b dub 

I own a 4" digital caliper which I use for seat posts and bearing sizing all the time.

But it's too small for measuring the length of a bottom bracket spindle. So I'm ready to get a bigger caliper.

Which one do you use and can you recommend?

I noticed this one but an 8" might be better.

CV-6 

I use a Harbor Freight digital caliper. You can often pick them up for around $10

Road Fan

I use a metric ruler that I bought at a French office supply store. It reads in mm on one side and 1/2 mm on the other. It tracks with my Starrett and mitutoyo dial calipers.

If I use the calipers, I keep my calculator handy, since they read English. But not a big problem, the exact conversion factor is 25.4 mm/inch.

busdriver1959

I've been using the six inch HF caliper for 5 or 6 years. It still works well despite being dropped lots of times. Watch out though. When the battery starts dying, it will give inaccurate readings. If you double check the digital readout against the analog scale every once in a while you'll be ok. To the OP, the one you posted looks like a good choice. It looks like it won't measure inside measurements but since you already have their 4 inch caliper (I'm assuming it's a just a smaller version of the one I have), you're covered.

dddd

Another thing to watch for as any dial caliper ages is the zeroing function.

Pushing the zero button of course always gives you the reassuring "zero" on the LCD screen, but as these instruments develop a tiny amount of freeplay in the gears (accellerated by rough handling of course), the first few thousandths of an inch (or hundredths of a mm) of jaw movement do not register on the screen.

An easy check for ACTUAL zeroing of these calipers is by measuring a brand new ball bearing of known size.
As the caliper ages, you'll see that the known-accurate 1/4" bearing ball appears to "shrink" over time, the tell-tale indication of a worn and thus hopelessly-inaccurate instrument, as there is no specific adjustment on these to correct for freeplay other than to add a known # of thousandths to each and every measurement that you make.

Of course this isn't important for measuring spindle length, but it sure is when measuring taper widths for example:



And from what I at first guessed that this thread was about, quoting one of my previous posts on this related subject:

"How it's done: Measuring a JIS spindle.
Note that the caliper jaws are exactly 3mm thick. The point of measurement is thus exactly 3mm from the end of the spindle.
12.9mm=JIS,
12.75mm is more like ISO and Campy,
Old Stronglite is about 12.67mm.
Dura-Ace 7400 spindle shown."

That is the second aspect of measuring spindles, called taper width.

The third aspect of spindle measurement relates to measuring a spindle's offset, which defines the difference between the lengths of the left and right ends of the spindle, out past each cone's bearing track.

All three measurement considerations will directly affect the positioning of the installed crankarms, and the taper-width measurement can by itself affect each arm's placement (relative to the frame) by as much as 3mm.

OK, a bit more info than the OP asked for, just sayin'.

Pars 

^ I use the same HF 6" digital caliper (not the long one that b dub posted). I'll have to check the readings when the battery gets low (often), which I had not done.

dbakl

I hold one spindle next to the other and decide if it looks like it will work or not...

rootboy 

I use my father's old Mauser direct reading Vernier caliper. Reads in Metric and Imperial. I have a Mitutoyo dial caliper but it reads in thousandths so I rarely use it for bike stuff.

JohnDThompson 

And then use spacers, etc. to get the proper chainline...

3alarmer 

Length in BB spindles is not exactly a measurement that requires much in the way of precision beyond 1 mm.

So for this particular job, these work fine, and we use them at the bike coop all the time for measuring just about everything.

b dub 

It is if you want to be accurate in your sales post. I've been planning on replacing some of my cone and spindle bottom brackets with cartridges and would like to end up break even so don't feel I can play the guessing game in this situation.

jonwvara 

Wow, some of you guys take this awfully seriously. I'm just a hacker, I guess. I seldom measure at all, since I typically use JIS spindles and they usually have a number/letter code stamped on them (3T or whatever) that tells you how long they are. If there's no length code and I have to measure, I just use a metric ruler.

jimmuller 

And then try putting it on the bike.

