I have a project coming up with a threw hole .750 x 6.00 inches long steel or stainless. I'm looking for a bar that can do this but would like to makeup a set of bars with a standardized insert if possible. Any affordable options suggestions?
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What inserted boring bar?
- Thread starter rodm1
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What tolerance is on the .750 diameter ? If it was close , I would drill undersize , run a boring bar thru just to true the hole and then ream it . You're approaching a length over diameter issue trying to bore to a tight tolerance . 
They do make solid carbide bars but they are pricey .
They do make solid carbide bars but they are pricey .
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What tolerance is on the .750 diameter ? If it was close , I would drill undersize , run a boring bar thru just to true the hole and then ream it . You're approaching a length over diameter issue trying to bore to a tight tolerance .
Agree. This is worth the investment of a 3/4” reamer. Besides it is a very handy size to have.
Cutting oil is my blood.
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If you want common inserts, this is CCMT territory. Unless a very specific fit is needed, the reamer is a one-trick pony, whereas a decent boring bar is highly versatile and will cost less than a big reamer.
I spent the money on solid carbide boring bars and even they are not infallible. I had aluminum chips pack up and push my carbide boring bar enough to oversize my hole on one end of a 4" bore. I had too big a bar in too small a hole. I should have went with a smaller bar.
6" is a long way for a 3/4" bore. I'd drill it 1/32" under and use a good 1/2" boring bar to straighten the hole as deep as you can while still slightly undersized. Then ream it letting the bored part guide the reamer as it cuts the drilled portion.
6" is a long way for a 3/4" bore. I'd drill it 1/32" under and use a good 1/2" boring bar to straighten the hole as deep as you can while still slightly undersized. Then ream it letting the bored part guide the reamer as it cuts the drilled portion.
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I know chip clearance is an issue, and seeing a taper with boring bars is a thing if you stop before the job is complete, but pecking and clearing is the solution to chip packing and the taper goes away with spring passes. The radius on your insert makes a difference on finishing, and the DOC is the elephant in the room when discussing the efficacy of boring bars, am I right?
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A steel boring bar is typically good for 3-4X the diameter of the bar for max depth of cut - unless you don't care about maintaining any kind of tolerance. A carbide bar is typically good for 7-9X diameter for maximum depth of cut. For this job you would need a 5/8" diameter carbide boring bar that is at least 8-inches long, and that will set you back over $500. Here's one example. Your best bet for this job IMO is to drill slightly undersized and use a 3/4" reamer.
TOOL$AVER Solid Carbide Boring Bar 5/8" x 8.75" C10-SCLCR3 (CCMT 32.52) USA MADE | eBay
NO coolant. When internal machining, the limiting factor on CNC turning centers or multi-task machines is often therigidity (or lack thereof) of the boring bar. While in the cut the steel shank deflects (pushes-off), even more so when extended beyond 3:1 (L/D) and when threading, machining...
www.ebay.com
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$500 is the retail price on that boring bar, and I'm just a private citizen, man!. I got some good ones from @mattthemuppet2 through this site for a proper workingman's price. Nice used boring bars aren't bad on eBay, either; toolhoding doesn't have to be thought-cripplingly expensive. I still think investing in a boring bar to do the job is a far better use of funds than a reamer, which is only good for one size. Precision can be obtained either way. But in the future, the boring bar will come in handy a lot more often than one specific reamer will. It's shoponomics.