Machinist straight edge or Steel ruler ?

[buckz6319]

I need to check my Marine cylinder head for warpage/flatness

I would like to know what y'all use for this procedure?

my father used a piece of glass, but can't remember how he did this.

I would like to use a Machinist straight edge, however there not cheap. I see on the net that some folks are using Steel rulers for this.

thanks for your input

 

[raytseng]

I suppose it depends what you intend to do. Maybe just start with the regular straightedge that's not floppy then go from there.

If the difference in results will mean you take different action, then that's your decision.

If it's not flat with a ruler what are you going to do?
If it's flat with a ruler, but not flat with a truebar, then are you going to do something different?

 

[ledslinger]

http://www.amazon.com/Central-Tools-6475-Precision-Straight/dp/B000HK9AIG

 

[buckz6319]

Originally Posted By: raytseng
I suppose it depends what you intend to do. Maybe just start with the regular straightedge that's not floppy then go from there.

If the difference in results will mean you take different action, then that's your decision.

If it's not flat with a ruler what are you going to do?
If it's flat with a ruler, but not flat with a truebar, then are you going to do something different?

I see your point. I guess I will have some decisions to make, take a chance, or purchase something that's true, or have it milled.
thanks for your input. I appreciate it

 

[buckz6319]

Originally Posted By: ledslinger
http://www.amazon.com/Central-Tools-6475-Precision-Straight/dp/B000HK9AIG

thank you for the link. I have looked at those, and there made in the USA

 

[Merkava_4]

Is a 24'' carpenter square long enough? They're fairly cheap at about $7.00 at Sears.

 

[Eddie]

Since you need a flatness to obtain a good head to block seal of +/- 0.002, I think you need a machinist straight edge. Take the head to a machine shop for the measurement.

 

[buckz6319]

Originally Posted By: Merkava_4
Is a 24'' carpenter square long enough? They're fairly cheap at about $7.00 at Sears.

I have one, but didn't know if it could be used in this manner?
thanks for your input.

 

[Rand]

since you need precision in the thousands of an inch.. I'd probably have a shop run a dial indicator over it.

 

[buckz6319]

Originally Posted By: Eddie
Since you need a flatness to obtain a good head to block seal of +/- 0.002, I think you need a machinist straight edge. Take the head to a machine shop for the measurement.

I may have to purchase a straight edge, or have it milled. I just wanted to see what other suggestions are out there for this type of flatness checking, btw it's a cast iron head, engine never ran hot.

 

[buckz6319]

Originally Posted By: Rand
since you need precision in the thousands of an inch.. I'd probably have a shop run a dial indicator over it.

I have a dial indicator, and may go that route.

thanks for your input.

 

[TxHeat]

The breadth of knowledge on this site never ceases to amaze me!

 

[buckz6319]

Originally Posted By: bornconfuzd
The breadth of knowledge on this site never ceases to amaze me!

I agree! well said...

 

[buckz6319]

based on the comments, which I appreciate. I will purchase a Machinist Straight edge, and do this right.

thanks again....

 

[buckz6319]

I'll just drive up the street 15 miles next week, and pick this up
http://www.summitracing.com/parts/cbi-56430

 

[WobblyElvis]

If I had the time I'd try it the redneck way.
https://www.youtube.com/watch?v=mc_gaGAf2pk

 

[Darwin1138]

You can use a piece of float glass, you just need to put oil or some liquid between the head and the glass. If the surface is truly flat the film of oil would be equal in all the surface, bubbles tend to appear were there is an imperfection or when the surface is warped.

The glass needs to be fairly thick to prevent warping, about half an inch or more.

 

[andyd]

I use a 3' level. If I can see day light underneath. I know there are issues. A feeler gauge could be used,I guess,to measure gap. The most recent head job was to replace 2 exhaust valves. Even though it is in side wise and runs backwards, the dual cam,16 valve Honda is a preety thing under the grimy cam cover. It may have been over kill, but I backed the head bolts out in three stages, just the opposite of the torque down. Anyway,put my 3' level on it and saw no light under it. The CRV has soldiered on 75 k miles so far.

 

[Shannow]

One of the cleverest I've seen is pressure sensitive paper.

The logic being that initial set-up, two flat surfaces are perfect fit, after service, if they are bowed, but matched, they are still OK.

To that end, some Prussian Blue can be used to check fit.

(Turbines, I've had casings that you can fit a 1/4" drill bit between pull down flat with enough boltage).

 

[Vern_in_IL]

use a precision machinist ruler, rigid, you can take the ruler out of a combination square and use it as your flat.

You would have the ruler upright, in a vertical position, and you would use flexible feeler gauges, to feel for the low spots as you check the ruler along the work piece.

You would know where your low/high spots are, and you would know your tolerances..... so you can decide based on the spec. tolerance if it needs reground, which is the WHOLE POINT OF CHECKING IT.