Hello and a part-built blowfly

[Jim]

Great to see your new mill doing the sort of jobs and to the standards you want it to. Having a mill really opens up a hold new dimension in the work you can do.
Great to see Lisa. 👍

Still hot here.

Jim.

[Lisa]

Dec 5, 2016 11:40:15 GMT Jim said:

Great to see your new mill doing the sort of jobs and to the standards you want it to. Having a mill really opens up a hold new dimension in the work you can do.
Great to see Lisa. 👍

Still hot here.

Jim.

It's certainly a nice little machine Jim, I saw a few complaints online from people about its rigidity, but I haven't had any issues and suspect they were just trying to take too big a cut for the size of the machine. I'm more than happy to take my time with small (0.25mm/10thou) cuts, it'll do bigger easily, but I don't see the point; it's still quicker than doing it on the Taig.

Still hot here too, I'd half melted into a puddle when I stopped for the night.

[johnthepump]

Still hot here too, I'd half melted into a puddle when I stopped for the night.
[/quote]


Hi Lisa,
I walked into my workshop at 10.30 this morning and the temperature was only 5.5 deg C, as the air temperature outside was a lot higher I have left the door open for a while.
John.

[Lisa]

A bit of rain lurking about most of the day made the it not too intolerable in the workshop, so I finished milling out the slidebar slot on the left crosshead (handed solely based on my reference corner/edges).

The slot is actually undersize by a thou; I'll draw file the slide bar for final fit.
Not entirely sure what order I'm going to do the next operations in, I think I'll drill and tap for the cover, use that to transfer the hole for the connecting rod pin, then bring the other crosshead to the same state, do the piston rod hole on each, and finally the connecting rod clearance which there are several ways for machining.

[Roger]

That's a really good surface finish Lisa, what a cracking little machine that's turned out to be.

[Lisa]

Dec 7, 2016 10:17:49 GMT Roger said:

That's a really good surface finish Lisa, what a cracking little machine that's turned out to be.

I think the secret is light cuts and patience.

[Roger]

Dec 7, 2016 11:07:28 GMT Lisa said:

Dec 7, 2016 10:17:49 GMT Roger said:

That's a really good surface finish Lisa, what a cracking little machine that's turned out to be.

I think the secret is light cuts and patience.

Agreed, if the cutter chatters you'll never get a good finish. There's no rush, it's much better to take your time and make a good job of it first time. Sometimes it's quicker to take lots of small cuts at a higher speed than it is to slog away with a deep cut anyway. Having a good sense for what feels and sounds right is just as important. If you can tell it's not happy and adjust things to make it better, you can make a huge difference in how it machines. It seems like you have the measure of your machine from the results you're getting.

[joanlluch]

Dec 7, 2016 12:28:32 GMT Roger said:

Dec 7, 2016 11:07:28 GMT Lisa said:

I think the secret is light cuts and patience.

Agreed, if the cutter chatters you'll never get a good finish. There's no rush, it's much better to take your time and make a good job of it first time. Sometimes it's quicker to take lots of small cuts at a higher speed than it is to slog away with a deep cut anyway. Having a good sense for what feels and sounds right is just as important. If you can tell it's not happy and adjust things to make it better, you can make a huge difference in how it machines. It seems like you have the measure of your machine from the results you're getting.

Hi Roger. You are of course right, but one key aspect here is "patience". If you are on CNC that's easier to have because after all, all you need to do is to wait. If you are milling manually, patience is a lot tougher to have.

[Lisa]

Letting the machine do it for you (CNC, or other mechanical feed) requiring less patience reminds me of about 20 years or so ago, when the (horizontal) bandsaw's blades were constantly snapping. We eventually discovered that my brother would lean on the machine to try to make it cut faster.

Speaking of breaking things, I broke an M3 tap in the crosshead today; fortunately there was enough sticking out that I could unscrew it with some pliers. Still a nuisance though.
But I did get one and a half holes tapped at least:


At this point I set about doing something different, so with the bench grinder back in working order (it was just the capacitor, so thanks again Roger) I set about grinding up a hooked boring bar:

Mostly done on the bench grinder, but the tight corner was done with the not-a-Dremel and a little smoothing with a stone.
This is needed for cutting internal o-ring pockets; it'll probably grow in length over time, but is fine as-is for the first job it'll do.

[Roger]

Hi Lisa,
Good progress, and I'm pleased the grinder was cheap to fix. That's a neat tool you've ground there.

I broke the tip off a centre drill in one of the flanged plates yesterday, with no chance of getting it out. A few minutes later it was gone, drilled out with a carbide PCB drill using an ultra fine feed and fairly high spindle speed. It's worth investing in a few of these for this sort of situation, they cost about £1 each from eBay.

[Lisa]

I also found this series of images last night, someone building a Blowfly in 7¼" gauge; essentially the same dimensions everywhere, except for longer axles and spacing the frames further apart:
www.bsme.com.au/blowflypage.htm

[Lisa]

So I drilled all the holes in the left crosshead, and have made a start on milling out the slidebar slot on the right crosshead.

Then clamped things together again, to see how they look:

The clearance for the connecting rod I think I'll bore out on the lathe.

