.  I see in their comparison that the geared head has more power in lower ranges.  I don't mind going slower in aluminum so maybe the geared head is the better choice.  Anyone installed a VFD on the geared model?


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## davidpbest (Feb 16, 2020)

I had a VFD on my RF-45.  Bolted it to the side of the head as replacement for the forward/ stop/reverse switch and used the VFD front panel for on/off & speed control.  Worked great.  Added an E-stop switch at knee level.  You’d have to ask Matt at PM if he could supply a 3-phase motor on the 833 if you want to use a VFD.


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## parshal (Feb 16, 2020)

I'm all over the place now.  I think you guys made this more difficult rather than easier.  LOL

I may just opt for the 220 single-phase 935TV.  Plug and play but way spendy.  I'm sure someone will come along and here and give me fantastic reasons why I should choose a different one, though.


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## davidpbest (Feb 16, 2020)

Good luck fixing the Reeves drive on that when the time comes.


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## davidcarmichael (Feb 16, 2020)

davidpbest said:


> I had a VFD on my RF-45.  Bolted it to the side of the head as replacement for the forward/ stop/reverse switch and used the VFD front panel for on/off & speed control.  Worked great.  Added an E-stop switch at knee level.  You’d have to ask Matt at PM if he could supply a 3-phase motor on the 833 if you want to use a VFD.


I bought an 833 from Matt with a single phase motor but later bought a 3-phase motor from PM and a VFD.
I love having a VFD and hardly ever have to change belt positions. Matt did tell me the 833 would be available sometime with a 3-phase motor but as prices were going to rise I blew $500 on the new motor and never regretted it.


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## parshal (Feb 16, 2020)

davidpbest said:


> Good luck fixing the Reeves drive on that when the time comes.



I've read this a few times now.  I watched zmotorsports video review of the TV and the plug and play aspect is very appealing to me.

What is someone in for if (when?) that drive fails?


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## davidpbest (Feb 16, 2020)

Watch this video.


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## parshal (Feb 16, 2020)

I watched the first 16 minutes.  That guy makes me laugh.  He reminds me of a comedian I hear on Sirius.  Thanks for the link.  That does look like an interesting set of issues to fix.

Are they more prone to failure or is it just a total PITA to fix when they do fail?


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## davidpbest (Feb 16, 2020)

Put that video on 2X speed when you watch it.

The Reeves drive system is described in the PM-935 manual which you can download from the PM site *by clicking here*.
Here is the essence of how it works, and you'll notice there is a rather wide belt trapped between to angled drive pulleys ("cone discs") compressed by high tension springs, and thus the belt is a wear item:







You might also want to more fully acquaint yourself with the J-head.  If you read *the document I put together for you*,  you will know that I am NOT a fan of this type of head due to it's complexity and the crudeness of the design.   That is why I suggested you consider a geared drive system or a BLDC motor driven belt drive, either of which are available on the PM-833.   

The J-head is a pain to work on, and I have done plenty of work on mine.  I recommend you review the photos and videos about my 935 here:

*J-head issues*

*Power down feed mechanics*

I think this is a case where Occam's razor applies:  when faced with two alternatives of apparent equal function, pick the simpler of the two.   If you must have the flexibility afforded by a knee mill with the head on a ram that will nod as well as tilt, then you will be looking at a J-head.   But if you don't absolutely need the nod function or extra reach of the ram on the knee mill, I think you'd find the geared head or BLDC belt drive head on the 833 will be less frustrating and troublesome.  End of rant.


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## parshal (Feb 16, 2020)

I did read those docs again. I didn’t realize you wrote that. 

For just the reasons you state I was thinking the 833 is the right one. On the 935, the depth the knee affords is a draw as well as the power Y and pneumatic draw bar.


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## davidpbest (Feb 16, 2020)

I wrote that doc just for you.

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:


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## mksj (Feb 16, 2020)

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.


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## kb58 (Feb 16, 2020)

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.


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## parshal (Feb 16, 2020)

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.


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## davidcarmichael (Feb 17, 2020)

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.


I don't where you saw that. My 833 certainly has a spindle brake.


