Help choose between two mills

[DavidR8]

Rigidity is moot if you can't get your work and tooling in place.
I have a mill similar to the square column mill the OP posted and I have never lacked for Z-axis clearance. I would not buy the knee mill pictured because of the small Z-axis distance.

 

[Ben17484]

I was planning on ordering a mill today but am still in two minds as to which to pick.

I’ve been considering everything you have all posted on here and I think I need a bit more consideration time.

I watched some videos on making riser blocks on YouTube, and it certainly seems do-able,

I think a big reason to choose the cheaper 3 phase machine with no DRO is that I can make it variable speed in the process of fitting an inverter.

I can also pick up a DRO and scales for about £250 and do it myself (I’ve fitted them on previous mills and lathes myself).

So now the question comes down to: buying a ready to go square column mill (with a slow top speed) and buying a mill that would need an inverter fitted and at some point in the future perhaps a riser block made and fitted.

My goals over the next few years is to build my own tooling and work up to being able to make a model engine. I’d imagine the knee mill would have enough space for that.

I would also guess that if the size and nature of making my own riser block were outside of what I could do (hopefully not by that point) I could get an engineering firm to make it for me.

I think at the moment I’m leaning towards the knee mill as the extra mass and the fact it’s a knee rather than column mill sure does sound nice!

 

[DavidR8]

I was planning on ordering a mill today but am still in two minds as to which to pick.

I’ve been considering everything you have all posted on here and I think I need a bit more consideration time.

I watched some videos on making riser blocks on YouTube, and it certainly seems do-able,

I think a big reason to choose the cheaper 3 phase machine with no DRO is that I can make it variable speed in the process of fitting an inverter.

I can also pick up a DRO and scales for about £250 and do it myself (I’ve fitted them on previous mills and lathes myself).

So now the question comes down to: buying a ready to go square column mill (with a slow top speed) and buying a mill that would need an inverter fitted and at some point in the future perhaps a riser block made and fitted.

My goals over the next few years is to build my own tooling and work up to being able to make a model engine. I’d imagine the knee mill would have enough space for that.

I would also guess that if the size and nature of making my own riser block were outside of what I could do (hopefully not by that point) I could get an engineering firm to make it for me.

I think at the moment I’m leaning towards the knee mill as the extra mass and the fact it’s a knee rather than column mill sure does sound nice!

It's your call of course but I would opt for the larger work envelope vs having a knee given the kind of work you want to do.
Model engineering may be small parts but the tooling to work on them is basically the same size regardless.

 

[Eddyde]

I've worked on both knee mills and column style mills (As is my current mill), there is no "advantage" to a knee mill in my opinion. Bothe styles have their pros and cons. Also, the extra mass doesn't necessarily mean the knee mill will be much more rigid, if at all. It also depends on the design and quality of the machine. Buy what you want but Z clearance is very important on a mill, I have 21" (533mm) z clearance on my mill and often come close to running out of room.

 

[verbotenwhisky]

Sure, there could always be a situation where the extra rigidity would be nice, but if I had to choose between that and a larger work envelope I choose the latter. Reason, you can always work around a lack of rigidity by taking lighter cuts but when you run out of room, there really isn't much you can do about it. Especially in the Z axis where the vise and tooling quickly eat up available space. The knee mill only has a 328mm (12.9") clearance spindle to table, the bench mill has 450mm (17.7") clearance, that's pretty significant in my opinion.

Yes a touch DRO would offer more features but you need the scales anyway, So getting a factory installed DRO then upgrading the readout wouldn't be a big or costly deal.

Exactly, the extra 5" is most of your tooling.

 

[verbotenwhisky]

I was planning on ordering a mill today but am still in two minds as to which to pick.

I’ve been considering everything you have all posted on here and I think I need a bit more consideration time.

I watched some videos on making riser blocks on YouTube, and it certainly seems do-able,

I think a big reason to choose the cheaper 3 phase machine with no DRO is that I can make it variable speed in the process of fitting an inverter.

