Topics include, Machine Tools & Tooling, Precision Measuring, Materials and their Properties, Electrical discussions related to machine tools, setups, fixtures and jigs and other general discussion related to amateur machining.
For real accuracy I think most would. To me a layout is just keeping myself from making too many mistakes. Doesn't always succeed of course. Rarely to maybe never I'd be machining to that layout line without measureing anyway. And hole C/Ls are located by edge finding and coordinates unless it's something that if done on a drill press it could be thought of as good enough. I doubt many of the larger commercial shops even do hand layouts much anymore. DRO's and for sure CNC has made it it an unnecessary extra cost and with CNC it's not needed since the layouts already in the CAD design. Or that's my understanding of how it works. For years I used a heavy piece of plate glass for my surface plate or just preset the combination square with a set of dial calipers and did my layouts with that. At best that maybe got me within .010" on a good day.To be honest owning a really good height gauge and small surface plate now just speeds things up a bit faster. But it's still layout lines and I'm going to measure the part at some point to be sure. There's been some unbelievably complex parts done using hand layouts and center punch marks in the past so it can be done.But Wes is certainly correct that the scribed line with calipers would be slightly short of the true position.
In the old texts, they talk about using a rule and calipers. I have Geo. Hodges' calipers. They are tools from that era. I'm a retired millwright, when I retired, I outfitted my shop to do some machining and one of my purchases was a set of tools from a retired machinist who was down sizing, he was 10 or more years older than me. He had bought the Geo. Hodges tools as an apprentice when George was retiring.
When I was in construction I did a lot of layout and alignment, in the days before lasers . We used the terms inside the line, outside the line and splitting the line. What's a line on a tape, .010 ? A machinist should be able to cut that in half when laying out in nice shop.
I have three sets of verniers , two are nice NSK combination inch /metric and cheap Chinese inch which makes a great tool for layout . One of the NSKs I inherited when a fellow millwright retired. I also have a couple of dial calipers, I like the Chinese $20 one much better than the Starretts.
A man of foolish pursuits, '91 BusyBee DF1224g lathe,'01 Advance RF-45 mill/drill,'68 Delta Toolmaker surface grinder,Miller250 mig,'83 8" Baldor grinder, plus sawdustmakers
Going back to the original post it seems that what he wants in the form of a bench scriber. If I remember correctly Starrett make one - No. 29B?
It has a 1/64" graduated shaft and one of their square 4 pointed scriber thingeys. They are very well made as their current price of about $95.00 would indicate. Used ones come up from time to time. For dead simple make one and use a carbide dental burr (from your friendly dentist) and screw on the end of a 1/4" dia. shaft about 6" + and turn a body that would slide on the shaft about 3/4" dia. with a thumb screw of some convient size. All made in your shop. Use you caliper to set the length from the body flat to the point at the end of the shaft. Simple and works.
Cary
ccfl:
Of course you were absolutely right. The HF SKU62569 digital caliper maintains the display for 8 min by the stopwatch. Better yet it keeps the last reading when it is turned on. The odd thing is that the inch number and the tenths numbers are large and the hundredths and thousandths numbers are half the size, but I can get along with that since the dang thing doesn't shut off prematurely.
The only bad thing is that I forgot to take my 20% off coupon to the store.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.
If you get HF flyer emails, you can just show them the email on your phone to use the coupon, no hard copy required.
They are pretty rough out of the box but polish up nice. Diamond needle files to knock off the corners, 400 grit paper to blend, 1/2x1/2x4 India stone to finish.
"Never trust a man who puts a witty quote in his sig line." -Mark Twain
Rarely to maybe never I'd be machining to that layout line without measureing anyway. And hole C/Ls are located by edge finding and coordinates unless it's something that if done on a drill press it could be thought of as good enough. I doubt many of the larger commercial shops even do hand layouts much anymore. DRO's and for sure CNC has made it it an unnecessary extra cost and with CNC it's not needed since the layouts already in the CAD design. Or that's my understanding of how it works.
