Concept for "keeping the X"

Tomzo

H-M Supporter - Silver Member
H-M Supporter - Silver Member
Joined
Jul 27, 2021
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I am enjoying my RF30 clone and have done a number of mods to it already (3 Phase VFD, TouchDRO, power head lift) and I want to tackle the main round column issue. I have seen many of the installs here on HM and while they are great they all seem to be based on clamping to the column. I am sure there is a good reason why but I just can't quite figure out why the system can't be attached to the head and the base rather than the column.

I was thinking that I could get some very stout angle iron and run two lengths of that from the base out the back. From there the idea would be to attach a precision ground rod (25mm) to the angle iron rising vertically. I would attach two more lengths of angle iron to the head and extend them out similarly. The upper arms would have a precision linear bearing installed so that the bearings run up and down the ground shaft while the head was raised and lowered. I have attached a very crude mock up of what that might look like.

There are several issues to resolve here:

- Getting a rigid attachment at the bottom will be tricky. I would need to add some cross bracing and other types of supports that attach to the ground rod below where the head would travel. I would also think another connection back to the base may be needed.
- I will need some sort of adjustment ability in the connection to the base (and the head) so that the rods can be brought parallel to the column and each other. I would imagine that some slots and jack screws would do the trick.

I figured before I spent to much time working on this I would float this out there because my guess is that others may have tried something similar and there is something I have not considered that will prove this idea worthy of the dustbin. In my dream scenario I would make this rigid enough not to even use the clamps, but that may be fantasy.

Please burst my bubble before I waste a few weekends on this!

Thanks

Tom
 

Attachments

  • RF30 Idea.JPG
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OK, here goes. The parallel guide bars will have to be straight and perpendicular to the table in order to hold the x position accurately. They will also have to be rigid enough to avoid flexing as you muscle the head around. They will need to be far enough outboard to clear the pulley guard on the right. That part is actually a plus as the further out they are, the more accurate the positioning will be. You idea to mount them at the base is an improvement over previous designs I have seen. I would also add a tie bar at the top to keep the guide bars perpendicular and make the guide arraignment more stable.

I have an RF30 clone and I usually use a dowel pin located in a convenient hole for alignment after a head move. I have a DRO on the mill and I will mount a dowel pin and fit it to the hole and zero one of the subdatums on the x axis. When I move the head, I will drop the dowel pin into the hole again and tighten the head clamps If there appears to be a bias in the x direction, I adjust the x axis and note my subdatum point reading, correcting my x position if necessary. This will get me to within a thou or two. If I need to be more accurate, I will re-reference my work. Using this method, any variation in y is negligible.

I also try to set up my work and machining order so any critical work can be done without moving the head. This works most of the time. Sometimes, it takes a bit of ingenuity. The biggest issue is with drilling as the length of the chuck plus the drill is usually quite a bit greater than any milling tooling. I switched to using collets for holding drills which brings the difference more in line.
 
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Thanks to both of you. My main question was why most designs attach to the column and it seems that this related to parallelism.

@RJSakowski - you are probably right. A much simpler idea would be to just use a dowel pin in a convenient spot - probably somewhere on my vise.
 
Check out @Gravydog posts about his head alignment build. I copied it and I can raise and lower the head of my RF 30 clone and with repeatable location to within .001 every time.
 
I keep throwing out what I do that doesn't require building anything. I use a DI in combination with a rod on a magnetic base. Place the rod and the DI against the head. Zero the DI. Move the head to do what you need to do. Then bring the head back till it just touches the rod and the DI reads zero. The head is back to position.

IMG_3922.JPG
 
Someone in the past built something with levers that kept the head straight.

Was fairly simple but seemed to be good idea.

Sent from my SM-G781V using Tapatalk
 
I’ve been using the same setup as mickri. Too lazy to build anything :) But one of the simplest setup was one of the first I ever saw where the guy drilled and pinned the lift rack to the column and installed brass guides on the top inside where the rack goes through the head. He claimed <.001 after height change. My only problem is I don’t think my rack is less .001 straight as the previous owner rotated the head often as he used it to cope DOM tubing to make roll cages.
 
Another simple solution that I have thought of was scribing two parallel lines on the column with witness marks on the head. One line would not be accurate enough due to any slight misalignment of the line and the witness mark. Two lines if they were an inch or 2 apart should get you accuracy within .001. You could chuck the column in a lathe and scribe the lines with the carriage. That would ensure that the lines are the same distance apart throughout their length. Scribe witness marks on the head to match each line. If I ever take my mill/drill apart I will try this.
 
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