Member postings for JasonB

While up at the head end of the engine I thought I would get the last couple of small castings out the way. Starting with the silencer (muffler) halves these were held in soft jaws to turn the overall diameter and the cast surface was cleaned up a bit at the same time.



The halves could now be held the other way around and the flange machined to thickness, a cavity turned with a boring bar and in the case of the half that screws to the exhaust pipe that was drilled and tapped 1/8" BSP.



Most builders will probably opt to turn three spacers to fit between the halves but I left the flange on one half thicker so I could mill most of the material away and just leave three integral spacers.



The other casting that can be dealt with now is the Mk2 carb. I started by holding it in the 4-jaw and got the needle boss to run as true as possible then faced the bottom and the stub that can be drilled part way and tapped M8 x 1 before continuing the hole right through and tapping M4 x 0.5 for the needle.



Holding by the spigot in a square collet block I could index the casting about to drill the long inlet hole and also drill and tap for the pipe that joins carb to head.



The last thing to do was spot face the four mounting holes with am 8mm milling cutter and then drill through 3mm for the screws that will hold the carb to the fuel tank top. Make a note of where the hole positions end up so they can be used when tapping the tank.



A quick group shot of the exhaust parts and carb.

The ARC ones are also 18tpi.

Why not measure the overall length and then unscrew the arbor 1 full turn and take another measurement, difference between the two will be the pitch of the thread.

The inverter drive of the WM250's AC motor should not have the issues that some people may have had with DC brushed or brushless motors and their control boards found on your typical "Mini-lathe"

What sort of things are you expecting to machine? The loss of grunt at low speeds really only comes into play when you have to run a bit slower to keep the cutting speed reasonable on larger diameter work.

The average model engine be that loco (wheels) traction engine (gears & Flywheel) and stationary engine (Flywheel) don't have that many large diameter parts when compared to the multitude of smaller items so it is possible to live with the loss on the odd occasion when it may actually be noticed. Carbide can go a long way to reducing the need to run slowly as the spindle can be run at about 3 times the speed that HSS can

I had a good quality geared head Emco before I got my Warco 280 and would go with teh Warco's variable speed which has been fine in over 10 years with a lot of use.

Better still use the side of the cutter not the end then if there were any burr it would just be at one end of the long cut.

I'd be tempted to try a carbide cutter to mill the edges and not bother with initial ginding. Finish the edges with a diamond stone.

As your pulley is between two bearings I'd go with the round urathane or green round belts that can easily be joined at home rather than having to cut less grippy O rings

That is why I show sketching and then extruding equally each side of the plane, that way you don't have to place a new plane or join two parts together

The later part of yesterdays first video "half Crosshead" shows how to stick two halves together with basic constraints.

I have also shown that if you mirror the features of one of your "half parts" you will get a solid that you can cut the cavity from that just so happens to have a plane down the middle which is ideally placed to sketch the cavity shape onto..

Suggest you watch the last couple of days videos again, slow them down and watch what is being done then try it the way shown.

Edited By JasonB on 10/08/2023 07:14:54

Existing gears would give 24tpi which is an imperial pitch and not too far off something like 1 1/8" BSB @ 26tpi or M28 x 1

 Put the 75T on the leadscrew and use the others as idlers

if there is a hole through the adaptor that may dictate pitch if the wall is thin

Edited By JasonB on 09/08/2023 19:33:32

5/16 x 32 in brass should not be a problem under power, if it is slipping then die is blunt of chuck not done up/worn

Hard brass should not really need backing off as it produces small chips anyway

The problem I find with a lot of ball turners, even Bernard's one is there is a lot of the tool rotating beyond the radius needed for the ball so you end up having to form the ball a long way from the chuck/collet.

The ones that use a boring head type arrangement or even Andrews copy attachment can generally get in a lot closer which saves chatter or having to have a thick stick on the lollypop shape being formed.

The problem with Tracy is they don't sell specific makes so you might get something nice from Tap & Die Co or you could just get Apex which is what RDG mostly sell

And there is a message waiting for you from me.

I've had a couple of poor ME dies from RDG in the past, don't buy from them now.

Also checK if he is putting an imperial OD die into a metric holder

Why not bring him into the modern world with Metric Fine.

Suggest he dumps the oversize 2BA fixings and drops down to at least 3BA with 4BA heads or M4 with small hex again as they are oversize.

Watch which drawings and errata sheet he uses some have the wrong length conrod ctrs and the bearing blocks above engine ctr height of 5/8". Piston rod assembly also wrong on the errata sheets

Edited By JasonB on 09/08/2023 09:52:18

I showed how to do the internal cavity in my second video yesterday by cutting it out of the single solid block, here it is again

Video of how you could do if it initially modelling one half of the cross head firstly by simply mirroring the features down the left side which keeps it as a single "part" and secondly how you could have gone about the assembly using the flip tool to get the two halves face to face and then using constraints to line the two halves up and lastly using the "show ref geometry" to do the same thing. Suggest you try these with the part files you already have.

