Homann Designs TM20LV (BF20,G0704) conversion

[phomann]

Peter,
On my RF31, there are no alignment pins. Never has been and like you say, it has to be aligned each time. However in ten years or so, I haven't had to do that more than a couple of times. Also, the original lead screw nuts look exactly the same as my RF31 did. When I made my X axis one I kept having a problem with the two bolts not holding the nut mount tight enough and it would work loose causing backlash. For the nut mount, I used a couple of alignment pins and haven't had a problem since.

Hi Art,

I was thinking that there was not much "meat" on the mounting flanges and wondered whether it would be a problem.

How did you align the nut onto the saddle since it can't be adjusted once the table in put on. Is it a matter of tightening it so that there is a little movement, fit the table, get it aligned then remove the table and fully tighten the nut?

Then once it is all aligned, drill and insert the pins?

I am also considering having clearance holes in the saddle for mounting and threading the nut holder. That way, I could tighten the bolts from underneath.
The saddle would be mounted to the upside down table on a bench.



Cheers,

Peter

[Bubba]

Peter,
On the X axis, I followed some instructions that was on the old IH site. I made the nut mount and loosely bolted it to the saddle. Then using my highly calibrated :}) digital caliper, made the lead screw parallel to the dovetails as I could. At this point, I tightened down the bolts for the mount. Next, I drilled the holes for the roll pins that I used to anchor the mount in one place ( see picture on my old web site:
My CNC Homepage ). Then the table was placed on the saddle, the gib strip put in and snugged down. At this point, the end plates were loosely mounted and using a socket wrench, we moved the table to one end of max movement and that end plate was tightened down. Then we moved the table to the opposite extreme and the procedure repeated.
The Y axis was done in a similar manner except there are bearings on only one end.

HTH

[phomann]

Hi Art,

Thanks for the link. It all makes sense and I think I may copy what you have done.

Cheers,

Peter.

[Bubba]

Glad it helps

[phomann]

I started looking at what will ve required for the Z axis conversion. The Z-axis on the TM20VL is quite different from the grizzly as the crown and pinion is attached an the angle plate that holds the Z-axis bearing.

Ho remove the Z-axis screw. The bearing plate need to be removed. It is bolted to the side of the column and also has a couple of dowel pins.

First the Z-axis nut is unscrewed from the head. The bolts holding the plate are removed and a soft mallet is used to knock the plate and the pins out off the column.

You can see where the bog (body filler putty) has flaked off during the removal.

The last photo shows the inside of the column. At the bottom you can see the mill stand splash guard

[phomann]

Before I dismantled the Z-axis I tried to understand a few of the issue I might face in the conversion.

The Z-nut is right at the bottom of the head as can be seen in the first image.

As can be seen in the next few images, there is a lot of Z-travel. And, when I put the Z-axis bearing on the top of the column, I'll gain about another 2". Already it can be seen that the top of the tead travels above the top of the column.

At the moment, the problem I'll likely face is that I won't be able to get the head as low as I like. The last image shows the head in the lowest position.

[phomann]

I took a photo with the quill fully lowered. Even with this, I don't think it would touch the table. Especially if I was using a smaller bit.
And once converted to CNC with a timing pulley spindle drive, the quill will be locked in the fully up position.

Has anybody machined the slot in the Z-axis to give more travel so as to get the head lower?

I'll have to get a local machine shop to do it as only have a Taig mill.

[phomann]

On the side of the head there is a small glass (plastic actually) window that just looks into the cavity inside the head.

Does anybody have an idea as to what that is for?

[manton]

On another thread it was mentioned (probably by Hoss, since he is the expert) that perhaps there is another version of this mill that used metal gears, and required an oil fill. The versions with plastic gears use grease instead, so the plastic window is rather redundant.

[phomann]

My Mill has Metal Gears. That said, it does look like a window for checking the oil level.

Cheers,

Peter.

[manton]

All three gears are metal? I think the G0704 has a plastic gear for the center one.

[phomann]

Hi Michael,

Yes they are all metal.

Cheers,

Peter.

[hoss2006]

Has anybody machined the slot in the Z-axis to give more travel so as to get the head lower?

I'll have to get a local machine shop to do it as only have a Taig mill.

Sure, I showed how to do it with hand tools here as an option.
Projects
Hoss

[phomann]

Hi Hoss,

Thanks for that. I had it on the DVD all the time.

Cheers,

Peter.

[pippin88]

Peter,

Moving the Z Axis Nut mount to the middle of the carriage should allow the carriage to go further down. There looks to be enough dovetail to get further travel down. Possible?

(I haven't torn down my mill to look at these details)

[phomann]

Hi,

The Z-nut has a boss that fits into a machined hole. I'm not sure it would be easy to move.

Cheers,

Peter

[phomann]

A little more progress, that is if dismantling is called progress.

I've removed the column although I had to buy a 12mm Allen Key first. You can see where I plan to extend the cut-out.

As can be seen on the photo of the base, I could also extend the Y-axis but as the Y-nut is at the far end of the saddle, it already extends over the end of the dovetail when fill extended, do for the moment I'll leave it as it is.

The last image shows the underside of the base. I thought about looking at driving the Y-axis from the rear, but I'd need to drill a hole throgh the back and the webbing. That looks a bit beyond by skills.

Would it be possible to drill the hole on a drillpress?

It would be nice to have the Y-Axis stepper out of the way though. Also, the Y-Screw would need to be a little longer. Currently a 300mm long screw is needed for a front mounting.

Cheers,

Peter.

[Bubba]

Peter,
When I drilled the webbing on my RF32, I did it by using a hole saw on the end of an extension rod and powered that with a normal power drill. Worked very well and as you know, cast iron cuts fairly easily.

[phomann]

Hi Art,

Thanks for the reply. I rechecked the base, and it is too low at the back. The hole would almost break the top surface of the base where the column attaches.

Cheers,

Peter

[Bubba]

Oh well, the best laid plans and all that rot:{(

But it was a thought.