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Post by nutty32670 on Mar 4, 2018 21:57:56 GMT
Hi All I have a 5 inch gauge terrier that I bought a while back and over the course of time ive had to remachinng and repair the bits that are already finished! (lesson learnt don't buy a half finished engine!)
I am more a machinist than a boiler maker... ( my next project I will be making my own boiler from scratch hopefully )... However my question is....
On the boiler barrel there a 2 4 BA countersunk screws that are clearance hole then into a tapped hole on the regulator casting ( with radius to match the ID of the boiler barrel.)
Some nitwit has drilled the two holes not Parallel and then followed suit with drilling the casting. I've had it up to pressure on a highdyrolic test at home and surprisingly it was ok but I don't like it and want to change it! Also I feel that it wouldn't pass a test. Plus the fact that the countersink is the wrong size 45 deg not 60!!
The question is can I "Plug" one of the holes with a tight fit of machined copper bar and then subsequently silver solder it / braze it? Then after that a new hole can be drilled??
Hope you can help/ advise!
Nathan |
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Post by 92220 on Mar 5, 2018 9:07:47 GMT
Hi Nathan.
I have no experience with boiler making, but have done a lot of silver soldering. Don't make the copper plug a tight fit. You should have at least a couple of thou clearance for flux and the silver solder to flow down the cavity between the plug and the hole. No gap means no silver solder. One way of using the tight plug is to make up the plug as you want it, and then relieve the the diameter with a file, over most of it's area, and just leave a few high spots to locate it. I don't know what size your plug is intended to be, so don't know if that is a sensible suggestion or not, but however you fit it, there must be a clearance for the silver solder to flow down.
Good luck with your build. Keep us informed of your progress with a build thread.
Bob.
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Post by Cro on Mar 5, 2018 9:13:42 GMT
Nathan,
Considering the fact you are planning to heat the boiler up and silver solder in the problem, would it not be worth coming up with a better mounting solution for the regulator casting and then silver soldering this fixture into the boiler at the time? Say a block to mount it on internally that uses the two countersunk screws for location during soldering?
Just a thought,
Adam
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Post by nutty32670 on Mar 5, 2018 10:09:21 GMT
Hi Adam that thought has crossed my mind providing that the boiler inspector would be happy with it! Id have to think up a method because the boiler is fully assembled and obucasly soldering on the inside is a problem but will have a think!
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Post by RGR 60130 on Mar 5, 2018 14:51:04 GMT
Nathan,
At the moment you have a boiler which passes a hydraulic test and applying heat could change that radically. Don't under estimate how much heat it takes to get a boiler up to soldering temperature, even for a spot repair. Unless your boiler inspector insists on a change, I would leave well alone. Custom screws could be made to fit the countersinks if required.
Reg
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Post by 92220 on Mar 6, 2018 8:56:08 GMT
Hi Nathan.
Reg makes a very good point. Also remember that you don't really want to do any drilling or tapping into the regulator parts that are inside the boiler, where the swarfe could fall inside. It would be almost impossible to guarantee getting every little bit out, and no way do you want to risk a bit of swarfe getting into the cylinders when working. Whether it would or not, I don't know, but it's not something I would like to risk. No problem if you can do all work outside the boiler but that obviously depends if the tapped holes are in a removable piece or in a piece already silver soldered inside the boiler.
Bob.
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Post by nutty32670 on Mar 9, 2018 13:06:32 GMT
Hi Guys thanks for the input! I am quite please that I investigated this further as some how the 4ba countersunk screw had sheared off on one side!!! so I have removed from the boiler cleaned up and
making a new regulator valve as we speak will be much better than the previous! I haven't needed to heat anything up just patiently removing the sheared screw off.. Will leave the countersunk holes were they are and make valve to fit suit. will not look asteticly pleasing however be good enough to hold pressure. Thankfully lagging will be going over it!
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twombo
Seasoned Member
Posts: 120 
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Post by twombo on May 26, 2018 7:46:24 GMT
Bob, How much material depth do we have to work with? 4 BA is nearly equivalent to 10-32, So A Time-Sert may be a proper repair. www.timesert.com/html/aFull information on the technique is here. my words here are based on a Stroudly type regulator. Is this a Martin Evans design? Repair the holes by drilling to a tap drill of .203” 4 fluted end mill. Once the insert is installed use studs and nuts to reassemble the regulator. spot face the cover and use the appropriate washers. Future maintenance avoids mishaps like, the dreaded stuck or broken screw! Truing the Holes up saves much grief here!! Give it a read, Give it a thought! The tackle is a complete package of finely crafted tooling. I am doing this to all my iron or GM castings. A ounce of prevention! Mick |
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