taper pins

[Garry ColesParticipant @garrycoles69390]

Hi, I WANT TO MAKE A FEW TAPER PIN HOLES, AND AM NOT SURE HOW TO GO ABOUT IT. I’VE GOT A 1/16 TAPER PIN REAMER, SO DO YOU DRILL UNDER SIZE AND JUST KEEP REAMING IT OUT UNTIL IT’S A RIGHT FIT.

GARRY

[JasonBModerator @jasonb]

That is basically it. Measure the small end of the reamer to get your drill size. If it is quite a thick part I will use a couple of sizes to give a stepped hole which reduces the load on the reamer.

[Garry ColesParticipant @garrycoles69390]

Thanks Jason, that’s what I thought.

[Julie AnnParticipant @julieann]

Imperial taper pins have a taper of 1:48 while metric taper pins have a taper of 1:50. To add to the confusion imperial taper pins are specified by the large end diameter while metric is specified by the small end diameter.

Julie

[Bo’sunParticipant @bosun58570]

Thanks Julie Ann, a new school day for me.

[John PurdyParticipant @johnpurdy78347]

According to Machinery’s Handbook the drill size for a 1/16″ (#7) taper pin is .0469″, see chart below. Drill size, shown in the left most column,  is determined by following the line to the left of the right most dot on the heavy line corresponding to the taper pin size. As mentioned above if the pin is large and/or long two or more drills should be used to step drill the hole, shown as the other dots to the left on the line for that pin.

John

[NimbleParticipant @nimble]

Hi Garry,

When installing taper pins I place a dot punch mark beside the thick end of the pin, the logic being that when inserting the pin you would dot punch at the same time. Probably useful when the pins are small and short  or hard to measure.

Nimble Neil.

[Mike HurleyParticipant @mikehurley60381]

The table kindly inserted by by John Purdy is fascinating.

I’ve never trained as a professional engineer so may be just ignorant of the practicalities of its use?

Can you really get a drill of say 0.1875 as shown in one example ? Even assuming it’s a one off, or custom made / d-bit etc would it ever cut to this accuracy anyway?

I’m not being cynical or anything, just really interested to learn.

Mike

[JasonBModerator @jasonb]

Unless I’m mistaken 0.1875 drills are readily available. Most people tend to call them 3/16″ drills.

As the page is from an American book the dimensions will be in Banannas inches. it also shows the way the US sizes their small pins by using zeros.

[duncan webster 1Participant @duncanwebster1]

I think you’ll find thd drill sizes are decimal equivalent of 1/64 increments.

[John PurdyParticipant @johnpurdy78347]

As Duncan says the drill sizes in the left most column are in 1/64″ increments.  The only pins I have used are 1/16, 5/64 and 3/32 (#s 7/0 6/0 and 5/0). To determine the drill size I run a line from the point on the heavy line for that pin that corresponds to the length of the pin in question, over to the left where it ends at the drill size column then interpolate between the two drill sizes it lies between and use the nearest smaller, metric/number/inch drill I have.  Hope this makes sense.

John

[old martParticipant @oldmart]

And the number drills and letter drills besides the common 1/64″ fraction drills, and then your metric drills, easily found in 0.1 mm steps.

[howardbParticipant @howardb]

Has anybody heard of or used these to drill the taper hole before cleaning it up to size with a taper pin reamer?

https://www.drill-service.co.uk/products/drills/taper-pin-drill/dtp-hss-taper-pin-drill/

When working for a UK subsidiary of a US company who designed and made their own labelling and packing machines in the US to process their own products, these taper drills were in common use in our maintenance workshop the UK.

There were a lot of taper pins on those machines when replacing drive shafts etc.

[Julie AnnParticipant @julieann]

I know of them but have never fitted enough, or large enough sizes, to justify the cost.

Julie

[duncan webster 1Participant @duncanwebster1]

Wrong button

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