I need to make a couple of adapter plates for the new 56HP Yanmar to fit
the CV
joint to the prop shaft. The gear box flange has four M10x1.5 threaded
holes on a 78mm
pitch circle and the CV joint has six M10x1.5 holes on a 93mm pitch circle.

At anything other than a 15 degree offset between the two circles the holes
interfere. At 15 degrees I have 3mm between the holes. I am limited to
22mm in thickness so I can't drill blind holes on either side. Is 3mm
between holes sufficient or is there another way to lay out the bolt
circles?

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Glenn Ashmore wrote:
I need to make a couple of adapter plates for the new 56HP Yanmar to fit
the CV
joint to the prop shaft. The gear box flange has four M10x1.5 threaded
holes on a 78mm
pitch circle and the CV joint has six M10x1.5 holes on a 93mm pitch circle.

At anything other than a 15 degree offset between the two circles the holes
interfere. At 15 degrees I have 3mm between the holes. I am limited to
22mm in thickness so I can't drill blind holes on either side. Is 3mm
between holes sufficient or is there another way to lay out the bolt
circles?

Hi Glenn,

Surely the least metal you can have between the holes is 5 mm? The outer
edge of the holes on the 78 mm circle will be at a radius of 83 mm, and
the inner edge of those on the 93 mm circle will be at a radius of 88
mm. So I figure there's a minimum of 5 mm between them. Someone correct
me if I'm wrong here...

I reckon 5 mm will be okay, but I'd be inclined to make the adaptor
plate the full 22 mm thick.

There is a mathematical way of figuring out an optimum hole spacing, but
right now I can't think of a simple mathematical way. But I'll have a go
if you like.

Best wishes,

Chris

Glenn Ashmore wrote:
I need to make a couple of adapter plates for the new 56HP Yanmar to fit
the CV
joint to the prop shaft. The gear box flange has four M10x1.5 threaded
holes on a 78mm
pitch circle and the CV joint has six M10x1.5 holes on a 93mm pitch circle.

At anything other than a 15 degree offset between the two circles the holes
interfere. At 15 degrees I have 3mm between the holes. I am limited to
22mm in thickness so I can't drill blind holes on either side. Is 3mm
between holes sufficient or is there another way to lay out the bolt
circles?

Having thought about it a little more, I think 15 degrees may very well
be the optimum offset. I don't think there is much to be gained by doing
a load of maths :-).

Chris

"Christopher Tidy" wrote in message
...
Glenn Ashmore wrote:
I need to make a couple of adapter plates for the new 56HP Yanmar to fit
the CV
joint to the prop shaft. The gear box flange has four M10x1.5 threaded
holes on a 78mm
pitch circle and the CV joint has six M10x1.5 holes on a 93mm pitch
circle.

At anything other than a 15 degree offset between the two circles the
holes interfere. At 15 degrees I have 3mm between the holes. I am
limited to 22mm in thickness so I can't drill blind holes on either side.
Is 3mm between holes sufficient or is there another way to lay out the
bolt circles?

Hi Glenn,

Surely the least metal you can have between the holes is 5 mm? The outer
edge of the holes on the 78 mm circle will be at a radius of 83 mm, and
the inner edge of those on the 93 mm circle will be at a radius of 88 mm.
So I figure there's a minimum of 5 mm between them. Someone correct me if
I'm wrong here...

It's customary to specify bolt circles as the diameter, not radius. It's a
tight fit.

I have no answers for the OP, but I will say this. It might be better to use
only four of the six mount holes rather than compromise all four of the
other set.

Mike Young wrote:
"Christopher Tidy" wrote in message
...

Glenn Ashmore wrote:

I need to make a couple of adapter plates for the new 56HP Yanmar to
fit the CV
joint to the prop shaft. The gear box flange has four M10x1.5
threaded holes on a 78mm
pitch circle and the CV joint has six M10x1.5 holes on a 93mm pitch
circle.

At anything other than a 15 degree offset between the two circles the
holes interfere. At 15 degrees I have 3mm between the holes. I am
limited to 22mm in thickness so I can't drill blind holes on either
side. Is 3mm between holes sufficient or is there another way to lay
out the bolt circles?


