My feed rates were limited by chatter with the stock 300W spindle. I just upgraded to an 800W GMT spindle and wanted to stiffen the x-rail at the same time. I inserted M5 50mm hex cap bolts vertically in the gap between the x-axis maker slides. They are a perfect fit for the gap. I used 5 bolts spaced about every 6.25".
I used a small washer on top (any larger would interfere with the idler wheels), and used a larger washer on the bottom. It is important to use washers which will not bend into the gap when the bolt is tightened. I used extra M5 waste-board inserts as the nuts, on the bottom.
I wanted to preserve the spacing of the x-axis maker slides so that the v-wheels would track true. So I clamped the maker slides together while tightening the M5 bolts, and took care not to over-tighten. It would be easy to get carried away with the wrench and force the x-rails apart, possibly damaging them. It doesn't take much bolt tension to get the desired stiffening effect.
The x-rail is rigid now. There is no visible x-axis deflection when I press on the spindle in any direction.
I like this chatter-reduction mod because it
- stiffens the x-rail substantially in bending and twisting
- preserves the x-rail spacing for the v-wheels
- does not require dis-assembly of X-Carve
- does not require drilling the X-Carve
- adds only a few grams of weight
- can be done in 30-60 minutes
- is fully reversible
- costs about $10 in commonly available parts