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## parshal (Feb 17, 2020)

Thanks David! I did a search for 'brake' in the pdf manual and no hits.  What page is that on?


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## davidcarmichael (Feb 17, 2020)

parshal said:


> Thanks David! I did a search for 'brake' in the pdf manual and no hits.  What page is that on?


Page 4.


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## parshal (Feb 17, 2020)

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.


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## davidcarmichael (Feb 17, 2020)

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.


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## parshal (Feb 17, 2020)

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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## davidcarmichael (Feb 17, 2020)

I really love that 7 x heavier thing. 
Are you sure about your cost comparison? 
How do you add it up? Mine didn't cost over $8K with 3 power feeds (not counting the spindle feed) and a DRO, but then that was  couple of years ago.

I bought my 833S to replace a Seig mill and the difference is indescribable. I wanted to buy my last ever mill and this seemed to fill the bill.
Even so there are things I do where even more rigidity (and probably weight) would be welcome. I would certainly never go back to a bench mill unless I was planning to do a CNC conversion and even then I would think twice.


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## parshal (Feb 17, 2020)

I put every option, including installation where possible, in my cart for each.  That's how I came to the cost difference.  Granted, the installation for the power feed installs isn't an option on the 833 but I'd order the 935 installed so it's a fair comparison (only) to me.

The LMS 3990 is, essentially, a Seig built to better standards.  Mine has a variable drive and I put on an X power feed and a spindle stop for the drawbar.  I can only imagine the difference between it and the 833.

I placed an order for the 833TV today.  It'll take a couple weeks to install the DRO so I'm looking at mid-March.  In talking with PM, they have to clean the cosmoline to install the DRO so that alone is worth the cost.  I'd pay them to remove all the cosmoline before delivery.  I wish that were an option!


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## wrmiller (Feb 17, 2020)

Congrats on the 833TV. Comments and pics are required when you get it.


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## parshal (Feb 17, 2020)

Regarding a power drawbar setup, I found *Priest Tools* which makes things specifically for PM and LMS mills.  I talked to him and he said using his on the 833 would only involve making a different mounting bracket and the correct length drawbar.  It's doable but spendy.


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## davidcarmichael (Feb 17, 2020)

parshal said:


> Regarding a power drawbar setup, I found *Priest Tools* which makes things specifically for PM and LMS mills.  I talked to him and he said using his on the 833 would only involve making a different mounting bracket and the correct length drawbar.  It's doable but spendy.


Yeah. I designed and built my own power draw bar for the 835 (and previously for my Seig mill). It uses twin pneumatic cylinders to lift the ratchet and linear shafts and bearings to guide it.  I made it difficult for myself since the draw bar drops by 5" when fully extended and I wanted the power draw bar to operate throughout the range. It didn't cost much and it works pretty well (as well as an HF butterfly wrench can manage). I think others have done the same but I don't know if they operate over the full 5" travel. 
For machines with a draw bar that does not move up and down with the quill then building your own is easy and cheap, though some YouTube videos seem to make it unnecessarily complex.


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## ahazi (Feb 19, 2020)

davidpbest said:


> Before you make a decision, don't discount the larger more advanced benchtop mills with their factory supplied base.   READ the attached before you decide on a PM-935.   If you'd like more information, let me know.



David,

First many thanks for all your wonderful postings and documentation here and on the Felder Forum (FOG) over many years.

I just ordered a PM-833TV and in the process of validating what is actually on the machine I noticed one error in your comparison document - the belt drive on the PM-833TV has only one speed, also it is not BLDC motor but rather a 3 phase AC motor driven by a VFD. This was confirmed by Matt from Quality Machine Tools.

As I see it there is good and bad with this configuration.
The good:
Standard AC motor with probably standard mounting vs proprietary BLDC motor
AC VFD vs proprietary BLDC motor controller

The bad:
Lower low speed torque
No option for changing the belt gearing to get more torque in low speed

The area of advanced VFD is developing rapidly and there is a chance that in the future a better VFD, maybe with closed loop encoder will be able to replace the current VFD and get more low RPM torque. I don't have the machine yet so this is a speculation...

