taper pins

a newby to the forum. could i get advise about what size hole to drill for taper pins ? do i measure the small diameter and use this help please.

Generally yes, but you can allow for how far the pin will stick through. Shown below are two fitted 1/16" taper pins. For the one in the bevel gear I drilled 1.2mm as it doesn't stick through very far. However, for the pulley where the boss is a smaller diameter, and hence the pin sticks through further, I drilled 1.3mm:

The bigger the drill diameter the less likely you are to break it.

Andrew

I have never needed to use a taper pin but for some reason I thought you needed a taper drill. Am I completely wrong about this and a plain drill is all you need?

Doug

I used a taper pin reamer after drilling the hole. Much safer than using a taper drill. The tapers on the pins are very shallow; a couple of turns too many with the reamer and the pin sticks through too far.

Andrew

Nigel

Normally you would drill a hole slightly larger than the small end and use a taper pin reamer to open it out till the pin fits in the distance you want. A taper pin reamer is like a normal hand reamer except that rather than being parallel it is ground to the same taper as the taper pin of the same size. This allows the taper pin to fit the hole for it's entire length. If you have access to a copy of "Machinery's Handbook" there is a table in it of suggested drill sizes (for pins # 7/0 to 10) including step drilling for the larger sizes which makes reaming easier. ( page 1654 in my edition, #20). Suggested sizes are .0469 for a 7/0 up to .5781 for #10 ( which requires 4 drills at different depths with the largest being .7031). Step drilling is recommended for sizes 2/0 and up.

John

There is metric and imperial taper pins, metric is 1 in 50, imperial is 1 in 48, so you need to make sure the reamer matches the pin.

Neil

drill small end of pin size, then drill with taper drill, then finish with taper reamer to fit pin required, tapered pins can be over length eg 8mm to 3mm dia x100 mm long fit pin then cut to length.

In thirty years working on printing machines I never came across a taper drill. If fitting a new pin, drill same size as the small end and then use a taper reamer till the pin will just seat. Fit pin and cut to length. ie small end should just protrude. To remove use a pin punch

Roy

This information seems not to be included in my 11th edition.

Can anyone provide the step drilling recommendations for size 0, please?

For an (American) size 0 taper pin, small end diameter 0.156", I don't bother step drilling. You aren't removing much metal with the reamer in that size.

Edited By Mark Rand on 22/11/2018 17:21:38

ega

According to the table I have whether step drilling is recommended depends on the length of the pin. For a #0 pin only one drill is required if the length is 1 1/2" or less. For longer pins two are recommended. The reason for step drilling is to make reaming easier and quicker when using straight flute taper reamers.  If using helical flute reamers then step drilling is not required and the drill size is the same as the small end of the pin.

John

Edited By John Purdy on 22/11/2018 18:22:25

John Purdy:

Many thanks.

My reamer has straight flutes and, as I suggested in another thread, I was concerned about the possibility of breaking it, particularly as the load on the flutes must increase as the cut progresses. In the event, I compromised by measuring the diameter of the pin at half way and drilling accordingly (the actual depth of my taper is only 15/16".

I think you mean large end.

Yes, that's what I meant!

I find that taper pin reamers cut fairly gently if one does not push them into the hole too hard. I've only needed to step drill when using much larger pins.

Mark Rand:

Thanks for the advice - I found it helpful to use a suitably small tap wrench.

eBay sell el Cheapo ratchet tap wrenches that I have never found much use for tapping as you can't back the tap off to break the chips, but for small reaming jobs they do work OK (but don't expect them to last forever!)