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Lathe

Problem with my lathe

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Ronen Burstein01/04/2020 09:21:51
4 forum posts
1 photos

Thanks again for your reply. Fantastic.

But if I may, one more Q. Is there optimal spindle speed for fine cut in mild steel or once i set the gear for factory fine cutting it will cut fine no matter what spindle speed?

Ronen

Journeyman01/04/2020 09:29:39
avatar
776 forum posts
131 photos

Ronen, once you have set the gear train to the finest feed as per your chart it remains at a constant ratio of feed to speed. The lowest I can get on my WM 250 for example is .07mm per rev, your lowest may be different but once set that's it. It doesn't matter what speed you run the lathe at the feed stays the same it just moves along quicker the higher the speed but the ratio of feed / spindle speed is fixed.

John

Edit: Typo

Edited By Journeyman on 01/04/2020 09:31:50

SillyOldDuffer01/04/2020 09:59:59
5605 forum posts
1153 photos

Posted by Ronen Burstein on 01/04/2020 09:21:51:

...Is there optimal spindle speed for fine cut in mild steel or once i set the gear for factory fine cutting it will cut fine no matter what spindle speed?

Ronen

As John says, fine feed once set is constant.

I usually keep mine at 0.07mm per turn because it works on almost everything without fuss. Occasionally though it pays to use a coarser setting to either rough cut metal fast or because sometimes and counter-intuitively, a coarser feed produces a better finish.

In my experience Coarse=Better seems more likely to be true of carbide than HSS, but if you have trouble getting good finish on a difficult material, it's worth experimenting with different depths of cut and feed rate. I emphasise the finest feed recommended by the lathe maker is good most of the time though.

A point that had me confused: the Warco gear setting diagrams refer to 'H'. Just in case you've not twigged already, this is a spacer. It allows single gears to be positioned as necessary on the axle. For example, in fine feed, the gear that drives the leadscrew is positioned on the inside, but for thread cutting the 'H' spacer goes on first and the driving gear is on the outside.

Dave

Howard Lewis01/04/2020 10:04:09
3127 forum posts
2 photos

Ronen,

As a starting point, in terms of cutting speed for Mild Steel, try 100 feet per minute, (surface speed ), using High Speed Steel tools..

So if you were starting to turn a piece of 2 inch (50 mm ) diameter mild steel, the circumference is (2 x Pi ) so say very approximately 6 inches. So you would run at 200 rpm.

Replaceable Carbide tips can be run at much higher speeds, so that the swarf comes off brown or blue, if not red hot.

As a beginner, I would suggest that you stick with HSS, so that you can learn the basics of grinding tools to the correct shape. A correctly ground tool will cut nicely, a blunt one never will!

One thing which will optimise the surface finish is that the tool,must be mounted at the height of the centre line of the lathe. If the tool is too high, it will not cut properly, but will rub. Too low, and it will not be ideal. In both cases, you will leave a pip on the end of any work that you are facing.

For this, to speed up tool setting, and save a lot of experimenting each time, it is worth making a centre height gauge.

This will also give you a little practice at turning and facing, so will be a win-win for you.

To adjust the tool to the centre height, you can pack it up with pieces of tin cut from food tins (washed! ) or from biscuit tins. Cans are often about 0.010" (0.254 mm ) thick.

If you want a picture of a centre height gauge, and instructions on how to make one, PM me.

H T H

Howard

Journeyman01/04/2020 11:10:59
avatar
776 forum posts
131 photos

The following charts may help:

turnspeed.jpg

cuttingspeeds.jpg

John

Ronen Burstein03/04/2020 09:54:44
4 forum posts
1 photos

Thanks for all your reply.

Ronen

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