Stuart S50 (Want to cry)

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I am feeling particularly dim-witted this morning, Jason

Could you please explain that advice, in words or in pictures.
... I don’t have much experience of machining of iron castings.

Thanks

MichaelG.

Thanks guys.some really good feedback. I will hold off and wait to see what the next cover is like.

The mill I have is a Boxford VM30 with 30International taper (30int takes up a lot of throat space). Looking to make some low profile 30Int adaptors at some point. because if you put in a co-axial indicator or drilling chuck it will only fit if knee is all the way down and the job is low on the table. Even trying to put a spring loaded tap follower in can be a challenge.

Morning Michael, sorry for not getting back to you sooner but I had to pop out to site this morning, hopefully in the mean time you have been able to get a couple more cups of coffee down you to get the brain a bit more active.

1. I'll assume you are familiar with screw cutting

2. If the casting is hard then a HSS flycutter bit will fare no better than the OP's HSS milling cutter probably worse but carbide will hopefully cut the harder material.

3. A left handed holder for the insert or even a left handed brazed carbide tool bit is needed as it presents the insert correctly to the work so that the flycutter can be rotated in the usual direction and keep the edge of the tip more or less tangental to the cut as a line drawn from the top of the tip passes through the ctr of rotation

If you use a right handed holder there are two problems, firstly the tip will not be tangental so you get a negative rake and secondly the cutting force is going against the ends of the grub screws not the solid side of the tool slot.

Hope that has cleared things up for you.

For the other Michael this is a 4 flute cutter that has been given a second life by grinding arross the end as I suggested earlier, in this case I also rounded the leading flute to give me an internal fillet on teh part being machined. Main thin is that slop goes down to a cutting edge, you will have to pick the right one on your ripper that has the lowest full diameter cut.

Edited By JasonB on 13/12/2019 10:30:13

Thanks for that, Jason

(1) and (2) are given

(3) makes sense now

My own [self made] flycuting head looks nothing like yours, so I was struggling to understand the importance of using the ‘left-handed holder’ ...

MichaelG.

Thanks JasonB will certainly do that this evening. Saves throwing the cutter away.

I can certainly vouch for using carbide on chilled cast iron. When I used the flycutter on the large lump of iron when making the new cross slide for the mini lathe I came across a chilled area in the centre of the block. It made short work of the HSS tool. so I changed to a left hand brazed carbide tipped tool. Even that made hard work of it to start with but I pressed on and got through it. So now I would always go with carbide on cast iron and only use HSS if I know the iron is not chilled and machines well.

Hi Michael,

Have a look at the 30Int taper collets that I keep recommending to people on here.

Link in this thread https://www.model-engineer.co.uk/forums/postings.asp?th=146359

Edited By Nick Hughes on 13/12/2019 15:23:49

Well had a good day all round today. New steam chest cover has arrived in post.

Also RDGTools are replacing the milling cutter. Fairplay I cant fault them for doing that for me.

Nick those collets look to be the bees knees for gaining that extra throught depth back on the mill. Problem is now have to convince her indoors that I want them all.

My experiences with the cheap Chinese shell mills with APMT type inserts has been better than Jasons'. I have 5, two 40mm and three 50mm, they all fit snugly on their R8 arbors and run within 0.002" tir. One of the 50mm ones is not as good as the others, as it will not face and shoulder. The shoulders are sloping about 2 degrees. That one is labelled as such. They are cheap enough to have inserts for steel on some and for aluminium on others, saving the bother of changing inserts round. They all run on 22mm arbors, the 50mm size uses APMT/APHT16 and the 40mm use APMT/APHT11 inserts.

I also have Ceratizit, Maydown, Kennametal and Hertel shell mills, from 50mm to 80mm. 

Collets in an ISO30 fitting mill should work just as well as they do in R8, as the taper is the same within a few minutes of arc. The only difference is that the drawbar thread, 12 X 1.75mm is coarser than the 7/16 X 20 UNF of the R8. Slightly more torque will compensate.

Edited By old mart on 13/12/2019 21:57:33

I've just noticed that Arc have an ISO30 X 25mm cutter which uses APHT style inserts, (060-282-00260). This is one piece and although not illustrated, should be quite short, and certainly save some valuable Z height.

Should be about the same stickout as their R8 version which is 48mm with inserts fitted.

I still have the S50 engine that was bought for me as a bolt together kit when I was 12 years old. In those days, the cylinder assembly was all gunmetal. It sounds as if it’s a pity that this no longer so.

Maurice

How's it coming along Michael? Hope you're making progress now.

Can you not just heat the casting to red heat and let it down gently.?

regards Martin

I Must admit Martin, when I built my S50, as a beginner, I didn't know this until I'd ruined 2 end mills. It's frustrating. I've only just got myself a MAPP gas setup too. I do hope Michael, the OP has moved forward in his build though. It's very rewarding to see the engine run for the first time, even on air.

Yes! Beware chilled cast iron. It can be EXTREMELY hard.

When casting camshafts, we used to have chills put into the box, so that cam lobes WERE chilled to harden them.

On another occasion, every inserted tooth carbide cutter on a multi station transfer line was ruined by a batch of cylinder blocks; which had been chilled at the foundry. Once loaded, the transfer could not be stopped to pull out the castings. We could only watch as every cutter was destroyed HORRIBLE!

Howard

Sorry been a while Lainchy, I am on my 3rd Cylinder The other two had flaws in the castings. All replaced by Stuart so excellent service so far. Got the new one all machined this week and now working on the cylinder covers. The new steam chest cover machined really nice also.

Regards

Mike

Edited By Michael Edwards 1 on 27/05/2020 15:07:35

That's good to hear Michael. I too had issues with the cylinder, but as you say.. Stuarts are pretty good. I wasn't happy with my machining on the 2nd, so ordered a third. All finished now and it looks great.