As part of a continuing quest to make a decently working gear toy
for my granddaughter, I came to the point of needing to use a 1/8" router bit with a set of CNC cut gear patterns.
I'd have used a bearing guided flush trim bit but I haven't found any available.
So, I started looking for pin guided routing setups. I found the table type with the router overhead, which is a dead end for me. I found found few setups for an overhead guide pin on a typical router table. I did find two commercial products, the MLCS Daisy Pin Guide
and the Veritas® Pin Router Arm - Lee Valley Tools
. Even before completing my homemade pin guide, I could see the value in having more working capacity, both in XY and vertical (Z) directions. I decided on the Veritas pin guide arm (VPGA), without actually realizing its size and mass. In hindsight, I think the Daisy pin guide would have been a good alternative.
But, I have the Veritas, so I set about mounting and setting it up. I tried fitting it on the corner of my Bosch table, similar to the instructions, which really only apply to Veritas tables. The VPGA would not fit my table, so I needed to make an extension, which I needed anyway for the Incra LS position, that should arrived today. Nominally, I would use MDF, even two layers of 3/4" with the top sheeted with melamine, but the extension needs to be large (27"x27") and the sheer weight of that would tip over my table.
So, my plan is to build what is essentially a torsion box extension table using a new-to-me product, resin impregnated honecomb (source of the honeycomb material)
. That also is on order, due to arrive today. I also plan on making a couple of lightweight table tops for two folding tables, replacing the heavy particle board tops. Making the router table extension with the honeycomb will be a good learning exercise for the larger table top projects.
But, in the meantime, I opted to make a temporary extension from 1/2" MDF and brace it with 1x2s. I tried it first without the bracing, but the weight and leverage of the VPGA was too much for the unsupported, thin MDF (no surprise). With the bracing, the VPGA is quite solid and stable. Where the unsupported table flexed and resulted in the VPGA pin/holder not being perfectly vertical, the supported table allows for it to be quite acceptably perpendicular to the router table.
Lack of perpendicularity with the unsupported extension (very narrow band of light towards the lower end). This is probably good enough for woodworking, but the table flexed enough I felt it was not rigid enough for actual use.
The VPGA comes with three guide pins, 3/8", 1/2" and 3/4", with 1/4" being available as an option. I need both 1/4" and 1/8" guide pins. So I machined some out of brass.
My first go at using the VPGA and a 1/8" bit was working well until I snapped the bit. As thin tools can go, I probably took too big a bite or used too much pressure. This caused me to assess the situation. With at least the gear that I was cutting with when the bit broke, there was a lot more stock to be removed than I realized. I decided to rout out the bulk of the extra material in the base of my hand cut gears using the 1/4" bit to be followed up with the 1/8" bit.
I cut one gear of each size with the
and tried them on the peg board. They worked great and now I think there is no need to even use the 1/8" bit. I will proceed to complete the other gears with just the 1/4" bit. That bit has 1" long flutes, so I am thinking of stacking two of the gears, in part to spread the wear out on the flutes, but also so I am not having to cut each gear individually. I am, however, sensitized to not use too much pressure, which raises questions about how much material can be cut and in a trimming operation, rate of feed to avoid burning. For another post, eh.