Attempt to fix, or re-purpose, or just scrap?

[Bill PhinnParticipant @billphinn90025]

I recently bought off Amazon an R8-MT1 adaptor to enable me to use my increasing stock of taper shank drills in my milling machine.

Unfortunately, unlike an R8-MT2 adaptor I have that I bought from a UK-based supplier before they ceased trading, which had only a few microns of runout up the taper, this MT1 adaptor has about 0.1mm runout up the taper and is never going to let me do good drilling with it.

Question is, how feasible is it to re-bore the internal MT1 taper in a way that improves concentricity? I can hold the top section of the adaptor in a 3- or 4-jaw chuck but what would I indicate off to keep the 7/16-20 threaded section held in the chuck jaws as perfectly in line as possible with the bore I want to create anew? The black central section of the adaptor isn’t straight-sided but has a very slight and uneven taper on it, and the male taper doesn’t look like a very good reference surface either, especially as it may be contributing to the overall eccentricity of drills placed in the adaptor, which typically show considerably more than the 0.1mm runout measured in the bore.

As an alternative I could make it into a side-lock holder for end mills, but there isn’t really anywhere suitable to drill for a set screw as, unlike on dedicated end-mill holders, there is very little in the way of a straight-sided section down below the male taper.

After receiving a partial refund, the adaptor cost me less than £5, so whatever I do with it it won’t be a great loss.

[Trevor Drabble 1Participant @trevordrabble1]

Rotagrip have them on offer at £32. Maybe worth a phone call to check the accuracy of them before going any further ?

[bernard towersParticipant @bernardtowers37738]

Why did you take a partial refund?

[Bill PhinnParticipant @billphinn90025]

Thank you for the replies.

Trevor, I see their £32 one is branded Omega. I’m confident that neither that one nor the one they have for nearly £20 less improbably branded Bison is likely to have excessive runout, and if either did I’m sure a return would not be a problem.

Bernard, I suppose I could have pushed for a full refund, but the sales description made no claims as to the maximum allowable runout and the seller was unwilling to pay for a return to China, the cost of which would have comfortably exceeded the purchase price. I felt there was room for mercy.

[Clive FosterParticipant @clivefoster55965]

Your reference is the external taper of the R8 shank.

The options are either :-

1) get that running true in the lathe and correct the MT taper by boring

2) make some sort of MT1 shank accurately drilled for a centre in the end so it can be supported in the tailstock then trim the R8 taper so tit runs true to the internal bore. May need to add some clearance at the parallel end to ensure it fits in the spindle.

Classic can be done but life is too short jobs.

Clive

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