I just purchased a new-to-me machine for my workshop:
This is a DoAll DH-612 manual surface grinder. Based on the serial number this one was made in 1959 and that may have been the first year of production for this model as I have found no references to earlier serial numbers.
The machine needs a good cleaning, and I’m hoping the ways (the surfaces the work table slides on) are in good condition, though if not they can be refurbished.
It is partially fitted with DoAll’s patented (US#2470350) “Cool Grinding” feature which injects coolant into the grinding wheel itself (which is porous) so there is a positive flow out of the working surface, lifting away grinding swarf better that the typical flood coolant system would. By “partially fitted” I mean it has the special coolant control valve and the special grinding wheel flanges required, but otherwise no provision for coolant: No pump, no tank, no hoses, minimal splash shielding, but all these can be made up from generally available items.
This big issue is that the motor runs on 550V 3-phase power, and all I have available is 240V single-phase. A VFD would be able to run a 3-phase 208/220/240V motor but not a 550V one. Some combination of VFD and (auto)transformer(s) might be able to do the job. My first thought was to step the 240V single-phase up to 600V and use a 600V VFD but VFDs in that voltage range require 3-phase input. Another possibility would be to use a 240V VFD and a 3-phase autotransformer to step up to 550V but this would be bulky and the VFD might not like the transformer on its output. There is also the concern that using VFDs (which generate high-frequency electrical harmonics) on older motors can cause issues with the motor lifetime because current is induced in unexpected places like the bearings causing them to wear prematurely, and voltage spikes can also cause premature insulation breakdown.
The grinder has an integrated spindle and direct-drive motor, so I will have to disassemble part of this to allow me to fit a pulley and mounting for a single-phase 220/240V motor to use belt drive. On one other DoAll model (VS-612) the motor can clearly be reversibly disassembled leaving the bare shaft, but on this machine removing the existing motor may be a one-way trip.
Once I have this working I hope to be able to use it to recondition Monotype parts, particularly worn wedges (which determine the width of the cast type) and worn moulds (assuming I can first build up some replacement metal). I might also try to modify some display mould blade insert kits to allow me to cast unusual sizes like Didot-point-sized type. The Didot point (0.0148″) is slightly larger than the almost-American point (0.0138333…″) the Monotype system usually works in, so I currently have to cast Didot-sized type faces on the next size up of type body.
Although this post is tagged “Basement Workshop” this grinder is very much never going anywhere but ground level!
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