A Real Dirty Job
Moderator: Harold_V
Re: A Real Dirty Job
Machining the heart shaped rocker blanks.
It takes hours of tense slow work to produce these from the solid but it has to be done. Again, lots of rotary milling involved which is not my favourite operation.
The first operation after laying out the heart shaped rocker shape on a 3/8" thick HR steel blank is to locate, drill and ream the 4, 3/32" dia. centres needed by the rotary table to produce all of the curved surfaces involved. Three of these centres are on the blank itself while the fourth is external to it. Lots of time needed just to get to this point.
I was certain that Murphy was going to have something to say about this but I was lucky here as nothing happened although I was certain I would destroy either the drill or the miniature carbide reamer in the process. Use a sharp drill, peck drill and clear the chips frequently as this is a deep drilling operation.
Next bandsaw away the extra metal around the heart shaped end of the rocker. I use a very fine tooth bandsaw blade for this operation (32 tpi) as holding and manipulating these small parts by hand is difficult and I find that a coarser tooth blade will grab and snatch at the part. I know this is far from the correct procedure but being able to hold these small parts trumps everything. The part will heat up quickly and the more one pushes, the hotter the part will become so proceed slowly.
Next some "coarse" rotary milling with the setup shown on the rotary table. "Coarse" wasn't really coarse at all, it is just the first operation to have a smooth curve. Again, ensure that all is firmly clamped, use a sharp cutter and take only very, very light conventional milling cuts (I take a 0.002" DOC max. with my equipment and from my experience) and employ good lighting.
After I clamp everything, I yank and pull on the part to know that it is firmly bedded and even then it can move - it has happened. Rotary milling is a tense operation at the best of times. Be especially careful when feeding the cutter into or to a corner and don't try climb milling unless you have absolutely backlash free equipment which no manual (used) mill can achieve and no manual rotary table will have.
It takes hours of tense slow work to produce these from the solid but it has to be done. Again, lots of rotary milling involved which is not my favourite operation.
The first operation after laying out the heart shaped rocker shape on a 3/8" thick HR steel blank is to locate, drill and ream the 4, 3/32" dia. centres needed by the rotary table to produce all of the curved surfaces involved. Three of these centres are on the blank itself while the fourth is external to it. Lots of time needed just to get to this point.
I was certain that Murphy was going to have something to say about this but I was lucky here as nothing happened although I was certain I would destroy either the drill or the miniature carbide reamer in the process. Use a sharp drill, peck drill and clear the chips frequently as this is a deep drilling operation.
Next bandsaw away the extra metal around the heart shaped end of the rocker. I use a very fine tooth bandsaw blade for this operation (32 tpi) as holding and manipulating these small parts by hand is difficult and I find that a coarser tooth blade will grab and snatch at the part. I know this is far from the correct procedure but being able to hold these small parts trumps everything. The part will heat up quickly and the more one pushes, the hotter the part will become so proceed slowly.
Next some "coarse" rotary milling with the setup shown on the rotary table. "Coarse" wasn't really coarse at all, it is just the first operation to have a smooth curve. Again, ensure that all is firmly clamped, use a sharp cutter and take only very, very light conventional milling cuts (I take a 0.002" DOC max. with my equipment and from my experience) and employ good lighting.
After I clamp everything, I yank and pull on the part to know that it is firmly bedded and even then it can move - it has happened. Rotary milling is a tense operation at the best of times. Be especially careful when feeding the cutter into or to a corner and don't try climb milling unless you have absolutely backlash free equipment which no manual (used) mill can achieve and no manual rotary table will have.
Re: A Real Dirty Job
Stage two of the heart shaped rocker machining.
I used a sub plate here for, as as you machine the rocker blanks, they become more and more difficult to hold securely.
I think the remaining photos are self explanatory.
I used a sub plate here for, as as you machine the rocker blanks, they become more and more difficult to hold securely.
I think the remaining photos are self explanatory.
Re: A Real Dirty Job
Stage two milling of a rocker.
After band sawing, the bulk of the remaining metal was removed by gradual plunge milling down to the quarter circle layout line. I used a new sharp 1/2" dia. 4 flute HSS end mill for this purpose.
All of the plunge milling was done on the side closest to me with good lighting so I could see what was going on. This meant that the rocker blank had to be flipped over and made square again after the first side had been plunge milled. The mill's table stops were used to limit the position of the end mill.
After that a final cleanup pass was made on each side of the rocker blank (flipping it over as before) as seen in the photo. Again, use the mill's table stop to limit the travel of the cutter to have only a scraping clean up cut in the corner.
Make certain that everything is firmly bedded as if anything moves that will be the end of the part.
After band sawing, the bulk of the remaining metal was removed by gradual plunge milling down to the quarter circle layout line. I used a new sharp 1/2" dia. 4 flute HSS end mill for this purpose.
All of the plunge milling was done on the side closest to me with good lighting so I could see what was going on. This meant that the rocker blank had to be flipped over and made square again after the first side had been plunge milled. The mill's table stops were used to limit the position of the end mill.
After that a final cleanup pass was made on each side of the rocker blank (flipping it over as before) as seen in the photo. Again, use the mill's table stop to limit the travel of the cutter to have only a scraping clean up cut in the corner.
Make certain that everything is firmly bedded as if anything moves that will be the end of the part.
Re: A Real Dirty Job
The start of stage three rotary milling on a heart shaped rocker to cut the rocker foot to 3/16" thickness so that it will fit down into the rocker base block slot.
For the first time I am employing one of my home gashed and sharpened two flute HSS end mills to do the rotary milling. I am extremely happy with the results.
