Will this fix the round column issue?

[AlanR]

Thanks for digging it up. I'm planning on doing this mod to my mill drill.

Tom S

I save links to posts I like. I like the mod but for me I don't think it's worth the time, I agree with swatson144, the round column is not a major issue for me, just plan your work.

 

[Canuck75]

There is a thread somewhere on this site (I looked but couldn't find it) that shows how the rack gear was pinned to the column and "alignment" blocks bolted to the column that capture the rack gear. If I remember correctly the author claimed .001" of repeatable rotational accuracy with this setup.

Tom S

Tom S

Look under "Asian Import Machinery" and for the thread "Keeping The X On a Round Column Mill". I would be glad to answer any questions you may have.


Canuck75

 

[Canuck75]

I had thought about bolting the rack to the column but I wasnt sure if I'd be able to drill through it with a regular power drill once I got everything aligned. His idea is definitely simpler and a lot cheaper. If only I could notch the head assembly somehow and bolt a linear rail to the other side of the column and have the bearing block riding inside the head......

I like the power lift also. Now I just need to source a motor that I could use for it.

Sorry, I answered Tom S when I should have replied to you direct. If you go to "Asian Import Machinery" and look for the thread " Keeping the X on a round column mill" you will see how I pinned the rack to the column and by using tight fitting guide blocks bolted to the head, am able to keep an accurate X during raising and lowering of the head.

I pre-drilled all the holes in the rack on a drill press because this keeps the holes square and true. The rack is not hardened so it is easy to drill. The pin holes are drilled between the teeth and when the roll pins are driven home are flush with the bottom of the rack gear teeth so do not interfere with the pinion at all.

Make sure your rack is parallel and true top to bottom. The guide blocks have to be snug when moving the full length of the rack. Also, make sure you use top and bottom guide blocks, this assures more rigidity for the head.

The real secret in getting the rack in the proper position is bolting one end of the rack to the column first, then working your way to the other end from pin hole to pin hole, dialling the rack to .000" precision at each hole. I did this by setting the column on V-blocks on the mill table and clamping it down. Then, with a dial indicator anchored to an angle plate to ride against the column, I moved along to each predrilled roll pin hole, made sure the DI riding against the side of the rack read 000", used a C clamp to hold the rack in position, and with a hand drill, finish drilled the hole through the column and hammered the roll pin home (1/8" x 3/4" roll pin). You must be patient and get this step right. I have a dial indicator reading of .000" from top to bottom of the rack, thus assuring it is dead parallel with the centre line of the column. The guide blocks do the rest.

Happy to answer any questions you may have.

Canuck75