Boring bar – a lesson learned

[Roger HartParticipant @rogerhart88496]

Been latheless for a while,  last Summer got a used Sieg C3.  Changed bearings,  gibs and dials,  now fairly workable.

New project needed some cups for ball races – I always found internal boring in MS a bit of a hassle so bought an 8mm indexable boring bar.  Found it had a considerable negative rake so a bit of looking on the web showed how to use it.

It worked too well,  cut lovely and smooth and I ended up cutting too deep and removing the step drilled into the bottom of the hole.  No problem,  but learned not to rely on feel and judder alone,  ended up making pencil marks on the bed.

The next rainy day project will be a carriage stop.   Usually grind conventional HS tools but very impressed with the indexable boring bar.

 

[old martParticipant @oldmart]

Most indexable boring bars have a flat on the base which takes care of the optimum inclination of the insert, which ideally should be very slightly above the centre line, say 0.05-0.1 mm or 0.002-0.004″. One boring bar will never be enough, you need to use the biggest that will start in the hole, but there are likely to be a range of sizes which share the same inserts. Having a stop makes a huge improvement, and later on you might consider a second one for the other side of the saddle (carriage).

[Howard LewisParticipant @howardlewis46836]

Well worth spemding the time to make a stop, preferably adjustable.

Having a spare Micrometer barrel, incorporated it, to give better control of depth.

Howard

[David George 1Participant @davidgeorge1]

Recently I decided to screw cut a large thread and found I wanted to use a full form insert which needs an insert size which will only fit into a 20mm diamiter toolholder/ boring bar. I found a piece of steel which will bolt to the crosslide with T bolts and which will allow me to drill a hole which will come on center height as that is the proper height fot the cutting edge of the tip. I drilled the holes using the main spindle to make sure the holes were correct height. When the holes as i cut two one 20mm and one 12mm side by side all I had to do is drill clamp screw holes on the center line of the two tool holes. The holder worked perfect and a solid tool holder for other jobs.

 

 

David

 

[Michael GilliganParticipant @michaelgilligan61133]

I like that, David !

Excellent design and execution.

MichaelG.

[OldironParticipant @oldiron]

Great job David. Excellent idea. Only trouble now I need one. Oh well another day in the workshop coming up. 🙂

 

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