Knee mill or Dovetail?

[Gfrost]

I was reading an earlier post by MC and I notice that some suggested a knee mill if budget would allow.
Is this a weight thing or are there specific operations that pertain to gunsmithing that a knee mill would be advantageous?

 

[PHPaul]

Complete amateur here, but my understanding is that a knee mill is much more rigid and more accurate.

 

[markba633csi]

Paul is right, knee mills have fewer problems with head droop and vertical accuracy and they are generally more rigid. Usually heavier too.
Mark

 

[Silverbullet]

The real advantage is the forth axis the table can be raised and lowered without losing your setup zero . Changing tools in bench mills tend to be a problem always reindicating to zero for the next cut .

 

[Ray C]

Speaking in ballpark terms, the smallest knee mill weighs about twice that of the largest bench mill. For many people, that is a show-stopper. The design of some knee mills also have tendencies for problems with head nod. Also, depending on the design of the knee mill, rotating the head can cause alignment problems. Head nod on bench mill is easily adjusted by shimming the column. On a knee mill??? -Good luck.

A square column bench mill with DRO on the Z axis can also maintain the zero when changing tools.

Having worked on both, I prefer bench mills for most things. The table can be placed at a sane and comfortable height without having to lean over the machine all day.

In general, I don't think there is a clear yes or no answer as to which is better.

For gunsmith work, the yes answer goes to "bench mill". You won't be working on parts that need a crane to lift. The heaviest thing that might encounter is your rotary table. Gunsmith work does not lend itself to hogging off massive amounts of metal.

Ray

 

[Gfrost]

Ok, here is another question. Belt driven or gear driven? Below are a couple that I have been eyeballing, the PM model are definitely and option as well! Big difference in cost between these two, but wondering if that says something?
http://www.grizzly.com/products/Mill-Drill-with-Stand-and-DRO/G0759
http://www.grizzly.com/products/6-x-26-Vertical-Mill-with-Power-Feed-and-LED-Worklight/G0802

 

[Gfrost]

This might be an option as well.

http://www.precisionmatthews.com/shop/pm-833t/

 

[Ray C]

Ok, here is another question. Belt driven or gear driven? Below are a couple that I have been eyeballing, the PM model are definitely and option as well! Big difference in cost between these two, but wondering if that says something?
http://www.grizzly.com/products/Mill-Drill-with-Stand-and-DRO/G0759
http://www.grizzly.com/products/6-x-26-Vertical-Mill-with-Power-Feed-and-LED-Worklight/G0802

The main difference between those two machines is that one is 900+ lbs and the other is under 400lbs. It's almost a foregone conclusion, the 900lbs machine will be more rigid and smoother to operate. Changing belts however is a royal PITA. A mill like that has 3 pulleys; a motor, an intermediate and a spindle pulley. I change speeds a lot in the course of typical mill operation and I'd go nuts changing the belt setup every time.

I'm personal friends with Matt at PM and was one of his early customers. As years went by, I did customer support for him. I'm biased -and there's no way around that.

Without a doubt, from a purely technical point of view, the PM 833 is a hands-down better all-around machine than the other two. Not even in the same league.

Ray

 

[Gfrost]

Well thank you all for the replies!! Very helpful!

Gary

 

[markba633csi]

I believe the feed on the 0802 is not 0.100 inch/rev for the x and y. PITA
Mark