Sine bar

[Alan Gordon 4Participant @alangordon4]

Hi Guys. I have aquired a set of Imperial Gauge Blocks but I need a Sine Bar. I would like the conventional 5" bar. There are a few on the net but some of them are giving a measurement of 125 mm which is less than the 5".( but is being advertised as 5 &quot This would I think give inaccurate readings but I am not sure, any advice would be helpful.

Edited By Alan Gordon 4 on 05/06/2021 08:51:23

Edited By Alan Gordon 4 on 05/06/2021 08:52:14

Edited By Alan Gordon 4 on 05/06/2021 08:52:48

Edited By Alan Gordon 4 on 05/06/2021 08:53:34

[Alan Gordon 4Participant @alangordon4]

[Pete RimmerParticipant @peterimmer30576]

You are very right Alan a 125mm sine bar will give you a different result to a 5". Not innacurate, just different. You could not use 5" sine bar tables but find 125mm tables or do a bit of trig.

[John HaineParticipant @johnhaine32865]

It depends what you mean by inaccurate. If you convert the imperial gauge block dimensions to metric, noting that if made in the last 50 years they will be on the basis that 1 inch = 25.4 mm exactly, then you just need to work out the stack of imp blocks you need to get the required metric height for the desired angle. Or, in reverse, work on the basis that 125 mm = 4.922 inches.

Going the first route, for an angle A degrees, the height required is 125 x sin(A) mm, so divide that by 25.4 to get required inch stack; or just use the formula h = 4.922 sin(A) inches. A scientific calculator helps, there will be one on your phone or if not there will be an app you can download.

But just how accurate do you need the angle?  A simple and cheap Wixey angle measuring box will resolve 0.1 degrees and they are pretty accurate according to my measurements, and probably cheaper than a sine bar.

Edited By John Haine on 05/06/2021 09:03:53

[Chris Evans 6Participant @chrisevans6]

Just multiply the sine of angle required by 125 then divide the answer by 25.4 Now you will have an imperial size to use your imperial slips.

[Alan Gordon 4Participant @alangordon4]

Thanks Guys, Very useful and constantly learning

[Tony Pratt 1Participant @tonypratt1]

As long as you know the roller centre distance of the sine bar it's simple trig to work out an angle.

Tony

[Mark RandParticipant @markrand96270]

Posted by John Haine on 05/06/2021 08:59:55:

But just how accurate do you need the angle? A simple and cheap Wixey angle measuring box will resolve 0.1 degrees and they are pretty accurate according to my measurements, and probably cheaper than a sine bar.

Edited By John Haine on 05/06/2021 09:03:53

Wow, the resolution is the same as 12 turns of the autocollimator dial!

[bernard towersParticipant @bernardtowers37738]

I’m with J.H. I have sine bars and slips plus a wixey gauge, I’ll let you guess which one gets used the most!!!

[old martParticipant @oldmart]

I think it is because the seller uses a tape measure during the listing. I now have three 5" bars and a 2" one. I use one almost annually.

I have seen them on ebay with the overall length listed.

Edited By old mart on 05/06/2021 17:12:54

[David George 1Participant @davidgeorge1]

I have a sine bar that I made. It was in the magazine a couple of years ago.

Made from gauge plate and silver steel easy to make. 45mm centers so I could use it in a small vice as well.

David

[Michael GilliganParticipant @michaelgilligan61133]

Posted by old mart on 05/06/2021 17:11:48:

[…]

I now have three 5" bars and a 2" one.

.

Just curious … Where did you get the 2” one, please ?

That could be very handy.

MichaelG.

.

Aha … Looks like David read my mind ! 

Edited By Michael Gilligan on 05/06/2021 20:35:26

[Mark RandParticipant @markrand96270]

I've never seen one, or a photo of one, but I believe that Hardinge made a 'double' sine bar or table. The principal was that, instead of having the stack of gauge blocks on the milling table etc. and the sine bar forming the hypotenuse of a right angle triangle, there were two hinged bars and the gauge blocks were clamped between them, forming an isosceles triangle.

The calculation was sin(angle/2)=(gauge stack length/2)/bar length. While the calculation is slightly more complex, the advantage of the system was that the gauge blocks would not have any tendency to be squeezed out of the assembly, even for large angles, since they were clamped between the tangents of two cylinders, not a cylinder and a flat.

If one ends up making a sine bar, this system might be worth considering.

[old martParticipant @oldmart]

A seller on ebay had a pair, a 5" and the 2", made by his father, I believe. The little one is good in confined spaces. There was already a 5" at the museum and another 5" one was with a box of slips that I wanted.

Back in the 70's a sine bar was found in a job lot of stuff which the boss had bought. I had never seen one back then, but it was memorable, and one of our apprentices told me what it was. The bar was curved, not straight. It got binned, nobody wanted it. It was quite big, about 9" long.

[duncan webster 1Participant @duncanwebster1]

I bought a 5" one years ago. It has only ever been used to hold things down whilst the glue sets. Much more useful is a set of angled bits of steel bought from Chester years ago

[DMBParticipant @dmb]

Not surprised that bent since bar got binned, about as much good as a 9 Bob note!

[DMBParticipant @dmb]

Duncan, I have a couple of sine bars, never get used, use the Wixey instead. However, I occasionally use a home made device copied from somewhere on the internet. It's a thick rectangular block of steel with an arm pivoted near a bottom corner, which swings to different angles and secured by another screw. Angles are 90, 60, 45, 30 degrees. Set up in machine vice like an extra and loose jaw, I've used it successfully a number of times.

John

[David George 1Participant @davidgeorge1]

My Sine bar in use to get the angle off edge holes at correct position relative to center bore.

This was on a tumbler reverse gear select plate.

David

[Rod RenshawParticipant @rodrenshaw28584]

I have a 5 inch sine bar and have used it a very few times.

I am intrigued by Mark Rand's description of the Hardinge double sine bar .I cannot see why the slips would tend to get squeezed out of a conventional sine bar when they are held betwen a flat and a tangent to the roller- which tends to a flat at the point of contact. There is a limit to the size of the angle which a particular sine bar can be set up for, determined by the amount of metal cut away to give clearance near the roller but I would have tthought that would equally apply to a "double" sine bar.

Rod

[old martParticipant @oldmart]

The curved sine bar that I mentioned must have had a very specific use, probably inside a matching radius, nobody either side of the pond has ever heard of the like. I now have difficulty remembering what the radius might have been, possibly 3 to 6 feet.

[John ReeseParticipant @johnreese12848]

I have a 5" sine bar, a 5" sine plate, and a 3" an 2.5" sine bars plus a compound angle magnetic chuck with 5" roll distance. While I do have gauge blocks (slips) I often use an adjustable parallel or a shaper gauge to set the height instead of using the gauge blocks. The 2.5" bar has an integral base. Once the angle is set the bar can be locked to the base to maintain the angle. The integral base incorporates a magnetic V. It works great on the lathe for setting the compound to exact tapers.

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