Hello and a part-built blowfly

[Lisa]

Well the general rule has always been to "err to slow side" meaning that if the tables say 500rpm, and the pulleys give the choice between 400 and 600, then opt for 400. The tables have always worked well, so I've stuck with using them.

Meanwhile, today I got into machining the crossheads to size; one machined to height now, the second is mounted in the chuck ready to go.


This also shows up my horrid lack of skill with a hacksaw; but it'll get machined off, so doesn't really matter. On the plus side, I did manage to cut one end fairly square.
I'd forgotten how much of a mess there is with cast iron, had to stop every other cut to brush the dust off, and my hands were black in no time.

[Lisa]

A couple of bolts arrived in the mail today, these were the missing bits needed to use the mill; specifically to clamp the vice to the milling table.

Thus a bit of fiddling to get the vice square and I did some work on one of the crossheads:

I had to take 1.5mm off to get below a blow hole in the casting, but the mill handled itself nicely with .25mm (10 thou) cuts of about 1/3 the cutter width: I tried a few depths of cut, and it seemed happiest at that.
I think the gibs will need tightening though, as while it all went well it just felt a little loose to me. But this is a nice little(ish) job to get a feel for the machine with in any case.
The axlebox stick I'm using for the crossheads is quite thick, so there's a fair bit to come off the other side when I flip it over.

[Jim]

Good to hear your new mill is working just as you wanted it to. That looks like a very nice sturdy milling vice too.

Jim

[Lisa]

Thanks Jim, I think the vice weighs more than my lathe!

[Lisa]

It occurred to me this arvo', while milling away at the crossheads, that the sensible way to remove this much material (about 10mm) would be to cut it off with a slitting saw. At this point I realised I've never actually used a slitting saw as in the past I've always just cut with the bandsaw (which I don't have); I also don't have any blades (I bought an arbour but no blades).

So, any advice for using a slitting saw on cast iron? And what to buy for that matter in terms of number of teeth etc.

[Jim]

Hi Lisa,
My first attempt at using a slitting saw led me to ruining the saw. When I asked a close friend who worked as a volunteer fitter and turner at the War Memorial's Mitchell Warehouse why this was his immediate comment was, 'Because you ran it too fast, they should run at the slowest speed you have.'
Since then I've followed his advice and not had any further problems and the replacement saw blade is still going strongly.

Jim.

[Roger]

Hi Lisa,
Personally I wouldn't use a slitting saw on such a light machine for that kind of thing. You'd be better off rolling up your sleeves and using a hacksaw in my opinion.
Slitting saws are troublesome things that can catch you out and jam unexpectedly. You also need a really big one if you're to reach any distance, and often you can't get close because of the mandrel. I do use them for slitting parts and then I use the slowest of spindle speeds and feeds and plenty of cutting oil. The mandrel types I make don't use a keyway so that the cutter will slip if it all gets too much. Large thin ones will sometimes wander too.
They're very useful things when used for appropriate jobs, but I don't think this is one of them.

[Lisa]

Roger, my main issue with using a hacksaw is that I'm utterly hopeless at cutting squarely with hand tools; though sometimes I fluke it. Thus why I'm looking into mechanical options.

The mandrel I have doesn't have a keyway; the idea of locking the blade on with a key was not at all appealing.

I found this video about slitting saws that was quite informative.
www.youtube.com/watch?v=1SudBYa-8VA

Other than using a slitting saw, my next idea was to come in fairly deep from the side, and rip it down that way... the saw just seemed less wasteful.

[peteh]

Could try cutting a couple of mm away from face and then milling the last bit to square it up

[Roger]

Nov 22, 2016 13:01:20 GMT Lisa said:

Roger, my main issue with using a hacksaw is that I'm utterly hopeless at cutting squarely with hand tools; though sometimes I fluke it. Thus why I'm looking into mechanical options.

The mandrel I have doesn't have a keyway; the idea of locking the blade on with a key was not at all appealing.

I found this video about slitting saws that was quite informative.
www.youtube.com/watch?v=1SudBYa-8VA

Other than using a slitting saw, my next idea was to come in fairly deep from the side, and rip it down that way... the saw just seemed less wasteful.

