Member postings for Gareth Thomas

Thank you Bill and Dave for your inputs. Things are now beginning to dawn on me that I have perhaps asked too much from my measuring techniques and the instruments I use. After using a vernier height gauge I bought myself a digital one in order to get away from all the arithmetic (and mistakes!) but I still seam to have a lot to learn.

Using the height gauge and a 'finger' Mercer Type 301 DTI I thought the measurements would be a doddle by touching the bottom and top of the hole with the stylus and reading the height gauge. Ni eve! Following the input received from yourselves I have adopted the following method:

1) with DTI attached to height gauge zero Mercer clock with about 0.005" (0.127 mm) deflection of the stylus on a gauge block of a known dimension. The height gauge is also zeroed and ABS zeroed. Raise the height gauge and adjust the height gauge to zero the Mercer clock on the lower edge of the hole. Note height gauge reading and zero the height gauge. Now place a piece of round bar in the hole and wedge it to touch the top of the hole with a piece of Plasticine. Then bye again adjusting the height gauge to zero the Mercer clock on the top of the round bar I have got a hole size. Magic! Also using the ABS button on the height gauge I have also an ABS dimension to the hole top edge as a check for the hole size. I am now more confident of my measurements. Don't forget to add the gauge block dimension to the ABS dimension!!!!

Thinking about it, the way the Mercer DTI reads has perhaps led me astray, the needle only rotates clockwise whether the 'finger' is raised or lowered. Pesky thing!!

Regards Gary

Thank you for your reply Jason. I am still trying to understand it but I am working on it! it has become clear to me that I could do with some fundamental instruction on how to measure with a height gauge. Is there a web article on it? What I am trying to do is measure hole centre positions on a plate in order that I draw up the item. In my wisdom I thought that by using a 'finger' DTI would give me a more better 'feel' for the bottom of the hole edge and the 'top'? Which would also give the hole dia.. I thought about making dowels to fit the holes then measure the bottom and add half the 'plug' size but that seems a awful long winded method. Any help appreciated.

Gary

I have got myself thoroughly confused using my height gauge and ask if someone my help. I am trying to measure a hole size and position. In order that I can 'feel' the hole edge I have used a 'finger DTI' mounted to the arm of a digital height gauge. I zero the DTI and readout on a gauge block on the surface table. Move the height and touch the bottom of the hole, adjust the height gauge to zero the clock, measurement 1.(18.25 mm) Now move gauge arm up so the stylis of the DTI finger touches the top of the and adjust the height gauge to zero the clock, measurement 2. (26.28 mm) The dia of the stylis is 2.00 mm.. 26.28 - 18.25 = 8.03 mm. Adding the stylis dia gives 10.03 mm. I check the hole dia with a caliper and it measures 9.05 mm. So I am 1.00 mm adrift with my height gauge measurement and for the life of be I cannot see my error. There has to be a simple explanation and someone has been through it all before. Help please!!!

Regards Gary