You will also see that creating the rebate that forms the half guide bar groove is just a simple random rectangle that is then dimensioned for depth and width before being cut.

Why did you still do it as a group of assembled parts I wonder if it is worth answering soemtimes.

If you want to do it in two halves than sketch and extrude the half and then simply mirror that extrusion and it will become one part.

There is a drop down arrow below the rectangle/polygon tool that allows you to construct one from it's centre point out which will give it symmetry and the two axis of the 2D sketch

Regarding inside out an backwards, Again just a sin real life mirror reverses things so would have been a way to do it in the assembly.

Flip tool that I have mentioned several time sin the last couple of weeks will solve the back to face and change to face to face

180deg out of position can again as I have said be done by right clicking the part and selecting "show reference geometry" then constraining one of the assemblies axis to one of the parts axis

failing all that if the two gudgeon pin holes were constrained concentrically you could drag one half round with a mouse and then set its final exact position with simple coincedent constraint.

Edited By JasonB on 09/08/2023 07:14:20

Is the shiplap already fixed to the frame? You don't mention a breatheable membrane for the walls so I assume it is. Best option will be to take the cladding off and then fit a breathable membrane then refit the shiplap. That way water droplets then ge behind the shiplap won't get any further but moisture vapour can still get out.

Polly will do though not as insulating as PU, vapour barrier over that (polythene sheet) then your boarding. This barrier will stop air bourn moisture from breathing or burning propane from entering the wall construction and condensing within the structure.

As said fibreglass can act like a sponge so poly or PU would be better, either way don't fully fill your rafters/studs, leave an air space between insulation and outer surface. 

This is a job I went to put right after the builders got their vapour barriers wrong and other failures, nice £100K job for me. This is fibreglass pulled out through a downlighter hole.

Edited By JasonB on 09/08/2023 07:02:18

Compared to what I get yours are at least 10 times worse. On a piece of ground HSS I'm reading 0.0005" which is approx 0.013mm

One other thing to consider is that by putting a collet block into the chuck you are moving any workpiece further from the bearings this may result in chatter when taking a large cut or in mind of your other thread when parting off. Your chuck jaws also look quite worn so there is a good chance of them being "bell mouthed" where the gripping surface becomes worn towards the end of the jaws reducing their grip

I suppose the cylinder head is the next logical casting to get out the way. After a quick clean up I made a start by holding it in the 4-jaw slipping a parallel under each of the stud bosses in turn to make sure the outer cast surface was reasonably true across the lathe's axis and than machined the underside of the head so I had a good flat surface to work with. I also took the smallest of cuts off the OD to get the head round but not far enough up the sides to remove the draft angle.



Next the head was clamped to the mill table on a piece of MDF, I held a straight edge against the two valve bosses and eyed that up along the X-axis so the valves would sit horizontally. Then the three ends of the "Tee" where milled flat, the inlet and exhaust ones just want the minimum taking off so you get as much thread depth as possible for the pipes but the one for the rocker bracket should be machined to dimension. The clamps will need moving about to allow access to all three faces. The tops of the valve bosses can also be levelled off at this stage.

The bosses for the four head studs are not equally spaced around the head so I spend a bit of time getting the best centre for each boss and noting the DRO readings before spot facing and drilling 4mm. Ignore the fact they are tapped in the photo, I was going to hold the head one way for the next op but did it another.



I like to do the valve guide, valve cavity and valve seat on the lathe rather than use a CSK bit in the mill which can chatter and I've not yet had to make a valve seat cutting tool for any of my engines doing the seats with the topslide set over. So I made some simple standoffs from tube and screwed the head to a scrap piece of square aluminium plate which could then be held in the 4-jaw to position each valve hole in turn.



The square piece of plate also made it easy to index the head around to drill and tap the inlet and exhaust connections. The M3 tapped hole for the rocker could also be done at this stage though I did mine later as I wanted to tweak the rocker post casting to suit having the exhaust valve on the far side



Still holding you the plate the spark plug hole was drilled, spot faced and then tapped M10 x 1 for a CM-6 plug



When I did get round to doing the holes for the rocker post this is how I set it up to do the tapped hole using two drill bit sin the valve holes to set the work vertical and then using the side of a drill bit to run the edge finder against.



The two drill bits were used again for the 3mm clearance hole being pressed against a table tee slot to line up the head and run the edge finder against then the hole was drilled and the opposite side countersunk.



lastly the carefully noted stud hole positions can be used to locate the holes in the cylinder so they can be drilled and tapped making sure not to go too deep and break into the water space. You could spot the positions from the head but I seldom use that method since fitting the DRO.