O/T Looking for gage shop

[JAMMAN]

I need to find a shop that can lap a 16mm shaft to a bore with a fit in the .000014" to .000018" range. Any takers please e-mail [email protected]

 

Thanks all!

 

PS. MC9 on the way!!

[Rekd™]

Unless it's ceramic, thermal expansion alone says it's not going to work outside a controlled environment. Prolly not even in a controlled environment.

 

What's the application?

 

Honing will prolly be your best bet.

 

'Rekd

[JAMMAN]

Ty Rekd for the response.

 

These are plunger and barrel assemblies for a diesel fuel injection pump. We need an alternate source since it is a one year lead time where we buy them from Italy at the moment; and they claim that is the tolerance. We can't even measure the damn things.

 

We know for sure on the test stand they work fine till the fuel reaches the 140deg F range then the plunger ceases.

 

These pumps go on high performance tractors for tractor pulls.

[crazy^millman]

Have you tried Moore or Someone like that who does this really tight toleracne work. I had a guy working for me back in Florida that use to be a supervior there and he use to talk about the toleracnes all the time.

 

Crazy Millman

[Rick Damiani]

Are you trying to repair an existing injection pump, or are you trying to make one? The plunger and barrel assembly for diesel injection pumps that use them are hand-fitted and, becasue of the extremly tight tolerance, not interchangeable.

[Müřlıń®]

quote:

---

Unless it's ceramic, thermal expansion alone says it's not going to work outside a controlled environment. Prolly not even in a controlled environment.

---

+1

 

Doesnt it take at least .0001 or .0002 clearance on anything to fit in the real world?

 

I have never even heard of those tolerances, even on hand lapped guage blocks. + or - .00004 is the best I ever saw.

 

You sure you didnt add an extra 0 JAMMAN?

 

 

Murlin

[Steel Surgeon]

Even with a slip fit with no shake you need .00005/.0001( I like .0002) clearance and thats using some type of lube. No lube and I think it will seize up. I always had to put grease on the item in order for it not to totally lock up and score the walls up.

 

If you fart sideways the size will change.lol

[Jack Mitchell]

I do not know of any gage making company capable of building a go/no-go gage to even check a part such as described.

 

Bet best is leave this one to the Italian manufacturer, otherwise, this search could be endless.

 

Good luck and please tell us the result.

 

 

Regards, Jack

[crazy^millman]

Well I heard of them and thought they were crazy then. I have heard of moving part that needed to be within .00008 but would not even want to think about trying to do it. I was lucky t ohave meeet the guy I did that was from moore and have him wrok with me at the company I was running and I say work with cause even though I was the boss and still am a boss I treat everyone with that type of respect.

 

Crazy Millman

[skeetboy25]

I desined a stirling cycle engine a few months ago that would need a piston to barrel tolerance of about .00005" to work, what i ended up do ing was cuttin the graphite piston to +.0005", then bands of tissue paper held against the stock to reduce it further. To check the dimensions, i set our electro static perthometer on a guage block held level with the base of the part (using anoth guage block), i was then able to measure the difference in dimension between them to a tolerance of .000002". This strategy of measuring (when ambeint heat can be controlled) might work well for you.

[Müřlıń®]

Skeetboy WOW 50 millionths clearance....what kind of fuel did it burn, propane?

 

JAMMAN Scrap rate would be very high if one tried to hold tolerances of 14 to 18 millionths.

 

I would say the way those Itallian guys do it is to grind up the pistons and bores and get super finish to start with. Then using a stone hone machine and flood oil, lap the bore to match the clearance on the piston.

 

To make just one part would be extremely hard and scrap would be high. The only way to do it is like Rick said and do a bunch of them and pick and choose the ones you want to match up.

 

You would need a way to measure inside and outside diameters in millionths, and be in super controlled environment.

 

I'm with Jack on this one, I dont think you could make a go/no-go guage pin.

 

Murlin

[Rick Damiani]

quote:

---

To make just one part would be extremely hard and scrap would be high. The only way to do it is like Rick said and do a bunch of them and pick and choose the ones you want to match up.

---

That is how the injeciton pumps are manufactured. After a mating pair is found, the pump's output is calibrated. Even then there are variations in output between new pumps that can cause rough running (or worse) if the injection pump set is not mached.

[Quickmike]

Just curious, but is that how gasoline injectors are manufactured? If so where are they manufactured.

[JAMMAN]

quote:

---

quote:

--------------------------------------------------------------------------------

To make just one part would be extremely hard and scrap would be high. The only way to do it is like Rick said and do a bunch of them and pick and choose the ones you want to match up.

--------------------------------------------------------------------------------

 

That is how the injeciton pumps are manufactured. After a mating pair is found, the pump's output is calibrated. Even then there are variations in output between new pumps that can cause rough running (or worse) if the injection pump set is not mached.

--------------------------------------------------------------------------------

---

This is precisely what I was told on how these things are made. Make a "gob" and individually match them to each other depending on how they come out.

 

I too thought this was an unusual tolerance and still have my doubts about being able to measure it. We have a sheffield precisionaire gage that with the addition of an "amplifier" is supposed to be able to measure that accurately. I know right now it's set up so an inch of linear travel equals .001" but even adding the amp you have to have something to set it up with........

 

I do appreciate all the responses and if I find a real answer to this problem or a good work around I'll make sure to post it. Thanks again!

[Rick Damiani]

quote:

---

Just curious, but is that how gasoline injectors are manufactured? If so where are they manufactured.

---

'Injectors' for gas engines are totally different from the injeciton pumps used for diesels. On a diesel, the injection pump meters the fuel as well as delivers it. i.e. it has to deliver a specified amount of fuel in a certan period of time. The amount of fuel injected is determiend by the effetive sroke of the piston, which in turn is determined by the rotational position of the piston in the barrel (via some helixes cut on the piston and ports in the barrel). To get the fuel into the cylender, the injector needs to develop extremly high pressures (between 600PSI and 2500PSI) which accounts for the small tolerance. Note that the tolerances quoted are for the size of the piston, *not* the clearance between the piston and the barrel. i.e. to re-fit a piston for a given barrel, you need that piston to be exactly the right size. The size tolerance is too small for these to be interchangeable parts, which is why they are mached at assembly.

 

On a gas engine, the injectors don't have to work at high pressures as they spray into the intake tract. Gas injectors, rather than being metering pumps, are more like solinoid operated vavles. How much fuel is delivered is determined by how long the valves are held open. Fuel pressure is maintained at a constant value (~50PSI) in the common rail the injectors are attached to.

 

There are some common-rail diesel fuel systems in use on a number of different engines. VW uses and elecronic one on the TDI motors. Cummings has a mechanical system used on some of their engines, though I only encountered it in school. The extremly high fuel pressures required rather limits thier popularity, as leaks are nasty in about a dozen different ways.