Cylinder Boring Techniques for Steam Engines

[Will RobertsonParticipant @willrobertson16447]

Can anyone point me to a good web page with advice about using a slitting saw on a milling machine?

Because of the dimensions of the stock available, it looks like I might have to slice through some fairly big chunks of metal to make efficient use of the stock. I'm a bit nervous of doing this because of the risk of the slitting saw shattering if I get it wrong and lumps of shattered saw going flying. Any advice about where I could read up on how to select and use a slitting saw to safely make deep cuts would be very valuable.

[Ian S CParticipant @iansc]

I know very little about using slitting saws, but I run my mill at low speed (it goes down to 90 rpm), thats the best I can do, pleanty of soluable cutting oil, same thing if I use the saw in the lathe, run it a good bit faster for brass and aluminium. Ian S C

[Clive HartlandParticipant @clivehartland94829]

OK Will, firstly keep the speed low as Ian has suggested. Further to this if you are cutting off pieces then use a saw of at least 1.5mm thickness as it is less likely to stray. Use almost flood lub/coolant as it clears the chips better. I have only ever split one saw and that was jammed and I tried to withdraw it while it was still switched on.

If you are cutting big solid sections be aware that the saw will make it shift off the work piece as its severed. Feed very slowly and only upcut, do not downcut as the diameter of the saw will have a lot of force at the cutting edge.

I have mentioned thickness and now I will mention diameter, I use a 150mm dia. saw and only use smaller dia. for slotting etc.

Take care, Clive

[Sub MandrelParticipant @submandrel]

I'll agree with Ian and Clive.

Slittings saws don't run at 'angle grinder' speeds, but much more slowly. If it's going fast enough that you fear it sending things flyin, it's going far too fast.

I keep a lubricant loaded brush on the saw while it is cutting.

But they are slow, precision tools meant for gettinga quality cut, not as general puprpose chopping up tools.

Neil

[Will RobertsonParticipant @willrobertson16447]

Hi Iain, Clive and Neil,

Thank you very much for your advice. I'll keep down at about 90 RPM.

I'll also follow your advice and go for 1.5mm thick and about 150mm diamiter – how many teeth should I go for? Is 108 teeth at 100 – 150 mm dia. about ok?

>Feed very slowly and only upcut, do not downcut

Thanks – very good point.

>But they are slow, precision tools meant for gettinga quality cut, not as general puprpose chopping up tools.

Thanks – I'll look over the dimensions of the stock available again and see if I can re-think to reduce the amount of cutting or do most of it on the 250mm saw.

Will

[Will RobertsonParticipant @willrobertson16447]

One snag that's come up… I can get metric coarse taps and dies no problem but the two suppliers I use stock metric fine taps but not metric fine dies. I could cut the threads myself but most of the lathes I have access to here nolonger seem to have their complete collection of gears for setting the pitch for thread cutting. Even if I can lay my paws on the gears, I suspect that the lathes weren't designed to cut threads as fine as metric fine threads on small components for model engines. Not sure how to handle this.

[Clive HartlandParticipant @clivehartland94829]

I am sure brutsch Ruegger will have everything you need Will, try them for fine Metric dies.

By now, if you have been dealing with them you shauld ask for their book catalogue. It lists everything you will ever need.

Clive

[Will RobertsonParticipant @willrobertson16447]

Just finishing off the order for stock. It looks like the piston valve cylinder will be machined out of a 22 by 22 mm piece of gun metal and the main cylinder from a 31mm diameter piece – I'm not sure if this will look right – it might make the piston valve assembly look un-naturally large compared to the main cylinder – should i consider making the main cylinder a little larger? – 41mm outside diameter is the next largest sise the gunmetal stock comes in. I drew some sketches in Draftsight to help me decide but that didn't seem to help me.

[Will RobertsonParticipant @willrobertson16447]

Hi Clive,

Thanks for your reply re. the fine metric dies. I checked and Brutsch Ruegger do have them – I should have thought to look there before asking – many thanks! I can't afford to buy all of the tooling I need from Brutsch Ruegger but they do have a wider range of high quality tools than anywhere else I know of.

Will

[Will RobertsonParticipant @willrobertson16447]

Apologies for the pause – work became heavier than usual and I had to do a re-design of the cross-slides so that they could be machined sensibly from the stock I can buy. Also spotted errors in the design that needed attention.

I've run into an unexpected problem – I can't find anywhere that sells metric cylinder drain valves (formerly known as "cylinder drain cocks" but I think we're not supposed to use that any more because it's not politically correct or something). I'd thought that one supplier over here sold them but I can't find them in their catalogue. I can easily get drain valves with non-metric threads but everything else is metric and I'd like to stick to metric (my generation…).

Any ideas who might sell them?

[Paul LousickParticipant @paullousick59116]

I have just machined the bore and the location flange on the steam chest for my 6" scale traction engine. The steam chest was too big for my mill and lathe so borrowed a friends.

The far side of the steam chest is tapped to mount a cover plate and I used these holes to mount it to an old car brake disk. First machined the the faces of the brake disk, then bolted the steam chest to it.

This mill is a little bigger than my Sieg X3 (table is 1m wide x 8m long). The steam chest is the little thing under the cutting head.

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