To X-hatch ot not to X-hatch?
 

An interesting side issue that came out of the recent "babbit tolerance" discussion was the Ford process for finishing cylinder bores. Being a engine manufacturing guy I found it unusual that the Ford process for cyl bores as described in TerryButz post #23 Ref Ford Drwg, A-6015 called out "Ream 3.873 - 3.874 then Rolled to 3.875 - 3.876" . No mention of boreing or honing. The video posted by Railcarmover post # 32 of the Ford V8 process shows reaming and what looks like a roller burnishing process, again no Honing is shown.
Roller burnishing renders a smooth finish to metal surfaces, no pronounced profile as with the now common hone cross hatch pattern. So what is the deal here??
I talked to a friend that was a long time Ford engine development engineer ( one of the benefits of living near Dearborn) and he said that the now common X hatch hone principle was a late development from the post war era that came into play with the introduction of hard thin piston rings. Back in earlier times rings were soft cast iron and broke in with out the need for the X hatch profile surface.
This I thought was an interesting bit of engine development history. It would be interesting to learn just when Ford changer the process and introduced honing on cylinder bores.

Joe B

Re: To X-hatch ot not to X-hatch?
 

Many aspects of engine production changed during the Model A production cycle. Elsewhere is mentioned the "burning in" of Model T engines, a practice which continued in probably similar but lesser degrees as Model A engine production climbed.

Ford pioneered "surface finish" requirements and one of the complaints I have had about modern crank journal grinding is that it probably is not being done as "fine" as was done originally by Ford. Rather modern grinds are centered more around pressurized lubrication and lifting the crank away from the bearing surface by hydraulic pressure. A lot less requirement for surface finish: only need surface finish smaller than the average hydraulic film/bearing clearance.

The original Model A babbit/crank relied more on "hydrodynamic" lubrication - which is a sort of "boundry lubrication" which does not preclude the parts rubbing together, nor eliminate it largely as is found in pressure lubrication. Rather improved surface finish was used to ease the interference in - and eliminated by degrees the "burning in period."

Hence with "rough" cranks a tendency today for rebuilt engines done with babbitt to NOT last as long as they did when originally done.

My Model A mentor Arnold Goff commented that he thought a typical Model A engine life today was 60-70K miles. He put a lot of this to "no air cleaner" - but roads today are measurably cleaner than they were "back in the day." And air filter DO exist.

It would not surprise me to know that Ford finished cylinder bores "differently." As explained. And with good reason.

We've all seen the engine/motor/generator breaking-in stands used both on the Model T engines and later adapted to the Model A. Some have claimed the burning in step was eliminated completely late in Ford 4 cylinder production and the stands became test stands in fact.

http://beracuda.files.wordpress.com/...gine.jpg?w=593

Joe K

Re: To X-hatch ot not to X-hatch?
 

I thought Ford still used hydraulic motors on test stands to run in engines?

Re: To X-hatch ot not to X-hatch?
 

Skiving and roller burnishing is still used for a lot of hydraulic cylinders. Their idea in those days was that it provided a better wear surface. The use of wide profile cast iron rings in 3 and 4 ring placements allowed for break in. They likely ran those electric run in motors with little or no oil to aid is some sort of break in.

The modern cross hatch surface finish works pretty fast and full lubrication can be used for cast iron or chrome rings. There are a lot of different ring materials available too. We use plasma coated rings for the ceramic carbide nickel or cermanil cylinders. They won't break in without them. We used to use the channel chrome but the process became cumbersome and the cast iron rings didn't always break in as they should. Using the nickel carbide coating keeps the cylinders from corroding if they set too long. Nitride cylinders are still used but they can rust up over time and lack of use,

Re: To X-hatch ot not to X-hatch?
 

11A parts series sleeves were honed, the hardened "tin"sleeves were honed
For over 20 years I haven't honed bores on "in chassis " re- ring jobs , never had ring seating problems -- I started this after reading about not honing in the instructions that came with rings
I also have carried experiments further--- reuse of used rings, I have put rings with as much as 300,000 miles back in the original bore, and followed some of the jobs for over 100,000 miles of further use, my latest car got used pistons/rings from a engine with bad rods put in a block with 200,000 miles (it's a diesel), and there's some oil consumption at first-(the donor parts were running crooked in the bores due to bent rods)---now 50,000 miles later I don't add oil between changes, but it starts out at 500 per quart
If there's a ridge I cut it a little so the top ring won't hit it, but I don't remove all of it

Re: To X-hatch ot not to X-hatch?
 

Way to do it, Kurt. Thus you are a 'repair technician', not just a 'parts changer'!

Re: To X-hatch ot not to X-hatch?
 

The engine plant in Cleveland actually runs them on an automated test run station. Approximately 6 to 8 minutes

Re: To X-hatch ot not to X-hatch?
 

I've seen so many worn out and broken piston rings over the years that I just have to say your lucky. An experiment on your own stuff is one thing but building engines for paying customers is another. When I do that, I take no chances on luck. It's just not worth the extra work when it all goes bad.