10" pressure plate exact drilling dimensions.

[Robert Dip]

Hi, it's been a long time. I need the drilling dimensions for a 10" pressure plate. ( Baby Hemi engine to '39 box ) What I came up with is the dia. is 11.375" and the 3 sets of paired holes are at 32 degrees apart. Help on this would be appreciated. Could not find it on past searches.

[JWL]

I think I understand your question. I went through some gymnastics a few years ago trying to find a quick guide to the X and Y coordinates for drilling a flywheel. I called some of the manufacturing companies and NONE could(or would) come forth with the numbers. Finally I had to do a Solidworks drawing. The sad part of this story is all that information is lost in a blown hard drive two computers ago. And, no backup.

[Robert Dip]

Thanks JWL. Not many of us have proper equipment to do such an operation, but it sure would help one and all if they have to bring a flywheel to a machine shop. I have a milling machine and use a rotary degree indexing unit for such a job. Easy when one has these dimensions...whether X & Y or dia. & degrees. To clarify, the 11.375" dia is the bolt circle of the pressure plate and the 32 degrees is the stance between the 'paired' holes.

[PeteVS]

If you have a pair of calipers, you should be able to measure the hole diameters and the spaces between them. Then, do some trig and it should all come out to some nice fractional dimensions. (If you can come up with those dimensions, PM them to me and I'd be willing to help with the math.)

[Mart]

Interesting subject, I also have a milling machine and a rotary table, and was considering trying a bit of redrilling as a project. I wonder, does anyone have the equivalent numbers for the 9" unit?

May I ask, Robert, how did you arrive at the 11.375" / 32 degrees data?

[rotorwrench]

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I would use the pressure plate to get the set up dimensions. I don't think I would try it without one. 2 sets of 3 centers. 120 degrees figures for equal spacing on a 360 degree table then find the distance in degrees between the paired centers. Use the PP to check for accuracy before machining.

[Robert Dip]

Mart....I traced the holes on a sheet of stiff paper. I then placed it on my old drafting table and used the dial angle to obtain the complete 360* numbers.

0* to 32* to 120* t0 152* to 240* to 272* and back to 0/360* Spacing between the 3 paired sets of holes are at 88*.

Naturally, all of this is eyeballed, and that is why I would appreciate getting the
real drilling specs. Using calipers between holes does very little in this case of using angles and arcs, or even x & y grid.

[JSeery]

Originally Posted by Robert Dip

Using calipers between holes does very little in this case of using angles and arcs, or even x & y grid.

That's where the math comes in! What you really need is to have a machine shop with digital dimensional inspection equipment to figure it out for you.

[cmbrucew]

Here is something saved from the web on drilling wheels.
Bruce

[Ol' Ron]

have an adapter that registers in the crankshaft location in the flywheels. By bolting them together I can accurately transfer the bolt holes from one flywheel to another with my drill press. Have been doing this for quite a few years I then have them balanced, jut for kicks.

[rotorwrench]

Centering the pressure plate is more important for balance but not super critical. The starting ring is more critical than the PP. The clutch disk can float around a bit under the PP when the clutch is released. A person can use a rotaty table on a drill press but the table might cost more that the drill press I don't know. It depends on how large a diameter rotary table a person has. The main thing is get it marked accurately then use the best drilling machine you can gain access to. At least that way the holes won't tend to try and wander during the drilling process. A Mill is a lot more stable but not every one has one setting in there shop either. The drill guide idea is a good one. It's accurate enough to work OK for centering and it will keep the drill bit from wandering during the drilling process. You still have to make the guide block though and it should be made as accurately as you can.

[George/Maine]

If you have a vert machine with table that can move in and out and a rotory table.
One way is take the dia and half that for radious 5.6875
Center rotorytable and move out on long machine table 5.6875 don,t move again
mark zero now if the holes a 4" apart guess
Move the table half way 2" in and center drill then drill
Now move rotory table 120 degs drill move another 120 degs back to zero
Now move the table out 2"
Now move rotory table 120 degs drill move another 120 degs back to zero
This is how it was done years ago.

[Dec211975]

A machinists calculator #4087 by calculated industries will give you the x,y position if you have a dro on your mill. If you like I can run the numbers by tomorrow night.

Regards,

Brian

[Binx]

Math is fun until you take it too seriously. Farmer logic will win this race.

Lonnie

[Dec211975]

Robert,

Here are the X and Y dimensions to drill your flywheel on an 11 3/8" diameter circle


The first hole would be located at the 3 O'clock position all X, Y coordinates are from the center of the flywheel. All negative numbers are in parentheses.
I have double checked my work but will not be held responsible for errors.

X= 5.6875, Y=0.0000 this is at 0 degrees
X=4.8233, Y=3.0139 this is at 32 degrees
X=(-2.8438), Y=4.9255 this is at 120 degrees
X=(-5.0218), Y=2.6701 this is at 152 degrees
X=(-2.8438), Y=(-4.9255) this is at 240 degrees
X= 0.1985 , Y=(-5.6840) this is at 272 degrees

I have it drawn up but I have not been able to export it to a PDF if I can get that done I will attach it.
The linear distance between the matched holes 0,120,240 =9.8510" that would be the same between the 32,152 and 272 degree holes as well.

The linear distance between the 0 and 32 degree hole would be 3.1354"
The linear distance between the 32 degree hole and the 120 degree hole would be 7.9017"
Regards,
Brian

[PeteVS]

What is the diameter of the holes??

[Robert Dip]

Thanks guys for all of your input. Thanks also for the X & Y drilling, but, at this point. I am also assuming the circle diameter is at 11.375. ( eyeballed on my template )

Here are the c/c dimensions I took of a 10" Ford PP. The hole dia. is 0.312, and the c/c distance between the paired holes is at 3.1345" ( digital caliper ) The longer distance between the paired sets of c/c holes is at 7.903". Since I have been using my degree indexing rotary table for years with great results, it would be nice to have the proper dimensions for this set-up.
PS...it would be nice to have in the 'Ford Barn Archives' these dimensions for the 9, 10 & 11" PP. Is there such a thing as the 'Ford Barn Archives' ???

[Ross F-1]

There is an old thread on here with the shape of the holes including the counterbores. I can't find it tho.

[George/Maine]

If you have a vert machine with table that can move in and out and a rotory
table.
One way is take the dia and half that for radious 5 11/16
Center rotorytable and move machine table 5 11/16{ Don,t move again)
Put zero on rotory table.
The first 3 holes can be done by moveing the rotory 120 Degs for each hole.
The next set of holes move the rotory 32 degs for first hole, this should give you the spacing, Now you will add 120 degs to second hole and 120 to last hole.
This will give the best results and be most accurat.
Some times when the hole is drilled, first center drill then hole
size drill then take a 5/16 or 3/8 end mill and go down .062

[Dec211975]

Robert,

It looks like your measurements match my calculations within a few thousands 3.1345
Vs 3.1354 and 7.903 vs 7.9017. 0.0009 difference on the first measurement and .0013 thousands on the second. I would say you hit the mark on the flywheel PP bolt pattern being 11.375 and the angle of the second set of holes to the first being 32 degrees. As the 3.1354 and 7.9017 calculations came from Autocad and if you go out only three decimal places which is the most I would trust a caliper they are within .001"

Regards,
Brian