"Set-on" saddles-on-hole and "size-on-size" fits have gaps in the gutter

"Set-on" saddles-on-hole and "size-on-size" fits have gaps in the gutter

There are two types of "size on size" fittings: "Set-On" and "Inner Edge Fit".   Set-On are the most common and are significantly easier to get a good fit.  However it is not uncommon for users to get a gap where the saddle toes reach to the hole gutters.

Set-On hole settings
Most Common Reason for Set-On fit issues. 
 When cutting holes with diameters that are nearly the diameter of the pipe, a large negative bevel angle will cause the torch to overburn through the hole gutter.   To prevent this, limit the negative bevel to zero or something near zero.  You can set the default negative bevel limit for holes in Settings-->Default Cut Values-->Hole-->Negative Bevel Limit.

Here are the settings for this Set-On type of fit.
Set-on Hole

Preview

Set on Saddle




Size-On-Size:  inner edge fit
This type of size on size fits the inner edge of the hole to the inner edge of the saddle.   There is also a PypeServer training video "Size on Size Saddles and Holes".
To cut a size-on-size saddle and hole:
  1. Check the "Size on Size (override)" checkbox for both hole and saddle. This overrides the Mate Diameter to effect an exact fit.  This is an override because operators will need to (should) enter the exact pipe wall thickness when creating the cut program.  For these cuts it's not enough to rely on the standardized wall thickness.
  2. To create a bevel in the gutter of the hole where the toe of the saddle sets, set each cut with half of the desired bevel.  For example, for a 30 degree bevel, set both hole and saddle bevels to 15 degrees.  

Everything must be accurate
A size-on-size fit is considerably harder to achieve vs Set-On types.  Size-on-size requires, 1) a very well-tuned machine with 2)  exact pipe wall thickness measurements, and 3) lower amperage with accurate feedrates to prevent overburn on the saddle tips and hole gutters.

Common problems include:
  1. Poorly tuned machine.  If your pivot height is low (even a little) then that will cause gaps between saddle toes and hole gutters. Kerf and beam divergence are also important.  Make sure to get the kerf right when running at the correct (low) amperage and feedrate as discussed in 3 below.
    1. As mentioned above, too much bevel will increase errors and give excessive large gaps to fill.  Set desired bevels to half for each cut.
  2. Incorrect pipe wall thickness. Actual wall thickness of the pipe might be thinner that what is entered in the design.  When beveling it is very important to get the wall thickness exact since the torch must offset to effect the correct intersection on the inner edge.  The actual wall thickness can be entered at the time of loading the program.  You typically would not enter the true measured wall thickness in the design itself since that would cause problems with nesting.  Enter it when loading to the machine/creating an program cut file. 
  3. Amperage & feedrate combination might be too hot and over burning.   Higher amps commonly overburn saddle tips and hole gutters. Try lowering amps to the lower/lowest range for the given pipe wall thickness.  For example on a mild-steel .280" pipe, you might try amps in the 40-60 range with a feedrate in which the torch "flutters" through the cut.  By that I mean move the torch nearly as fast as you can at that amperage.  Feedrate will vary with torch type, air pressure, gasses use, and even how a given machine interprets feedrate.

Use the No-Grind Feature if you can have a small gap
In cases of saddle laterals (tilted saddles), or with a torch has limited tilt capability, there will likely be cut surfaces that exceed the torch's bevel limit.  The torch will limit and preserve the inner fit edge, but the limited section will require grinding to eliminate the fit interference.  To get a fit without grinding, consider checking the "No Grind" box.  This causes the torch to transfer its intersection edge from inner edge to outer edge where the the bevel is limiting.  Where this happens, you will get a gap on the inside fit.  If that is not allowed, do not check "No Grind" and you will have to grind out the fit (since the torch simply cannot lay that far over).  For more information search for "No Grind" in the training tab of the PypeServer Enterprise app.