I am eager to hear your thoughts and other users experience with this machine.

Ariel


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## davidpbest (Feb 20, 2020)

There is NO published documentation with specifics about the motor, electronics or belt drive on the PM-833TV.  I put my head together with the guy who designs most of the VFD systems for PM equipment and we strategized that this system must have a 2-position belt drive to provide decent torque/HP at the extreme ends of the ranges, and we made the (apparently wrong) assumption about the motor and electronic drives.   If Precision Matthews says it's a 3-phase motor with a VFD running it, who am I to argue and I will update my documentation.   But first I want to see more specifics about the performance.   There is no free lunch here.   

This is why I'm skeptical:  Assume for a moment the motor is 1000 RPM at 60HZ with a 1:1 spindle drive.  Getting to 3000 RPM implies the motor is being driven at 180Hz, or three times it's normal frequency.   To get to 50 RPM with that same configuration would imply the motor is driven at 3Hz (three Hertz).   Here's that in spreadsheet form:







And here is a performance graph for 3-phase motors driven by VFD:






Look at the likely power at 3Hz - something like 6 percent of rated HP.   Maybe there is something I'm missing here, but looks to me like if the PM-833TV motor is being driven at 3-5Hz to get down to 50RPM, you're going to have the power of a Kitchen-Aid mixer.   

I will be interested to hear how this 833TV configuration performs in real situations.   For aluminum it's probably just fine.   But my stock and trade is machining stainless and tool steel, and for that type application I would feel way more comfortable with the geared head version of the 833T, and possibly a 3-phase motor with a VFD to get up to higher speeds for aluminum.   With the heavier geared head the machine is likely to have more rigidity, and six-speeds covers most of the typical workflow sequences like spot, drill, tap, chamfer.  Minority opinion perhaps, but I did grow up in the Show Me state.


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## parshal (Feb 20, 2020)

Hey Ariel, do you have the 833TV in your hands?  I swear I'd seen something in the manual or somewhere else that it had a two pulley belt.  Searching the manual now doesn't produce it.  Mine is a few weeks away from delivery.

It machine more steel than aluminum.  I initially wanted to the geared version but I was told the TV will work but just slower for that.  Looking at David's graph I'm wondering now.  I guess I'll see.


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## bakrch (Feb 20, 2020)

davidpbest said:


> There is NO published documentation with specifics about the motor, electronics or belt drive on the PM-833TV.  I put my head together with the guy who designs most of the VFD systems for PM equipment and we strategized that this system must have a 2-position belt drive to provide decent torque/HP at the extreme ends of the ranges, and we made the (apparently wrong) assumption about the motor and electronic drives.   If Precision Matthews says it's a 3-phase motor with a VFD running it, who am I to argue and I will update my documentation.   But first I want to see more specifics about the performance.   There is no free lunch here.
> 
> This is why I'm skeptical:  Assume for a moment the motor is 1000 RPM at 60HZ with a 1:1 spindle drive.  Getting to 3000 RPM implies the motor is being driven at 180Hz, or three times it's normal frequency.   To get to 50 RPM with that same configuration would imply the motor is driven at 3Hz (three Hertz).   Here's that in spreadsheet form:
> 
> ...



Wow, if this is the case it seems like an extreme oversight. I've come very close to buying this mill since it came out, and almost hope it is true so I stop it already.


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## ahazi (Feb 22, 2020)

parshal said:


> Hey Ariel, do you have the 833TV in your hands?  I swear I'd seen something in the manual or somewhere else that it had a two pulley belt.  Searching the manual now doesn't produce it.  Mine is a few weeks away from delivery.
> 
> It machine more steel than aluminum.  I initially wanted to the geared version but I was told the TV will work but just slower for that.  Looking at David's graph I'm wondering now.  I guess I'll see.


parshal, I don't have the PM-833TV on hand. I placed an order and realized that given the very wide speed range and the fact that it is NOT using a BLDC motor/controller the power available at low speeds will be very low for some of my demanding work at low speeds. For general usage it is probably OK and very convenient but given the lack of published experience I am looking at alternatives such as getting the PM-833T and replacing the single phase motor with a 3 phase motor and a VFD.

