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View Full Version : Knee or Quill I want to hear from you guys



cybor462
09-19-2007, 09:40 AM
First I want to say I know this must have been discussed before here. That is ok as I want to know the thought on this now not a week or a month or years ago.

Many may have changed their minds on this subject and we also have many new users that can offer their opinions.

Here goes....

I have some down time so I pulled out my folder that is busting at the seems with tools I want to make for the shop. This pile is large and I now have some time to work on some.

I am wondering if making a knee handwheel for my Grizzly mill is worthwhile. The reason for making it in my view would be if I used the knee to advance the cutting depth of the tool rather than using the Quill fine feed to do this.

I hope to hear from you guys and if you offer your opinion please give your reason behind it.

Let me also ask that you look at this in a wide perspective. Remember not everyone here owns a real BP and for those that own either another US made or Import that there are many levels of quality, and machine condition will vary and even a new Import mill could be in better shape and hold better tolerances and repeatability than a US made but heavily worn or abused machine.

I ask how many of you use the knee to advance the cutting depth or use the quill.

I am not a long time user of a mill so I want to use this discussion and weigh all the info I gather from this to decide if I will go the knee route. I now use the quill. This does not mean I am correct and I hope to end up doing it the right way. If I go the knee route I will make this handwheel.

Let the discussion begin!:confused:

Philt
09-19-2007, 10:02 AM
Cybor462:

I am a little confused about your question(s), but here goes. You state:
"I am wondering if making a knee handwheel for my Grizzly mill is worthwhile." So, you own a Grizzly knee type mill (what model?) and you want to know if you should make a handwheel for it? Answer: Make the handwheel.

Next question seems to be involved with whether you should use the knee "to advance the cutting depth of the tool rather than using the Quill fine feed to do this" in the event you make the above knee handwheel. This depends on how much you need to change the cutting depth. It is useful to have the ability to move the mill table using a knee and then it is also useful to be able to change the depth using the quill. So, the answer to the second question is: it depends.

I would use the knee and the quill.

SGW
09-19-2007, 10:21 AM
It depends on what I'm doing. I find that the fine quill feed on my mill tends to have backlash in it, so getting an exact depth is sometimes difficult. For using a boring head though, the quill handwheel feed is invaluable.

The knee, on the other hand, with a couple hundred pounds loading the screw, has no backlash at all. If I need to make a cut 0.003" deeper, with some certainty that I'll get 0.003", I'll use the knee.

sidegrinder
09-19-2007, 10:25 AM
I vote for the knee also...just seems more rigid with the quill tucked up tight.

John R
09-19-2007, 10:29 AM
I use the knee to increase the depth of cut.
If you don't have a hand wheel or hand crank on the knee then how do you raise or lower it?
John R

Al Messer
09-19-2007, 10:37 AM
I was taught in Shop Class to always adjust the depth of cut with the knee. The spindle was supposed to be locked when milling.

MickeyD
09-19-2007, 10:43 AM
I use the quill for drilling but the knee for almost everything else. It has less backlash and a locked quill gives a better finish.

Alistair Hosie
09-19-2007, 10:44 AM
Al said
I was taught in Shop Class to always adjust the depth of cut with the knee. The spindle was supposed to be locked when milling.
That's what I was taught also Alistair

A.K. Boomer
09-19-2007, 10:53 AM
I also dont understand the handwheel question, But when it comes to Knee or quill it varies on the machine, On my machine I have 2 axis DRO on X & Y, there is no accurate way for me to gauge the quill depth but I still have my incremental scale on the knee, its still very accurate and I only have one set of numbers to remember as the other axis of X&Y are already taken care of, the knee is also more stable if your cuts have to travel a large distance for multiple step depths or such and you dont want to do this with the quill as it will get more unstable the further it sticks out, In most cases I would say Knee, but if you have dro on your quill and the depth is not a prob. then it might be quicker and handy to use it ---- I like my set-up and recomend that if you dont want to spend the extra moola for 3 axis dro you can do just fine with 2, If you dont have dro then your still in the same boat, the knee is more accurate... I dont trust the little Increment nut on the quill and would much rather lock it out if it doesnt have dro...

