Stuart No. 9

[Michael S.]

Today I continued working on the Stuart 9. I drilled threaded holes for the cover. Then I had to drill the other side of the cylinder. The first owner of the parts had only drilled the holes in the frame. I then transferred the holes to the cylinder cover and cylinder and drilled them. The valve body is well positioned at a right angle. The slotted screws are only temporary. I drilled threads for the condensate valves at the bottom of the cylinder. The holes on the side will be sealed with threaded plugs.

I screwed in the 6 threaded bolts for the valve body and discovered the next problem.

Michael

[crueby]

All looking great until that last picture, with the leaning towers of Pisa for steam chest studs! Ouch.

[Michael S.]

The threads got loose during drilling and thread cutting because there were already other holes. I'm not sure yet how to straighten them.
Should I close the holes again or secure them with glue? But I think it's better to be able to remove the bolts.

[Sanjay F]

It's looking great and you've made great progress. Sometimes a valve chest and cover are tight to put on, but that looks more than a little bit out. I'll be interested to see how you correct this as I have no doubt I'll come across the same problem.   Not altogether surprising given the number of restorations/part builds we both seem to do! 

[Charles Lamont]

How irritating. I suggest trying a rescue first. Using a tapping guide block that can be clamped to the port face, and having a hole drilled a minimum clearance fit for the tap. Put the tap through the block and just into the hole, clamp the block, re-tap the hole and see what it is like. It will be partially cross-threaded, but it may be useable. If it is good enough to hold the stud square and allow it to be tightened without stripping, all well and good. The guide block could also be used to make sure the studs start square into the reworked holes. If not, you are no worse off, and can think about, for example, re-drilling larger and sleeving - in effect home made Helicoils. I would never try to tap those holes without some kind of mechanical guide.

[crueby]

How irritating. I suggest trying a rescue first. Using a tapping guide block that can be clamped to the port face, and having a hole drilled a minimum clearance fit for the tap. Put the tap through the block and just into the hole, clamp the block, re-tap the hole and see what it is like. It will be partially cross-threaded, but it may be useable. If it is good enough to hold the stud square and allow it to be tightened without stripping, all well and good. The guide block could also be used to make sure the studs start square into the reworked holes. If not, you are no worse off, and can think about, for example, re-drilling larger and sleeving - in effect home made Helicoils. I would never try to tap those holes without some kind of mechanical guide.

One thing to beware of if trying that is the tap may catch on one of the angled bits, and if you force it it will snap the tap off. I did that on one last month where two holes had intersected and I tried tapping across the gap.

[john mills]

if the location is close enough it would be worth trying the tap through the hole in valve test if it fits a sliding fit assemble the studs which will fit with that bolted up with the ones which will fit then try the tap if it will enable the stud to screw in .
the threads may not be far off and slight re cut might be enough.

[internal_fire]

I believe they make special fasteners for situations like this.   

Gene

[pirmin]

I had a similiar problem with my Otto Engine Casting.
Somwhow i had not paid enough attention when i was tapping the M 2,5 holes and the exhaust casting was not able to be mounted.

The Cure was to drill a hole and tap it M 4 x 0,5

I then machined threaded plugs ,secured them with Green Loctite and then Redrilled and tapped  M2.5 .

once the exhaust casting is mounted, Nobody will know 

[Michael S.]

Hello everyone,

I'm currently cutting new threads into the cylinder for the valve body. I have absolutely no experience with BA threads. I also have two taps that say 4 BA on them, but they're not the same. The long 4 BA drill bit fits the nuts and bolts. What size should I drill for the core hole? 3 mm?

Best regards, Michael

[Jasonb]

3mm tapping drill for 4BA

[PaulR]

I believe they make special fasteners for situations like this.   

Gene

Brilliant 

[Michael S.]

3 mm, thanks Jason.

[Michael S.]

Cutting the 4 BA threads worked well.
First, I sealed the hole in the cast iron on the valve box with silver solder. I had previously finished the hole with a grinder.
Since I turned the cylinder with the exhaust hole facing down, the hole for the valve box no longer fits. So I drilled out all the holes to 4.5 mm and cut an M 5 x 0.5 thread.
I closed them again with plugs made of free-cutting steel and smoothed the surface again with the milling machine. I only milled off a very small amount, 2 hundredths of a millimeter.
I'm happy with it.

[Michael S.]

Then the cylinder went back under the milling machine. The valve box was held in place at the top with a bridge. The valve box already had 4 mm holes drilled in it. I used a 4 mm drill bit to mark the holes and drilled a short hole. Then, with the 3 mm drill bit, I drilled the core hole for the new threads and cut the first four threads. Finally, the last two threads were cut without a bridge.

The valve box is now mounted on the cylinder.

Best regards, Michael