Help please with boring head on a drill press

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I started a new thread to be more specific with what I need help with. I was so happy I got my drill press aligned and squared up to the backhoe frame. I tried the boring head with the brazed carbide boring bars but it didn't go well. The 1st boring bar had the biggest shank but the carbide chipped trying to take a very light cut about half way down the bore. I didn't have the bore ground perfectly square top to bottom. Then I tried a boring bar with a smaller shank and it didn't have a big chip taken out but seemed to round itself and dull. I set the carbide pretty much straight up and down after watching a couple video's on the net. They didn't cut well at all and caused a lot of vibration. It might have been more due the carbide chipping or dulling.  This tells me I need to strap and clamp the drill press better and get it as rigid as possible to the backhoe frame. I should be able to do this pretty easily. I plan to put a block of wood between the base of the drill press and the lower swing pivot (they should be very close to parallel) and then either use some 1/2" ready-rod and clamp them together or use a ratchet strap. Then I plan to put another block of wood cut to length between the drill press column and the upper pivot I'm boring and put a ratchet strap on it. I can also clamp the drill press table to the underside of the top pivot I'm boring with a wood spacer. I think this should hold the drill press as solid as possible top and bottom. I kind of doubt there'd be any warranty on the boring bars but the worst they can say is no. I read the import boring bars aren't very good and often need to be re-ground so they actually work. I plan to go to a machine shop supply to get a better quality boring bar. Should I try to find an HSS boring bar or would a better quality brazed carbide work? What about spending more for one with a replaceable insert and what type of insert? I've also read you need to turn faster with carbide but I think I'm at about 180 RPM which might be a little fast already. I'm doing a little under 3" bore. Is straight up and down the correct angle for the cutting head? What do you guys with machining experience suggest to give me the best chance of success? Thankfully I haven't ruined anything expect a couple cheap boring bars.Last edited by Welder Dave; 3 Hours Ago at 12:07 AM.
Reply:Simple formula for surface speed, and consequently rpm's.  Steel cuts at 100sfm give or take.  100x4=400  Divide 400 by the diameter of the hole.  400/3=around 130rpm.  You can run a bit faster with carbide, but I'd stay around 200rpm, considering you're probably doing interrupted cuts.Check the rake on the cutting tool.  I like a bit of a positive rake.  (The cutting edge pointed slightly up, not at 90* to the steel)Don't take too big a bite of the apple.  Keep your depth of cut between 10-15 thou, and be patient.  I'd imagine your setup isn't very rigid, being as it's not welded to the part.  Lack of rigidity, and deep cuts, equals ruined tooling.........and ruined cuts.  Same with your downfeed.......keep it slow.Use oil, just a squirt with each pass.
Reply:I like HSS boring bars, but I grind them myself.  If you don't want to do grinding, the brazed carbide is your best bet.  Buy ones that are the thickest you can find that will fit your boring head, with the proper depth.  Thicker bar means better rigidity
Reply:Thanks Sam,I was only hitting one section of the bore with a very light cut. Is there a minimum amount you need to remove? Hopefully getting the drill press as solid as possible will make a big difference. I think someone posted that HSS is more forgiving. I have some Rapid tap cutting oil I can use and will tip the cutting edge forward a touch.Last edited by Welder Dave; 3 Hours Ago at 12:50 AM.
Reply:

Originally Posted by Welder Dave

Thanks Sam,I was only hitting one section of the bore with a very light cut. Is there a minimum amount you need to remove? Hopefully getting the drill press as solid as possible will make a big difference. I think someone posted that HSS is more forgiving. I have some Rapid tap cutting oil I can use and will tip the cutting edge forward a touch.
Reply:Circle is boring bar, rectangle is carbide, interrupted line in centerline, Centerpoint is blue. Grey lines are where I suggest you grind the carbide to to get proper geometry.


Edit: not exactly... but close enough. I'd give more support to the cutting edge (as much as you can without rubbing when cutting.Also, excuse the ugly doodles. I did that on my cellphone.Sent from my Lincoln Buzzbox using Tapatalk
Reply:Ok... I have videos from other channels to link to, but these are a start

I know those don't relate directly to boring bars (I think... haven't seen those videos in a long time), but a boring bar is just like any other lathe tool. The drill bit video... I dunno. Shows cutting geometry? The HSS grinding video does a better job of it for this application, though. TOT makes some good content.
Reply: And somewhere in THIS video is where Tony talks about the chity import boring bars he has and how he fixes them.
Reply:I'm sure the boring bar set I got is imported, probably from China. HSS seem to be hard to find. Are the indexable a good option?
Reply:

Originally Posted by Welder Dave

I'm sure the boring bar set I got is imported, probably from China. HSS seem to be hard to find. Are the indexable a good option?
Reply:Also, how big is the bore? Since you're having to order stuff, anyway....Keep in mind this is a post beer...What about buying a taper shank that fits your drill press, welding a large diameter piece of bar stock to it, cross drilling it to fit a piece of drill rod (HSS round rod) and then drilling and tapping holes that intersect the first hole, so that you can lock the drill rod in place. All you have to do then, is grind the drill rod into a decent cutting geometry, stick it in your newly made tool, adjust the stick out so you have about a... maybe a 10 thou cut? And go to town.Just like a line boring machine... makes sense, considering you're doing the job of a line borer

https://www.amazon.com/ApplianPar-Sl...a-849380364223It doesn't have to be anything fancy and runout doesn't matter at all, since it's a single point cutting tool. Just make sure the Morse taper stays relatively concentric. Just make sure you don't put too much heat in the part when you weld it.The link is to literally the first result I saw on Google.Sent from my Lincoln Buzzbox using Tapatalk
Reply:Bore is just under 3 inch. I'm pretty limited as to tools. I have a couple angle grinders. Hoping I can find a decent boring bar that isn't too expensive. I think solidly strapping and/or clamping the drill press to the backhoe frame will make a big difference once I have a decent boring bar. When I checked the run out on just the arbor is was the same as the morse taper on the drill, .003". I have an adjustable boring head so I could probably grind a 1/2" piece of drill rod to fit in it. Thanks so much for your help 52 Ford!
Reply:

Originally Posted by Welder Dave

Bore is just under 3 inch. I'm pretty limited as to tools. I have a couple angle grinders. Hoping I can find a decent boring bar that isn't too expensive. I think solidly strapping and/or clamping the drill press to the backhoe frame will make a big difference once I have a decent boring bar. When I checked the run out on just the arbor is was the same as the morse taper on the drill, .003". I have an adjustable boring head so I could probably grind a 1/2" piece of drill rod to fit in it. Thanks so much for your help 52 Ford!