pcarpenter
09-19-2007, 11:07 AM
The quill is most rigid if its not extended. You wouldn't use a 4" long tool holder if you didn't have a really good reason, so I say, why extend the quill if you don't need to. I can see reasons why you would need to (as in reaching around a feature on a workpiece) and I can also see where its handier when going from say a milling cutter or edge finder to something long like a drill chuck, but in general the knee is the big feature of a knee mill and I use it.

After rebuilding my bridgeport, and having everything apart, its clear that there are certain parts of the design that are more fragile than others. While a crash is never good, I would not want to have one with the quill extended. The quill is a very precise assembly, hand lapped to its bore. Bend or crack something and you can pretty much figure the cost of a new mill. Likewise, I want to minimize wear there. I can re-scrape way surfaces to solve wear problems there while a quill loose in the quill housing turns the mill into a very heavy drill press.

Paul

cybor462
09-19-2007, 12:38 PM
First let me add I have a Grizzly 6760 mill.
Philt..to try to answer your questions.. I change depth during each cut. If I want to take .080 off a part I would do so in increments. In past discussions many have said they would only use the knee to do this. I have been using the Quill. If I continue to use the Quill then I will not make the hand wheel as that would only help with depth as the crank that comes stock with the mill works fine for making large movements of the knee.

JohnR.. I have the stock crank but was wondering if I wanted to make a handwheel which is better suited for fine adjustment if I were to use the knee to set depth of cut.

Al, Mickey, Allstair...You confused me on your reason. You all said the quill needs to be locked when milling. Not sure what you mean as I do lock the quill after I make the fine adjustment with the quill fine adjustment wheel. Each and every time I mill the quill is locked as is the knee. Did I miss something?

AK..I do have a 3 DRO but use the 3rd for the knee. I have added a stand alone 4th axis dro on the quill. It is extremely accurate.

Lets talk about rigidity of the quill. My machine is new and the quill is rigid the whole length of travel. As it wears it may be a problem. Of course the amount of material one tries to cut at a time is another factor.

Paul.. you have hit a nerve..I never thought of the wear factor in that way. I am starting to picture a decision.

Good stuff so far. Any other takers?

Marc M
09-19-2007, 02:53 PM
I use both. I have a Bridgeport clone with a DRO. The Z axis is on the quill, and I haven't gotten a scale to make the knee the W axis yet. I'll do the rough cutting with the quill fully retracted and use the knee for depth. When I start getting close, I'll lock the knee and take over with the quill. With the DRO on the quill, backlash issues are mitigated. Even when using the quill to adjust depth, I still lock it before making the cut. All fixed axis should be locked when making a cut. Because my knee locks are on the back, I don't lock it when roughing, but I do before the finish cuts. I've got to get around to making a pnuematic knee lock. This technique minimizes quill extension while allowing me to take advantage of the DRO.

John R
09-19-2007, 03:31 PM
Klem,
I used to have a mill drill and to control the depth I built a dial indicator into the down feed. It could be engaged for use and was arranged so that you could not over stroke the indicator. The dial indicator had a 2 inch stroke.
Good luck,
John R

lazlo
09-19-2007, 04:49 PM
I change depth during each cut. If I want to take .080 off a part I would do so in increments. In past discussions many have said they would only use the knee to do this. I have been using the Quill. If I continue to use the Quill then I will not make the hand wheel as that would only help with depth as the crank that comes stock with the mill works fine for making large movements of the knee.
...
My machine is new and the quill is rigid the whole length of travel. As it wears it may be a problem. Of course the amount of material one tries to cut at a time is another factor.

Like Paul and others have said, most machining texts tell you to set the Z with the knee, because it's more rigid than extending the quill. Use the quill for drilling and boring.

