How to machine a flat and a slot on each end of small bar that are in line with eachother

[Chris ThornParticipant @christhorn]

This may seem simple but I am a bit stumped how to do this

In the drawing below I and have to machine a slot on one end and a flat on the other , If I hold it in stevensons collet holder to use a slitting saw for the slot , i have to remove and turn it round to mill the flat on the other end, thereby losing the horizontal plain. It is too short to get a DTI on the other end to adjust for flatness as this will be inside the collet.

Can any of you season engineers give some pointers on the process for doing this

Cheers

Chris

[Chris ThornParticipant @christhorn]

[Robert Atkinson 2Participant @robertatkinson2]

Hi,

Do the slot first in the collet block. Then make a T shaped bit of flat material to extend the reference out of the end of the collet when turn it around. The long leg of the T goes into the collt and engages the slot and you clock across the top of the T.

Robert G8RPI.

Edited By Robert Atkinson 2 on 09/08/2022 12:33:59

[Rex HanmanParticipant @rexhanman57403]

Make a small V block to hold it and mount the v block in the vice or clamp it to an angle plate. Mill one end then invert it for the other.

 

 

Edited By Rex Hanman on 09/08/2022 12:42:06

Edited By Rex Hanman on 09/08/2022 12:48:15

[BikepeteParticipant @bikepete]

Use a scrap end of rectangular bar stock to hold it by the 3mm diameter section (split and clamp screw). Then you can do slotting & milling operations on both ends in one operation, assuming you have enough travel, or easy enough to re-position if not. And you can just flip it over to do the other side.

[DC31kParticipant @dc31k]

Will it go in the collet at all? The end is 4mm across. The middle, where the collet will close, is 3mm dia. and only 17mm long. If the gripping length of the collet is longer than 17mm, there is a problem. It might be necessary to make the slot and flat on a 5mm dia. piece of material and then reduce the diameters.

The methods available to you will be influenced by whether the slitting saw is vertical or horizontal.

[Rex HanmanParticipant @rexhanman57403]

Posted by Bikepete on 09/08/2022 12:44:22:

Use a scrap end of rectangular bar stock to hold it by the 3mm diameter section (split and clamp screw). Then you can do slotting & milling operations on both ends in one operation, assuming you have enough travel, or easy enough to re-position if not. And you can just flip it over to do the other side.

Had the same idea but the 3mm part won't pass through a 3 mm hole, though something like a big end cap or bearing cap would hold it.

[Martin Johnson 1Participant @martinjohnson1]

Start with 6mm square bar. Mill the end slot & tab. Grip in 4 jaw and turn 5 dia. Reverse & grip in collet to turn 3 dia.

Martin

[Tony Pratt 1Participant @tonypratt1]

Posted by Bikepete on 09/08/2022 12:44:22:

Use a scrap end of rectangular bar stock to hold it by the 3mm diameter section (split and clamp screw). Then you can do slotting & milling operations on both ends in one operation, assuming you have enough travel, or easy enough to re-position if not. And you can just flip it over to do the other side.

Not sure what equipment you have got but Bikepete has the right idea.

Tony

[BikepeteParticipant @bikepete]

Posted by Rex Hanman on 09/08/2022 12:53:18:

Posted by Bikepete on 09/08/2022 12:44:22:

Use a scrap end of rectangular bar stock to hold it by the 3mm diameter section (split and clamp screw). Then you can do slotting & milling operations on both ends in one operation, assuming you have enough travel, or easy enough to re-position if not. And you can just flip it over to do the other side.

Had the same idea but the 3mm part won't pass through a 3 mm hole, though something like a big end cap or bearing cap would hold it.

Good point!

[Chris ThornParticipant @christhorn]

Thanks for the ideas guys

It has got me thinking out of the box

I will probably try Roberts or Bikepetes suggestions

I will let you know how I get on

[John HaineParticipant @johnhaine32865]

Start by drilling the two 1.1mm cross holes at each end of the parent bar, parallel. Now you have a reference at each end.

[JasonBModerator @jasonb]

What was that recent thread about leaving it on the stock.

If you do the turning and don't cut it off the 5mm parent stock then the collet block can hold by that for all the milling and not have to reposition the collet . With a cunning bit of packing in the vice jaws you can saw and drill the forked end without excess overhang. Smaller end is easy enough while up against the collet.

Better with slightly wider packing bearing on what would be the 3mm dia but gives the idea of what's needed. for all but the second flat on the 4mm dia

and for the second flat

 

 

Edited By JasonB on 09/08/2022 16:32:07

[duncan webster 1Participant @duncanwebster1]

Does it have to be 3 dia, having it 4 would make life so much easier.

[Howard LewisParticipant @howardlewis46836]

As Jason says, part of from the raw material afterwards.
Hold the work in the Stevenson collet block, and mill the slot.

If the nut is wider than the block, use packing pieces between the jaws and the block, or have the block overhang the vice jaws just far enough for the clamp nut to clear the jaws.

Rotate the block ready to mill the flat.

Reposition the mill table

Mill the flat, possibly, a few thou over length.

Remove the work from the block

Make up a collet to fit the shank of the work.

Split, so that you have two half collets to fit around the shank. Concentricity is less important since you are parting off and will face to length. So any slight lack concentricity will be purely cosmetic.

Hold the work in the two half collets in the lathe.

Part off, and face / chamfer to length.

Howard

[Chris ThornParticipant @christhorn]

Success using a spilt block , took longer to make up the split block than the part , always the way !

Rounded the flat end to suit the piston swing

Thanks for the advice !

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