Getting there wasn't so happy an adventure though. Not the least bit.
Off topic but the last photo shows the setup which I now employ to gash a two flute end mill using a very thin (0.035" thick) commercial cutoff wheel on the bench grinder.
For the first time I am employing one of my home gashed and sharpened two flute HSS end mills to do the rotary milling. I am extremely happy with the results.
Getting there wasn't so happy an adventure though. Not the least bit.
Off topic but the last photo shows the setup which I now employ to gash a two flute end mill using a very thin (0.035" thick) commercial cutoff wheel on the bench grinder.
Re: A Real Dirty Job
Stage three rotary milling which seems endless as I am only taking a 0.005" depth of cut per pass as I don't want anything to move or shift.
But the results are good.
But the results are good.
Re: A Real Dirty Job
The heart shaped rocker assemblies Installed and working.
The were a couple of issues related to the rocker assemblies installation on the engine as I had to slightly file down the trailing truck king pin to give it about a 0.002" clearance so the pin would freely slide down into and mate the trailing truck under the cradle casting as perhaps the original builder had not drilled and reamed the mating holes dead square or perhaps little construction errors had crept in elsewhere - I couldn't really tell. I also had to mill slightly the top surface of the hollow projection boss on the top of 4 wheel trailing truck frame where the king pin was located as now, with the rockers installed, the trailing truck had to slide down under the cradle and fit between all of the other restrictions at a slightly different angle to what it did previously so a little more clearance had to be found.
Other than that everything went together perfectly with the rockers moving as they should when the back of the engine and/or the trailing truck sways sideways.
All in all, I am very happy with the results.
The were a couple of issues related to the rocker assemblies installation on the engine as I had to slightly file down the trailing truck king pin to give it about a 0.002" clearance so the pin would freely slide down into and mate the trailing truck under the cradle casting as perhaps the original builder had not drilled and reamed the mating holes dead square or perhaps little construction errors had crept in elsewhere - I couldn't really tell. I also had to mill slightly the top surface of the hollow projection boss on the top of 4 wheel trailing truck frame where the king pin was located as now, with the rockers installed, the trailing truck had to slide down under the cradle and fit between all of the other restrictions at a slightly different angle to what it did previously so a little more clearance had to be found.
Other than that everything went together perfectly with the rockers moving as they should when the back of the engine and/or the trailing truck sways sideways.
All in all, I am very happy with the results.
Re: A Real Dirty Job
Carrying on to make two relatively simple parts, the engine/tender drawbar and the safety bar. One is just a straight dog bone but the other has a 5/16" offset in it which makes things interesting.
I probably have by now a total of seven different types of sheet metal, tube, pipe and mild steel strip benders but this job couldn't be handled by any of them as the most heavy piece of strip steel which was necessary to bend to date was a piece of CR steel 1/8" thick and 1/2" wide having multiple bends in it and that was pushing things.
The offset bar blank was 3/16" thick by 3/4" wide so it was over to Richard's shop as he has a 12 ton hydraulic press. It did the job but it was brutal. He suggested making a very simple press block to simplify the offset bending (which is seen in the third photo). Ignore the holes in the block as this was just a piece of heavy scrap.
After bending, I did put the offset blank in the bench vise and gave the blank a few whacks with a soft faced hammer and then checked it against a known straight edge to fine tune the offset and to ensure the two bent end sections were parallel.
When drilling the offset drawbar, include a spacer support piece (just barely seen in the last photo) behind the drilled hole if any part of the offset is not clamped firmly between the vise jaws as the part is now quite springy.
I probably have by now a total of seven different types of sheet metal, tube, pipe and mild steel strip benders but this job couldn't be handled by any of them as the most heavy piece of strip steel which was necessary to bend to date was a piece of CR steel 1/8" thick and 1/2" wide having multiple bends in it and that was pushing things.
The offset bar blank was 3/16" thick by 3/4" wide so it was over to Richard's shop as he has a 12 ton hydraulic press. It did the job but it was brutal. He suggested making a very simple press block to simplify the offset bending (which is seen in the third photo). Ignore the holes in the block as this was just a piece of heavy scrap.
After bending, I did put the offset blank in the bench vise and gave the blank a few whacks with a soft faced hammer and then checked it against a known straight edge to fine tune the offset and to ensure the two bent end sections were parallel.
When drilling the offset drawbar, include a spacer support piece (just barely seen in the last photo) behind the drilled hole if any part of the offset is not clamped firmly between the vise jaws as the part is now quite springy.
Re: A Real Dirty Job
Have some rotary table work scheduled for the near future. Mostly small parts. What size of rotary table are you using for the parts being made on your small milling machine?
Re: A Real Dirty Job
Most rotary table work done here to date is on the 6" dia. News (pre Yuasa) horizontal rotary table. It is fine for 3/4 " scale locomotives. But like everything, the add-ons or extra's made over the years make it much more useful. Probably there are 15 centre plugs of different diameters made for different size end rounding jobs as well as custom made clamps, spacers, chuck adaptors, etc.
Like Richard, I also have a 10" horizontal/vertical Vertex rotary table. Richard has his permanently fixed to the table of the Bridgeport but mine sits on the floor. I cannot even lift it now without help. It also has a custom made chuck adaptor which is very useful. If you are building 1-1/2" scale locomotives. These things get very heavy very quickly as the size increases.
Like Richard, I also have a 10" horizontal/vertical Vertex rotary table. Richard has his permanently fixed to the table of the Bridgeport but mine sits on the floor. I cannot even lift it now without help. It also has a custom made chuck adaptor which is very useful. If you are building 1-1/2" scale locomotives. These things get very heavy very quickly as the size increases.