D bit reamers

Sure Dave, They work just fine and to a decent tolerance. If you want to do valve guides it pays to do a stepped version where the first part at full diameter is to the original size then steps up to the size you need. Turn a small groove at the transition point between the two Mill or grind the 'D' shape so it's on the larger diameter and part of the pilot diameter and then hand sharpen the leading edge of the groove to act as the cutting edge.

With a pilot they tend to cut tight as regards tolerance. If you have access to surface grind the D after hardening then choose the rotation of the wheel so it throws the burr out over the cutting edge as opposed to the trailing edge.

-- Regards,

John Stevenson Nottingham, England.

: >

: >and if so how well did they work and to what tolerance? : >

: >It might be one solution to my need to ream various sizes of valve guides : >without buying dozens of custom ground reamers. : >

: Sure Dave, : They work just fine and to a decent tolerance. : If you want to do valve guides it pays to do a stepped version where the : first part at full diameter is to the original size then steps up to the : size you need. : Turn a small groove at the transition point between the two : Mill or grind the 'D' shape so it's on the larger diameter and part of the : pilot diameter and then hand sharpen the leading edge of the groove to act : as the cutting edge. : : With a pilot they tend to cut tight as regards tolerance. If you have : access to surface grind the D after hardening then choose the rotation of : the wheel so it throws the burr out over the cutting edge as opposed to the : trailing edge. : -- : Regards, : : John Stevenson : Nottingham, England.

Agree with John they are unbelievably simple to make just mill 1/2 thickness of silver steel angle end and polish, superbly effective they were better than the cheaper reamers on sale to use. Have a go it takes little time or material Chris R

I second the comments others have made - they work surprisingly well with close tolerance. Since you want to ream through holes (ie. not blind holes) then there is a varient that is even easier to make. Simply mill, or file, the flat at a shallow angle to the axis of the rod. IE. Something like this...

_ | \ | \ | \ | | | |

That way there is no need to carefully measure anything. Just try it, you will be surprised. You still need lubricant though.

-- Regards, Gary Wooding

Thanks John. When I get a roundtuit I'll make one and give it a try.

Dave Baker - Puma Race Engines

I did have a pile of roundtuits while I was at work - one of our staff made a batch and stocked up everyone with them. Sadly, with the passage of ime - non-power-transmitting, of course - my stock has dwindled, like the wind in a clock, to zero, so there is no power left to transmit rouindtuits to deserving recipients, nor are there any roudtuits to transmit :(

They were SO useful, while we still had them, and quite pretty with it, but now I just can't roundtuit to find any more roundtuits..........

Dave.

p.s. I expect that the twerps of the EU will have outlawed them, along with curly bananas, and other magical things, so the only permitted roundtuits will probably now be square ones, and will no longer fit wholely snugly in the round hole in your anvil...............