PM935TV

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.
 
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.

Any information on the topic will be appreciated.

Ariel
Click to expand...

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.
 
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.
 
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.

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.
Click to expand...
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.

Rong Fu RF-25 on Harbor Freight Drawers Stand c.jpg

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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davidpbest said:
READ the attached before you decide on a PM-935. If you'd like more information, let me know.
Click to expand...

Thanks for the interesting document, I enjoyed reading your perspective.
 
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.
 
1" twist drill into 316 stainless or 17-4ph. I'm even willing to donate material to the both of you if needed.
 
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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