Setting up for deep boring

good point Larry, that's kinda how I drill the holes for my boring bar tool post holders - set the holder to center it vs. the spindle, make sure the tool post is square and hold the drill/ reamer in the 3 jaw chuck. All the ones I've done so far have come out very true and when I've checked the cutting tip, it's at the correct height.
 
Matthemuppet mentioned it would be nice to use inserts, which i would love to do especially since there is no provision for adjusting the height of the boring bar. The thought of laying out and milling a pocket for an insert seems very daunting to me for some reason.
See my last post in the dividing head group project thread. I drilled and tapped a piece of 3/4" hot rolled stock and srewed the insert flat to the face. Worked like a dream.
 
Doug, it's not that tricky to mill the insert pocket, especially if you're going to use a triangle shaped insert. Stick it in the vise pointing up at the right angle (45 deg? bit more maybe?) and side mill the pocket until you hit the right depth (towards the center of the bar) and the center line of the bar. Rotate the bar 7deg (for TCxT inserts) and cut the back wall. Rotate it a bunch more to give chips somewhere to go above the insert. Take the bar out, put an insert in the pocket and mark where the hole is. Drill and tap the hole maybe a thou or two towards the back wall of the pocket, that'll help pull the insert into the pocket tightly.

Then when you set up the bar, rotate the insert tip down until it's on center height, that will give you the clearance under the tip.

It'll take a little while to do, but you'll only need to do it once!
 
I'd like to just shorten the shank on this style of tool, mount it at 90 degrees to normal, so it's cutting on the back side of the bore, and run the spindle in reverse.
Will it cut properly?

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Work continues on this project. I now have a P.O. for the bushings so this setup needs to happen asap.
Last night after a week of camping I was able to get back on the "tool post" and got it bored to accept the 1 1/4" diameter boring bar.


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Tonight I
  • Drilled and tapped four 5/16" setscrew holes in the top of the tool post
  • Turned down the shank of the tool
  • Milled a flat on the boring bar
  • Used that flat to register a hole exactly perpendicular for the actual tool
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Above photo shows milling the flat. 1 1/4" face mill, .025" DOC , feed by hand super slow (like 20 min.)
 
I can't get my head around how to mount the work on the cross slide ... at centre height:confused:
Yeah, without tee-slots on your cross slide it would have been a bit of a hassle.

I note that you successfully created a dedicated toolpost to hold the boring bar on center, though. (Nice work, by the way!)

I don't think it would have been much more difficult to cobble something together to hold the work. I wonder if you could have drilled and tapped some holes in the back part of the cross-slide to hold a fixture of some sort (maybe some way to hold a grinding vise with shims to adjust the height).

Much bigger work (and bigger lathe!) but Keith Fenner showed some dedicated fixtures he made to hold work for line boring several years ago:


With that rigid tool-post and chonky boring bar, I'm sure you'll get good results (and have a nice tool for future jobs).

I still want to try line boring on my little lathe someday, though. I like the idea of supporting the boring bar at both ends for long bores. I made a replacement cross slide with tee-slots for my little hobby lathe exactly for this sort of thing.
 
The bushings are ready for drilling, the two holes are 90 degrees apart.

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My indexing plates have a 2" opening , too small for this job.... wait Bostic 260 to the rescue. The indexing plate was simply glued to the end of the bushing..





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The setup
  • a plate is locked into the tee slots
  • vee blocks are up ajainst the plate
  • the work is slide up ajenst a stop
  • the indexing plate is squared to the table


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How to center the work in the x axis the od is 2.800 so e regular wiggler or centre finder .... so the ball edge finder is put to service.

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first hole is drilled then the index plate is used to index the bushing.


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Thanks for looking
 

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Hot glue? Really?!

Pretty sure a real machinist would have at least have used carpet tape. ;-)

I really need to make some indexing plates like that. They look handy! I've been able to get away with just collet blocks so far (I rarely make anything very big) but I'd like to have something like that in my arsenal.

I guess hex and octagon plates should cover almost any indexing need. If you were to remake yours, would you stick with the 2" ID?
 
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