Scott vacuum engine (flame gulper)

[crueby]

Looks like there are set screws on the flywheel and crank, visible on the left side of the completed ones hubs.

[Sanjay F]

Well that's me for the day - I ended by making a start on the hopper; its good to see all 6 sides have their own 'unique' characteristics

This could take a while to get things square(ish)........

[Sanjay F]

The critical sides are the base and where the cylinder is fixed so for the moment I think I'm done - luck more than judgement the top is level in both x and y axis; great given how many 'anomalies' the casting has 

Right now onto the cylinder and a hefty bit of stock has been provided with the kit

[Sanjay F]

Boring bar question

My preferred boring bar (top of photo) is not long enough to get all the way through the cylinder.

Are any of the others in the picture usable; the second one down is nice and rigid but not sure about using that type of tip for boring?

The others don't look like there up to the job?

[internal_fire]

the second one down is nice and rigid but not sure about using that type of tip for boring?

The others don't look like there up to the job?

It looks like the tip on the second boring bar is designed for internal slotting. That sort of insert is not typically good for cutting in its sideways direction.

Any of the other bars are of the same type that was used for many years, in the age before carbide insert tooling.

If they are sharp, correctly positioned, and suitably sized, they can work.

Gene

[Sanjay F]

Thanks Gene - the others look quite new and were in a box of tooling that someone gave me, maybe I'll give it a try.

Machined the stock to size, then used the trusty old Hexacut powersaw to approx cut to length. Take a look at the piece which I want to keep and the offcut - looks like there was some sort of deformity in the metal and even when I've machined the flange to width is still there  - annoying! 

I think I'm still going to proceed with the workpiece as the fracture is on the outer edge and I can make sure its no where near one of the fixing holes; worse case a bit of JB Weld?

[Sanjay F]

Hmm all my large drill bits are 2MT and have a tang and won’t fit the tail stock, so I’m going to use this boring bar to open up the bore large enough to take a 16mm boring bar I’ve just bought 2nd hand from eBay; hope it works 

[uuu]

You might find the blue coloured ones in your picture work well on cast iron.  They look like they have carbide tips.

Wilf

[Sanjay F]

I tried using the blue ones and the bottom of them was scraping the cylinder so tried grinding the underside away but it still had issues.....the black ones look better but wouldn't fit the hole I had 

so in the end did this, which I know is not right as its not rigid enough, but took very light cuts forward and then reversed back out using the power feed and got to just over 18mm diameter. Managed to get the same diameter front and back and should the 16mm boring bar I've got coming should easily fit..... 

[Jasonb]

Your typical 16mm indexable boring bar has a minimum diameter cut of 20mm.

Another option is a bit of steel bar, cross drill near the end for an old ctr drill or milling cutter shank, tap a hole in the end for a locking screw to grip said cutting tool and bore away with that once the tool bit has been ground to shape

[Sanjay F]

Hmmm, I have no idea how to grind a tool bit, however, I reckon with some more patience I could bore out another 4mm. The final bore diameter is 1.313" or 33mm so still plenty of metal cut even once the 16mm boring bar is here.

[Jasonb]

It's a pity you did the OD first and cut it off from the bar as that limits your options for holding. You will also have to watch out when holding it by the OD for boring that you don't get distortion as the wall thickness comes down which when removed from the chuck can cause a trilobed hole to form

[Charles Lamont]

Hmmm, I have no idea how to grind a tool bit, ...

As mainly an HSS tool user, I would say that is the single most important part of the skill of using a lathe.

[Sanjay F]

It's a pity you did the OD first and cut it off from the bar as that limits your options for holding. You will also have to watch out when holding it by the OD for boring that you don't get distortion as the wall thickness comes down which when removed from the chuck can cause a trilobed hole to form

Noted - I'll have to remember that for future and ease the chuck jaws off now - I've got the boring bar and you were bang on 20mm to get the bar into the hole

[Sanjay F]

The previous builder stated this, is 0.025" at lot, seems lot, it is a new tip though?

Anyway, back to cutting out this hole. I rough cut out at 0.025" cuts for the first few, until I got within say 15 thou of required hole size. Then remove the material until it leaves about 0,002" to be removed. The closer you get to size, the finer and slower the feed you use.
I do the final cut, measure that it is either spot on or very close to size, then using a very fine feed, take another half dozen cuts with no more cut on at all, just using the same setting as the final one used to get down to size. This is to take off any material that wasn't cut because of the tool flexing as it went down the bore.