Constructing the Martin Lewis Little Engines Northern Tender

[Odyknuck]

Perseverance seems to be the answer to most things in this hobby lol. Nice work.

[Carrdo]

On with trying to have everything re-assembled again.

The first job was to cut some fibrefrax pieces to re-insulate the one side of the cylinder where the original insulating material had been removed. This was the easy part as fibrefrax is very easy to cut with scissors, punch circular cutouts, form into tight corners and drape around compound shapes.

Next, was to make some custom transfer screws and install them in the inspection ports. The inspection port location could then be dimpled on the inside of the brass cylinder skin to precisely locate them for the cutout drilling operation.

The transfer screws themselves were made from water hardening drill rod and water hardened. They had to be installed backwards to have their pointed ends facing outwards. This is where I encountered real problems as I forgot to chamfer the back face to make for an easy entry and they would not go in.

Well, no problem, put them in a collet and use a new brazed carbide cutting bit to cut the entry chamfer. Well, no as the carbide bit which I was using was obviously offshore and it was pure c..p; it just polished the drill rod and immediately ruined the cutting edge by grooving it. And I had the correct grade of carbide for steel (C6). I have run into this before and obviously have not learned my lesson - don't buy any of this offshore junk being offered for sale.

In the end, the required chamfer was produced with a diamond coated coarse file. Yes, I could have tempered the steel, but despite this any quality carbide would easily have done the job.

Installing the new stainless steel socket head cap screws. The miniature "punch" to make the 12 peripheral 5-40 NC holes in the new gasket, set the steam chest cover on the cylinder with the gasket in between, align it carefully and use a tap size drill to gently punch through. It will work well if nothing moves and all of the holes will end up in their correct locations. But the gasket itself will now be very weak (I use tweezers to gently pick it up and move it around) and it can kink and break very easily so be warned. Just my experience.

Cleaning out all of the original 12 tapped holes proved to be another challenge as they still had plenty of corrosion "dirt" left in them after the original slotted head screws had been removed. I don't have a good solution here other than plenty of dog work and carefully running a fresh tap down into the holes again. This can be quite an issue with the inner six (having no space to turn the tap) being located right next to the vertical face of the cylinder casting.

[Bill Shields]

looks good...dog work is a perfect description

don't forget the never-seize on the stainless screws.....it may well be 2 decades before they need to come out....and drilling out a stainless screw is really dog work....

[Carrdo]

Hi Bill,

Yes, I hope that I have harped on that enough by now (for any or all fasteners subject to a moisture/water/steam environment and repeated heating and cooling).

[NP317]

These transfer screw sets (or similar ones) have proven invaluable in my model locomotive construction.
https://www.mcmaster.com/products/transfer-screw-sets/

RussN

[Bill Shields]

I have a very short memory...

[Carrdo]

Russ,

The problem with the commercial transfer screw sets (which I would like to have some additional different sizes - I have a few) is McMaster won't ship to Canada and Victor Machinery who also carries them, has suspended international shipments also for some reason. The offshore ones I won't buy (garbage) and places like ebay only seem to have the larger sizes > 1/4". I want the originals (USA made) and they are not made anymore and when they do come up used, they go for an arm and leg with the cost of shipping here.

[NP317]

Carrdo:
That is most inconvenient for Canadians. Bummer.
Hopefulyl trade will open up more in the future.
The situation is idiotic!
RussN

[Harold_V]

This is where I encountered real problems as I forgot to chamfer the back face to make for an easy entry and they would not go in.

I don't know if you care about this, but the real problem isn't the lack of a chamfer (although it is a solution to the problem). When a thread is parted there's usually enough resistance to cutting that the thin area at the face of the cut area on the side of the thread is deformed (displaced inward), in effect increasing the pitch diameter in the deformed area. If you could carefully remove the deformed area without a chamfer, you'd find that the piece would install perfectly well, although it might offer a little more resistance to starting.

I have shortened innumerous bolts in my many years in the shop. To minimize the deformed area I make sure that my parting tool is exceedingly sharp, even with considerable positive rake, so cutting effort is minimized. That really helps, and can provide a cut that isn't deformed if taken with care, but when that option isn't at my disposal, to overcome the rare occasion when I am unable to cut the desirable chamfer you spoke of (I prefer that solution, needless to say), I use a belt sander. It isn't always easy to hold the part being sanded, so, assuming I'm able, I'll often turn to a pin vise or even a drill chuck so I can hold it securely. With a spinning motion by hand, it is lightly touched to the running belt (parallel with the threads, not at a right angle). The resulting chamfer isn't always perfect, but unlike generating one with a grinding wheel, it is usually free of deformation, and with a little practice it forms a surprisingly uniform chamfer. Best of all, if the fastener in question is inserted in a blind hole, no one can see how it was "deburred", for lack of better description. I NEVER use a grinding wheel for this task as it often just changes the nature of the problem, unlike a belt.

Sorry to interrupt your thread. It was a golden opportunity to provide a tip for those who aren't aware.

Back to the normal program.

H

[bushav]

Did you get it running properly on air? Enjoying seeing the progress.

[Bill Shields]

some Canadians have friends south of the border who know how to affix postage stamps to small packages...

[partime]

Bill has a good solution. I often have items shipped to my sister in TX and then sent up.
McMaster will ship to a business in Canada if you know someone with an account. We use them all the time.