Boring a partially tapered hole?

[Spookydad]

Can anyone tell me the best way to bore a tapered hole if the taper starts part way down?

In this case the material is oak or maple, inside a steel sleeve. I am thinking that installing the sleeve first may be the way to go.

This drawing has the dimensions in mm.

[TGTool]

I think a form tool is your best, or maybe only shot. You can drill the large diameter or slightly under down to where the taper starts, then drill to depth at the small end diameter and finish with the form tool. I've bought spade drills for wood just to modify for particular shapes I needed. You can grind and file them since they're not hard. You'll want at least a jury rigged V-block to check both edges as you work on them to maintain reasonable symmetry.

[Toolguy]

I would use a small diam. boring bar. Drill a hole a little under 9mm. Set the compound to cut the taper. Bore the straight part using the carriage as normal and stop at the depth where the taper starts. Then wind the compound slide to the bottom of the hole and you're done! You will have a perfect transition from the straight to the taper. Do rough and finish cuts, not all at once.

[Don Young]

I believe that taper could technically be bored on a lathe by doing the straight and taper sections separately with a taper attachment or compound rest. It would require some careful measuring and would require an extremely long and small diameter boring bar. I think a form shaped reamer/drill could be made much easier. Removing most of the wood by step drilling would make it easier to finish the taper, regardless of the method used.

Edit: Toolguy's idea sounds best for boring.

[RussZHC]

Cross your fingers and hope there is a taper drill that you could tweak to fit?

Most of the taper drills for wood I could find referenced screw sizes but if you could find one large enough so that the max diameter at the largest part of the taper matched the straight section above and just bore down? The issue would appear to be those taper drills would be longer than necessary at that taper than you need for the bore bottom so that would have to be ground away.

Edit: looked at the diagram again, the basic idea should work but you would have to bore the top straight wall sided area to correct diameter after the taper was done

[beckley23]

I don't see a dimension for where the taper starts.
Harry

[Stepside]

There is a dimension missing or I just don"t understand. How far down the bore is the 14.5 diameter? I also think it says the straight bore is 6mm deep and 16.8 diameter. It then tapers to 14.5mm and from the 14.5 it tapers to 9mm. All in all a confusing drawing with missing numbers. Does the drawing of the mating part have the needed information?

If one had the dimensions, then turn the shape out of bar stock (something that will take and hold an edge. Remove one side down to the midline for the 70mm length. Remove the opposite side until your bit is about the thickness of a spade bit. File the needed relief on both cutting edges being careful to preserve the shape.

Pilot drill and maybe even step drill so you are using your bit as a tapered reamer. I would install the steel/metal sleeve before doing any of the drilling.

Let us know how you end up doing the job.

[Spookydad]

This is the other half of the drawing and a picture of the wooden poles. They aren't an "exact" fit. In practice they can be quite wobbly when put together.

[justanengineer]

I would use a small diam. boring bar. Drill a hole a little under 9mm. Set the compound to cut the taper. Bore the straight part using the carriage as normal and stop at the depth where the taper starts. Then wind the compound slide to the bottom of the hole and you're done! You will have a perfect transition from the straight to the taper. Do rough and finish cuts, not all at once.

x2. Use a carriage mic stop to get a uniform depth on the straight portion, then simply use the compound to cut the taper.

[baldysm]

Looks to me that the 2 pieces aren't designed to go together. The male shaft is straight on the end, and then starts a taper. The female shaft is straight and then tapers at the bottom of the hole.

The male shaft is 13.5 mm diameter on the straight part, and the female taper is 14.5mm in diameter necking down to 9mm. So the male wont even come close to the bottom. Yup, the end of 1 will fit into the other, but it's gonna wobble.

I don't know what these poles are or what they do. I would be tempted to just bore a straight hole in the female end so the straight diameter just slides in, and use the taper on the male to jam/lock the shafts together.