Metal on plugs?
10-25-2010 | 07:27 PM
#22
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From: St Louis, MO / Table Rock
Never heard of that grade steel. I wouldnt have thought that it could get in the hard. Do you know if it is a through hardened steel? I am more fimilar with tool steel grades - A2 D2 D5 S7 CPM etc.
11-07-2010 | 08:57 PM
#24
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Case hardening
The metallurgical process you are talking about is "case hardened" steel. The "case" provides for a lasting long wearing surface and the steel is soft and shock resistant underneath. Surface breaking or "brinelling" is result of insufficient design strength of the whole part sort of welding itself together under pressure and load. This causes the breaking of the overheated steel surface.
Case hardened crankshafts were used for early roller bearing engines and connecting rods as well as gears and shafts - 1920's technology. Charred bone was packed around the part and it was heated, cooled, heated then finish ground. Later hardening method was carburizing oil treatment. Deep case could be reground and the part reused. Once the case breaks the flaking of the steel continues and the part is basically not repairable. Welding will not work, chrome will just flake off, stellite resurfacing was used with success in the WWII era. Most of these methods are used today in repair of antiques, but it is often easier to just have new parts made from scratch. Be glad you can just get the stuff from Merc.
You might try the gears from a diesel drive as I hear they are substancially stronger.
Case hardened crankshafts were used for early roller bearing engines and connecting rods as well as gears and shafts - 1920's technology. Charred bone was packed around the part and it was heated, cooled, heated then finish ground. Later hardening method was carburizing oil treatment. Deep case could be reground and the part reused. Once the case breaks the flaking of the steel continues and the part is basically not repairable. Welding will not work, chrome will just flake off, stellite resurfacing was used with success in the WWII era. Most of these methods are used today in repair of antiques, but it is often easier to just have new parts made from scratch. Be glad you can just get the stuff from Merc.
You might try the gears from a diesel drive as I hear they are substancially stronger.
11-08-2010 | 04:50 AM
#25
Charter Member #601
Joined: Dec 2000
Posts: 3,276
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From: Holland, Mi USA.
There is no difference between the diesel gears and the others. It used to be they did a shop peen process to them, but they were thin floored gears and that was over 10yrs back.
Merc used to supply decent quality gears, but as of late, they seem to fail at a much higher rate than they did 5-6 yrs ago.
The hardening on the lower gears does not go very deep. The hardness falls way off as you remove metal in .010" increments. Friend of mine has played with them extensively.
Dick
Merc used to supply decent quality gears, but as of late, they seem to fail at a much higher rate than they did 5-6 yrs ago.
The hardening on the lower gears does not go very deep. The hardness falls way off as you remove metal in .010" increments. Friend of mine has played with them extensively.
Dick
11-09-2010 | 01:58 AM
#26
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Merc and the failing parts
Dick - have been reading the 105 or so pages of this site - you seem the man in the know on sterndrive. As for me, just left the antique world and bought a Donzi - getting aquainted with the whole Merc thing - Dr. d
