Cross Over Tube for Pizza Oven

[Don52]

My friend John’s brother Dave owns a bar in Northern Michigan, which is an economically depressed area. He has an industrial pizza oven that was purchased in 1984. Over time the cross over tube has rusted out and the welds holding one of the two brackets have rusted off. The oven manufacturer is still in business, but doesn’t sell the cross over tube as a replacement part. A new double oven similar to this one would cost $26K. Pizza ovens are very hot. The pilot light ignites flames in a cross over tube, which lights four burners.

1. Burner assembly


Before John retired, he owned a Fluid System Engineering company, so he asked one of his former technicians Harry bend up a replacement tube.

2. Old and new tube assemblies


3. Rusted tube


The first step was to make the brackets. I like to scribe shape of the bracket as well as the hole and slot locations. I find that this gives me a second check on locations and dimensions.

4. Scribing bracket


5. Cutting out bracket

[Don52]

6. Sanding edges of bracket


7. Center drilling bracket


For non-critical slots I like to drill a hole in each end of the slot and then plunge the cutter into one hole, make a pass then increase the depth of cut on the other end before returning to the starting hole.

8. Drilling bracket


9. Milling slot


I typically use the power of the mill using the back gear to reduce speed, to tap the holes, because I don’t own a tapping head. For thru holes I use spiral point taps, which push the chips ahead of the tap and through the back side of the hole. For blind holes I use spiral fluted taps which pull the chips out of the hole.

10. Tapping holes

[Don52]

11. Brackets done


I really like to use hog mills to square up stock, because they cut fast and leave a decent finish.

12. Squaring up crimp tool


13. Drilling crimp tool


I chose to bore the hole in the tool for the tube and for the crimp area in the same setup to assure that they would be concentric. I had a 3/8” reamer which I used for the tube bore in the tool. I didn’t have a .340” reamer, so I bored the hole for the crimp portion of the tool.

14. Boring crimp tool


15. Reaming crimp tool

[Don52]

16. Crimp tool 1st op reamed


17. Installing dowel


18. Using center finder


19. Reaming crimping tool



20. Crimp tool done

[Don52]

The swivel fitting on the end of the cross over tube is actually just a standard barb fitting. The tube was crimped loosely to hold the barb fitting in place, but still allowing it to rotate for installation. The barbed fitting has an .040” orifice in the end, which acts as a jet which accelerates the air as it leaves the fitting. This creates a low-pressure area, which in turn creates a vacuum. The cross hole through the tube near the end of the barbed fitting allows air to suck into the tube. This means that gas doesn’t leak out of the small space around the barbs, but instead sucks in air past the barbs.

21. Crimped barb fitting


22. Crimp Mark on old tube


I drilled a larger hole most of the way thru the orifice and just drilled the .040” hole through the last 1/16”.

23. Orifice pieces


I used my arbor press to install the orifice.

24. Orifice press fit


25. Orifice installed

[Don52]

26. Arbor Press with crimping die in place


27. Crimping swivel fitting


28. Fitting crimped


I had to rotate the waist of the Bridgeport to allow the tube to pass the left end of the table.

29. Setup for drilling holes


I installed tight fitting blocks in the Tee slot and then bumped the 1-2-3 blocks against them. (a red arrow points to one of the blocks.)

30. End view of setup

[Don52]

I used a parallel against the back side of the 1-2-3 block to set the position of the tube.

31. Parallel to set tube position


First I center drilled a drill point and then I drilled the 112 holes with a #76 (.020”) drill.

32. Drilling hole


33. Close up of hole


34. Crimping end of tube


35. Tube crimped

[Don52]

I used my Fireball Tool magnets to hold everything in place for welding.

36. Setup for welding


Here is a picture of me welding the brackets.

37. Welding brackets to tube


38. Brackets welded


39. All done


40. John holding the completed cross over tube


John plans on going to the Upper peninsula in two weeks to visit his brother and to install the new cross over tube.

-Don

[ryanjones2150]

Did you go back with stainless?

I envy the patience you have in documenting your work.

Do you have a DRO on the Bridgeport?

[Don52]

Did you go back with stainless?

No, John's friend Harry just used the tubing that he had on hand.

I envy the patience you have in documenting your work.

Thanks.

Do you have a DRO on the Bridgeport?

Yes, my Bridgeport came with a Mitutoyo DRO with glass scales.
It works great but doesn't have the features of the DRO Pros one that I purchased for my Lathe.

41. Bridgeport with DRO


-Don

[tarry99]

Nice Job again Don..............But all I'm really interested in is....... How is the Pizza?

[Don52]

Nice Job again Don..............But all I'm really interested in is....... How is the Pizza?

David's pizza place is called Nutini's and it is in Hancock Michigan. Dave makes great pizzas. He would have to be doing something right to be in business for 35 years. Stop by if you are ever in the Houghton / Hancock area. Tell them Don and John sent you.

-Don