Tapered Dowel Pins

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Excellent idea ... it also avoids the risk of:

1. corrosion increasing the diameter of the small end
2. heavy hammering bruising the small end

MichaelG.

Just like to say a public 'thank you' to Julian for his kindness in sending me some dowels.

Big thanks Julian

H

Great idea, never seen that done.

Strongly agree Alan had calls to make our own twin taper pins on high value hand made products, workings good fit on both protruding ends and two caps after locking down as well, no play. Cosmetically the ends were protruding with a dome and colour hardened.

Problem is talking microns on metal removal diameter to see massive movements in length, leave long. Easily filed and better than trying to cut taper than in a lathe.

I can't see the point in leaving a recess either. An ideal taper pin in say a machine handle would just show a slight dome at each end and no sharp corners. A simple tap on small ones via a suitable drift will loosen it sufficiently for it to be knocked out easily. Larger ones are much the same even when driven firmly home. They don't need hammering in that hard really due to the fitting pressure gain the taper gives.

John

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Hi everyone,

I cannot claim credit (or dis-credit ??) for the concept of leaving the taper pins short in a hole. The text was included with the details of a taper pin which I copied from another web site called The Home Shop Machinist & The Machinists Workshop.

The address is : www.homeshopmachinist.net

Paul.

As far as the angle to offset the top slide when you have to make your own taper pins, well you are not going to read the necessary fractions of a degree off the top slide graduations.

I recently made a full set of taper pins for the change gears on my old Drummond lathe, because I did not want to wait three weeks for a packet to arrive from the UK.

Method I used was to do the math and calculate the amount of taper over one inch of length. Divide it by two. This is the amount of offset required "per side" and so is the amount the tool needs to travel outwards per inch.

Set up a piece of scrap one inch diameter bar in the lathe, turn true and parallel. Mount dial indicator on the top slide with plunger against the turned surface. Set top slide to about the angle where it should be. Set dial indicator to zero. Run the topslide along for one inch according to the graduated collar and observe the amount of in/out movement recorded by the dial indicator. Adjust topslide angle, amongst repeated mumbling, until the dial indicator reads the correct amount as per the math calculations using Pythagoras Theorem, Sine tables etc.

If you want to get real fancy, you can caluclate the length of the hypotenuse and feed the topslide by that exact amount, a gnat's whisker over the nominal one inch.

As already mentioned, once you get the right angle sorted, make the pins longer than needed at both ends, fit pin to the job and trim accordingly.

And do not POUND the pins into cast iron change gears too hard. The taper will force the metal apart until it cracks the gear. Do not ask me how I know this!! A gentle tap is all that is needed to seat the pin.

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Paul,

Please accept my apologies if I have [by quoting your quotation] inadvertently led others to associate you too closely with this concept.

I thought, and still think, that it was an excellent idea ... but I chose that word carefully ... It is clearly inappropriate in many situations, but may have merit in others ... it is therefore worthy of consideration.

MichaelG.

Edited By Michael Gilligan on 22/06/2015 06:33:11

No problem Michael,

The post started a lot of good discussion. All ideas, whether good or bad are part of our learning experience.

Regards, Paul.

Take care when taper reaming small diameter holes,the reamer flutes soon fill up with swarf and break quite easily,withdraw the reamer frequently and clean the flutes,also lubricate with oil or Rocol, It was accepted practice to use taper reamers with straight flutes for hand reaming and spiral flute for machine reaming,though for one offs straight flute taper reamers can be used in a pillar drill at about a third to half drilling speed.

Myself and several others were given the exercise of turning a morse taper adapter, 3 to 2 if I remember correctly and also provided with accurate gauges to test them with using raddle rather than blue. Resetting the compound slide by truly tiny amounts was causing everybody a lot of grief. I went to the stores and got a dti and stand and used that to see exactly how much I was moving the slide by. Job done in no time at all. All of the other people quickly did the same.

John

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