Turning Caliper

[Mike Holbrook]

I am making straight and tapered mortises and tenons on: chair legs, chair rungs and chair spindles. In the class I recently took we used simple antique outside calipers set to the required size to check our work for accuracy. There are a myriad of mechanical and digital calipers available these days. I found the old simple mechanical devices tended to be hard to set exactly and easy to move off their mark. Peter Galbert came up with a design that I believe Benchmade is making, $59.99 at Highland Woodworking. The design is made to work in the groove made by a parting tool. I wonder if a regular digital dial caliper might be more accurate and a better general purpose woodworking tool? The Starrett 6" fractional Dial Caliper goes for $99.99 at Highland Woodworking while the Woodworker's 6" Dial Caliper is $29.99. Both digital calipers are calibrated in 64ths of an inch with an inner scale reading hundredths of an inch. I see turners using these measuring tools on spinning wood which seems like it could be dangerous. I do not see anything in the design of the Galbert Caliper that would suggest it might be less dangerous to use on spinning wood than a regular digital caliper, but maybe I am missing something?

My question is how accurate do I need to be? The classes I have taken thus far did not seem to suggest that extreme accuracy is necessary. The emphasis seemed to be more on eyeballing and testing for accuracy in the actual joint. I'm not exactly sure how one might make a tapered tenon dead accurate? The $30 digital caliper seems well worth the peace of mind and speedier automatic, probably more accurate, measurement with the one tool. I am thinking such a devise would be great for checking all sorts of mortises & tenons, other joints and stock measurements. I'm just not sure if there is a best tool for turners to check these measurements with?

[Michelle Rich]

I have used open end wrenches for 30 yrs..if I need 1/2, well all I do is grab the 1/2 open end..calipers would catch on me if i was not totally careful..wrenches have rounded edges, and I don't worry about catching.

[John Keeton]

I don't do a lot of spindle turning, but recently decided to do a three legged stool like the ones done by Alan Leland, with ornate Windsor style legs. Replication of the legs was a must. I have used wrenches as well, but decided to get the Galbert caliper and love it! It works reasonably well with a thin parting tool so long as you keep it straight. With a regular parting tool, it works perfectly. I highly recommend it.

[Dane Riley]

If you don't mind stopping the lathe, Digital calipers work extremely well. The points will catch in spinning wood. The 12 inch HF ones I have seem as good as the expensive Japanese ones. They have survived being dropped. They eliminate math errors you can get with dial ones. Most used tool in my shop.

[Mike Holbrook]

Dane you mention a major issue for someone new to checking work for size on a lathe. In the class I took with Drew Langsner, he was checking spinning spindles with calipers or open ended wrenches, as he was doing it he was questioning the sanity and IQ of anyone foolish enough to do such a thing. I know the Galbert Caliper is designed to do exactly that. Watching the YouTube video on Peter's Blog page though he mentions wallowing the parting tool to keep from pinching his caliper in a narrow groove. I admit to not being comfortable checking a spindle while it is turning, at least yet.

I am thinking about starting with the popular $30 iGaging EZ Cal, which I can use for many different general woodworking measurements. I also see iGaging makes a Digital Multi Gauge that shares some design features with Galbert's gauge. I am trying to figure out if one of these devises could be used more safely, realizing that it might require a solid surface behind the work to register from.

[John Keeton]

The forces against the Galbert while the work is spinning largely want to push it out of the groove preventing an accurate measurement. I didn't feel apprehension regarding my safety. However, I found it better to stop the lathe to get a true measurement.

It would seem digital calipers can only work to the length of their jaws on spindle work. When laying out the various depth cuts for a Windsor style spindle, I would be hard pressed to find anything that would work better than the Galbert. Others may disagree.

[Bob Hamilton]

If you are using regular dial calipers on spinning work you should file the sharp points off the ends of the jaws or they WILL catch. Filing a small chamfer on the very ends won't affect the accuracy of the tool but you won't be able to use the points as scribes anymore.

