Maching flats

[Roger HulettParticipant @rogerhulett83124]

I need to machine two flats opposite to each other on a 1.5inch dia brass round. How do I do this accurately. I have a South Bend lathe and a small horizontal mill.

Thankyou.

[Roger HulettParticipant @rogerhulett83124]

[Ian ParkinParticipant @ianparkin39383]

Hold it in a vice on your mill and mill one flat

Then flip it around rest the previously machined flat on a flat and machine the other

[Jon GibbsParticipant @jongibbs59756]

Hi Roger,

How long are the flats and how long is the brass round?

[Roger HulettParticipant @rogerhulett83124]

The flats are 1.5" long the brass round is 9" long but will be cut to 4.5".

[Jon GibbsParticipant @jongibbs59756]

Ian's method will work if you can return the bar level again. If you know how deep the flat is you can pack with shim or a feeler gauge stack or if you can't do that then use a dti to tram the top in the vice.

I'd be tempted to extend the bar out of the (vice trammed to one axis of the mill) vice to give access to both sides of the bar and leave it in place throughout. Then you can use the sides of an end mill to mill each flat in turn. You will need to mill these in opposite directions to avoid climb milling.

This will also mean that your end-mill needs to be stiff enough (big enough diameter) and long enough to reach the base of the flat from above the bar and will leave a curved end to the flats but there's no alignment error (provided your end-mill doesn't flex).

HTH

Jon

[Roger HulettParticipant @rogerhulett83124]

Can you explain trammed for me please.

[Jon GibbsParticipant @jongibbs59756]

It's making sure that the vice or material remain the same distance from the cutter across the full range of movement.

This video from Tom Lipton at Oxtools shows how to tram a vice. You can use the same procedure to tram material.

**LINK** (To save you watching the pre-amble start at about 8 minutes)

HTH

Jon

Edited By Jon Gibbs on 23/04/2018 16:58:38

[Dave HalfordParticipant @davehalford22513]

Roger,

Pretty much as Ian Parkin says.

I would clamp your round at 90 deg. to the mill table using an angle plate (assuming as you have a small Horizontal mill you will have neither a vice large enough to hold 1.5inch dia, nor anything to hold an end mill vertically.)

Mill the first flat at what ever your required depth is by adjusting the knee height.

Rotate the round 180deg and reclamp with packing in the flat just milled (a piece of square lathe HSS will do) so that it is above the table. the untouched end needs packing with the same size HSS + the gap left between the table and your round so that the round is parallel to the table as before.

Adjust the table height for the correct depth of cut

Mill your second flat.

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