Hi Glenn,

Surely the least metal you can have between the holes is 5 mm? The
outer edge of the holes on the 78 mm circle will be at a radius of 83
mm, and the inner edge of those on the 93 mm circle will be at a
radius of 88 mm. So I figure there's a minimum of 5 mm between them.
Someone correct me if I'm wrong here...


It's customary to specify bolt circles as the diameter, not radius. It's
a tight fit.

If that's the case, it's a very tight fit. Mike's idea of only omitting
a couple of bolts could be a good one. Perhaps other people can add
their thoughts?

Chris

Without looking at the flanges, it's hard to make any recommendations, but
I'd be tempted to plug the holes, weld an "extension ring" (if it's needed)
on the small flange to match its outside diameter with the larger one and
redrill the holes, or make a new flange (although the thought of creating
splines in the inside of the new flange would give me pause...).

Peter

"Glenn Ashmore" wrote in message
news:w6B0f.429$784.384@lakeread08...
I need to make a couple of adapter plates for the new 56HP Yanmar to fit
the CV
joint to the prop shaft. The gear box flange has four M10x1.5 threaded
holes on a 78mm
pitch circle and the CV joint has six M10x1.5 holes on a 93mm pitch
circle.

At anything other than a 15 degree offset between the two circles the
holes interfere. At 15 degrees I have 3mm between the holes. I am
limited to 22mm in thickness so I can't drill blind holes on either side.
Is 3mm between holes sufficient or is there another way to lay out the
bolt circles?

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

"Glenn Ashmore" wrote in
news:w6B0f.429$784.384@lakeread08:


At anything other than a 15 degree offset between the two circles the
holes interfere. At 15 degrees I have 3mm between the holes. I am
limited to 22mm in thickness so I can't drill blind holes on either
side. Is 3mm between holes sufficient or is there another way to lay
out the bolt circles?


3 mm will be pushing it. Have you looked at LHSHCS? (Low-Head Socket-
Head Cap Screws).
Check:
http://www.mcmaster.com/itm/find.ASP?
tab=find&context=psrchDtlLink&fasttrack=False&sear chstring=93070A215

Head height is only 6 mm, leaving you 15.5 mm of material thickness
without a washer (0.5 cbore clearance), subtract another 1.25 mm if you
use a serrated cone (bellville style) lockwasher.

Anthony

"Mike Young" wrote

I have no answers for the OP, but I will say this. It might be better to
use only four of the six mount holes rather than compromise all four of
the other set.


I got a look at a "stock adaptor for a 100mm PCD adaptor. Only 4 holes are
drilled for the 6 hole side so that looks like the solution.

Never realized how much I have saved with my mill and lathe. Took the
drawings down to a local machine shop and got a price of $240 each for the
adaptors. They are just a 4.5" diameter round 7/8" thick bored 1.75" with
a 3"x 1/4" relief on one face and a 1/8"x1/8" spigot around the bore on the
other. I can turn them both out in half a day on my antique 10K. In
making parts for Rutu I figure I have paid for both the mill and the lathe 5
or 6 times. Of course, I bill my time at $.01/hour after the satisfaction
discount. :-)

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

In article w6B0f.429$784.384@lakeread08, says...
I need to make a couple of adapter plates for the new 56HP Yanmar to fit
the CV
joint to the prop shaft. The gear box flange has four M10x1.5 threaded
holes on a 78mm
pitch circle and the CV joint has six M10x1.5 holes on a 93mm pitch circle.

At anything other than a 15 degree offset between the two circles the holes
interfere. At 15 degrees I have 3mm between the holes. I am limited to
22mm in thickness so I can't drill blind holes on either side. Is 3mm
between holes sufficient or is there another way to lay out the bolt
circles?



I can't imagine why it would be a problem with a reasonably strong and
malleable material (e.g., mild steel or 300 series SS). Consider that
the wall between the holes at the thinnest point is only 0.5mm less than
the wall of a standard M10 nut.

Is there a specific failure mode you're concerned about?

Ned Simmons