Cast Iron Tips

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Hello peoples.

Just had this delivered.

I have new cast iron D1-3 backplate for my Boxford. I now have to machine a rebate into the backplate.

I have never machined cast iron before so some general tips for machining, drilling and tapping this job would be appreciated.

Or shall I just stick it on with evostick or no nails.?

Nick

As its a part machined backplate there should not be any skin on it so just tackle it with what you would normally use to turn steel. Drills fine, taps nicely do it all dry as the graphite in teh iron will be your lubricant.

J

PS don't blow your nose in your best hankie afterwards

When I last did one I mounted the back plate in the lathe and machined the rebate and mounting face, make sure when you mount it the faces are clean as you want the back plate to run true.

I then made up a bush for the tapping drill and drilled one hole and tapped the hole once one was done I used the tapped hole as a location and drilled and tapped the other three. It does not need accuracy to the 0.001mm but it is nice to get it close as the rebate and the face are the location and the bolts/cap screws hold it all together.

If you can try to make the finishing cut at least 0.003" I usually aim at 0.01", other wise the chances are the tool will just rub on the surface and not cut.

It's an idea to cover the bed of the lathe but not with a rag/cloth that could get caught up in the work piece and also wear a mask as it is likely to be a dusty job, do not be tempted to use any coolant as cast iron is machined dry.

Bob

Further to Johns point about marking the spindle do check that it isn't already marked, whether by factory or a previous user before adding your own. I reckon around half of the, admittedly small, selection of D series spindles I've seen were so marked probably 50 / 50 factory - shop split.

Whilst you are checking its wise to verify that the recess in the part machined backplate hasn't been cut too deep so the chuck doesn't align repeatably. Rare but not completely unknown and the sort of thing you just don't think about when doing diagnosis on a running machine.

Also verify that the holding pins screw in pretty equally so that the locks are reasonably close to the middle of their operating range. One of my D1-4 ones comes out around 35° offset to the others and I had a high old time switching tapped holes and lock positions to make things work out OK. Twice as it was originally fitted to my Southbend Heavy 10 before migrating to my Smart & Brown so naturally best fit positions were different.,

Clive

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Cheers for the replies guys.

Nick

In a previous thread about calculating cutting speeds I suggested that 70 fpm for steel and 40 fpm for cast iron were suitable cutting speeds. Another poster observed that with modern tooling, higher cutting speeds were applicable and my suggested speeds were rather conservative. That is true I'm sure, but I think its worth noting that you should run a rather slower speed for CI than you would for steel, it is lovely stuff to machine though.

For a job like this use HSS toolbits ,with no top rake at a cutting speed of 80 ft per min, final cut should be about a thou. the fit of chuck to backplate should be a "knock" fit ie they should go together with a knock from the handle of a plastic screwdriver handle,make sure the chuck seats fully on the backplate and does not ride on the edges of the spigot, if you make a cock up and the chuck is a sloppy fit on the spigot ,dont worry set the chuck true with a dial gauge and really tighten the allen screws,the chuck will not move a unless you accidentally hit it hard with the saddle or toolpost ,

I read a lot on here about people always moaning about machining cast iron,perhaps our current generation do not like getting their hands dirty,they should have worked in machine shops up to the 1970s,some were like coalmines, cast iron machines nicely,no cutting lube ,though tallow was sometimes used for tapping and reaming.Though you did see slideways on well used machines that looked as if a big cat had used them for a scratching post .

I have only once seen soluble oil used in high volumes on cast iron (mill and lathe beds)on a futureistic automated machining cell where cleaning was impossible unless the line was stopped so the lubricant was used to flush away the swarf and it was very noticeable that there was no black dust anywhere.

Cast iron is the only thing I've known produce a more disgusting handkerchief than snuff.

Neil

I worked in the toolroom as an electrician when I came out of my time, our workshop was next to the spotting presses where the toolmakers would bed one die to the other half which involved a lot of grinding, I would go home filthy just from the fallout. It was an interesting place to work but like the press shop you went home dirty and could see the dirt run off you in the shower.

Mike

Nick

This may be of interest to you. I constructed the adjustable plywood bracket that clamps to the rear of my lathe bench. A hole accommodates a tapered Shop Vac Nozzle that can be maneuvered close to the work. Cuts the airborne dust down significantly.

Bill

Don't be tempted to do what one of the guys on Traction Talk did. He set up an extractor fan in his workshop wall and spent a happy couple of weeks machining bits for his engine over the summer. Unfortunately the first time it rained every horizontal surface at the back of his and next doors house turned a nice shade of orange/brown, the window cills were the worst