How to use a B&S 729A Hole Attachment

jbacc · Nov 23, 2020

Good Evening,

I know this is probably a ridiculous question but I am perplexed and hope some of you might shed some light on the issue. A while back I purchased a B&S 729A hole attachment (photos below). I thought it was similar to the Starrett 670B as it looks very much the same. Unfortunately, the B&S does not fit on a standard dial indicator.... Is there a specific size indicator these are made for?

Any and all comments/insight are most welcome and much appreciated.

Thanks as always.

Joe

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L Vanice · Nov 23, 2020

My 1978 B&S catalog does not have any tools numbered 729.

In the 1978 B&S catalog, a similar-shape hole attachment has "ordering number" 599-7802. It fits the number 7040 back plunger heavy duty dial indicator. You could buy the whole number 7740 set of indicator and its attachments in a mahogany case. They also had a number 7039 back plunger dial indicator, apparently not "heavy duty," and a number 7739 full set. That set included hole attachment number 599-7739-3, which has a different shape arm from the curved arm on the 599-7802 hole attachment. Both of these hole attachments have .375 inch indicator mounting holes.

The B&S back plunger indicators and the attachments look just like the equivalent Starrett back plunger set and like a Mitutoyo set I have. I do not know if you can mix different brand parts. Note that these back plunger indicators are not made to the standard AGD dimensions/design, which may be what you mean by "standard dial indicator.".

Larry

jbacc · Nov 23, 2020

L Vanice said:
My 1978 B&S catalog does not have any tools numbered 729.

In the 1978 B&S catalog, a similar-shape hole attachment has "ordering number" 599-7802. It fits the number 7040 back plunger heavy duty dial indicator. You could buy the whole number 7740 set of indicator and its attachments in a mahogany case. They also had a number 7039 back plunger dial indicator, apparently not "heavy duty," and a number 7739 full set. That set included hole attachment number 599-7739-3, which has a different shape arm from the curved arm on the 599-7802 hole attachment. Both of these hole attachments have .375 inch indicator mounting holes.

The B&S back plunger indicators and the attachments look just like the equivalent Starrett back plunger set and like a Mitutoyo set I have. I do not know if you can mix different brand parts. Note that these back plunger indicators are not made to the standard AGD dimensions/design, which may be what you mean by "standard dial indicator.".

Larry

Larry,

Thank you so much for the detailed response, it is educational and I appreciate it. Yes, I guess when I said the standard dial indicator sizes I should have said the common size I have which is indicators with a .375 stem?

Just so you know I am not hallucinating, I attached two more photos which confirm that the model is a 729A. I have not measured the hole which would make sense but it certainly does not fit my .375 dial indicators.

Thank you again for taking the time to educate and guide me, I am grateful and appreciative.

Joe

awander · Nov 23, 2020

My 1914 B&S catalog shows a plain Model 729-it is quite primitive looking compared to the later models:

My 1952 catalog shows 729 A, B, C and D, and gives details on what size indicators they are to be used:

This is also from the 1952 catalog, and shows a set including the 729B attachment and an indicator, Model 740:

jbacc · Nov 23, 2020

awander said:
My 1914 B&S catalog shows a plain Model 729-it is quite primitive looking compared to the later models:
View attachment 305599

My 1952 catalog shows 729 A, B, C and D, and gives details on what size indicators they are to be used:
View attachment 305598

This is also from the 1952 catalog, and shows a set including the 729B attachment and an indicator, Model 740:
View attachment 305597

That’s it, mystery solved The 729A is for indicators with a .275” stem which does not fit any of my indicators. Thank you for taking the time to help a neophyte like me, truly appreciated.

Joe

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