best lathe tool for cast iron

Hi all, I have just started turning down a new cast iron backplate to fit a collet ER32 chuck onto my new Warco wm240 lathe. I am using a new replacable carbide tool from ARC euro which is fine on all other jobs I have done, its has a sharp edge on it. but on this cast iron backplate the amount I can take off per run is very small, its all fine dust. should I be using some special toll apart from the normal range of tolls we all have. So far today I have taken off about 0.5mm in 2 hour, I need to remove 7mm, it will take days, must be doing something wrong. regards David

I don't bother changing tips especially for cast iron.

What you may be finding is that the cast backplate has a hard skin on it and the tool is having a job getting through that with fine cuts. Better to take a decent depth of cut and fine feed rate and you should get through it without too much trouble. On the vari speed lathes its best to run a bit faster so you don't loose torque or overheat the slow running motor. Assuming its about a 5" backplate I would be running at 300rpm and 0.5mm depth of cut, finest feed rate should give you chips not dust.

This is a bit bigger dia but you can see teh chips

Edited By JasonB on 02/07/2016 16:18:18

I found that on my lathe the lead screw guard (Long springy thing) end cover prevent getting close to the backplate without a lot of tool overhang. I roughed out on the rotary table/mill then just did final few thou on the lathe.

The metal you take off will be fine , dusty chips, I fold up a bit of news paper under the work to collect the mess. Wipe all the oil off the lathe bed before you start, and don't use any cutting oil, or coolant (except, you can use air). Ian S C

I found a carbide tool, upside down, on the back of the lathe, and using the backgear, the easiest approach.

A nice tidy mound of lron filings at the back of the lathe could be sooked up.

The mess at high speed on the front of the lathe was unbelievable so I only used that approach for the final cuts

0.5mm in 2 hours suggests you are taking very small cuts indeed. This is appears to be a much more substantial lathe than my old ML7, but even with that I'd have taken 0.5mm off in one cut, with a feed of 0.004" per rev. If your collet chuck is arounnd 4" diameter, I'd have done it at about 80 rpm (backgear) with High Speed Steel, or about 200 rpm with carbide. Taking very small cuts with very low feed rate is not the way

Thanks for all the advice. think I was going at it too easy, should have had bigger cuts, its was the mass of dust that put me off . I turned a cast iron flywheel about 12 years ago on a mini lathe but that was a long time ago. I will have another go this week, I think my speed was too high as well 800 rpm if I can remember.