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Educate me on tapered pins, reamers & drills

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petertha:
Thus far I have not had to deal with these, but I can envision their usefulness in model engineering & tooling/machines in general. I'll lay out what I think I've gathered thus far, please correct me or add any other useful information I should be paying attention to.

It seems to me the N-Am standards for tapered pins are numbered 0 through 7, with a taper of 1/4" per 12" (1:48) and metric/DIN are 1mm per 50mm (1:50). So far so good?

https://www.mcmaster.com/products/taper-pins/taper-pins~/?SrchEntryWebPart_InpBox=taper+reamers

I see tapered reamers and I see tapered drills which match these taper ratios & pin sizes. In 1:48 I see both reamers & drills, but in 1:50 thus far I have only seen reamers (no drills unless I missed it). Both are quite spendy. Reamers are a bit less spendy. Asian reamers are quite a bit cheaper than N-Am but I don't have a read on quality yet. They come in different flavors: straight & spiral flute.

What I don't understand is some reamer shanks have an extended cylindrical section but typically always have a square end like a tap. Some cylindrical extensions are every short inferring they probably are not intended to be chucked as in drill press mode. If the reamer has an extended shank can it be carefully run in under power to the point of finishing to depth by hand using a tap handle? Or when they say 'hand reamer' they really do mean (entirely) reamed by hand? With reamer in mind you would obviously pre-drill with pilot hole. I have read somewhere they actually stagger increasing diameter drill sizes presumably to leave less material for the reamer to use. I'm looking at ~ 3mm size just to play with, do you think this staged drilling is necessary in plain mild steel?

On the Asian/AliExpress sellers, there are also carbide tapered reamers for not that much more - any pros & cons to consider? (generally I've found carbide to be of better quality than HSS but of course every order is a surprise on way or the other).

Re the pins themselves, is the general procedure to tap them home & that friction fit is sufficient for most running shaft type installations? Is retaining glue ever recommended for more permanent installations? I've seen some applications where the small hole end is chamfered & the pin is peened over for retention. But if memory serves that was a much softer pin alloy, maybe like a shear pin. Most pins I see are mild steel or hardened steel.

What about length sizing. Should one be targeting that the pin head & tail both end up shallower than the shaft they penetrate? Or is that just too fickle & one should assume it will end up proud once mated & then finish the excess lengths to suite?

crueby:
I've been using one of the smaller pin sizes on my models for several years, the 4/0 (they run from 0 up, and 1/0, 2/0, 3/0, etc smaller than the '0'). I started out with the reamer, and step drilled the hole before reaming it. The reamer was meant for a hand tap handle, not chucking, in this small size at least. Later on I splurged on the matching drill, which goes a lot faster. The drill looks fragile, and at that cost I always pilot drill the size of the narrow end of the pin first, then slowly run in the drill to give the hole the taper. Great for crankshaft webs, have not used them for anything else yet. I got mine from McMaster as well, have not seen the drills many other places.They sell the matching 4/0 (and other) drills for the pins.

petertha:
What do you make of this? A metric 3mm tapered reamer but 1:48 ratio. Must be a typo somewhere? Either converting the nominal pin OD from IMP or the taper ratio?

https://www.kbctools.ca/itemdetail/1-139-0300

Overbuilt and Overkill:
I won't say there just not made, but I've not seen metric taper pin reamers made with the imperial 1:48 ratio so far. So a good chance that was a typo. The older Machinery's Handbooks all have a fair amount of information about both the pin and reamer dimensions. In my opinion, taper pins work well as long as there not being used in any area with high amounts of vibration. I've also not seen any mention of using loctite with them. There friction fit and wedging action seems to work well enough on it's own.

There also a joining method where a bit of judgement is called for when reaming that tapered hole. With higher loads, I'd ream deeper so there's a larger pin diameter resisting the load. For something like a shapers clapper box pivot pin where at some point either the holes or pin is going to wear. I'd ream to minimal depth for that size of pin to allow gently re-reaming the holes and fitting a new pin when it's required later. Used in that situation, either the clapper needs to pivot on the taper pin, or with a tight friction fit on that clapper and the pin pivoting within the ears of the clapper box. Getting that precision friction or very slight clearance fit in the parts would be easiest by rotating the reamer by hand. Most of the better made shapers I know of all used a taper pin in that spot and for that reason. So there's more than one use for taper pins. I'd also not use them in any area that might be susceptible to corrosion. An impossible to remove taper pin would be there major down side. In the larger taper pin sizes there's also further options. Either the normal plain end or a male or female thread on the pins large end. That's very helpful when trying to extract that pin. You also don't want to go too heavy with a hammer while driving the pin in. Like a lot of things, it's very hard to explain how much is enough. If the pin remains in place, it's in tight enough, if it falls out after some hrs. weeks, months then drive it in a little tighter. Goldilocks tight is what you want.  :) And if it were me and your filing each pin end so it's flush with the surface the pin is driven through, I think I'd dot mark the pins small end with a Dremel or similar so that small end is easy to identify where the pin is and which end is that small one. You or someone in the future might be very thankful you did.

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