# Taper Pin Reamer



## walterwoj (Jun 12, 2020)

I have to make a taper pin reamer for my Induma Power Feed Project.  I looked at buying them but $60 for a tool I'll use twice is a little excessive.  The pins are metric 5mm taper pins (got them from mcmaster-carr)  I purchased some 1/4" A-2 Drill rod to make it from.  I planned on turning a matching taper on the rod but make it extra long (so I can use it for more than 1 size).  Then I plan on using my smallest carbide end mill to cut a flute (maybe 2) in the taper.  Then I'm going to red-neck harden it and draw it back with a map gas torch.  Hopefully I can ream out 2 holes to take the taper pins!

Any thoughts or pointers?


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## T Bredehoft (Jun 12, 2020)

Your cutting edge will need relief in front  of it. You might get away with free handing it on a grinder. Just a light skin off the diameter.


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## cathead (Jun 13, 2020)

How about grinding down an appropriately sized drill bit?  Maybe try putting the bit in a drill and
grind it on a disc or belt sander.


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## JRaut (Jun 13, 2020)

Is a metric taper the same angle as a ‘Mercian taper?

I’ve got standard taper pin reamers you could borrow for the cost of the postage. 

I’d be concerned about actually being able to machine a good shallow taper on such a slender rod without escesive flex.

Or you could make what I think Clickspring refers to as a taper, or clock-maker’s broach. Would be much easier to make, only concern there would be that those are usually used on brass, not steel.


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## projectnut (Jun 13, 2020)

There are currently over 800 taper pin reamers listed on eBay.  Nearly 600 are new in the box, with over 600 in the USA.  They start at less than $10.00.  I had a project that needed several sizes a while ago and managed to find all I needed on eBay for less than $20.00.  Maybe you can find the one you need for a similar price.  I'm not sure you could buy the drill rod much cheaper than the finished reamer.


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## RandyWilson (Jun 13, 2020)

What I'm seeing in the interwebs is Merican tapers are 1/4" per foot. Metric is 1mm in 50mm.  Mathing it down to a ratio, you get 48:1 for imperial, and 50:1 for metric.  So a 3/16" reamer and a slightly larger than normal hammer? Maybe?


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## benmychree (Jun 13, 2020)

Yes, USA and Metric reamers are different taper, but why not just ream for a USA taper and use a USA taper pin, easy if not hardened parts.  Trying to make a reamer without proper equipment would be nearly impossible and would likely result in a poor fit between the hole and the pin; don't wase your time trying.


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## gjmontll (Jun 13, 2020)

Three years ago I needed two custom reamers for a project. I made them as D-bits from O-1 drill rod. They worked well on both Al and steel.
You can read about this and see photos in my "Greg's French 75 Mm Field Artillery Model" posted at https://www.hobby-machinist.com/threads/gregs-french-75-mm-field-artillery-model.34665/
It is a long series of posts, the custom reamer is discussed in my postings from 7 June 2015 through 12 July 2015. 
    Greg


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