Starrett Back Plunge?

Buggy Chief

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Looking at buying a pre-owned starrett indicator and prefer a plunge indicator. When I look on eBay all of the used sets with wooden boxes are back plunge. Can someone share the rationale for back plunge? I am obviously new to this hobby and understand how to use a normal plunge, but can't understand the back plunge? Thanks in advance!
 
I don’t have a back plunger type DI.... yet, but I can see how one might be handy for checking things like mill table X-axis tram using just one indicator without needing a mirror. I'm sure others will chip in with other uses, too.

Tom
 
It seems to me that the back plunger was a step in the process, earlier than the 'through the body' types. All the ones I've seen were old looking, well used.
 
Can someone share the rationale for back plunge? I am obviously new to this hobby and understand how to use a normal plunge, but can't understand the back plunge? Thanks in advance!

Starrett and others made back plunger indicators many years ago. The advantage was that the indicator faced the user. This was an advantage when tramming your mill so you didn't have to bend over to see the face like you would with a standard indicator. They typically came with an arm that allowed you to also read things that were out of position or in a deep hole. As far as I know, they were only made to read 0.001" increments and I've seen a lot of them in auto mechanic's tool chests. They tend to need more force than the typical AGD-type indicator but are still accurate and useful. I have one that I use on occasion, mostly for tramming.
 
If this will be your first test indicator ,Then I would get one like this http://www.ebay.com/itm/Vintage-Sta...987689?hash=item43f9fe1729:g:HLoAAOSw5cNYPMt1 .The back plungers are limited in there use , however no one can deny back plungers are SEXY .

I'm not sure I would buy any measuring tools sight unseen unless the seller offers a return guarantee. The Starrett 711 or "last Word" indicators have been around for in the neighborhood of 70 years. Many on eBay and other auction sites are from the 50's and 60's and show their age. One of the main problems with them is the older they get the more tendency they have to get sticky. I have 4 in the shop and 3 of them have started to stick. The only one that is still flawless is the one I purchased new in the early 1980's. The other 3 came from fellow workers that retired and sold off some of their tools. They all worked fine for a while but I know they are much older than the one I purchased new. I can send them out for repair, but past experience has shown that the cost of repair is nearly the same as the cost of buying new.

I also have a Brown & Sharpe 321b test indicator and a Mitutoyo 513-202 test indicator. Both of these are about the same age as the Starrett I purchased new yet work much smoother.

As a side note the first indicator I purchased new was a Starrett 196 back plunger style like this.
http://www.ebay.com/itm/Starrett-di...322683?hash=item3d2c6ca4fb:g:3EEAAOSwEzxYO50C
Again it was in the early 1980's and it still works flawlessly today. They're great for use on a surface plate, between centers, and of course foe tramming the mills.

A few years ago a former fellow employee offered me another one at a price I couldn't refuse.
http://www.ebay.com/itm/Starrett-No...384786?hash=item3d2c9b5e52:g:LmcAAOSwux5YPjou
It's much older than the one I purchased in that it's in a wooden box. This one must have led a sheltered life because it to works flawlessly. The only drawback to both of these indicators is that they only measure in increments of .001"
 
I use the back plunge gage on a weekly basis. I check model airplane engine crank shafts for bends and out of round with my bench centers.

"Billy G"
 
I have collected through the years many, many indicators and from all makers (except China and the like). But when I want to use an indicator and not just make a pile of them in the shop. I use the Interapid test indicator.
 
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