Long tapered pins on a manual lathe

[Overland]

A guy has asked me for 25 long tapered pins for use in timber frame work.
He wants a piece of 1" mild steel bar, with a taper 10" long, down to 3/8".
I have a taper attachment.
I'm thinking I can't avoid using tailstock support, but the photos he shows me don't show a center hole in the end. Maybe just cut off after.
Any other suggestions please ?
Bob

 

[eKretz]

Use tailstock support.

 

[WHHJR]

As above and make it 11" long and remove the excess at the end......

 

[Nmbmxer]

You can always make the first inch or two close to the chuck then pull the stock out and use a cup center for support while you turn the rest of the taper.

 

[Mtndew]

Any other suggestions please ?

Use a false center, then cut it off when you're done.

 

[michiganbuck]

All the above, and another method is to use a female headstock end and tail end machine center. A simple concave center point that would hold to a ball end part, or intersect a chamfered edge.

We used to put a point on both ends of a reamer or other tools to be ground, and then just have a hole in our machine centers, so as to be able to snub off the point when done.

Perhaps used to grind the Od of a drill, just grind the out end with a little bit of a 60* circle-grind / didn't even have to be full round... and then take a little more stock to resharpen the drill.

* OPS, Nmbmxer mentioned this in post 4....

 

[MilGunsmith]

Why not ask the customer if a center hole is OK? It would make them easier to make and you could give him a better price on them. I dont think that the center hole will affect the final use of the pins.

 

[Joe Gwinn]

Won't the cutting forces be a bit large for the 3/8" diameter end, 10" long, if this is done between centers?

 

[eKretz]

Won't the cutting forces be a bit large for the 3/8" diameter end, 10" long, if this is done between centers?

Should be just fine if supported at both ends as long as he doesn't try to take it in one cut... Hell, even then he might be fine at a light enough feed with a sharp tool. I wouldn't recommend that though, unless the taper is a nothing and not a fit. Starts at 1" and tapers to 3/8". Ought to be pretty easy.

 

[redlee]

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Bull Pins are available, probably cheaper than you can make them.
Cut the head off , charge him extra or tell him where to buy.
Im sure if they are for timber framing they are for alignment and center holes wont matter if you chose to make.

 

[gustafson]

I struggle to think of what they are doing with those on post and beam construction
A lot easier to winch the parts together and drill in place than locate with a big tapered pin

 

[mike44]

A guy has asked me for 25 long tapered pins for use in timber frame work.
He wants a piece of 1" mild steel bar, with a taper 10" long, down to 3/8".
I have a taper attachment.
I'm thinking I can't avoid using tailstock support, but the photos he shows me don't show a center hole in the end. Maybe just cut off after.
Any other suggestions please ?
Bob

Ask him if the pins are for draw peg construction. If so a center hole makes no difference. I have seen steel pins used as a drift to pull the tenon tight to the mortise. Then the pin is backed out and a wood peg installed. Not sure why he needs 25 pins.
If a center hole is a problem then do like you said and cut the hole portion off.

 

[Bill D]

I would think these would be hot forged, less waste.
Bill D

 

[michiganbuck]

Time and money, just go to ALRO steel for stock, and run the parts
For me, that would be quick and easy.
3/8 is fairly stout so turning mild would be easy.

 

[Overland]

Well I've done the job, with tailstock support.
25 pieces from 1" bar and 25 from 3/4".
He wanted the 1" bar down to 1/2" with the taper 10" long. And the 3/4" down to 3/8" at same taper. He was fine with the center holes.
My lathe, a Colchester 21" x 80" is pretty tight, but as always a little backlash in the cross slide. I've never fully got my head around it, but the taper attachment seems to take up the back lash, even though you put the cut on as normal. Maybe not clear, but if I watch the DRO, at this taper it takes about 1" of X axis travel to take up this backlash, before the Y axis moves. So it cuts parallel for 1st inch of travel, then cuts the taper.
I can take this into account, and deal with it easily, except when using my Royal center, which has a 7/16" dia about 3/4" long, on small dia jobs.
So for the final cut, I need to back out the center to get my tool about 1"+ to the right of the starting position, and then "follow" it in with the tailstock to ensure the center is in just before the tool bites.
For those interested, about 60 thou depth of cut, at 8 thou per rev, 800 rpm, seemed to work quite well.

 

[JohnMartin]

I struggle to think of what they are doing with those on post and beam construction
A lot easier to winch the parts together and drill in place than locate with a big tapered pin

Except that for good construction with wood you want the holes drawbored, which adds some tension/compression to the joint and keeps it tight over time. The hole in the tenon is marked out but then drilled closer to the shoulders than marked.

 

[Overland]

They use a steel pin with a small point set about 1/8" off-center to mark the hole in the tenon. They drill the thru hole in the mortice, assemble the joint, then mark the tenon hole off-center, dis-assemble then drill.
Now my "customer" wants me to help him make a dowel machine.
We'll see what ideas he comes up with - there's lot of simple "machines" out there.
Bob

 

[Blackrainstorm]

A dead zone of backlash take up is normal in a taper attachment that uses a telescopic leadscrew. This happens when using the cross slide to dial in successive cuts and cutting OD from small to large. Essentially, feeding in with the cross slide dial pushes on one side of the leadscrew nut, and the taper attachment pushes the opposite way when going small to large. It is most noticeable on shallow tapers when the backlash take up is spread over a long carriage movement length.

A way to minimize this is to cut from large OD to small. This way the taper attachment pulls the cross slide into the work the same way the cross feed pushes into the work when advancing successive depths.

 

[JohnMartin]

They use a steel pin with a small point set about 1/8" off-center to mark the hole in the tenon. They drill the thru hole in the mortice, assemble the joint, then mark the tenon hole off-center, dis-assemble then drill.
Now my "customer" wants me to help him make a dowel machine.
We'll see what ideas he comes up with - there's lot of simple "machines" out there.
Bob

There are lots of tenon cutters commercially available. The only problem with them is that they are designed to be used in a power drill and are driven by a stub arbor, so that the length of the tenon they will cut is limited. You could bore one out and figure a way to drive it, or drive the dowel stock instead.

There was a hand tool made to do just this. Do a search for “stail engine”.

Stanley used to make a tool to turn dowels - their #77 Dowel and Rod Turning Machine. I have one and it works well. It is cranked by hand, but I have heard of others that have motorized theirs. There were cutterheads available from 3/16 to 3/4” - but the 3/4 may be too small for you.

Old timber framers often didn’t use round pegs. They would split out a piece of oak, hickory, locust or similar and shave it with a drawknife to maybe an octagon. Usually a bit larger than the hole. No need for it to be perfectly straight either, as driving it into the hole would straighten it to the bore.

If he really wants round pegs, simple way is to split stock out a bit oversize and then pound it through a hole drilled in a steel plate.