Thread: Hm50-52 Y axis extension (160 to 280mm+)

Hi,
I thought I had posted this but realized I haven't

These mills are advertised at the moment as having 220mm travel in the Y. The first 2 mills I got were advertised to be 180mm. When I got this last one it had stops for the power feed that limited it to only 160mm travel.
The X axis is advertised at 600mm as well but you only get 560mm travel.(more later)
When I confronted the manager with this mis advertising I was told you could get 220mmY and 600mm X with a bit modification

To get extra travel out of these mills you need to start by removing a small piece of the casting at the front of the knee to let the Y axis nut come forward further.
You can see this marked out in picture 1 and a shot from underneath in picture 2.
In picture 3 you can see the block of steel I used to space the Y axis thrust bearing block out, to allow the saddle to come further forward. This needs to be made with matching steps to what the mill has in the middle, seen in picture 4, so the sheet metal covers slide in them and a large hole drilled through it to clear the screw.

In picture 5 you can see the 3 new sheet metal covers I made up out of gal sheet which was about 1.2mm thick. The original sheet metal covers had 2 sliding and one fixed with 2 screws at the front. Doing away with the fixed one leaves that track to be able to be used for a third cover. The third cover is needed because of the extended travel, otherwise the Y axis screw would be exposed to chips and dust from above.

I had templates made up out of cardboard for these but have given them to Retromilling from this forum a while ago, so I don't have measurements.
If any one is serious about doing the extension I could muck around and get the measurements off mine, their not easy to get at but I think I could measure them.

I could have taken the travel a little further to around 300mm but was limited to my Y axis 270mm DRO scale, I can just squeeze 280mm out of it without damaging it.

Having the extra travel makes a huge difference, as you don't have to set up a job to suit the travel, you have a bit of travel to play with. Also it is not much use having a Y axis power feed for 160-220mm travel
The mod does nothing to the rigidness of the saddle, because it is only the step that has the swivel table degrees is marked on it that over hangs the knee. The table is still fully supported by the knee and does not overhang.

Dave
PS
If anybody else has got any mods for these mill, post them up I would be interested.