I am replacing a 35 years old RF-25 (Enco private label) that served me well over the years.

Any information on the topic will be appreciated.

Ariel


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## parshal (Feb 22, 2020)

I do a decent amount of low speed work, too. I’ll keep this thread updated with what I find but is probably a month out before I’m making chips.  I also only have an LMS 3990 to compare which won’t be fair.


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## davidcarmichael (Feb 22, 2020)

ahazi said:


> parshal, I don't have the PM-833TV on hand. I placed an order and realized that given the very wide speed range and the fact that it is NOT using a BLDC motor/controller the power available at low speeds will be very low for some of my demanding work at low speeds. For general usage it is probably OK and very convenient but given the lack of published experience I am looking at alternatives such as getting the PM-833T and replacing the single phase motor with a 3 phase motor and a VFD.
> 
> I am replacing a 35 years old RF-25 (Enco private label) that served me well over the years.
> 
> ...



Can you tell me what (other than a minor initial cost difference) would make you choose a PM-833T over a PM-835S? 
The first is a "precision" gear-head bench mill and the latter a very large knee mill. The difference in initial cost is $600. A 3-phase motor will probably cost you well north of $400 and Matt did tell me that it will be possible to get the 835S fitted with a 3-phase motor in future when I bought mine 2 years ago. At that time I was trying to make the decision you are making and am so glad I chose the knee mill.

All of the (expensive) add-ons you will need cost about the same except that you may wish to purchase a power feed for the knee, but that is strictly optional. I have a 6" Kurt vise (don't consider any alternative), the 3-axis DRO and every add-on you can imagine, all of which more than doubled the original basic cost.

I did buy a 3-phase replacement motor for my 835S ($500) but it is 3HP rather than 2HP so the cost may be slightly different. It is a direct replacement for the single phase belt drive unit and very easy to fit.

Yes there are belts to change in the 835S rather than gears in the 833T but I think that silence is golden. Besides the 835S is a true Bridgeport clone with a head that can nod when required (for real precision set up), it is very rigid, has a very high precision spindle (all Taiwanese), it has a large height advantage which I have found very useful when drilling large holes or using a tapping head, and with a VFD can do a great deal on one belt especially when combined with back gear. Since I got my VFD I have not had to move the belt for a very wide range of jobs. Its top speed with a VFD is much higher than the 833T  At the low end with back gear, the available torque is huge). The 833T does not appear to have a proper power feed with auto stop for drilling and boring (I do not consider the Z-Axis power feed an equivalent feature).

Certainly it takes up a LOT of space and is very tall. With 5" of quill travel the fitting of a power draw bar is challenging (but possible).

I would be interested in how you come to your final decision.


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## parshal (Feb 22, 2020)

I went with the 833TV rather than the 833T.  The table size, overall height, table travel, quill travel and front/back size is very similar.  The 835 is wider, handle to handle, at 48" vs ~42" for the 833TV.  The 833TV has a 3-phase 2 HP motor  while the 835 has a single phase 3 HP.  The weight of the 835 is nearly double at 1400 vs 750 (880 with stand) of the 833TV.  I have the room in the garage for the knee mill and cost wasn't a huge issue.  Effectively ever moving that once in place is nil, though.  Even 833 will be difficult.

To be very honest, I went back and forth on the 833 vs 935.  I liked the Y power feed and power draw bar of the knee mill.  I think David's documents talked me into the 833.  Quite frankly, the 833 will do everything I need to do.  It's seven times heavier than my current mill and comes with a VFD and 3-phase motor.  Of course, the discussion of the T vs TV and low end power is a very real deal.  We'll see what it does when I get it.


