Base Plate Out of Square

So I’m having some troubles. I ran through the entire set of calibration videos and yet my base plate is out of square. The machine is peerfecrly square to its self but the base plate is out of square by 15 thou over the from to back length of the baseplate (~20”)

I hope there is a way to fix this and still have the machine square to its self.

I am thinking that the only way to fix this is to adjust the linear rails on both sides in the front. Moving them to the right side ~0.015” to make up for the 0.015 to the left that the dial test indicator is reading.

I wanted to get everyone’s opinion on the best way to go about this. As by only other option besides this would be to re drill and tap work holding holes that way they match up with the axes themselves. I’d rather not have a bunch of useless holes though.

Let me know your thoughts.


EDIT: and before you say anything I know the plates are rough cut. But the hole pattern is off by this amount as well. I used precision dowels and a 123 block to see their angle front to back and it matches the angle on the baseplate side.

Don’t worry about it. As long as you get it surfaced correctly. Both types of vises will
Tram in fine.

1 Like

Nothing about the method of installing the baseplate involves squaring it to anything more than the front of the pan, which isn’t accurately square to the rails. Anything clamped to the baseplate needs to be squared with an indicator.

I’m planning to make my own subplate to mount to the baseplate, with away more mounting holes, and reamed pin holes. That way it’ll be perfectly square to the machine, and I can use the pins to square fixturing quickly.

1 Like

@microarms See that was a thought I had too but it seems a shame to waste all the current holes. Like if I put a vise on there and can’t get it square considering it would be using the holes already there, it wouldn’t be of much use.

And on top of that I’m close to broke after Thai spend and would love to not have to buy a $400 piece of aluminum lol.

I know if I did buy some it’s be MIC-6 and that stuff runs about $700 for 24x24” 1”thick

@Bigdaddy2166 See the problem is I didn’t buy Langmuir vises. I bought a mod vise and I’m adding in the smw hole pattern int the middle of the baseplate. Lo and behold this un-squareness is making it hard for me to Locate the holes between fusion and the program.

For instance I drew out the hole pattern in fusion and then noticed that the places where the holes are at in the model when the spindle moves there, there are no holes or they are slightly off. This would cause me to run into one of the holes while running my program as it’s pretty precisely in between the current holes.

The base plate (and therefore grid pattern) was never designed to be precisely square to the travel. The base plate positioners will get it very close but it is not perfect when you start talking alignment to thousandths of an inch.

Usually when bolting down a piece of work directly to the base plate, or a vise or fixture to the baseplate you will always use an indicator to precisely square it up to your travel.


I’m a noob when it come to machining but if I would have had known of the possibility of getting that more square I would have put In the extra effort. Everything else on the machine I dialed in to exactly 0 on a tenths indicator and fly cutting the baseplate was amazing.

But besides all that the real question I was asking was not did you guys intend for it to be dialed in but, since my base plate is tilted 15thou to the left is it possible to loosen the bolts on the rails and tap it over 15 thou? Like do you think that if I did that i would be able to theoretically get it in line with the rest of the machine?

Sketch example :

Basically if I can move them left in front and right in back I can effectively take up the tilt by moving 7.5 thou in those directions theoretically and still keep the machine square x:y. But do you guys think this will work? I feel like the linear rails probably have 0.007” play in them

That wouldn’t make your machine square, it would make it into a rhombus.

1 Like

@amosdudley Not unless it was done incorrectly. the key is that i would unscrew all Linerar rail screws except the senter ones allowing the axis to stay perpendicular to the X axis while rotating around 7thou. you almost have to draw it out to see it but its def “theoretically possible” i just wonder if doing so might not work out practically. Trying to get 15 thou out of square over 20" might end up adding more than that back.

Just wondering if anyone can see the problem im having and had done something like this before without issues.

Why do you need the wholes to be square? Even if they were you would still want to dial in the vise or fixture with an indicator. If you want a reference just mill some holes in the base plate for some ground pins to fit in.

Well I want all holes to be reference pin compatible. Also I’d like all the holes the I locate the vise with to be as well. I guess since I’ll be cutting in those holes they will be.

You might want to take your square reference off the 2x2 bolt hole pattern and not off the side of the base plate. I am enlarging my base plate and as I was checking things out to ensure I could keep a constant 2" spacing across the original and new base plate sections, I noticed the perimeter of the base plate is not square to the bolt pattern - at least on mine. I used my other mill to square all 4 sides to the bolt pattern as well as clearance as necessary to maintain the 2x2 pattern across the entire enlarged base plate.

1 Like