Sorry for flogging a tired horse - I did read some other threads about deep drilling, but still not confident.
I need to make a punch/die for a pattern of holes a little over 1/8 inch. Just to punch a few hundred prototypes.
I will finish the holes with number drills to get the exact diameter, but obviously twist drills will not be straight enough.
To drill through the block, stripper, and die, is 1.5 inches, 12:1 depth ratio. I was going to pre-drill with an available 1/8 carbide endmill, but I can see that thin flat-end mills start to wander right from initial contact (surprise!).
To improve the outlook, note that the hole only has to be accurate at the stripper/die interface. Also the die can be thinned out from the back beforehand.
Also the punches will be 1/4in A2 drill blanks, ground to size at the end. That means the upper block (and maybe the stripper) can be pre drilled at 1/4 inch, almost down to the die block interface. So the current plan is:
1) Pocket the die block underneath the working area
2) Clamp the stack face up (die block on the bottom)
3) Drill the guide pin holes (4 x 3/8in) & insert guide pins before proceeding (with carbide tool)
4) Drill 1/4 inch through the top block & halfway through the stripper (carbide)
5) Drill 1/8 inch through the rest of the stripper and die block down to the pocket (carbide)
6) Number drill to size (HSS)
So the actual DOC can be about 1/2 inch and the critical interface only about 1/8 deep.
Unfortunately the material is 4140 half-hard rectangular bar (which has a crust) and will be fully hardened. That's all I have to work with. All work done on a BP with Accu-rite DRO, no coolant (just air nozzle).
I'm mainly wondering what to drill with. I'm leaning toward drill-pointed mills, but don't know if 2- or 4-flute is more rigid?
Can pointed endmills plunge cut? They don't look like the tip is good for that. I have some carbide "spot drills" with utterly useless points (well, they're eBay)
For the 1/8 inch hole x 1/2 deep, maybe a spade blade? Seems like the lack of side cutters would be an advantage (if I peck & blow the chips out)? Even though the DOC is limited, it still has to stick-out about an inch to reach the hole.
I do expect the 4140 die to last long enough punching 16-ga mild steel for the qty needed, and we have a surface grinder.
(We used to have scrap D2, S7 etc. but they threw it away!!!) We do have a press with enough force & can stagger the punches.
Everything has to be out-of-pocket, including the die springs, product material, etc. & I already spend $100's a month on tools, so I'm broke... nothing fancy!
I wish I had enough expertise to give back to this forum as I have received, but unfortunately I am only an electrical engineer. Any electrical questions I would be happy to help, but please, no more "free energy" projects (yes, I have been asked)!
I need to make a punch/die for a pattern of holes a little over 1/8 inch. Just to punch a few hundred prototypes.
I will finish the holes with number drills to get the exact diameter, but obviously twist drills will not be straight enough.
To drill through the block, stripper, and die, is 1.5 inches, 12:1 depth ratio. I was going to pre-drill with an available 1/8 carbide endmill, but I can see that thin flat-end mills start to wander right from initial contact (surprise!).
To improve the outlook, note that the hole only has to be accurate at the stripper/die interface. Also the die can be thinned out from the back beforehand.
Also the punches will be 1/4in A2 drill blanks, ground to size at the end. That means the upper block (and maybe the stripper) can be pre drilled at 1/4 inch, almost down to the die block interface. So the current plan is:
1) Pocket the die block underneath the working area
2) Clamp the stack face up (die block on the bottom)
3) Drill the guide pin holes (4 x 3/8in) & insert guide pins before proceeding (with carbide tool)
4) Drill 1/4 inch through the top block & halfway through the stripper (carbide)
5) Drill 1/8 inch through the rest of the stripper and die block down to the pocket (carbide)
6) Number drill to size (HSS)
So the actual DOC can be about 1/2 inch and the critical interface only about 1/8 deep.
Unfortunately the material is 4140 half-hard rectangular bar (which has a crust) and will be fully hardened. That's all I have to work with. All work done on a BP with Accu-rite DRO, no coolant (just air nozzle).
I'm mainly wondering what to drill with. I'm leaning toward drill-pointed mills, but don't know if 2- or 4-flute is more rigid?
Can pointed endmills plunge cut? They don't look like the tip is good for that. I have some carbide "spot drills" with utterly useless points (well, they're eBay)
For the 1/8 inch hole x 1/2 deep, maybe a spade blade? Seems like the lack of side cutters would be an advantage (if I peck & blow the chips out)? Even though the DOC is limited, it still has to stick-out about an inch to reach the hole.
I do expect the 4140 die to last long enough punching 16-ga mild steel for the qty needed, and we have a surface grinder.
(We used to have scrap D2, S7 etc. but they threw it away!!!) We do have a press with enough force & can stagger the punches.
Everything has to be out-of-pocket, including the die springs, product material, etc. & I already spend $100's a month on tools, so I'm broke... nothing fancy!
I wish I had enough expertise to give back to this forum as I have received, but unfortunately I am only an electrical engineer. Any electrical questions I would be happy to help, but please, no more "free energy" projects (yes, I have been asked)!