Meanwhile I went to do a little job on the new lathe, just a quick face-and-drill of some square stock, and came across a problem:

Not entirely sure it shows, but the tail stock is off-centre by quite a bit. So I'll have to sort that out. I'm glad it is so far out though, had it been close to centre I may have not noticed till I ended up with a tapered axle or something.
So there's a lesson in not trusting factory settings.

Dad came up with a unique method of centring the the tailstock, by trying to feed it a sandwich. It didn't seem to help much though.

[Roger]

Good progress Lisa, and well spotted with the tailstock. I find that it doesn't matter how good you get the alignment at one length, it will always be slightly off at another. That's miles out though. One way to get it really close is to lock it up near the chuck and attach the clock to the chuck in such a way that you can turn the chuck and probe the inside of the taper on the tailstock. That will also show you how good the height is.
That would get you close for when you need to set it up more accurately on something you're turning.

Now that's lateral thinking, I'd never have thought of using a sandwich... you must be very patient.

[Deleted]

Hi Lisa

Just an observation re the tailstock, I had a look but couldn't see how you've held the square bar in the chuck, I'm assuming that it's via a 4 jaw independent chuck. My point is are you sure that the bar is running true first before looking at the tailstock as being at fault, it does look an awful way out to be that alone? I'm sure that I've got it wrong and you've already checked the bar is running true but thought I'd mention it just in case....

Kind regards

Pete

[Jim]

In addition to Roger and Pete's valuable comments your card trick of balancing a card between the point of a centre in the head stock and one in the tail stock should give you a pretty clear idea where the problem is. Does your tail stock have provision for lateral adjustment?

Cheers

Jim.

[Lisa]

Roger, thanks for the tip.
Pete, it is in the 4-jaw, but isn't centred on one axis. However, the facing cut was taken with it mounted as it is, and shows where the centre of the work is compared to the tip of the dead centre; as such attempting to drill would most likely the shear the tip off a centre drill.
Jim, I'll need to scrape some paint off to get at the screws, but there is adjustment there.

[Lisa]

After about an hour of fiddling, I got the tailstock as close to centre as I figured possible (about +/- quarter of a thou), which is more accurate than the lathe itself claims to be (1 thou). At this point I decided that anything more was just me being silly, so stopped there.

Thus I was able to drill a hole, which let me finish this:


Which lets me do this:

So I can now mount the dti in the tool holder at centre-height (though the angle of the pic' makes it look low), which will help in centring things in the 4-jaw.
While the lathe spindle has a 20mm bore, the 3-jaw chuck only has a 16mm bore; thus to pass 20mm material through the headstock one needs to use the 4-jaw, which has a 20mm bore. So this simple holder will likely see a bit of use.

I also did end up getting some indexable tip tooling for the sake of trying it out, as you can see in the last pic'. I think I prefer the diamond holder though, it just has a better 'feel' to it for some reason.

[Lisa]

New M3 tap arrived in the mail today, so I finished tapping the cover retaining holes on the left crosshead. I then draw filed the slide bar, with regular checks, to get a nice sliding fit between it and the crosshead.


The right crosshead is still being milled, as weather permits. Once they're both to this stage I'll machine out the connecting rod clearance in the lathe. Also the oil holes still need to be drilled.

Also in the mail today was the threading angle gauge, which will no doubt be useful. The only one I could find online with BA included was from the UK, hence it took a little longer to get here; but I wasn't in a hurry for it, and I think getting one with all the common thread angles was worth the wait.

[Lisa]

Quite a pleasant day here today, so after drilling the right crosshead, I spent a little while sitting out on the patio with dad; crosshead in one hand, tap holder in the other, tapping the holes for the cover bolts.
Thus both crossheads are now to the same state, with the cover plates fitted and the slidebars filed for a nice fit.

Most pleased that I didn't end up with 2 of the same hand.
I noticed that I don't have the material for the connecting rod pin, nor the tapping drill for the piston rod hole, so those will have to wait; probably till the new year.

Currently working on a little adapter / bit of packing so I can use 1/4" tools in the new lathe; basically a bit of 10mm square with a slot milled in it to put the smaller tool in the right spot. Only half done so far. Dad was helping out by brushing the swarf away whenever I stopped the mill; he's had a good day today so far.
Then I've got part of the main steam pipe made, so I'll finish that up next.

Then I think I'll make a start on the cylinders, might do the valve chests before the cylinder proper, we'll see.
Slightly annoying, I discovered that my 4" milling vice is more like '4" less the thickness of the jaws' or to put it another way 'about 3mm less then the length of the cylinders.' Not really that big of a deal, just means instead of gripping by the end faces I'll have to grip by the sides. But if I give a quick cut along the bottom face of the cylinder (90° to the port face) where the drain cock mountings are it'll give me a straight flat edge to hold against the fixed jaw of the vice, which sounds appealing.

[Jim]

You've done a great job with the cross heads Lisa, they look great. Nice too that your dad has had a good day and obviously enjoys time with you and 'helping' where he can.
For those of us following your thread I must say that the love you have for your dad and the care you show him is really heart warming, may you both have a wonderful Christmas and a very productive New Year.

Jim 😊👍🍾🎂