stick out

I'm attempting to build a vertical head for my Centec2 horizontal mill . My thoughts are ,seeing as I'm going to all this trouble I might as well try and use beefy materials because for it's size the Centec 2 is a beefy little machine . For the spindle I'm planning 80mm od steel .I need to bore this out for the spindle bearings and draw bar . My question is , The round bar I'm using will be 80mm x 250mm long is this too much for a 6" 4 jaw ,I don't have any kind of steady rest . The through bore hole isn't critical ,but the seats for the bearings are and need to be bang on .

Sean

Sean,

I would say that a fixed steady of some sort is essential for success.

It doesn't need to be fancy ... something fabricated from plywood should suffice.

MichaelG.

I figured out how to do most of the machining without a steady rest. The one thing I could not figure out how to do without a steady is bore the taper. I suggest you search for a steady that fits your lathe.

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John,

I think Sean's text may be a little ambiguous:

I believe that it's the bearing-housing [i.e. the body of the vertical head] that he is currently wanting to machine, rather than the spindle.

MichaelG.

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[quote] For the spindle I'm planning 80mm od steel .I need to bore this out for the spindle bearings and draw bar . My question is , The round bar I'm using will be 80mm x 250mm long ...  [/quote]

Edited By Michael Gilligan on 03/11/2017 08:46:08

The only thing I have never managed to do is to set up a steady,never seem to get it right.

Any advice?

Larry

Fit a short length of material in the chuck and turn to the exact diameter of the material to be fitted into the fixed steady, do not use a centre.
Fit the steady onto the bed and slide it towards the chuck so the fingers are able to bear on the turned diameter.
Tighten the steady down before adjusting the fingers onto the work, lock fingers in position.

Open the steady top and slacken steady to bed clamp and slide steady to the position required and clamp to bed.
Fit work and close top finger and tighten, ready to go.

Emgee

I usually do it by feel. I start with the jaws backed off a bit. I advance the front jaw until it touches the part. I continue to advance the jaw until there is 360 deg. contact. Next I bring up the back jar until it firmly contacts the work. Last I bring the top jaw into contact.

I haven't needed to do it yet but if I had test that the alignment were perfect I would attach an indicator base to the chuck. The contact point would touch the work as far from the chuck as possible. If the steady were in perfect alignment there would be no deflection of the indicator needle as the chuck were rotated through 360 deg.

If anyone has a better idea I am willing to learn.

Michael,

Indeed I thought he meant making the spindle. If it the housing he intends to make that is a whole different problem. It would be far better if he could scrounge a piece of suitable tubing. It would be possible to do his spindle housing by clamping it to the saddle. Once there was a hole through the part the bearing seats could be done with a boring bar supported between centers.

I don't remember where I got it from, possibly Sparey, but my rule of thumb maximum for unsupported work is 3 times diameter. As 3 x 80mm is 240, 250mm is high risk without a steady or a tailstock centre.

Even at 3x diameter you have to be careful. I dinged my bed when a dig-in popped a 6" by 2" diameter steel rod out of the chuck. I think I was lucky not to do more damage. An unconstrained rod is a lever that multiplies the sideways force at the chuck end like a crow-bar. As my lathe has a 1500W motor the forces involved when the chuck let go were considerable. One moment I was turning, then there was a loud bang, and I remember wondering why the work had completely disappeared!

Dave

Y'know, for less than what it will probably cost to buy the steel and bearings, you can buy a BT30 Milling head with spindle for $135 here link That's less than 100 quid.

A mate of mine just bought one and it seems a good solid unit. Uses radial ball bearings rather than taper rollers but may be able to be be converted. He's busy attaching it to an old cast iron engine block to make his own milling machine using an xy table etc. Mad scientist at work!

What is the capacity for your 4 jaw? To copy a mini lathe headstock that has a MT3 socket and 35mm shaft. If you use a 32007X bearing with an OD of 62mm you could use 70mm stock and have a decent 4mm wall to your bearing housing.

Thanks Rainbows ,I have quality bearings ,the biggest has an od of 62mm and the smaller has an od of 55mm I think .I don't think 4mm is enough meat I'd rather a bit more . I can't remember off hand what the capacity of 4 jaw is ,but the max capacity of 4 jaw will dictate how long my spindle will be .

This is what I'm planning ,hopefully with adjustment on the vertical axis .The collets I'll be using will be ER32 and MT2 

Sean

Edited By sean logie on 04/11/2017 13:05:50

Edited By sean logie on 04/11/2017 13:07:12