Dog Star
Western Thunderer
We have submitted out first QCAD produced drawing to PPD... and PPD has advised that details on our drawing are outside of the recommended limits. PPD has suggested that the smallest holes in our drawing are not guaranteed to etch through... rather the "etch through" holes could become "dimples" on either side of the material.
Our drawing is for brake parts which are suitable for a 7mm scale version of a 9'0"wooden underframe with 12" solebar, the drawing is produced from the appropriate drawings of the RCH 1907 specification for 8T and 10T mineral wagons. We have used the PPD guidelines for etching tolerances and recognise that some aspects of our work does not conform to those guidelines, specifically the diameter of holes for "pins / bolts", for example to pins/bolts at either end of the brake push rods and it is just these holes which are the subject of PPD's concern.
We have asked for 0.45mm Nickel Silver... PPD says that changing to 0.3mm reduces the recommended tolerances such that our drawing is acceptable. We do not want to go to 0.3mm as we feel that 0.3mm is not thick enough for all of the parts in the drawing, for example:- V hangers, brake levers and brake lever guards. Separating the parts into two sheets, one at 0.3mm and one at 0.45mm makes the project non-viable on a cost basis.
Seems to me that there are three options:-
1/ use a different photoetch company which works to more relaxed standards;
2/ accept PPD's warning and go-ahead, see note below;
3/ enlarge the holes and risk break out to edge of the part, (think adjustment holes at one end of a brake push rod).
What does the WT-experience suggest is the way forward?
Note:- many of the parts on the Exactoscale brake gear etch require holes to be drilled to size, Exactoscale used 0.5mm N/S and some holes are circa 0.4mm diameter after etching. I am lead to believe that Exactoscale may have used PEC in Walsall for their etch products.
thank you and regards, Graham
Our drawing is for brake parts which are suitable for a 7mm scale version of a 9'0"wooden underframe with 12" solebar, the drawing is produced from the appropriate drawings of the RCH 1907 specification for 8T and 10T mineral wagons. We have used the PPD guidelines for etching tolerances and recognise that some aspects of our work does not conform to those guidelines, specifically the diameter of holes for "pins / bolts", for example to pins/bolts at either end of the brake push rods and it is just these holes which are the subject of PPD's concern.
We have asked for 0.45mm Nickel Silver... PPD says that changing to 0.3mm reduces the recommended tolerances such that our drawing is acceptable. We do not want to go to 0.3mm as we feel that 0.3mm is not thick enough for all of the parts in the drawing, for example:- V hangers, brake levers and brake lever guards. Separating the parts into two sheets, one at 0.3mm and one at 0.45mm makes the project non-viable on a cost basis.
Seems to me that there are three options:-
1/ use a different photoetch company which works to more relaxed standards;
2/ accept PPD's warning and go-ahead, see note below;
3/ enlarge the holes and risk break out to edge of the part, (think adjustment holes at one end of a brake push rod).
What does the WT-experience suggest is the way forward?
Note:- many of the parts on the Exactoscale brake gear etch require holes to be drilled to size, Exactoscale used 0.5mm N/S and some holes are circa 0.4mm diameter after etching. I am lead to believe that Exactoscale may have used PEC in Walsall for their etch products.
thank you and regards, Graham
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