Instruction Letter For Machinist To Drill Oil Pump Disk

[BL92]

Can we kindly check over these instructions for the machinist, whom will be drilling my oil pump disk?
Happy for this to be shared / forwarded / copied


To CNC operator / machinist

The task involves precision to ensure the new holes eliminate the slack between the exhaust hub tabs and the pump, preventing VANOS failure. The goal is to drill two new holes, 90 degrees offset from the original worn holes, with a tighter tolerance.


1. Job Description & Goal

• Part: S54 Vanos Oil Pump Disc (hardened steel).
• Goal: Drill two new holes for the exhaust hub tabs to reduce play.
• Key Requirement: The new holes must be precisely 180 degrees from each other and offset 90 degrees from the existing holes.
• Tolerance: The holes must be perfectly centered to ensure both drive tabs engage the hole sides simultaneously.

2. Technical Specifications

• Hole Diameter: Target a final diameter of 9.80mm
• Positioning: 90 degrees offset from the original worn holes.
• Tolerance: Extremely high precision is required for positioning to ensure zero play between the new hole and the hub tab.
• Method: CNC Mill / Drill
• Finishing: The holes should be reamed for a precise fit

3. Summary Table

Parameter	Value
New Hole Diameter	9.80mm
Angular Position	90° Offset from Original Holes
Indexing	180° apart from each other
Fit Requirement	Minimal to Zero play on Tabs
Process	Drill and Ream/Bore

Reference visualisation

Quick 16 second video here

https://www.youtube.com/watch?v=GZ17OdqU0pk

[cobra]

Ideally all of those words would be converted into a drawing for the machinist. "Extremely high precision" is meaningless, what he will need is a tolerance to know what the nominal, minimum, and maximum sizes are. For example: 9.80mm +0.02mm / -0.00mm

[samthejam]

Nothing is ever made perfect, an acceptable tolerance should also be specified like Cobra said.

Diameter and depth of the holes

[bmwfnatic]

I gave one to a guy that was drilled by someone else, and he wrote a CNC program for it to repeat them, I have many discs in stock.

[cobra]

Is there a problem getting the Beisan disks overseas? To me that seems like the easiest option.

[Keith_MN]

Is there a problem getting the Beisan disks overseas? To me that seems like the easiest option.

Thought the same. I know some people prefer to keep the original piece as part of the system. I would much rather have the Beisan disk than an original part modified by someone with questionable experience.

[BL92]

Thanks for responding and helping me out, love your support here

Q and A

Yes prefer to reuse my disk

Found someone 10 minutes from my house with CNC 4 and 5 axis,

Might as well try here 1st before ordering in from overseas

Depth is an issue actually, mine is currenly bottoming out and rubbing against the disk

Just want to get the instructions right before contacting them

[Obioban]

Why not just use someone with a proven history of doing this successfully? Machinists have a wide range of ability/attention to detail, and if you get a bad one... the price could be your engine.

Lots of people doing this for reasonable prices, that have been proven out at this point.

[BL92]

bottoming out issue by the looks of it, holes have increased in depth?


Obi

I do not know if anyone here in Australia can drill them and don't want to post it out to the USA so i am exploring Australain options 1st

[oceansize]

Reach out to CMP Engineering (from Australia), I can guarantee he can put you in touch with someone.

[cobra]

bottoming out issue by the looks of it, holes have increased in depth?


Obi

I do not know if anyone here in Australia can drill them and don't want to post it out to the USA so i am exploring Australain options 1st

It is normal to have those marks. There is some axial play on the components that can make those marks.

If I was dead-set on having a local shop do it, I would simply give them the part and tell them to match the existing holes at 90 degrees. Leave it to them to measure and set it up since they will have all the tools. If they are competent you will be fine.

I wouldn't worry about having "matched" part sets, as the one I received looked brand new. I recall talking with Raj about this and he said he never saw any wear on any pump and the tolerances are held tight so it was a very low risk swap.

[1000hp]

Just tell them the diameter and the description (90 degrees from current hole on both sides, centered in the disc). If they're skilled/competent that's all they'll need.

All machinist's tasks require precision. They're dealing with 0.001mm or 0.0001mm precision. You should probably omit that (somewhat patronizing) statement from your instructions, IMO.

[Slideways]

Just tell them the diameter and the description (90 degrees from current hole on both sides, centered in the disc). If they're skilled/competent that's all they'll need.

All machinist's tasks require precision. They're dealing with 0.001mm or 0.0001mm precision. You should probably omit that (somewhat patronizing) statement from your instructions, IMO.

^ This, I would just give them the diameter of the new holes and tell them to match the depth and set them 90 degrees from the original holes. They tackle stuff that is much more difficult. This is probably a walk in the park versus setting up a cylinder head or block for machining.

[fattycharged]

y'all must have better experience with machine shops than we do, no chance I would “leave it up to the machinist” and install it


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[sapote]

[FONT=Arial]

• Key Requirement: The new holes must be precisely 180 degrees from each other and offset 90 degrees from the existing holes.
• Tolerance: The holes must be perfectly centered to ensure both drive tabs engage the hole sides simultaneously.

2. Technical Specifications

• Hole Diameter: Target a final diameter of 9.80mm
• Positioning: 90 degrees offset from the original worn holes.
• Tolerance: Extremely high precision is required for positioning to ensure zero play between the new hole and the hub tab.

Drill holes dia = 9.80mm.
Depth is same as old holes
Position: Their centers must be on the same circle with the old holes; roughly 90* from the old holes, and their centers are on the straight line through the disk center.

To spec the holes tolerance, what is the width of the driving tabs?