Myford ML7 mandrel speeds

The Myford ML7 is perfectly adequate with the standard speed range,higher speeds will spoil the bearings, too many amateurs nowadays seem to be obscessed with high speeds,carbide tooling, and digital readouts and powered feeds.I would suggest that beginners start by learning to use a lathe correctly ,learn to sharpen tools (HSS) ,and learn to handfeed by winding handles. By feeding by hand you learn to feel the tools cutting action ,soon find out if it is blunt or has wrong cutting and clearance angles,the usual problem with grinding tools for brass turning ,is not enough side clearance and then careless honing with the stone ,too much stoning will tend to round off the sharp edge,keep the stone flat against the face you are stoning do not let the stone roll in an arc. Stone the front and side clearance faces first then lightly stone the top face to remove the slight burr. The top face of the tool bit( for brass) should be left as it is and not hand ground. When I was apprenticed a lot of the instrument turning (brass ,nickel silver,)was done on a Boxford and a 125 mm centre height plain lathe ,work for a month on these you soon learnt to sharpen tools,the plain lathe had large handles 3 or 4 times larger than a Myford and spun easily in your hands,for 8 hrs a day .the Boxford had power feed in both directions but was only used on one job about once a year ,its quicker to wind handles than mess about with feed clutches and if you are good at the job the finish is no different . The most common oilstone used was triangular India slipstones .,medium grade. The HSS toolbits were 3/8th square on the Boxford,and 5/16 square on the instrument lathes,any grade of HSS bit is ok for non ferrous material, the super HSS grades are better on stainless and tough steels.

A sharp tool with the correct geometry and at the right height should ensure success even at "LOWER" speeds.

If it still gives a poor finish I would suspect the material. So called "HARD" brass is required for a good finish.

Some brass is very chewy, particularly sheet that is intended for bending or forming : round rod is less likely to be like this but bending rod is a possible requirement in manufacture (although unlikely above 1/2" diameter) and hence soft material is required. This soft brass will turn as badly steel reinforcement rods do if you are foolish enough to try!

The simple solution is I am afraid to buy material of known specification.

If using unknown material any hexagon rod is almost certainly OK as it is intended for turning nuts and hexagon headed bolts.

John

My lathe (not a myford but similar) runs on the following speeds --485-350-245 and on back gear--100-65-45

These speeds have been adequate for anything I have ever needed to turn, I use hss tools and generally feed manually, I've tried tipped tools and never liked them , the money spent on tips would buy hss tooling which lasts muuch longer,I quite like the old carbon steel tools, give a good finish just need sharpening more often and as for tool angles I use common sense, the tool I use the most is a knife ground approx for steel does just about all I need, apologies to the purists

Mick h

I just gave myself a good proof that speed isn't everything. I've just been chewing a 2" square bit of steel down to a 43mm disc Because of the interrupted cut I used a tangential HSS cutter to take off the corners, ten thou at a time at about 4-500 rpm.

Once I got down to a 2" disc, I upped the speed to 1000 rpm and increased the depth to 20 thou - but forgot to switch to a carbide tool.

The red-hot swarf looked really impressive, until after three or four cuts I realised I had completely taken the tip off the tool...

Neil

Thanks for all of the contributions. I will re-double by HSS grinding efforts/geometry, and see where that takes me! I acknowledge the opinion, expressed by many, that the standard ML7 speed range is more than good enough.

On my first Myford I fitted a 2,800 rpm motor with no problems. Kept it for a couple of years before upgrading. The myford C7 capstan had bronze bearings and a faster motor.

Edited By David Clark 1 on 25/11/2014 08:46:51