Extending the quill is like sticking a long piece of stock in a lathe chuck -- it makes a long lever arm for the cutting forces to twist the head.

If you want to prove this to yourself, extend the quill all the way, lock it, and stick a magnetic indicator on the table and indicate on the shaft of a cutting
tool. Now gently, but firmly push on the quill. You'll be surprised how much the head deflects.

Frank Ford
09-19-2007, 06:37 PM
Me too, I use the knee for all fine adjustments of depth. That's why I put the DRO on the knee axsis. Sometime later, I splurged for a quill DRO, but hardly ever use it.

As to the handwheel, I recommend it, you bet. After I got tired of bumping my thigh into the crank (I know, I could reverse it) I thought a handwheel would be cool. I stuck an eight-inch diameter handwheel on there, and couldn't be more pleased with the result:

http://www.frets.com/FRETSPages/Machining/Tooling/MillHandwheel/handwheel01.jpg

With its shorter stroke, the handwheel makes cranking up and down about twice as fast, too. I have the long handle nearby, but haven't used it in years. Of course, I don't work on heavy stuff.
Cheers,

Frank Ford
FRETS.COM (http://www.frets.com)
Gryphon Stringed Instruments (http://www.gryphonstrings.com)
My Home Shop Pages (http://www.frets.com/FRETSPages/Machining/index.html)

BadDog
09-19-2007, 06:56 PM
Along the same line, I wanted power on the knee. Cranking up for roughing with an end mill (quill retracted), then down for a 1/2" keyless drill chuck plus jobber drill, then back up for another op, all at 115*F in the shade (my shop was hotter) made me want it bad enough to do something about it. So I made a drill adapter for my knee. Using my gear head 1/2 drill, it moves smoothly up and down to my heart's content, and no more sweat pouring off.

But I use the long handle to dial it in. The added lever arm gives finer control. I previously thought the wheel would add nothing for my use. But now I'm thinking the wheel wouldn't be so bad since you could get both hands on it for smooth/fine control, offsetting the length advantage. But who am I kidding? The perceived potential benefit is not enough to motivate me to actually do anything about it. It took me over 6 months to get around to the knee adapter for the drill...

Edit: BTW, I do all roughing ops with the quill up. I do all "precision" ops with the quill up. But if I'm just doing some regular stuff with a relatively small load, I'll use the quill to limit horsing around with the knee. Other than that, the quill is for drilling and other vertical ops, and the knee is for setting DOC when milling. That's my newbie take on things, applied to my Bridgeport 2J S1.

cybor462
09-19-2007, 07:09 PM
I am sold. I will make an adapter for a hand wheel and fit it to my mill. I guess I had half a brain when I installed the DRO I set the Z axis on the knee. Maybe that little bird was whispering in my ear. At least there will not be any changes needed there.

I will use the Quill for boring and drilling and the knee for the rest.

Paul set the stage for my decision when he talked about undue wear on the quill. He was right and it woke me up.

All you guys are right and I thank you.

My next project..... handwheel.

Thanks fellas

noah katz
09-19-2007, 07:57 PM
Frank, where did you get that nice handwheel?

mochinist
09-19-2007, 08:27 PM
You made a good choice, I use both the knee and the quill, but I only use the quill for real light duty milling, example I have a repeat job where I mill a .040"x.040" groove into some copper and aluminum and it is way faster to use the quill with the quill dro than to use the knee, but I would never do the same thing with a .5x.5 groove.




I love the handwheel, I get sick of bruising my knee on the damn crank.

Your Old Dog
09-19-2007, 09:27 PM
I was taught in Shop Class to always adjust the depth of cut with the knee. The spindle was supposed to be locked when milling.

I don't have a choice, I have to lock mine also. If I don't it retracts. I use the quill for fine adjustments but I have a digital read out on it so i can cut it pretty fine FOR A BACKYARD SETUP !