Calipers: woodturners, inside/outside

[Groggy]

anyone know where I can get a smallish 100-150mm pair of calipers that does not have pointed ends? I find the pointed ends catch and invariably widen or close the opening, resulting in remeasuring the ferrule. This is a pic of the tool, see the sharp points? If I file them I then have to file the other end exactly the same so I would prefer to get a set that is rounded in the first place. I have tried GP's, LV, CT and Carroll's. Jim has what looks like a nicely designed pair that are 305mm which is a bit big for what I am after (see second pic, note the rounded ends)
http://www.carbatec.com.au/images/product/CT-260960.jpg
http://www.cws.au.com/persistent/catalogue_images/products/ecr76gjc.jpg

[brendan stemp]

G'day Groggy, what are you using them for? When you say they catch this seems to suggest you are measuring while the wood is spinning. Is this right? You mention ferrules; are you making tool handles? More info needed because there maybe other solutions to your problem.

[TTIT]

Easy fixed Groggy! I've got the set in your second pic and they are very handy and the rounded tips never catch which is cool. Your smaller set can be rounded easily and accurately by undoing the pivot, flipping one side over then clamping them together again so that the tips are side-by-side. If you round the ends with a file now they will match properly when you flip one side back again - too easy :2tsup:

[Groggy]

G'day Groggy, what are you using them for? When you say they catch this seems to suggest you are measuring while the wood is spinning. Is this right? You mention ferrules; are you making tool handles? More info needed because there maybe other solutions to your problem.Brendan, when setting sizing marks I hold the caliper to the spinning work until it can pass over the spindle. for normal work I can use larger calipers or even a spanner of the correct size, for sizing though the spanner is too thick and I need something more like the thickness of a parting tool (1-2mm). It needs to be interior/exterior for the ferrule to be measured and convert the interior to an exterior dimension. I am doing a few handles at present and that is my current need, but I am wearing 'L's at this turning stuff so am quite happy to gather ideas :).


Easy fixed Groggy! I've got the set in your second pic and they are very handy and the rounded tips never catch which is cool. Your smaller set can be rounded easily and accurately by undoing the pivot, flipping one side over then clamping them together again so that the tips are side-by-side. If you round the ends with a file now they will match properly when you flip one side back again - too easy :2tsup:I'm a dunce :doh:

An elegant and simple solution, thank you Vern :2tsup:

[Jim Carroll]

Greg you should be using normal spring calipers for sizing spigots or on spindle work for your different diameters.

Those calipers are mailnly used for checking out the difference in wall thickness on your bowls etc.

We have the calipers in stock but not on the web site about $13.00 pair.

[Groggy]

Greg you should be using normal spring calipers for sizing spigots or on spindle work for your different diameters...Hi Jim, you are (I think) recommending a two-stage measuring process, measure internal then transfer to external, as shown below. That adds an extra step to what I am currently doing and I am not sure what advantage it gives me. [Pauline Hanson voice = on] Please explain? :?


http://www.tpub.com/content/aviation/14310/img/14310_65_4.jpg

[NeilS]

Groggy - old/cheap vernier calipers are also good for what you are doing. Don't need to be digital nor does the rule need to be accurate. Cost cost less than $10. Just round off the very tips of the outside legs so that they slide readily over the job without marking it while the job is still running. The rounded tips also let you know how close you are to size by how far they slide in towards the required size (the flats). Use the inside legs to measure the ferule ID then fix the calipers at that size and (in one step... :) ) then turn the OD of your job to match.

Of course, this vernier option is limited to smaller diameter jobs, in the case of spindle work. The depth of the OD leg (less any rounding over of the tip) is your max radius.

Neil

PS - metal verniers are also good for measuring bowl tenons and dovetails. In the case of the dovetails, which need to match closely to jaw size, I now use the sharp inside legs to mark the required diameter. The toolrest needs to be very close to the job while doing this to support the short caliper legs and increase your leverage. You can even have a vernier for each jaw size...:D. As you are working on the free 'end' of the job the size restrictions for spindle work don't apply here and the limit is that of your vernier slide.

