D bit help

[BOB BLACKSHAW 1Participant @bobblackshaw1]

I have started to make a 2/3 scale of A A Rayman high speed marine engine, a call for several small D bits are needed. I have made a few D bits from 10mm to 6mm but wondering if I have been using them correctly, when boring a hole I have the D bit at a slight angle so not parallel to the bored hole so only the cutting edge and not the bar side is touching the hole.

The reason I am asking this is that it is suggested that several D bits from 3/32 to 3/8 at intervals of 1/32 are to be made. Basically my question is this, say a 6mm bored hole, only use a 6mm D bit.

Thanks Bob

[BOB BLACKSHAW 1Participant @bobblackshaw1]

[Old SchoolParticipant @oldschool]

This perhaps a d bit is best described as a simple reamer and use as you would a reamer.

i built A A Rayman,s high speed steam engine along with a flash steam boiler. Alan supplied me with drawings and a lot of help to build the boat that goes with it. My boat gets up and planes no problem at all.

[JasonBModerator @jasonb]

Feed the in in line with the lathe axis, the tailstock chuck works fine. So you will need one for each size thought the larger holes could be bored with a small boring bar.

[Neil WyattModerator @neilwyatt]

The d-bit works by the hole steadying it and only cuts on the tip. It should be dead to size.

Neil

[BOB BLACKSHAW 1Participant @bobblackshaw1]

Thanks for the advice, I have been using the D bit wrong but luckily my bored holes have come out okay, I have been using it like a boring tool.

Bob

[Speedy Builder5Participant @speedybuilder5]

Would a 'D' bit correct a hole that has wandered away from the axis of a shaft. I have drilled some cast iron buffers and see that the 1/8" hole drilled through the centre of the buffer has wandered off and was thinking of boring with a larger 'D' bit to bring a larger hole true to the axis.

[JasonBModerator @jasonb]

Should do or you can just use a milling cutter

[Neil WyattModerator @neilwyatt]

Posted by BOB BLACKSHAW on 19/08/2020 16:20:46:

Thanks for the advice, I have been using the D bit wrong but luckily my bored holes have come out okay, I have been using it like a boring tool.

Bob

They work well as boring tools, especially if ground to a semicircle, rather more than you want for a d-bit, and some boring tools are very like d-bits.

[Mike PooleParticipant @mikepoole82104]

Don’t forget the toolmakers reamer if you aren’t reaming a blind hole, they are simple to make from silver steel, just grind the end at a angle and harden and temper or the other way round if you prefer.

Mike

[Speedy Builder5Participant @speedybuilder5]

I think it would have to be a "D" bit as there is 3/4" depth into the buffer before the 1/8" diameter starts, and then 3/4" of material to be bored. Perhaps I could turn the buffer around and bore from the other end, setting it up in a 4 jaw to ensure concentricity. This would reduce the 'overhang' of either milling cutter or D bit.

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