Tramming KBC mill question.

[JustaDB]

So, trying to tram the KBC mill. Have left-right within 0.001 over 7", now need front to back. My dial indicator shows +/- 0.005 over 7" (minus at the front of the table). Issue is, my mill doesn't nod so all adjustments will need to be on the 3 bolts attaching the head to the body. There is a single bolt closest to the table & two evenly spaced at the rear point.

Looks like this: https://dygtyjqp7pi0m.cloudfront.net/i/48157/40638826_3.jpg

I'm going to go out on a limb here & guess that shim stock can be used to raise the front of the head. My question is, what shape should the shim stock be cut to? Circular, like a washer, slotted to slip around the front bolt? More crescent shaped, an inch or two deep? Suggestions?

TIA.

 

[Susquatch]

More crescent shaped, an inch or two deep? Suggestions?

Looks like cast iron so the bolt area has to be supported or you could crack the casting. I'd shoot with crescent shaped shims with holes for the bolts. Unfortunately, you will have to remove the bolts to get the shim in. But you may be able to get close with a slip in shim and a lightly torqued bolt till you know what you need.

 

[jcdammeyer]

Looks like cast iron so the bolt area has to be supported or you could crack the casting. I'd shoot with crescent shaped shims with holes for the bolts. Unfortunately, you will have to remove the bolts to get the shim in. But you may be able to get close with a slip in shim and a lightly torqued bolt till you know what you need.

One other thing. I find my knee changes the front/back depending on whether I tighten down on the knee way locks. So before you insert shims see if tightening up on the vertical ways results in a change in front/back tilt.

 

[whydontu]

Crazy idea, but if you anchor a plate to your mill table, and flatten it using a face mill it will have a wedge shape pretty close to the nod of the column.

 

[Susquatch]

Crazy idea, but if you anchor a plate to your mill table, and flatten it using a face mill it will have a wedge shape pretty close to the nod of the column.

@JustaDB - This is a GREAT idea! Even if it doesn't work, there is a very good chance that it will be a linear relationship and therefore proportional. If you do it and it isn't correct. You could try using the result change to determine the correct amount and make another plate.

 

[Aliva]

You want something like this

 

[Ironman]

The joys of import mills, eh?
I have a Lister clone engine, and somewhere along the way when machining the base casting they never cleaned the chips off the table so the cylinder which bolts to the crank casting has a lean in the plane of the crank journals. So it would wear the rod big end and side of the bore in the line with the crank. The solution for them was to take a cylinder base gasket and cut it in half and slip the half gasket in the side facing the lean. And as they say over there, "good enough for India."
I would try paper gaskets as they are somewhat forgiving and will not endanger a casting. The nod is greatly magnified by the distance so you will need less than you think.

 

[Susquatch]

The nod is greatly magnified by the distance so you will need less than you think.

I don't think this is necessarily true. His only nod adjustment is at the top behind the head not the bottom like most other bench top mills. I agree it will probably be less but not by as much as the distance would suggest.

I'd expect the required angle to be close to the amount the tram is out by the ratio of the center of the table distance from the column to the separation of the bolts. But I confess that's just an eyeball guess. I'd have to draw it all out to get a better feeling for it. I think @whydontu's idea will get him close and if not I think there is a good chance it will tell him what it needs to be.

Just my two cents.

 

[John Conroy]

As others have mentioned, using shims around bolt hole on cast iron is a recipe for a cracked casting. I think epoxy is the best solution. Check out Stefan Gottswinter,s video.

 

[Susquatch]

As others have mentioned, using shims around bolt hole on cast iron iss a recipe for a cracked casting. I think epoxy is the best solution.

No offense John, but I'm not watching the video.

I do think it's a great idea!

 

[jorogi]

No offense John, but I'm not watching the video.

I do think it's a great idea!

Apparently you don't know Stefan.

 

[John Conroy]

I didn't look at the picture showing the type of mill it is. I assumed it was an RF45 type square column machine. The round 3 bolt flange on the machine in question has to remain movable to rotate the head/ram assembly side to side so epoxy is not a viable solution. I don't see how shimming would be possible either as the shims would be disturbed each time the head/ram is moved.

 

[John Conroy]

Is it possible the .005" discrepancy is caused by knee/table sag and not by head nod?

 

[Susquatch]

I don't see how shimming would be possible either as the shims would be disturbed each time the head/ram is moved.

Agreed. I missed that. Another reason to mill a machined collar with holes for the bolts so it stays in place.

 

[Susquatch]

Is it possible the .005" discrepancy is caused by knee/table sag and not by head nod?

I think so. Earlier in this thread someone suggested seeing if locking the Z axis helped.

If so, I'd rather try adjusting the head tilt than correcting a saggy knee. Sounds funny for an old man to say that.....

 

[Susquatch]

Apparently you don't know Stefan.

Apparently you don't know how much I hate YouTube......LOL!

Yes, I know Stephan is a very talented machinist. And I instantly liked the idea of using epoxy. I have actually watched a few of his videos. But there is no way in hell I'm gunna watch him mix and apply epoxy or discuss the situation itself. I'd rather clean my closet or chew glass. I just HATE YouTube.

If Stephan wrote a book, I'd prolly buy it.

 

[Ironman]

Pretty informative and didn't start off with"Hey youtube, what's happening?" bulshit.
I have to agree that this stuff is the answer.

 

[Raygers]

Is that lower round piece part of the casting or is it a separate ring?

 

[DPittman]

I didn't look at the picture showing the type of mill it is. I assumed it was an RF45 type square column machine. The round 3 bolt flange on the machine in question has to remain movable to rotate the head/ram assembly side to side so epoxy is not a viable solution. I don't see how shimming would be possible either as the shims would be disturbed each time the head/ram is moved.View attachment 43723

@JustaDB Just incorporate the needed shim distance on your column block riser you're going to eventually make.

 

[Susquatch]

@JustaDB Just incorporate the needed shim distance on your column block riser you're going to eventually make.

Had to laugh but so true....... In the meantime it might be easiest for @JustaDB to just make a vise base plate. Should be a piece of cake cuz the required angle will automatically happen. An easier more precise job can't be imagined.