Bench top mill questions?

[mksj]

I would recommend one of the following depending on your budget, they are all commonly converted to CNC and kits are available. They have good travel, often a major limitation is the Y and Z, less so the X for most projects. The Taiwanese made mill will have better fit and finish, the Chinese mainland less so, but that is a price point decision. There are numerous posts on the HM and on-line videos with the CNC conversion of these mills. One point to be made, these are small mills, and they all have some warts that one has to deal with. These are all run off of single phase input power. I would not recommend a knee if space is limited and for CNC conversion (will be more expensive).

NEW! PM-728VT Ultra Precision Milling Machine – Precision Matthews Machinery Co.

www.precisionmatthews.com

PM-30MV Milling Machine – Precision Matthews Machinery Co.

www.precisionmatthews.com

PM-833TV Ultra Precision Milling Machine – Precision Matthews Machinery Co.

www.precisionmatthews.com

PM-932V Milling Machine – Precision Matthews Machinery Co.

www.precisionmatthews.com

 

[Charles scozzari]

I've got to disagree. There are many knee mills that are single phase (220V) and several that are much smaller than a Bridgeport Series 1 (that's the "small" Bridgeport). Precision Mathews makes a very nice mini-Bridgy, there are the A1SA style made by Grizzly, Jet and others, Hardinge made some table-top knee mills, and I'm sure there are others.

A knee is typically much more rigid because it is uses the large vertical ways and carries the weight of the table. A knee generally has more Z-travel than a benchtop square-column mill and certainly more than any quill. Because gravity works against it there is virtually zero backlash. This is not at all true of most quills. A head that is geared to a square column might provide a similar benefit with respect to backlash. I think a knee is a worthwhile advantage, but after that things are very much about size - bigger is usually more rigid, more powerful, and with a larger work envelope.

IF you have the room the knee mill is the way to go. I think most would agree that with a small machine you outgrow it the minute you plug it in. I'm not talking about early American machinery, I'm talking about the smaller group of import mills on the market and on eBay.

 

[Aaron_W]

So what are the pros/cons of a knee vs a bench mill? Just a different approach to the same thing or does they have some different advantages?

I think the primary advantage of a knee mill is the knee is the moving part and it tends to work with gravity as well as generally having a more rigid connection to the column. A similar size knee mill is also often substantially heavier than a bench mill.

Two examples of current mills so materials used are comparable (vintage machines are almost always heavier), Harbor Freight's small 6x26" knee mill and a Precision Matthews PM25MV. The Harbor Freight 6x26" weighs 600lbs, the PM-25 weighs less than half as much at 275lbs despite having a little more capacity.

Harbor Freight 6x26" mill

Precision Matthews PM-25MV



Size really doesn't play into it, while there are many large knee mills, there are also some rather small knee mills. Benchmaster made a very small 6x16" bench top knee mill smaller than many popular bench mills. Clausing and Rockwell both made small knee mills comparable to the 7x27" bench mills several have suggested. Many of these are 120v or 240v single phase power. Going back to weight, that little Benchmaster mill is similar in size to some mini-mills, but weighs nearly as much some of the 7x27" bench mills.

 

[Jim F]

IF you have the room the knee mill is the way to go. I think most would agree that with a small machine you outgrow it the minute you plug it in. I'm not talking about early American machinery, I'm talking about the smaller group of import mills on the market and on eBay.

I have not found anything beyond the capabilities of my mill/drill, yet.
In fact, I would like it at work, so as not to deal with the BP I run at work.

 

[Charles scozzari]

I have not found anything beyond the capabilities of my mill/drill, yet.
In fact, I would like it at work, so as not to deal with the BP I run at work.

Good morning, the reason I love the Bridgeport is that from time to time I will get a job that involves a H/I beam that needs slotting or drilling, the fact that the knee can handle the weight and height if and when needed makes all the difference. BPs can handle 700lbs. I'm not against the bench top mills at all, they serve the purpose well, but you seem to always need that little bit more for whatever, whenever. We all know what's said about opinions, but that's mine. Thanks.

 

[mac1911]

Im new to this game and my first lathe was free.
From what l learned with most things you need/want
1. Has to fit your space
2. Has to do the min you expect then if possible up that requirement in the machine
3. Look at value vs output
Sometimes a larger machine cost is not buying much more capability.

Im at the point I need a shop to hold all my stuff

 

[epanzella]

I bought an RF30 knockoff round column mill from Harbor Freight for $962 with a coupon. This thing has gobbled up everything I've thrown at it. You won't find a mill that has more capacity in less space for less money than a round column mill. The loss of index when moving the head was annoying until I made an indexing system that fixed that. It won't do the heavy depths of cuts that a knee mill will make but it will do the same thing at a slower pace. I just didn't have the space or the $$$ for a knee mill and have never regretted my decision. I believe the table travel is 19 x 7. It will also get the spindle 17 inches off the table. You can work on some pretty big stuff and I have.

 

[Charles scozzari]

I bought an RF30 knockoff round column mill from Harbor Freight for $962 with a coupon. This thing has gobbled up everything I've thrown at it. You won't find a mill that has more capacity in less space for less money than a round column mill. The loss of index when moving the head was annoying until I made an indexing system that fixed that. It won't do the heavy depths of cuts that a knee mill will make but it will do the same thing at a slower pace. I just didn't have the space or the $$$ for a knee mill and have never regretted my decision. I believe the table travel is 19 x 7. It will also get the spindle 17 inches off the table. You can work on some pretty big stuff and I have.

Good morning, I'm interested in how you can keep the head on you column bench mill true without having to realign it after a hight move. I have a RF35. Would it be possible to post photos of your solution for the problem. Thanks.

 

[epanzella]

Good morning, I'm interested in how you can keep the head on you column bench mill true without having to realign it after a hight move. I have a RF35. Would it be possible to post photos of your solution for the problem. Thanks.

Hi Charles,
I made my head indexer from a piece of ground tool steel shafting and a pillow block that slides along it. The rod is currently attached to the mill stand and has served me well for years. I will be attaching the rod to the column at some point because it's in the way of a future project.

 

[davidpbest]

Yet another viewpoint. Read the attached.