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## ahazi (Feb 23, 2020)

davidcarmichael said:


> Can you tell me what (other than a minor initial cost difference) would make you choose a PM-833T over a PM-835S?
> The first is a "precision" gear-head bench mill and the latter a very large knee mill. The difference in initial cost is $600. A 3-phase motor will probably cost you well north of $400 and Matt did tell me that it will be possible to get the 835S fitted with a 3-phase motor in future when I bought mine 2 years ago. At that time I was trying to make the decision you are making and am so glad I chose the knee mill.
> 
> All of the (expensive) add-ons you will need cost about the same except that you may wish to purchase a power feed for the knee, but that is strictly optional. I have a 6" Kurt vise (don't consider any alternative), the 3-axis DRO and every add-on you can imagine, all of which more than doubled the original basic cost.
> ...


This is a very good question and it made me give another "structured look" at my thought process. Here we go...

First I am hobby user, I like to produce high quality work but generally speaking I am not driving income from this tool. My rule is not to buy cheap because often times you will have to buy again. The mill will be used a good portion of the time as a "super capable drill press" so ease of use in this configuration is important. I drill on variety of materials from stainless steel down to wood with drill size as small as 0.6 mm to 6" hole saw. I am using a similar style drill/mill (Rong Fu RF-25 sold by Enco) for 35 years so I know very well what works and what does not work.

The ease of spindle speed change led me initially to the PM-833TV, but I figured out after I placed the order for a fully loaded 833TV that I need to rethink it. I am going with PM-833T with a plan to use a 3 phase motor and a VFD. I found a drop in 3 phase 2 HP motor that should do the job for slightly more than $250 including shipping from England. So hopefully this portion will work well and I will not hate the noise from the gearbox...

Table working height is very important to me, I am tall (6'2") so the low height of the table on the 835  and even lower when drilling or milling large items is a negative for me. On the other hand being able to raise the head easily is important so with the motorized option on the 833 it looks perfect. My old RF-25 is very cumbersome when it comes to changing height.

Machine footprint is important to me as bigger machine means less space for other "toys" in the shop so even if floor space is about the same, the ability to put the 833 on a stand that in my shop is a Harbor Freight drawers case is a big plus. I don't think that I will be able to put the 833 directly on the drawers as I did with the RF-25 but I can weld a cage that will allow me that functionality. See below a picture of my current RF-25.






The PM-932 and PM-940 look as a great alternative especially with hardened ways and the motorized Z axis but I was led to believe that the Taiwanese machines are better and they also come with 5 year warranty which might be a reflection of the quality or it is just a marketing gimmick (pay me more and I will give you a longer warranty...) who knows.

Last item is that the 835 or 935 looked a bit "too much" or "too complicated" to me. If I bought an RF-45 35 years ago (it probably was not available) I will not have to buy a new machine or I might decide that I need something better, who knows...

I hope I answered your question.
Ariel


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## StevSmar (Feb 23, 2020)

davidpbest said:


> READ the attached before you decide on a PM-935.   If you'd like more information, let me know.



Thanks for the interesting document, I enjoyed reading your perspective.


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## parshal (Feb 23, 2020)

Hey guys, Ahazi and I have been exchanging messages about testing the two mills.  I figure I'd pose it here so as to get some input on what tests we can do.  Neither of us will have the mills for a few weeks so it's a ways out.

I have sacrificial 440 stainless rifle barrels I can cut in half and send him a piece.  All my other pieces laying around are of unknown type.  Perhaps we can find some pieces on ebay and each have the same pieces to test.

Test ideas are welcome.


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## bakrch (Feb 23, 2020)

1" twist drill into 316 stainless or 17-4ph. I'm even willing to donate material to the both of you if needed.


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## parshal (Feb 23, 2020)

I'd need to buy a 1" twist drill!


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## mksj (Feb 23, 2020)

Parshal I assume the $8300 price for the 935 is fully loaded, the base machine is $5400. Having come from a bench top mill similar in size/capabilities of the 833, I ended up with a full size knee and I am much happier. The increased weight aids in stability and having a full sized table I often have my 6" vise and a 6" rotary table mounted at the same time. It is nice to have the increased table size if you have the room and can deal with the machine weight, than consider a full size mill. I decided to go with a full sized knee mill after having limitations with my bench top mill, and planning on the upgrade would be the last mill I would own (and I am pretty sure this will be the case). I was just communicating withe another forum member who went with a PM-949 who was getting into gear cutting, and the bigger mill made a big difference. Even with a full size knee, I am often at the limit of my Z-axis travel, like when tapping and wish I had a few more inches. So just give it some thought, at the end of the day 1-2K when your spending this much, well get what works for you. Other than having to move a full size knee, I couldn't be happier when I upgraded.


