Well after a couple of years of lurking around on various machine web sites I finally took the plunge and ordered a milling machine of sorts. Yeah I know, most say buy old B-Ports and be happy, but not in the cards for me. I don't have the room for a big milling machine and my budget isn't all that great to jump into a full size machine.
The reason I opted for the G0729 was that it is a true knee mill and I liked that feature. It weighs about 700+ pounds and is small enough to fit into my modest workshop area. I am waiting for a Kurt vise to arrive and some other items so I haven't tried any real milling yet. I have played with some precision hole drilling and so far so good save for one area which I will describe in detail shortly.
Table movement was on the loose side in both X and Y axis so I adjusted the gibbs. Backlash for X-axis is about .005 and y axis is about .006. I haven't trammed a mill in over 40 years but if I'm doing it correctly I have about .001 on the X axis and less on Y. Y is what concerned me most because of the somewhat difficult process to adjust it on this mill, but until someone else checks it for me I think it is pretty good. There is one thing I noticed about the Y-axis table movement in that it gets very difficult to turn the hand wheel when the table is in the extreme far left position. The hand wheel starts getting difficult to turn about 2 to 2.5 inches before table movement is used up. there are no problems in the far right position. This problem existed before I adjusted the X-axis table gibb.
The other more concerning problem that I discovered deals with the quill movement. I ran several drill test holes in various materials and noticed I wasn't getting near the depth accuracy I thought I would. In fact my test numbers were in my estimation, all over the board. At first I blamed it on the fine down feed wheel as it is graduated one turn is .100 but in truth it is only supposed to give .080 in depth. So at first I believed it was me trying to get used to the .100/.080 ratio. To help myself out a little I installed a digital readout on the quill and I thought that would yield more accuracy. It was then that I discovered there was backlash in the quill that was creating the problem. I would reach my desired hole depth on the DRO and would stop the quill feed but I noticed the quill continued to drop after I stopped the feed.
Once I actually saw the quill drop I looked closely at it and noticed if I put upward pressure of about 8 pounds or so, the quill moved upward. When I released pressure on it the quill dropped down to a rest position. I placed an indicator on the quill and measured this up and down movement between .012 and .020 depending on how hard I applied upward pressure. This movement doesn't take place when the quill is all the way up or if it is locked. So at least I figured out WHY my drilled hole depth was always deeper than I wanted.
Now I know backlash in the quill and down feed control is ever present but I didn't think it should be quite this much. I have an old Craftsman DP that I had had for many years and it has backlash in the quill but only about .006. On a lark, I sent Grizzly Tech Service an email describing my situation and they called me and advised the amount of backlash in my quill is within their specs and that they don't consider this a problem until it exceeds 1 MM. I have about half that much in mine.
So my question to the educated members of this forum is this, is .012 to .020 too much quill backlash in this machine? I certainly can work around this issue and yes, I can use the knee if I had to, but I would like some opinions in this area. If in fact this isn't "normal" per se what can I do to eliminate or reduce this amount? Or am I being overly picky about this matter. Sorry for the long post just trying to understand what is going on......thanks in advance.
Rick H.
The reason I opted for the G0729 was that it is a true knee mill and I liked that feature. It weighs about 700+ pounds and is small enough to fit into my modest workshop area. I am waiting for a Kurt vise to arrive and some other items so I haven't tried any real milling yet. I have played with some precision hole drilling and so far so good save for one area which I will describe in detail shortly.
Table movement was on the loose side in both X and Y axis so I adjusted the gibbs. Backlash for X-axis is about .005 and y axis is about .006. I haven't trammed a mill in over 40 years but if I'm doing it correctly I have about .001 on the X axis and less on Y. Y is what concerned me most because of the somewhat difficult process to adjust it on this mill, but until someone else checks it for me I think it is pretty good. There is one thing I noticed about the Y-axis table movement in that it gets very difficult to turn the hand wheel when the table is in the extreme far left position. The hand wheel starts getting difficult to turn about 2 to 2.5 inches before table movement is used up. there are no problems in the far right position. This problem existed before I adjusted the X-axis table gibb.
The other more concerning problem that I discovered deals with the quill movement. I ran several drill test holes in various materials and noticed I wasn't getting near the depth accuracy I thought I would. In fact my test numbers were in my estimation, all over the board. At first I blamed it on the fine down feed wheel as it is graduated one turn is .100 but in truth it is only supposed to give .080 in depth. So at first I believed it was me trying to get used to the .100/.080 ratio. To help myself out a little I installed a digital readout on the quill and I thought that would yield more accuracy. It was then that I discovered there was backlash in the quill that was creating the problem. I would reach my desired hole depth on the DRO and would stop the quill feed but I noticed the quill continued to drop after I stopped the feed.
Once I actually saw the quill drop I looked closely at it and noticed if I put upward pressure of about 8 pounds or so, the quill moved upward. When I released pressure on it the quill dropped down to a rest position. I placed an indicator on the quill and measured this up and down movement between .012 and .020 depending on how hard I applied upward pressure. This movement doesn't take place when the quill is all the way up or if it is locked. So at least I figured out WHY my drilled hole depth was always deeper than I wanted.
Now I know backlash in the quill and down feed control is ever present but I didn't think it should be quite this much. I have an old Craftsman DP that I had had for many years and it has backlash in the quill but only about .006. On a lark, I sent Grizzly Tech Service an email describing my situation and they called me and advised the amount of backlash in my quill is within their specs and that they don't consider this a problem until it exceeds 1 MM. I have about half that much in mine.
So my question to the educated members of this forum is this, is .012 to .020 too much quill backlash in this machine? I certainly can work around this issue and yes, I can use the knee if I had to, but I would like some opinions in this area. If in fact this isn't "normal" per se what can I do to eliminate or reduce this amount? Or am I being overly picky about this matter. Sorry for the long post just trying to understand what is going on......thanks in advance.
Rick H.