[NeilS]

Easy fixed Groggy! I've got the set in your second pic and they are very handy and the rounded tips never catch which is cool. Your smaller set can be rounded easily and accurately by undoing the pivot, flipping one side over then clamping them together again so that the tips are side-by-side. If you round the ends with a file now they will match properly when you flip one side back again - too easy :2tsup:

Good tip, but of course you will have to replicate the same amount of metal removal from the other end so that you are getting an accurate gap transfer. Putting them back together and testing for and measuring any gap or overlap will indicate how much, if any, needs to be removed from where.

Neil

[Jim Carroll]

Yes that is the type

Easy to set up and use and will stay on size , they do still spring when you are sizing but when you drag them back with a deft touch you can get them to size properly.

If you are going to davids on the weekend get to show you how they work.

[brendan stemp]

I use verniers all the time for this type of application with great success. I now have about 8 pairs of them including a bigger set and use them to make recorders and pepper grinders almost every day. Some words of caution though: grind away the sharp tip of the jaws to create a small round that won't catch; make sure your parting tool is wider than the jaws of the vernier; use a sharp parting tool which will reduce the chance of creating any rough edges for the verniers to catch on; and hold the verniers away from the jaws so they wont injure you if they do catch. And last of all, add .5mm to the measurement to allow for sanding. All should work well. good luck.

[rsser]

Yep.

And rough size your spindle, rotate the ferrule onto it and go from the mark. Many commercial ferrules have a bevel on the inside of one end to aid this. Put one on yourself if it doesn't.

[Alastair]

Good tip, but of course you will have to replicate the same amount of metal removal from the other end so that you are getting an accurate gap transfer. Putting them back together and testing for and measuring any gap or overlap will indicate how much, if any, needs to be removed from where.

Neil

At the risk of being caught out to be an eeedjit, the problem with this solution is as Groggy said. For a given caliper setting, if you round the "outside" tips, the dimension will become larger by the amount of metal removed, and will no longer match the "inside" dimension end.

Rounding over the "inside " end will not correct this, as it will make that end even smaller, and more different from the enlarged "outside" end.

get my drift?

regards

[NeilS]

At the risk of being caught out to be an eeedjit, the problem with this solution is as Groggy said. For a given caliper setting, if you round the "outside" tips, the dimension will become larger by the amount of metal removed, and will no longer match the "inside" dimension end.

Rounding over the "inside " end will not correct this, as it will make that end even smaller, and more different from the enlarged "outside" end.

get my drift?

regards

Alastair - you are 100% right and I'm... :B

In fact, metal would have to be added to bring it back to 'zero'.

Won't go there!

Neil

[Alastair]

FWIW, I have always used the cheap vernier caliper method mentioned above.

regards

[tea lady]

You can get plastic versions of them from pottery supplies.:cool:

http:////z.about.com/d/pottery/1/0/R/5/-/-/gallery_inset_measure.jpg

Try Potter's Equipement in Ringwood. or Northcote Pottery, or Walkers Ceramics, or Clayworks. Or there is bound to be somewhere in Geelong. Can't remember now. Haven't lived over there sice the '80s.:rolleyes:

[Skew ChiDAMN!!]

Alastair - you are 100% right and I'm... :B

In fact, metal would have to be added to bring it back to 'zero'.

Which may offer another solution. Grind back all 4 tips a few mm, then glue/pin/bolt replacable tips (wood? neoprene? whatever) in place.

Sand back these new tips, rounding 'em over in the process, until it brings the calipers back to spec.

[hughie]

Which may offer another solution. Grind back all 4 tips a few mm, then glue/pin/bolt replacable tips (wood? neoprene? whatever) in place.
Sand back these new tips, rounding 'em over in the process, until it brings the calipers back to spec.
[/QUOTE]

yep I have done that with epoxy glue, need to rough the points up a fair bit, mine fell off after a time :C........ not rough enough :U

Now I make my own, for small ones I use 2-3mm aluminium sheet easy to cut and work with. For the bigs ones perpex or polycabonate 6mm+ also easy to work with.

[rsser]

Or use the time-honoured method of an open ended spanner of the right size.

[Tim the Timber Turner]

:aro-u:Sharpened on the top edge.

No other tools required.:2tsup:

Provided you rough close to size first.:)