Boring outside diameter

I need to bore an outside diameter on a 83mm diameter aluminium round bar. This is to make a flange, the part I cut has to be large enough so I can fit bolts arround the outside of the flange, probably m8 bolts.

I can cut the hole in the center of the flange using a 2 inch boring head. I have a Sieg SX2 mini mill. But is it possible to cut the outside diameter with this, or do I need a rotary table?

Also, to do this I have read that you need a reverse, which I don't have. Why is this?

David

David,

Can't answer the reverse question. 83mm on an X2 with a boring head ? I'm not sure I would want to try that on my SX3. A rotary table would be better. I take it that you can't turn it, is that due to lack of facilities or the part ? I have seen folks mount the parts on a mandrel/ arbour rotate tihe part in the mill and mount the tool in the milling vice slowest useable rpm is the key and you are working upside down but a simple flange should not be too difficult.

I don't have a lathe, so I can't turn it. Could I use an end mill in the boring head? Even if I could I have understood that this is too much for a boring head on the mini mill. I will get a rotary table. I wanted one anyway!

David

Should be possible. I've done 5" dia on my X3

I would avoid using reverse as a lot of the imported boring heads screw onto the MT or R8 shank and will unscrew if run in reverse.

All you need to do is grind up a boring tool with the right geometry to cut on the outside of the work not the inside. Also depending on the size of your boring head you may have to make an outrigger arm as you will probably run out of dovetail travel on the head. Run very slowly.

Bit smaller but this is one I did a couple of weeks ago, reground standard cutter and running in normal direction.

Edited By JasonB on 12/12/2015 09:08:33

Edited By JasonB on 12/12/2015 09:10:11

You want a Rotary Table, so this look like the ideal opportunity to buy one.

You will need to centralise the R T under the Mill Spindle, then lock the one axix, (Y would be my choice).

Since you are making a flange, the material will, presumably, be thin enough to allow use of an End Mill.

Having fixed the workpiece to the R T , (drill holes into the stock to allow it be clamped using nuts on studs in T nuts in the slots in the R T), and traverse the table in the X axis to the (Outer Radius plus Half Cutter dia). This should produce the O D. The R T should be rotated against the direction of rotation of the milling cutter.

If you are able, set as much as possible of the cutter over the material, and use downfeed to apply the cut.

Based on my limited experience, the feed (Table rotation) needs to be fine. It may help to damp vibration, if the table is lighlty clamped, This will increase the load that you apply to the handle, but will lessen the tendency to "bounce" between cutter teeth contacting the work.

Having produced the O D., the table should be traversed to the point where the cutter will produce the I D.

It would be a good idea to traverse the Mill Table and the R T to drill the holes in the Flange, before producing the Inner diameter.

It may be worth returning to the centre position, and then resetting to the radius for the drilled holes, and to (Inner Radius minus Half Cutter dia).before down feeding for the initial cut with the End Mill, and commencing rotation for the I.D.

You will then, effectively, produce the flange by trepanning it.

A Slotting drill can be fed down to whatever depth of cut that is apprpriate to the rigidity of machine, R T and cutter because it is centre cutting. Unless your End Mill is centre cutting, initially, the maximum depth of cut will be limited by the depth between the teeth and the cutter body.

Although, probably you will not want to be taking heavy cuts or feeding hard. An End Mill would probably not want a feed rate of more than 0.002"/tooth.

Howard

Thanks for the advice. Hopefully I will mill the flange over the Christmas holidays. I will write again when it is finished. I am slowly getting the hang of using the milling machine, (as long as it is nothing too complicated!).

David