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## wrmiller (Feb 23, 2020)

parshal said:


> I'd need to buy a 1" twist drill!



I won't/don't use a 1" twist drill on my 935!


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## parshal (Feb 23, 2020)

Mark, I’m sure in a few years I’ll wish I bought a bigger one! 

At the moment, I could probably fit a bigger one. We are considering moving and my wife wouldn’t be terribly happy if we had to base a purchase around a huge mill. LOL


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## mksj (Feb 23, 2020)

I hear you, getting my full size knee mill moved to my new house the previous year was probably one of the biggest hurdles. I lost a lot of sleep over it, and also when I ordered a new larger lathe, it was a big  very difficult getting it to the delivered to our new house at a reasonable cost. Best of luck whatever you choose.


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## Winegrower (Feb 24, 2020)

Would be nice to run your same mill test on somebody’s old Bridgeport or clone.   Now THAT would be interesting.   To me, anyway.


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## bakrch (Feb 24, 2020)

wrmiller said:


> I won't/don't use a 1" twist drill on my 935!



We want to test these machines, not baby them! 

I do it all the time on this 949. 3HP VFD setup for this, but you need the back gear to do it stall free.






Granted, my first choice for drilling steel is to use its bigger brother (5HP VFD), but both will get the job done just fine. Back gear not really needed for 1", but I use it anyway.


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## davidpbest (Feb 24, 2020)

bakrch said:


> 1" twist drill into 316 stainless or 17-4ph. I'm even willing to donate material to the both of you if needed.


The J-head on the 835 or my 935 will not power downfeed 1" into stainless without trashing the guts of the power downfeed mechanism.   3/8" is what the PM spec lists as max diameter into steel.   OTOH, my RF-45 would easily drive 3/4" drill into 316 with it's more robust and advanced power downfeed system (did it many times).  And to counter your other assumption, the 833 does have power downfeed and an adjustable limit stop that will disengage automatically, and is much easier to use compared to the J-head - fully documented in the user manual on the PM site.   Based on my direct experience with these "baby" knee mills and the original RF-45 from Taiwan, the idea that the knee mill is always more rigid is total fallacy.   I can't speak to the 833 specifically because I haven't used one, but the principals that give the RF-45 it's increased rigidity are the same, and fully discussed/documented in my attached revised write-up.


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## wrmiller (Feb 24, 2020)

If I have the requirement of drilling 1" holes (or larger) on a mill, I'm sure not going to buy a 935 or smaller bench mill. That just seems stupid. But, people do what they're gonna do...


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## bakrch (Feb 24, 2020)

wrmiller said:


> If I have the requirement of drilling 1" holes (or larger) on a mill, I'm sure not going to buy a 935 or smaller bench mill. That just seems stupid. But, people do what they're gonna do...



It isn't stupid at all. In fact, a genuine RF-45 is even rated for drilling up to 1.5" diameter in mild steel. This is with a 1-1.5 HP motor.

My test puts RPM's at about 100, which is in the vicinity of where we believe the 833TV to be weak. It is a perfectly reasonable test. I have drilled dozens of 11/16" holes on my PM25-MV in low range into 316 and Grade 5 titanium 1.5" deep. This is with a pilot hole big enough to clear the larger drill chisel/web.  No issues at all, asking a knee mill to do a little more isn't so much of a leap. This was before I had a lathe in the home shop, obviously now it is much faster to drill the same hole on a 2HP PM1236.


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## bakrch (Feb 24, 2020)

Also,


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## davidpbest (Feb 24, 2020)

bakrch I like the UI on your F/S app better than the FSWizard I use on my iPhone. I get the same results you do, but I like the look of yours better. What app are you using?


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## bakrch (Feb 24, 2020)

davidpbest said:


> bakrch I like the UI on your F/S app better than the FSWizard I use on my iPhone. I get the same results you do, but I like the look of yours better. What app are you using?



