[How-To] Improved Tramming for the PM-833T

[Lucas E]

FTFY

Yep, that's true. I was just trying to point out that even the cheap steels are significantly more stiff than aluminum.

 

[jwmelvin]

Yep, that's true. I was just trying to point out that even the cheap steels are significantly more stiff than aluminum.

We are in agreement. People often lump stiffness in with strength when it is not affected by heat treatment or minimal alloying.

 

[ahazi]

Ahazi... I have a question unrelated to the information you shared in post #1. What do you have for a quill downfeed wheel? Looks interesting.

Also, thanks for sharing your method for tramming and the link to tramming gauge tool. I need to do this with my mill.

I replaced the quill feed with a small (12.5") steering wheel. The steering wheel does not hit the table/vise when the mill head is down like the original design. Because of the smaller diameter you don't have as much leverage as the original downfeed but so far I did not find it limiting.

I turned on the lathe an adapter disc between the mill hub and the steering wheel. As you can see in the pictures the wheel is not symmetric and I had to offset the center. The attachment to the mill is very simple with one screw that replaces the hub screw. Removing the quill downfeed hub is not straight forward so I left it in place. It also allow me to revert to the original configuration by removing just one screw.

After installing the steering wheel I was not sure that I liked it but I got used to it and it is actually more comfortable than the original hub and spokes.

 

[ahazi]

Mine wasn't a whole lot thinner, and was made of steel. I was trying to dial it in to .0005" or less across roughly 12" and found the assembly had too much flex at that range. I was still fighting movement when I tightened the head. Are you shooting for that level of tram?

I can get 0.0005 or less over 6" but I am not sure that it can hold it when moving the head up and down even after locking it in the new location. For now I am ok but I will look some more into it. It seems to be very repeatable with quill movement.

Was the flex in the helper bars or in the mill itself? I don't feel any flex during the adjustment but there might be some non-repeatable engagement in the dovetail on the column that make the results less repeatable.

FYI low carbon steel has roughly 3 times the modulus of elasticity of 7075 aluminum. I.E. its 3 times stiffer

Thanks, you are right, my mistake.