Grizzly G0484 Mill Tramming Headache

[AirWolf]

Suggestions welcome!!

While perusing Craigslist for a machinist vice – I came across an ad for a Grizzly mill that had never been used… apparently a guys father was going to do some gunsmithing work but something changed and the mill and the lathe he had bought sat in his garage for years under a tarp until his recent passing.

It’s a G0484 mill/drill and the metal tag shows a manufacture date of 2009… there was cosmoline coating over just about everything. Tooling he had purchased with it were still in sealed plastic, boxes, etc. The guy offered me nice deal and I thought it a good choice for a first mill - being a complete newbie to this addicting hobby.

After clean-up the first item of business was to tram the thing… which for the yaw was relatively easy as the head does have tilt ability with this model. However the “nod” has been an ordeal and it is still not right. To “adjust” this means loosening the four ¾” bolts that hold the square column to the base, and installing shims..( ie feeler gauges) and tighten everything back down and retest….again and again and again… A Royal PITA!!!

Attached are a couple of photos from the latest attempt. (BTW I’m using Edge technology’s tramming tool and both indicators show the tram is correct, side to side or yaw – and front to back – nod.… but not according to the test cuts!

On the first pass at the top, the table moved from right to left. The second pass at the bottom section from left to right, and the table moved towards the machine, away from the OPerator. You can see the ridge between the two passes - .0015 difference. Also visible are the tooling marks… top is pretty much “crosshatched” (disregard the far left side—I hit the accelerator button on the table feed by accident). On the second pass the trailing edge of the tool left more pronounced markings and no crosshatch is visible. What might this mean? What am I doing wrong?

I’m starting to wonder if this machine just has a warped table or so much “stack tolerance buildup” in it that when the table is moved on the y axis it changes eveything somehow… I feel like I am chasing my tail trying to get this right.

Suggestions folks? (Other than relisting it on ebay and wait until summer to get a far better quality machine.. which I might end up doing anyway!) Also – I live in Sparks NV at 4,700 altitude and it’s like 30 degees now in the garage at night. The garage is heated to 60 degrees in about an hour before I work in my little “shop”… but maybe it takes longer for the machine to get to a higher temp? Just how sensitive are machines to 30 degree temperature changes?

 

[Bob Korves]

Assuming you are using the tramming tool correctly, you might be having issues related to your shimming or other loose or flexible machine parts. First, all the various adjustments must be right and snug before tramming the column. After shimming to find the thicknesses needed, the column must then be properly bedded so that it is as least as rigid as the original cast iron potted to cast iron joint. Also, with your tramming rig against the table, push and twist the head and table in various directions and twists and watch how the indicator moves. It WILL move, even if all is well, because metal flexes and any sliding way must have a gap to be able to slide. You should be able to notice the difference between flex and play watching the indicator. Make sure when doing test cuts that all the axes are locked except for the one you are moving to make the cut. Aside from the step in your photos that actually looks fairly good for a beginner on a mill drill. Rigidity in all things is what makes a mill treat you like a pro. There are references on the net and probably on this site as well showing how to properly test, adjust, and set up your machine.

 

[mksj]

Looks like something is not cinched down or rocking as it looks like you are getting both nod and chatter. Are both headstock lock levers and spindle down feed locked when your doing the passes. May also be an issue with the gibbs not being adjusted properly. Put a precision or digital level against the head and see if there is any change when applying pressure to the head.

 

[TomS]

Looks like your feed rate is a bit fast and may be a contributing factor. As mentioned in the above posts rigidity is great but all mills flex and move about when cutting. Slow your feed down to reduce the cutting forces and see if anything changes.

Have fun with your new tool.

Tom S.

 

[T Bredehoft]

Its not easy, but verify that (even though you are not using it) the quill moves square with the table. This is best done with a precision square and an indicator, measured in both X and Y.

 

[Silverbullet]

Small mills like that just aren't rigid enough to maintain the tolerance your looking for at best I guess 2 or 3 thousandths . If you move it up or turn it it will change all the settings a little bit. Not to be taken the wrong way they just are not sturdy enough to expect tite tolerance .

 

[RJSakowski]

Suggestions welcome!!
[/ATTACH]

When tramming to the table surface, you are assuming that the table is parallel to the x and y ways. If the surface is not parallel, what looks like a proper tram will in fact be tilted by the amount of non-parallelness.

A correct tram is to the ways. One way to do this is to face a plate and tram to the plate. The table is moving under the fixed spindle so the new surface will be parallel to the ways. You should be able to set your mill correctly by tramming to that surface.

The only concern would be if the ways are loose so the table can lift up when moving toward an extreme position. This can be minimized by adjusting the way gibs (this should be done first anyway) and making sure that the table is more or less centered over the ways so its weight won't cantilever the table. You should be OK on the y axis but you have a fair amount of overhang possible in the x direction.

Bob

 

[AirWolf]

Thanks for all the suggestions guys.

On this model, the small bolts with swivel handles that I thought were for just the stops - is also the only way to adjust the gibs... there is no separate gib screws. So tightened them all except for the x travel ones - which I just snugged enough to allow the table to be moved with only a bit of drag. That helped a bit - but still have chatter when the table moves from right to left. I have finally got the nod adjustment (shimming the column) so only about .001 of a ridge is left - that seems to be the best I can do until I get some .0005 shim stock.

I agree totally with your comments Silverbullet... and this mill will be going back onto craigslist come spring and I'll get a much heavier/larger mill as I know I won't be happy having to use rubbing compound and my orbital buffer to take out ridges.