T.I.R. probs drilling
T.I.R. probs drilling
(OP)
I'm haveing problems drilling concentric to the O.D. The work is being done in a Hydromat Indexing machine in which the tooling is rotated and moved into the material. I have tried gundrills and reaming and fluted drill to size, with or with out a previous hole, and we always end up with a fairly good entrance hole, but the exit is off around .003 to .005 or more. The machine is squared up and lined up as well. The part is compacted metal, cuts like a gray cast iron. Also the feeds and speeds have been brought up and down with little to no difference. Does anyone have any ideas?





RE: T.I.R. probs drilling
As for gundrilling, it seemed we got better accuracy by spinning the part and not the drill.
RE: T.I.R. probs drilling
RE: T.I.R. probs drilling
The proper way to solve the problem is to rotate the work or rotate both, the work and the drill.
Viktor
http://viktorastakhov.tripod.com
RE: T.I.R. probs drilling
Good luck, and let us know if anything works.
RE: T.I.R. probs drilling
RE: T.I.R. probs drilling
I believe I can help you out. Being a specialist in deep-hole drilling
http://gundrilling.tripod.com
, I can tell you that the problem can be solved if a proper approach is taken. According to your last message, you have a solid carbide bushing. The next step is to get proper gundrill to assure minimum possible runout and hole deviation. Gundrilling is a system which includes many parameters and components
(if you have a chance, look at my article published in Cutting Tool Engineering, December 2001: GUNDRILLING KNOW HOW).
Only when these components are coherent, the desirable result can be achieved. One missed link and you out. The prime concerns in your case are: gundrill design and geometry; alignment “starting bushing-drill holder”, accuracy of the feed motion in terms of it straightness (the drill path just copies this motion so the hole straightness cannot be better that the accuracy of this motion), clearance in the starting bushing (the difference between the drill and bushing diameters), the distance between the faces of the bushing and the part, type and pressure of the coolant.
Regards
Viktor
http://viktorastakhov.tripod.com
RE: T.I.R. probs drilling
RE: T.I.R. probs drilling
3000 rpm, 5ipm (it could then be increased up to 4000 rpm, 7 ipm)
the two-flute gundrills are not suitable for your application at all. The problem is that they are not self-centered (self-pilot, as we call this feature) so you cannot, even in principle, to get straight hole (I mean, as straight as with a self-piloting drill). Therefore, I would not recommend using these drills for your application unless you enjoy troubles.
Viktor
http://viktorastakhov.tripod.com
RE: T.I.R. probs drilling
Fulton Tool Co.
Peter Russell
WWW.Fultontool.com
RE: T.I.R. probs drilling
resulted in the use of 3/16 bore bars. The parts are pressed with a hole in them already and those holes aren't very straight. Could this reamer do the trick, straightening the hole out as it cuts.?
RE: T.I.R. probs drilling
RE: T.I.R. probs drilling
About “whipping” of gundrills. This is a myth. If a gundrill designed properly and has proper support including a whipguide, it should not whip at all. We use gundrill for automotive applications which we run at 8,000-12,000 rpm and whipping is not an issue when the drilling system is right.
The apparent low stiffness (or as we call it, bending rigidity) has nothing to do with whipping. It does not affect the performance of such drills. Gundrill MUST BE MADE for the application as well as the drilling system.
Viktor
http://viktorastakhov.tripod.com
RE: T.I.R. probs drilling
RE: T.I.R. probs drilling
RE: T.I.R. probs drilling
RE: T.I.R. probs drilling
RE: T.I.R. probs drilling
Viktor
http://viktorastakhov.tripod.com
RE: T.I.R. probs drilling
RE: T.I.R. probs drilling
RE: T.I.R. probs drilling
RE: T.I.R. probs drilling
RE: T.I.R. probs drilling
Excessive accuaracy is a sign of poor breeding. -Socrates.
RE: T.I.R. probs drilling
Make the cored hole as large as possible as long as you are removing material with each pass of the cutting tool.
Secure the bars as close to the spindle bearings as possible. Maybe Hydromat could help with this, it is unlikely that they will be much help regarding the tooling. They may need to upgrade the class of bearings at the station where you are making the final pass.
Instead of zeroing in on the cycle time, look at the total cost, including machine maintenance; tooling cost; downtime cost etc. If you do that properly my guess is that the cycle time will increase, but the number of acceptable parts produced per shift will increase.
Sorry for being so long winded, but I have been in your position in the past and can appreciate what you are going through. Good luck.
RE: T.I.R. probs drilling
WWW.cogsdill.com