Question About Concrete Core Bits

I own and have used many core bits before, but this is the first time I ever got any with a tapered shaft socket. The SDS+ shaft has a matching tapered shaft, that slides into the bit.
My question is: What holds it all together? Does the SDS+ shaft just spin the bit by friction? I know I could use a starter bit, right down the center of the shaft, but theres no threads anywhere for tightening the shaft to the bit.
These bits are:
Hitachi 725758 4-Inch x 4-Inch 8 Teeth Hollow Core Bit with 1:8 Internal Tapered Shank
and
Hitachi 725754 2-Inch x 4-Inch 8 Teeth Hollow Core Bit with 1:8 Internal Tapered Shank
the shank is:
Hitachi 725733 SDS Plus 4-1/2-Inch Long 1:8 Tapered Shank for Hollow Core Bits

Thanks.

Matching machined tapers hold the bit it place. Similar to the Morse taper that hold most drill chucks in place
on a drill press.

Bob

RMA wrote:Matching machined tapers hold the bit it place. Similar to the Morse taper that hold most drill chucks in place
on a drill press.

Bob

Thanks Bob, I had that idea, since my drill press uses a tapered chuck. I just never saw it used on a bit before. I thought the vibes from my Hammer/Drill would knock it out and allow it to slip.

Actually the vibration helps hold then in place, too. Normally, there is a centering pilot bit that may be held in by a taper or a simple rubber o-ring, as Hilti does. Either way, they work great, last a long time and will be in your tool box for years.
Don't worry about them falling apart as you are coring, just keep enough water on the operation. By the way, Hitachi does a terrific job with there concrete hammers, drills, breakers. etc. Fair prices, very durable tools. Enjoy! :pepsi:

whistlenut wrote:Actually the vibration helps hold then in place, too. Normally, there is a centering pilot bit that may be held in by a taper or a simple rubber o-ring, as Hilti does. Either way, they work great, last a long time and will be in your tool box for years.
Don't worry about them falling apart as you are coring, just keep enough water on the operation. By the way, Hitachi does a terrific job with there concrete hammers, drills, breakers. etc. Fair prices, very durable tools. Enjoy! :pepsi:

Great news! I was affraid of turning something this big, with just a friction connection. Yep, I got a pilot bit for it already.
I have a BoschHammer Model 11222EVs, that is fantastic. Its about 5 years old. And I have been taken for a ride or two, on my Milwaulkie Hole Hawg.
MORE POWER !!!!!

I wouldn't own a hole hawg! What an awful knuckle busting tool they are. Try a Dewalt 124 (and dewalt isn't generally my favorite tool). They have a clutch on low speed that works perfectly and on high speed they are long enough so you can easily hold a stall. Of course they are not a hammer drill, but to replace a hole hawg they are the answer.


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Yeah, I hear ya on the holw hawg Freddy, I used to use the handles from my emt benders for the hawg side handles and comandere a couple of extra boys to hold on in case of a stall.