I can also pick up a DRO and scales for about £250 and do it myself (I’ve fitted them on previous mills and lathes myself).

So now the question comes down to: buying a ready to go square column mill (with a slow top speed) and buying a mill that would need an inverter fitted and at some point in the future perhaps a riser block made and fitted.

My goals over the next few years is to build my own tooling and work up to being able to make a model engine. I’d imagine the knee mill would have enough space for that.

I would also guess that if the size and nature of making my own riser block were outside of what I could do (hopefully not by that point) I could get an engineering firm to make it for me.

I think at the moment I’m leaning towards the knee mill as the extra mass and the fact it’s a knee rather than column mill sure does sound nice!

Think of it like this, a decent machinist vice, a small one, will be 3" tall, a standard chuck is 1.5" and you'll likely add 1.5" to 2" for a drill or end mill, going with the smaller dimensions your tooling is 6" out and you'll want a half inch for maneuvering room and that leaves you with 6" Which sounds like a lot but it isn't.

 

[DavidR8]

For some hard data I measured the length of my keyed, keyless drill chucks. They are 3” and 4” long past the end of the R8 taper. Add a jobber drill bit and they would be over 6 and 7 inches respectively.
My boring head is 3” past the end of the taper. Add a boring bar and would be likely 5” or more.

 

[WobblyHand]

I have a PM25 mill and run out of Z fairly often. I work around it, mostly, but it is limiting. The PM25 fits in my current shop, I wouldn't want to go significantly larger. However, if or when I move out of my current digs, I'll be looking for something bigger. If you have room for it, go with a bigger work envelope as it really does limit what you can work on. Yeah, you can remove the vise and clamp direct to the table, but how often do you want to do that?

 

[SouthernChap]

Sure, there could always be a situation where the extra rigidity would be nice, but if I had to choose between that and a larger work envelope I choose the latter. Reason, you can always work around a lack of rigidity by taking lighter cuts but when you run out of room, there really isn't much you can do about it. Especially in the Z axis where the vise and tooling quickly eat up available space. The knee mill only has a 328mm (12.9") clearance spindle to table, the bench mill has 450mm (17.7") clearance, that's pretty significant in my opinion.

Yes a touch DRO would offer more features but you need the scales anyway, So getting a factory installed DRO then upgrading the readout wouldn't be a big or costly deal.

Yeah, the nearly four inches of difference in z height is a big one, and as you say, if the OP were to buy the knee mill and then find themselves needing that height, the howl of despair is likely to be heard where you are; where I am, it'll be shattering windows!

It all depends on what Ben will be working on, I guess.

(I started this post about 5 hours ago, so the latter question may have been answered)

EDIT: Nope, not answered yet.

@Ben17484 So, what kind of work will you be doing?

If it is going to be model engineering type activities then the nearly 13 inch z height should be enough. After all, the likes of Harold Hall, Tubal Cain (not MrPete but the 20th Century English model engineer) and the majority of other English model engineers, managed perfectly well with that kind of z height or less.

However, @Eddyde makes a very good point; the knee mill form factor doesn't automatically guarantee rigidity. I mean it looks like it should but I'm pretty sure there are knee mills built in some factories that take can take any sensible, good machine tool design and make a machine that compares badly with a piece of rubber!

From reading around about the Warco VMC, it does seem people are generally happy with it, but most posts on the various forums are from quite a while ago. There's no guarantee that a VMC you buy from Warco today will be the same machine that these people were talking about back in 2014 or even 2019.

 

[jwmay]

It all depends on what Ben will be working on, I guess.

I guess this is the hardest part to know.

I think my little knee mill has 17” of z. I’m not very sure. It’s never been a problem. But I’ve used full length reamers in a drill chuck on it, with part mounted in collet block facing up in a vise…i haven’t needed to stack any more crap than that. Lol