If in doubt, cheat. Set it up in the vice for sawing with a couple of pieces of steel bar clamped to it so you can't stray over the line. If you put those about 1mm clear of the line, you can saw away without worrying. Just keep looking at the cut often and make corrections. Who knows, by the time you finish, you might have surprised yourself at how you've improved!

[builder01]

If your slitting saw breaks, in a piece of cast iron, it may be possible that a small part of the saw will now be imbedded in the cast iron. It will be pretty much impossible to get out. If it is a casting, it may become scrap now. It is much easier to hack saw close, and then machine to finished size. before I got my band saw, I did a lot of hack sawing of everything from aluminum to mild steel. Then, machine to finished size.

[andyhigham]

I usually mill down one side then move the slide over and mill back up the other side. It saves a lot of handle winding when not cutting

[Lisa]

Tolerably not-as-hot this afternoon thanks to a gathering storm, so I spent a couple of hours in the workshop.

Thus I set about ignoring the crossheads while I decide on the best course of action there.
I may face them down to width in the new (bigger) lathe, otherwise hacksaw it is; and it was too hot for hacksawing today anyway.

Instead, I made these:

Part of the main steam pipe, these screw into the valve chest covers, while the smooth end fits into an o-ring seal. Kind of annoyed at the undercut needed on the threaded end, as the die I have has quite a bit of taper on it, at both sides. But there's still several good turns of thread there, so it should be fine.

[Jim]

The 2 parts look great Lisa, did you make them from hex bar or did you mill them on your new mill using a hex jig?

I've had the same problem with dies being tapered so preventing the part
screwing home properly. I guess you've done the same and made up a
narrow parting off tool to create the under cut or relief. I must say it comes in handy at times.

Jim

[Lisa]

Jim, it was made from hex bar, and the undercut actually took two passes with the parting tool; it's about 3/32" wide.
Most of the dies I have have a tapered side and a flush side; so one can start the thread with the tapered side, then flip the die around to bring the thread in close to any shoulder.
There was a bit of a surprise when I went to turn the die around this time!

[Roger]

Hi Lisa,
Does the new lathe have screw cutting ability? If so, why not screw cut any threads where you need to get up really close to a face? I usually undercut where the thread meets the face for the length of one pitch so I can finish in fresh air. It's always tricky to get theads that go all the way in, but it's usually easier to get really close if you screw cut them. You can grind a tool with the Vee to the left of the HSS bit so you can get right up close. I use carbide threading inserts, and occasionally grind the side of those off to achieve the same effect.

[Lisa]

Roger,

I don't have any tools for the new lathe yet, but they should turn up this week. I've bought the usual Diamond Tool Holder for it, a parting holder, and some 10mm HSS blanks which will likely come in useful. I've been tempted to get some insert holders for it as well, but besides boring I don't think it'd be necessary.

It does have screw cutting though (and I bought a thread dial indicator attachment), so I've considered redoing the parts on it (once I've got tools for it), but there are several full turns of thread on there, so I think they'll be fine. We'll see.

I foresee much screw cutting happening in the future though; particularly where concentricity matters.

[Roger]

Hi Lisa,
You might consider getting some smaller section HSS for screw cutting tools, it saves a lot of grinding. 1/4" square is pretty rigid for that sore of thing, but for small fittings you could get away with something even smaller. I don't know if you have one of those little angle gauges for threads, but it's worth getting one if you don't.

[Lisa]

Roger, that's actually the first time I've seen a gauge quite like that; it looks exceptionally useful.

A threading tool for the diamond holder is quite easy to make, the tool just gets put in a different spot on the grinding jig. But in any case I've got some ¼" HSS blanks as that's what the Taig uses for tooling (also what the diamond holder for the new lathe uses, I think).

[Roger]

Nov 27, 2016 10:22:54 GMT Lisa said:

Roger, that's actually the first time I've seen a gauge quite like that; it looks exceptionally useful.

A threading tool for the diamond holder is quite easy to make, the tool just gets put in a different spot on the grinding jig. But in any case I've got some ¼" HSS blanks as that's what the Taig uses for tooling (also what the diamond holder for the new lathe uses, I think).

Hi Lisa,
Those gauges are really useful for holding up to the light an checking you've got the angle right. Then you can use one edge against the work and the other engaged with the tool so you can set the tool up square to the work, even if it's not ground dead true to the stock. At least that purchase wouldn't put such a big dent in the credit card as your last one!