Member postings for Hopper

One thing about those fiddly nuts behind the chuck is you want them to be easy to get off. Those kind of locking flange nuts may not be so easy. And stainless threads can tend to gall and seize up. I would stick with what the lathe manufacturer used.

You do need to lock the carriage down when using the rear parting tool, for best results. And there are lift plates under the bed ways to hold the carriage down.

One of the old books ISTR says the cutting forces on the headstock bearings with the inverted rear parting tool are downwards, so the force is taken by the lower half of the bearings, solidly supported by the headstock casting. The front parting tool puts the cutting forces upwards against the relatively flimsy, flexible and moveable top bearing caps. That's one theory to add to the mix anyways.

I just know from long personal experience first on the old Drummond M Type and now on the Myford ML7 that the inverted rear parting tool works much better than the conventional front parting tool. I even managed to snap the end off an almost new Eccentric Engineering T section HSS parting blade running it in hard and fast from the front without much for oil on it on the ML7. Could not manage to do the same rear mounted and inverted. The old Drummond is the same on the old conventional shaped parting blades. Chattery and dodgy from the front. Competently parts 2" diameter steel from the rear.

I put it down to the chips falling out of the groove on the inverted tool. No scientific basis for that, just that I can observe the chip behaviour on the two methods vs the number of jam ups and heat generated. Whereas I can't really see or measure forces and flexes in the machine parts so can't really know if that  is a factor, or just a theory.

Edited By Hopper on 22/03/2023 11:42:40

This forum can't even agree on what constitutes an industrial machine, according to a recent thread on the topic.

That's very useful info for IC engines. Thanks for posting.

+1 on check shear pins. There is probably one at the end of the leadscrew where it joins the gearbox if it is like my ML7. Sheap pin could be sheared but still gripping sometimes and slipping other times.

Also check the change gears and make sure you have not lost a tooth off the small fibre gears on the tumbler reverse mechanism.

If still no good, check the gears in the gearbox for damaged or missing teeth from the crash you had.

Or it could be one of the woodruff keys sheared off in one of the change gears.

Edited By Hopper on 22/03/2023 08:55:59

An inverted parting tool on the rear toolpost allows the chips to fall out of the groove, giving less chance of jamming.

I'm thinking you could get away without using fitted bolts there. The eccentric would hold the two halves of the strap in alignment and the bolts just provide the clamping force to keep them together.

Looks like you are making good progress. And learning how to fix problems along the way, which is the secret to good machining.

Edited By Hopper on 21/03/2023 09:18:51

If as you say the boiler is riveted together in accordance with KN Harris specs, then caulked with soft solder, it could be ok for home use. I would hydrostatic test it first though, at least at 1.5 times the planned working pressure, and then set your safety valves for that working pressure.

If the rivets are up to the job, what is the worst that could happen? It could spring a leak around a tube end etc. Not the end of the world. Just don't hold your face next to it when firing it the first few times.

I can't think of any benefit to heating it in the oven between hydro tests.

Tracy Tools seem to supply reasonable quality at a reasonable price. Happy with the ones I have bought from them several times over the years.

Yes the Yanks tend to go on and get stuff done while the rest of us are still discussing why it could not be done and then making red tape to prevent it as much as possible. There is a lot to be said for their "can do" mindset.

+1. On full sized oil and gas-fired boilers, the furnace or at least large diameter furnace tube extends the full length of the boiler to allow full combustion without getting flame impingement on the metal surfaces. Then followed by one or two passes through banks of smaller fire tubes to get best heat transfer.

If it comes down to running model locos on gas, building from scratch might be better off, and certainly more efficient, to follow typical modern industrial practice.

For even better efficiency, but with much added complexity in the construction, you could make the rear firebox a wet back like a Scotch marine boiler. But probably the gain would not be worth the complexity of construction on a model.

Edited By Hopper on 20/03/2023 06:27:36

Edited By Hopper on 20/03/2023 06:33:29

Before you go setting your column square to the top surface of the table, you really should make sure the top surface of the table is parallel to the bed ways and dovetails the table slides on, in both directions.

To do that you would mount your dial indicator's magnetic base on the column, with the plunger of the dial indicator bearing on the table top. You then run the table through its full movement in both X and Y directions. It should return a 0-0 reading in both axes, or near enough, within say .025mm or so.

It is not unheard of for some "low cost hobby mills" to not be machined quite parallel in this area and that can throw your readings out when setting the column square to the base and when tramming the spindle. Or sometimes the table may be riding up on poorly machined dovetails or poorly fitted gib strips, or burrs on the same, etc.

It is a can o' worms once you start doing machine tool alignment.

Sometimes you can find an engineering workshop or machine shop locally that will sell you some of their left over offcuts of steel bar.

The other question is: Whose roof did the missing cylinder and piston land on?

You would have to think the change in pressure differential would be greater with a can left out in the summer sun where pressure inside the can could reach what? 50 psi? 80psi? Maybe even 100psi, when you judge by the spray that comes out of a hot can when opening.

The 12psi difference in atmospheric pressure between sea level and 30,000 feet pales into insignificance by comparison.

Still, I don't think I would risk packing one in my suitcase on a long haul flight. Just in case!

But if you look carefully at the sections, it shows the threads were engaging with each other on the tips of the threads, the thin, weak end of the triangle. Larger tapping holes remove that thin end of the triangle on the female thread but leave the thick mid and base section intact to engage and bear the load. I wonder if anyone has ever done any real-world tests on the thread engagement depth vs shear strength? It seems to be stated as fact by Tubal Cain and others in various books.

Seems like the big takeaway from the conclusion of the report is don't put high tensile nuts on lower tensile studs as it distorts the stud threads before it distorts the nut threads and the result is stripped threads on the stud. Who would have thought?

Bit remiss though that the problem had been encountered on assembly of several engines before but they did nothing, said nothing, and just replaced the studs. As usual, the accident results from an accumulation of several errors or faults.

Not in this case, ie checking the alignment of headstock spindle and bed. Leave the tailstock out of it. That is a separate adjustment done after the bed alignment is finalised and the lathe is turning parallel on a simple bar or dumbell held in the chuck only.

After that is finalised you can turn a test piece between centres and adjust the base of the tailstock to move the tailstock centre to get it to cut parallel between centres.

Two different things.

IF all else fails, break the rules and blow the swarf out with compressed air, covering the job with a large heavy rag to catch the flying debris. (And safety glasses on of course.)

Edited By Hopper on 19/03/2023 01:34:02

PS ISTR the design factor is usually four times the working pressure. So that would be 600psi on a 150psi boiler. From distant memory, inititial hydrostatic test was twice working pressure. Thence at 1.5 times working pressure at annual inspections.

I think as someone noted earlier, it looks like one of those stepped pulleys is on back to front, as they usually go opposite way round to each other so one belt fits all steps because the one pulley gets smaller as the other gets bigger, sort of thing.

It looks like some previous owner has changed things around, possibly fitting an extra small pulley in behind the motor pulley and possibly flipping the stepped motor pulley around in the process, unless the centre pulley has been flipped around.

EDIT: If you look on page 21 of the Grizzly manual Martin Connelly posted above, it looks like you motor pulley is on back to front and possibly has had an extra small non-standard pulley fitted behind it. Sort that out and one belt should fit all speeds.

Edited By Hopper on 19/03/2023 01:22:13