Same app just on the Android platform. I also use the paid version, not sure if that has anything to do with the difference.


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## davidpbest (Feb 24, 2020)

Thanks.


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## wrmiller (Feb 24, 2020)

bakrch said:


> It isn't stupid at all. In fact, a genuine RF-45 is even rated for drilling up to 1.5" diameter in mild steel. This is with a 1-1.5 HP motor.
> 
> My test puts RPM's at about 100, which is in the vicinity of where we believe the 833TV to be weak. It is a perfectly reasonable test. I have drilled dozens of 11/16" holes on my PM25-MV in low range into 316 and Grade 5 titanium 1.5" deep. This is with a pilot hole big enough to clear the larger drill chisel/web.  No issues at all, asking a knee mill to do a little more isn't so much of a leap. This was before I had a lathe in the home shop, obviously now it is much faster to drill the same hole on a 2HP PM1236.



OK, maybe I shouldn't have said 'stupid'. I'm just of the opinion that if I'm having to drill holes that large (I don't), then I'd own a much beefier machine to keep stresses on the machine lower. But to each their own.

And comparing a low-speed geared drill press to a 833TV? Really? Seems apples to oranges to me, but whatever.


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## bakrch (Feb 24, 2020)

wrmiller said:


> OK, maybe I shouldn't have said 'stupid'. I'm just of the opinion that if I'm having to drill holes that large (I don't), then I'd own a much beefier machine to keep stresses on the machine lower. But to each their own.
> 
> And comparing a low-speed geared drill press to a 833TV? Really? Seems apples to oranges to me, but whatever.



I agree, it may seem like that, but we do not know how it will perform under the conditions until we test it.

If you are able to give us the info we need as to not even bother with such a test, please do so!


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## wrmiller (Feb 24, 2020)

I'd never compare the two, sorry.


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## luxige (Feb 26, 2020)

davidpbest said:


> Before you make a decision, don't discount the larger more advanced benchtop mills with their factory supplied base.   READ the attached before you decide on a PM-935.   If you'd like more information, let me know.



Thanks, that’s a good read, and informative.


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## davidpbest (Feb 26, 2020)

luxige said:


> Thanks, that’s a good read, and informative.


Looks like you read the first draft, which I've now updated with fresh and accurate data with respect to the PM-833TV.   Here is the link to the new document if you're considering that specific model. _* Click here.*_


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## petertha (Mar 5, 2020)

Sorry for the tangent, I haven't seen that FS wizard app before. Has anyone seen a numerical comparison between an annular cutter to a typical 'full hole' 2-flute drill? I find myself grabbing AC's more often now for through holes. I like how they cut. My collection are only 1" length but starting to eye a 2"set... you know... precautionary thing....just in case of a Zombie attack.


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## mksj (Mar 5, 2020)

Annular cutters, you need to keep the speed down in the mill, smaller cutters 400 RPM maximum. You want to keep a constant pressure through the boring process, do not peck at the work. Use a lubricant for most metals, assuming the exception would be cast iron. I also use them on the lathe, a real time saver over drilling. Limit is the depth, I recently built a spider and used a 1.25" 2" depth annular cutter to punch out the center for a 1" boring bar. I used the annular cutter from both sides, around 250 RPM (I go a bit slower with the lathe, but I would use around 225 RPM for a 1.25" MT drill). I went with 2" depth annular cutters for the ones  that I have. I use them mostly in steel like 1045, 4140, plate, etc. They cut very nicely, I modified a 3/4" end mill holder to hold them on my mill.


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## petertha (Mar 5, 2020)

Your comments are spot on to my experience, including the don't peck recommendation. That might be one downside. When I let off to allow chip termination that was getting kind of snarly, it can take some fiddle farting to get the cut established again depending on the material. Aluminum I wasn't too worried about but the multiple steel strings were starting to get into places they didn't belong.

Another nice thing is when the material is valuable, you get a nice core of material to do something with as opposed to making a pile of chips. This was the case with a chunk of bearing bronze.


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