Recommendations needed for a long core-drill.

[danielm]

I need to core out two test coupons out of 3" diameter holes. Material is 35HRC steel.  Hole depths are 10.5" and 13".  The coupon needs to be no smaller than .625diameter.  

 

Thanks in advance for any suggestions!

 

DM

[crazy^millman]

That will have to be special made. There are few companies that make them. Should be able to do a google search and turn something up.

[Colin Gilchrist]

Get a Sandvik Tailor Made Trepanning tool. That would be my recommendation. Definitely have to get something custom made.

[Colin Gilchrist]

How are you holding the part? That is a long slug to have "bounding around" once you cut through the part. If possible, I'd Trepan down to near the bottom, leaving maybe .250 to keep the slug centered and upright, then flip the part, and Feed Mill or Face Mill the thin floor from the backside. That way the slug just falls into the cavity once you break through on the 2nd side. I'd ask the Sandvik guy. Maybe it isn't an issue if you break through, and the slug will just remain when you retract the drill?

[danielm]

Hey Colin!

Machine is a Horizontal HA12500. Big ole steel part that weighs 4 tons.. Two cores...one is 12.25"long and the other is 9.6".  (Cores are actually for test coupons).  

I have never done a core application...so this will be new to me ....and from the sounds of it, not just me.

The steel is soft though..32hrc.

 

Thanks man!

 

 

[Leon82]

Is it too thick for a water jet ?

[danielm]

Unknown on thickness as to the waterjet idea.  moot point tho...customer wants it all done on the horizontal...

[Colin Gilchrist]

Yeah, on a horizontal, dealing with the break through will be an issue, if the core is now bouncing around inside the drill. Do you have access to the hole from both sides, or only one? If both, you could drill half way from one side, then stick a cylindrical (hollow) temporary plug in the freshly drilled side. That way when you finish from the 2nd side, the core is supported.

Gotta love the idiot engineer who thought taking a test coupon inside the holes was a good idea. 

[Colin Gilchrist]

I would seriously consider EDM...