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Knee Mill vs Mill/Drill for Gunsmithing

Brian Stewart

Plastic
Joined
May 14, 2003
Location
Oldsmar, Florida, USA
Is a Knee Mill or Mill/Drill better for gunsmithing and to make a receiver. I have an 07 FFL to gunsmith and make guns but can't decide which mill is better. The Knee mill has higher spindle speeds which I thought would make milling the steels used in firearms more difficult. The mill/drill is less rigid but has a slower spindle speed. Anyone please share your thoughts as to which machine would be more versitile and why. I really can't afford a nice used Bridgeport at this point.
 
Hi Brian,

Get a knee mill. The vast superiority of a knee mill makes using a mill/drill look awkward. Depending on the manufacturer, you can get a knee mill with slow spindle R.P.M. BTW what do you consider too fast an R.P.M.?

If you can afford it, get a Bridgeport type (clone) or one of the smaller Clausing or Rockwell knee mills.

I hope this helps.
Good Luck!
Webb
 
Thanks Webb for the reply I agree I like the knee mills better but am relatively new and need all the info on the pros and cons of each. Why do the Knee mills come with higher spindle speeds? I am relatively new so can anyone tell me why mill/drill have slower spindle speeds and Knee mills have higher speeds? Can the higher spindle speeds such as 220rpm cut 4140 steel easily without ruining the endmill?
 
Hi Brian,

It is not so much the R.P.M. as the peripheral speed of the cutter (in Surface feet per minute). Of course it is related to R.P.M. but it is also the diameter of the cutter that you swing and what the cutter is made of (HSS or Carbide). Using "Tool Steel" (high carbon steel, 4140 is mediun carbon steel) as an example, roughing cuts using HSS can be made at 40 S.F.M. and finishing (light) cuts at 70 S.F.M. Therefore, at 220 R.P.M., you can swing up to a 5/8" HSS end mill for roughing cuts and up to a 1" HSS cutter for finishing cuts. If you use carbide cutters, you can effectively double the cutter size (carbide S.F.M. figures are roughly double that of HSS).

So, you can see that 220 R.P.M. isn't necessarily too fast. It all depends on what you are going to cut and how big a cutter you want to swing.

If you can get a Bridgeport or clone there of, you will have a "back gear" capability and slower spindle speeds. Another alternative would be to install a variable frequency drive on your mill. This would also give you slower spindle speeds.

I hope this is helpful.
Good Luck!
Webb
 
Brian,

The knee (for a knee mill) rides on dovetailed slides and maintains its position with height adjustments. Most mill-drills have a round column and when you raise or lower the head, it'll shift horizontally. That means you have to shut off and reset the head's position. In making any cut where a depth change is needed, this will cost you a lot of time.

For what you're doing, get a knee mill. There are other makes like Clausing, Burke and Millrite that are quite good and about 75% the size of a Bridgeport. They're just as capable, IMHO (I own a Clausing).

Hope this helps.
 
If your getting your used bridgeport prices from G&G down in Tampa, no wonder you can't afford one.
Shop around and you will find one.
I just walked away from a tracer mill due to a couple of unexpected problems, but the money was less than you can buy a mill/drill for. If I didn't already have a BP, I would have bought that one. David from Jax.
 
You might also try Sierra Victor in Port Orange. I've had good experience with them.

Don't rule out a good horizontal mill, if you can find one. Atlas, Benchmaster, Delta Rockwell, Garvin, Sheldon are all good names.

If you strike out at dealers, try calling around to some of the local machine shops and ask them if they have any equipment they're considering selling. They can be a good source of leads, too. Good used iron is there to be found. You just have to dig.

Good luck!
 
Look for an old(1960 0r so)Tree mill.I just bought a Mod 2UV,has two speed ranges on the spindle and a Vari Drive It will slow down to a walk in the low range.You will never look at a piece of Asian built excrement again.it has one shot oiling,built in power feed on the table,and a factory installed spray mist system.If you are a amateuer like me buy the best old American machine you can afford and cry only once--------TS
 
s7hss is right, in my opinion. I use my mill for more stock work than metal work building guns. My mill is a Grizzly knee mill and it does fine for what I do. I have used a mill/drill round column before, and it aint pretty.

Certain cuts for stock work requires more height than what the down feed will give you. Once you set up, you have to get the table down in order to change tooling, and that can't be done on a round column mill. You can lower the table and bring it back to the same place without loosing your setup, with a knee mill. You won't go wrong with one.
 








 
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