Take care
Bob

[Harry Goodwin]

I still use the old fashioned spring calipers that work great with parting tool. I hate to admit my expensive starrett digital caliper died and is still dead following lousy service from starrett. I do have a lot of great starrett tools. hg

[James Conrad]

Hi Mike,

Turning straight and tapered tenons for Windsor chairs requires accuracy yes, but not in the sense that a machinest uses. The tapered tenon requires that it be long enough for the seat material it is going in, the top of the taper to be of the same size as your pilot hole, 5/8" and then taper at your desired angle to match your reamer commonly 6 or 12 degrees. Lets say the taper is 2 5/8" long the top is 5/8" diameter and the bottom is 1" diameter. Here you can use a whatever your like to get to get to those 2 dimension a wrench, Galbert device, turning calipers using your parting tool to set those dimensions first, then remove material between those two points so you have the correct taper over that distance. Another trick is to create a template that is placed on the bed of your lathe so you can sight the profile, Curtis Buchannon uses this and I think he got that idea from Peter. Check out Curtis's YouTube series on the Comb Back chair, he shows his turning techniques for this. Back to my point, is with the tapered leg tenon matching the angle and length are most important as you are going to ream out the pilot hole in the seat anyway as you set your legs. So if you are off a little here it is not going to be the end of the world as the top of the tenon is going to protrude beyond the top of the seat.

With your stretchers you need accurancy in terms that the straight tenon will fit snuggly into the mortise. Let's say its going to be 1/2". Using any old 1/2" wrench is not going work as it is unlikely that it will be a fit to the drill bit you are using, or give you that snug fit required for these chairs. Option 1: you can find a wrench that is smaller than your drill bit and modify it to match or more importantly, provide you with that snug fit. Option 2: Use a rounder off the lathe first, these are adjustabe to get that proper fit for your mortise. Then it's back on the lathe to smooth the shoulder that these create. Option 3: Use a Sorby sizing tool with a Bedan or parting tool on the lathe. I say Sorby here as I don't know of any other maker of this sizing tool, Curtis uses this method, shown in his videos and Peter discusses it in his new book as well. Option 4: I'm sure there is another one, I just can't think of it, maybe someone else has one. I use 2 or 3. The important point here is having an easy, fast and repeatable method to provide the proper fit for the mortise, something along the lines of a Go / NoGo gauge. Don't get caught up in that the digital caliper has to read exactly what my drill bit size, you'll go mad this way.

[robert baccus]

If you are into big production I would cut my own on a bandsaw --of the ones you use a lot.

[Mike Holbrook]

One of the three classes I have taken which made legs for benches or chairs provided turned legs. The other two classes provided red oak boards. In one class we started with square 2x2 stock and tapered them ourselves using either a bandsaw and hand plane or just hand planes. The other class provided tapered red oak stock that we made into octagons using planes, drawknives and spokeshaves. I have not turned whole chair legs on a lathe yet. I worked short chair spindles on a lathe to rough out shapes and make finished tenons on either end to fit mortises in the chair seat and arm rest.

The method I was taught to make straight or tapered tenons utilized a parting tool to cut down close to finished size on both ends of the tenon. With two grooves on either end of the tenon, we just removed the waste from the middle section. It seemed to take forever to sneak up on a given diameter with only mechanical calipers or open ended wrenches, which is why I am researching a better tool for this work.

I plan to saw a few logs out of a half dozen trees (mostly large oaks) that came down over the winter but still have roots in the ground. I should have plenty of wood to experiment with various ways of making chair legs and tenons. If I can come up with a lathe in the next few weeks, I will try my hand at turning some simple legs. I imagine I could turn legs from dry wood. I am looking at plans for making a kiln to dry roughed out pieces with too. I have no interest in making chairs commercially. I would like to make a dozen or more chairs for my home & business.