Need More Z; Spindle Mounted Too Low

[Ajcoholic]

With the whole gantry assembly raised the 3" you suggest, Brady - do you give up any rigidity? I was looking at my machine this afternoon while I was machining a bunch of cabinet gables. Looks pretty straight forward with my concern just two places - getting the gantry squared up as good as it is now (I know that is just a bit of patience and trial and error) and the fact the wiring that comes from the control box, up along the side plate and up over to the cable chain thing doesnt have any slack on mine, and I would have to find some in order to raise my gantry the 3" of the extrusion height. I know it is do-able but might be a temporary PITA.

I am more concerned with not giving up any rigidity on my machine. Just due to the fact the spindle will be hanging on average 3" lower in the rollers, which might lead to a little more flex of the Z assembly?

[Simops]

Andrew....does it have to be 3" higher. As Joe says previously about raising 1.5"......for me that would be enough.....just an inch and a half would make all the difference!

Cheers

[Ajcoholic]

In my case, I can function just fine for 99% of what I do, with the stock machine.

The thickest I generally cut, is 2" solid wood which is cut on the deck with a 1/4" or 1/2" spoilboard usually.

There has only been a few times I wanted to use an extended length ball end bit for a carved out, thicker piece - where I kept hitting the upper stop and had to put the bit further in the collet than I would have liked to overcome this.

1 1/2" higher would be fine - but I guess if they make the matching extrusion in that size would be the key?

I found a place here in Canada not too far away that sells the correct 8020 extrusion and freight is dirt cheap.

[Brady Watson]

Andrew,
If you only need 1.5", then get a piece of 1515. In regards to rigidity, as long as you properly attach the risers, it shouldn't be any less stiff than stock. You can of course put it back. There is enough wire to pull some out of the control box and raise it up.

-B

[rhfurniture]

Hi, Have you looked at just mpounting the spindle a couple of inches higher on the z plate?

[Joe Porter]

If I raised the gantry by 1.5", I was thinking of getting some .5" aluminum bar and stacking three pieces and drilling thru holes and mount to existing extrusion with longer bolts. But, like Ralph says, I have been able to adjust my Z height t raising the router. The guys with a spindle may not have that option...joe

[Brady Watson]

There are plenty of ways to do this, guys. I just listed the parts & methods that I have used - feeling confident that the customer won't be calling me back with sad stories after I am miles away. AL extrusion is CHEAP...and pretty much a bolt on deal. When I did it, I had 6" stuff laying around, which was great for the indexer, but that put my table out of reach. The 3" should be perfect with a stock Z.

Yes, depending on when/what tool you have, you can flip the Z plate 180 deg and gain some additional Z, or drop the Z down depending on how it is setup now.

-B

[Ajcoholic]

Andrew,
If you only need 1.5", then get a piece of 1515. In regards to rigidity, as long as you properly attach the risers, it shouldn't be any less stiff than stock. You can of course put it back. There is enough wire to pull some out of the control box and raise it up.

-B

I wasn't referring to the rigidity of the machine body, raised - but rather the rigidity of the Z assembly itself. WHen it is lowered down, 3" past where it is presently sitting, the mass of the spindle and moving parts are hanging down 3" further past the rollers that guide them... does that part matter? I am just thinking of it as the bit/spindle mass is cantilevered past the lower guides and the further out it is - does it introduce any added flex?

AJC

[Burkhardt]

The issue of rigidity is being discussed here (and on other forms as well) but you rarely see a "scientific" discussion. But it is really simple and can be measured within a few minutes:
- Stick a rod in the collet (1/4 or 1/2")
- clamp a dial indicator in a drill vise (or other holding ficture) to rest against the rod horizontally.
- take a fishing or luggage scale and tug on the collet (or the rod) in x+, x-, y+ and y- direction with 10 and 50 pounds.

A) the difference between the 10-pound reading in either direction is a rough indication of your backlash (assuming everything is lubricated well).

B) the difference between the 10-pound and the 50-pound reading in one direction is an indication of the rigidity. For example if that difference is 20/1000" then the rigidity is 40 pounds divided by 0.02" which is 2000 pounds/inch. A general guidance is (within the range, obviously higher is better):
Rigidity less than 100 pounds/inch is good for machining soft cheese
Rigidity between 100 and 1,000 pounds/inch is a barely usable wood router
Rigidity between 1,000 and 10,000 pounds/inch is a good wood router and a decent mill for aluminum and brass
Rigidity 10,000 to 100,000 pounds/inch is getting into the area of reasonable metal mills

You can do such an assessment before any changes. If you are borderline that may not be a good idea. But if your machine is already quite rigid, why not extend the axis. The longer leverage will cause some more flex but maybe it is insignificant after all.

[genek]

Brady how much height can you get on a buddy? Mine now can handle up to 3" would love to be able to put a thicker board on mine.