16Victor

Measure the ball at the very inside of the jaws, and again at the very outside. Note any difference. That will give you a read on the parallelism of the jaws, and you'll learn the 'sweet spot' to best measure at. Good condition calipers will show no change and will probably be accurate longer.

Any digital caliper is just a linear encoder with a display, so accuracy of the cheap vs. expensive calipers is little different.

The long jaw version you link to might be good to measure, say, the over-locknut dimension on a hub when it's assembled into a wheel, but for general bike use that's all the benefit I see. Get the regular 6" or 8" with ID jaws and the depth measurement capability and you're good.

I have a few pairs of old 6" Mitutoyo digitals, an old 6" Mit. dial (mechanical) - don't use it much, it's been technologically eclipsed (like friction shifters ), plus a variety of micrometers. The digitals are always within an arms reach it seems.

Or, grab an old vernier caliper at a flea market. Get a good name (B&S, Starrett). They will never need batteries or have their mechanisms get clogged with dirt, but you may need glasses.

b dub 

I ended up ordering a 6" caliper, a postal scale and a luggage scale for about $16 total with free shipping. Might take up to a month to get it but that's ok.

dddd

After all these years, I take some pride in being able to "weave" a standard 6" caliper through the spokes to measure across the locknuts, although still having to "sight down" for a reading if perhaps a "tall" freewheel is in the way, LOL.

My first "CHEAP" digital caliper lasted many years before it lost accuracy, but no doubt I treated it with a lot more respect in those days when they were still $20 ($30 in todays coin).

I often rely on the stamped markings on JIS spindles, as long as a chart is handy.
I've always been impressed by the overall accuracy of JIS parts, which so often look more mass-produced than others but which never the less seem to have superb accuracy and usually good durability too.
It's important that the cups also be made to the JIS-compatible standard so that the chart dimensions are realized when the bb is fitted to the frame.

Victor, thanks for the heads-up on the jaw measuring position. My calipers that lost accuracy seem to have developed their gearbox freeplay from rough handling (i.e. dropping) rather than wear in the jaw slide area, but there is also a sprung leveler inside that can perhaps lose tension and allow tilting of the sliding jaw.

One easy way to absolutely confirm bb spec requirements is to have an assortment of clearly-labeled cartridge bb's at hand, and I've found that even "mildly" worn-out ones can be used to test-fit for the required parts order and even allow short term service while the order's delivery awaits.
So, when I have a crunchy cartridge bb in a size that I don't stock, instead of tossing it I put it in my parts-donor box of bb's for test-fits or for any of it's possibly-removeable parts like threaded cups and/or bearings.

Jonwvara, you're right that some of us take this seriously, at least to the extent that good chainline and front derailer function can keep a prized ride running neck/neck with the contemporary carbon crowd.
We're the ones who might also remove and re-torque the right crankarm several times, looking for the best rotational position for getting the chainrings to run at their truest.
When the chainline is right on, a rider can get the maximal sequence of possible gear combinations, such as 7 sequential-and-well-spaced ratios from a 2X5 gearing platform with only a single "double shift" along the way.
Only some of my triple-ringed bikes seem at all averse to fully cross-chaining big-to-big.

3alarmer 

.......read what I wrote, carefully this time. Now go to your ordering page for your cartridge BB units.

Do you notice anything in terms of the lengths in which they are manufactured and offered for sale ?

Michael Angelo 

So how do YOU accurately measure bb spindles? WIth one of these, Starret Dial Caliper.

JohnDThompson 

Park used to supply these calipers with their dropout alignment tools (Campy "H" tool clones):



Maybe they still do... Handy for measuring various things while installed on the bike.

jimmuller 

Why would anyone need to measure spindle length so accurately that it requires a caliper? Isn't to-the-nearest_mm close enough? The actual size of the taper can seemingly make a difference.

Michael Angelo 

Was making measurements for record keeping. The BB is off an Early 50's Italian "Stucchi".