Tach

[cobra428]

Hi All,
My dad was a machinist/ die maker in the 1930's/40's and I have his old tool box. In there I found this Tach. I can't figure how na heck how to use it. The needle just keeps going and going and going. Can anybody explain how it works.

Thanks

Tony

 

[Penguingeoff]

I have used one of these many moons ago. Rubber cone goes into the end of a shaft (centre hole) obviously. You need a stopwatch or one with a second hand. Count numbers in 15 secs, multiply by 4. There might be a ratio of dial to spindle that has to taken into account as well. This is not a direct reading rev counter. Count the number of spindle turns to dial turns, and how many marks on dial. Better ones around now thankfully. I could be way off line with this however.

 

[cobra428]

Penguingeoff
Thank You Sir, It's making a little more sense to me now. Guess I have to buy a stop watch now :big:
Tony

 

[Tin Falcon]

cobra:
I have one or a couple of those. I think i used it once to get spindle speeds on a AA109. It is a revolution counter mine appears to direct reading . but you do need a stop watch for time. Also it only counts to 100 so yo also need to count how many full turn of the dial you get. It is almost a two person job .I had my son help and switched between stopwatch and counter duties.
Like PG said count the res and compare to the time it take to get them or set 60 seconds on a time and then count the revs.
Tin

 

[joeby]

I have one of those stashed away in one of my toolboxes, and I seem to remember the inner dial being the revolution counter. Every 100 turns of the spindle turns the outer dial one revolution and the inner one graduation.

If you have set it to zero, you can hold it to the shaft being checked for a number of seconds (15, 30, etc.) and then directly read the revolutions by counting the number of graduations moved on the inner dial x100 and adding the number (1-100) on the outer. In other words, 15 seconds-2 graduations on inner dial, and 50 on outer dial would be 1000 RPM.

Kevin

 

[cobra428]

Thanks Guys,
I was going nuts trying to figure this thing out. I guess my modern tech head, didn't think about a clock being involved :big:
No internal clock in this instrument I guess!
Tony