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Thread: Reverse taper bit.
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14th November 2019, 10:38 AM #1Try not to be late, but never be early.
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Reverse taper bit.
Attended the Seniors Have a Go Day at Burswood yesterday, an elderly gent described a drill bit for putting a reverse flare in the bottom of a blind hole. Basically you bore a hole, lets say 3/4" dia x 2" deep, then insert the taper bit which has a springloaded ball in the centre. When the ball touches the bottom of the hole pressure forces it back into the bit which in turn spreads the (2?) cutters and as they rotate they create a reverse taper.
Has anyone seen one of these bits and if so could you post a photo please?
Cheers,
Geoff.
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14th November 2019 10:38 AM # ADSGoogle Adsense Advertisement
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14th November 2019, 09:50 PM #2
I couldn't find any pictures, but there are some patents in that direction Geoff.
GB178620A - An improved tool for boring undercut or reverse taper holes in timber and the like
- Google Patents 1921
US2594671A - Internal reverse taper reamer
- Google Patents 1948
US1013970A - Auger for boring reversed-taper holes.
- Google Patents 1912
US7589A - Expansible bit - Google Patents 1850
US3358722A - Reverse taper boring tool
- Google Patents 1967
https://patents.google.com/patent/US2638948A/en 1949
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14th November 2019, 10:17 PM #3
There was a tool you could buy to do that. I can't remember the brand name. If I recall correctly, Rockler sold them. It seemed a great idea but the price was not attractive enough to me for something for which I would have a very limited use. Maybe that will jog someone else's memory.
I'm pretty sure that Rockler no longer sell the product. It was pretty niche and would not have been a volume seller.
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16th November 2019, 12:44 AM #4
An Australian one. US1536208A - Expansible boring tool
- Google Patents 1948
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16th November 2019, 08:41 AM #5Try not to be late, but never be early.
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Thanks Paul and Mark, unfortunately I didn't get as much info' from the man I spoke to as I should've, hand or machine driven, single size or variable etc. This last one by Amos Gosper looks quite interesting, I wonder if it ever made it into production?
Cheers,
Geoff.
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16th November 2019, 09:43 AM #6
As an aside but on a similar theme we used a "belling tool" to open out the base of bored pier foundations for telco guyed masts in the late 1980's to mid 1990's.
Mind you it was quite impressive opening out 600, 750 & 900mm dia piers to about 1.3m dia (900mm piers) for the base of the bell. The tool was essentially a cylinder with a pressure/force activated cutter that would expand at the base of the 6+m deep piers when a downward force was applied by the auger boom. The spoil was forced by the cutter into the cylinder. When being extracted the cutter would return into the cylinder, but some times had to be "encouraged" if the soil was rocky.
The auger unit was a scaled up version of the styles you see the power authorities using to install power poles. It was mounted on a 6x6 Isuzu truck.Mobyturns
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16th November 2019, 09:52 AM #7Try not to be late, but never be early.
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Well what a coincidence, I had a similar conversation with a friend yesterday. His father, well over 50 years ago in England, was working on a machine boring pilings for a wharf, the machine would bore down through the sand and mud until it encountered rock. Once it had bored into the rock it would expand and create a bell.
Cheers,
Geoff.
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16th November 2019, 01:37 PM #8
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