What is a Jig Borer used for ?

Posted By: lc from the Chaski forum
January 2002

What movements does a jig bore do and what uses are those movements good for? I don't understand the "jig bore" part means as I have no idea what it is.

By: Brian Healy

Back in the dark ages, Back in the times we weren't blessed with calculators, that did trigonometric functions and square roots, it was really hard to locate holes really accurately. We didn't have digital readouts that indicates where the table is to a ten thousanth. You had to be a real machinist. When you're splitting a thousanth of an inch, you couldn't rely on your average milling machine leadscrew, and micrometer dials. You needed a machine with leadscrews that were accurate, dials that could split a thousanth. You needed a jig bore. Designed not for milling, but for the accurate placement of holes. The tables were moved in X and Y and the quill moved in Z. The jig borer was developed primarily to fill a need for precisely locating holes in jigs and dies. There has been a quantum leap in accuracy in machine tools in the last fifty years, and jig bores are getting to be pretty hard to find in a production shop. But if you want to bore a hole thats perfectly square to the table, or if you need absolute locational accuracy for one off parts- the machine is hard to beat. I use a Moore Jig Bore in my machine tool manufacturing company when I'm boring holes in a small run of parts. It's a wonderful machine tool. With it's quick to change toolholders, incredible mass, and a spindle thats dead nuts square to the table, it's hard to beat. Especially when you can get a jig bore for what they sell for these days. For a Home Machinist, it probably shouldn't be your first tool- get a good mill- but still even today there's a place for these great tools in production shops.


Posted By: Jim Glass

Hi Lc,
Brain did an excellent job explaining a jig boring machine.

To many people "JIG BORE" means to take a set or group of holes drill them undersize in most precise location as possible then increase the hole sizes by boring with an excentric boring head. Boring is a single point operation so hole size and position and squarness to the thickness can be established. Furthmore, boring means bore to finish size, no bore and ream stuff.

Most of us jig bore in our vertical mills (Bridgeports or copies of). The problem with a verticle mill is the Knee (verticle) movement which a true Jig Bore Machine does not have. The problem with the knee is this. When the table is moved to the extreme right or left, the knee is out off balance and shifts or tilts. This effects the table reference to the spindle. There is no indication of this knee shift in the dials or a DRO because they move when the knee moved. There are ways to cope with shifting but I'll not get into that.

A true jig boring machine like a Moore, the spindle is always square to the table and there is no knee movement. The tool room got a Moore jig bore about a year before I was transferred to a different positon in the company. I ran the Moore jig bore many times in that year. Great machine.
Jim

Moore wrote a wonderful book about Jig Boring, Grinding, and Measurement that brilliantly explains the problem and its solution. In the days before DRO's you had to mark-up work, transfer the work to the tool, orient it correctly, perform some operation, and then measure the result. Errors of transcription would build up and it was exceptionally hard to do things accurate to a tenth or better. The lack of precision in lead screws led to a lot of work with machinist buttons, gage blocks, scribers, etc. By making "perfect" lead screws, Moore made the machine as good as the measuring tool (Moore lead screws were designed to be as accurate as gage blocks). One might say that Jig Borers were the precursor to CNC machines and coordinate measuring machines. Moore's claim to history was to add a decimal point to the accuracy of machine work - this feat was an extraordinary one and makes a great story - I recommend Moore's book to anyone curious about the history of machine tools.

The book is called:

Holes, Contours, and Surfaces

Subtitled:
Located, Machined, Ground, and Inspected by Precision Methods

By Richard F. Moore and Frederick C. Victory

Published by the Moore Special Tool Company, 1955

I have loaned out my book "Jig Boring" which gives the history, and features most of the jig borers on the market in the 1960's-70's. (Lent to my cousin, who has and uses a Swiss "Dixie" jig borer). However, the first jig borer was actually a "pointing machine", and was made by SIP. (Societe Genevoise d'Instruments de Physique, Geneva).
This was in 1912, and it was used for marking out watch plates. They then built an industrial version in 1921. I believe this machine, or one similar is, in the Science Museum collection (London).
These machines did not just rely soley on accurate lead screws, here is an explanation of how the pitch-correction device worked....

" The lateral movement of the boring head and the movement of the table are controlled by lead-screws, set by micrometer drums. A pitch-correction device rotates the vernier sector, by which the setting of the micrometer drum is made, by an amount which eliminates the error at the position in which the table or head is being set. The amount of rotation is determined by a lever, in the ratio of 200:1, in contact with a metal template. The template was made for each lead-screw in terms of a high precision scale read with a microscope at one centimetre intervals."

The only SIP I have seen was back in the 1980's, when we apprentices went on an industrial trip - a huge machine in a humidity and temperature controlled room. Three things I remember - the tooling was clamped or ejected at the touch of a button, the clarity of the optical readouts, and even though the jig borer had a table several meteres long, and was in a much larger room, there was a sealed over hole in the wall which they had made to acccomadate a long job....

ps Moore Tool still sells the books "Holes, Contours and Surfaces" and "Foundations of Mechanical Accuracy" ($97 !!!who wants to organise a bulk buy deal on this one?).

[This message has been edited by Peter S (edited 09-30-2002).]

Ooooh! Jig Borers, I am all excited!

They got their name form the fact that they were used to put the holes in dill jigs. That is more difficult than most people imagine. They have to be super accuately spaced because the interchangeability of parts depends on the accuracy of the tools, fixtures and jigs used in their manufacture. Tha analogy here is the care with which a printing plate is made. Any errors will be repeated thousands of times in the product.

In Europe these things are also known as Co Ordiante Hole Borers. Yes, Europeans use jigs, but before the wars, they were not as production oriented as the USA. This probably explains why the Swiss jig borers had milling capabliity before the American machines had it. It was common practice to finish machine parts on the Borers. I have catalogs that show the headstock bearing and shaft holes in the American Pacemaker Lathe being bored on an American Hole Wizard Radial Drill Press using a massive tumble jig. Other catalogs I have show German headstocs being bored and milled on heavy duty jig borers in a much simpler set up. This is just one example of the differing approaches used by American and European machinery builders. and it may explain the differences in the American and European designs of jig borers.

There are three dominant design layouts of jig borers and three dominant setting systems.

The American pattern of jig borer resembles a drill press with a co ordinate table. A vertical column at he back of the machine carries a spindle head on sliding ways perfectly perpendicular to the table axes. The driving machinery is at the top of the column. The Pratt & Whitney was the first commercially successful American jig borer, Others ae the Fosdick and the Moore and the little Linley.

The Planer type machine is typified by the SIP machines. They really DO look like planers. Their table traverses on a heavy bed and the spindle head is carried on a cross rail supported by double columns. The driving machinery of the older ones was located on the base of the far side column and power was transmitted by shafting and right angle gearboxes to the spindle head. In the late 1950's SIP and Hauser designed spindle heads with the motor mounted within them. In 1934, SIp introduced their "Hydroptic" machine. It was revolutionary. The table had a hydraulic cylinder table feeding arragement and co ordinate settings were made by reading precision standard scales through optical maginfication. The machine was heavily built and could do some respectable milling. This enabled European machinery manufacturers to use the jig borers directly in the manufacturing process. The geometric accuracy of workpieces finished on the Hydroptic machines significantly reduced the amount of hand finishing required in the assembly of precision made machines. All drilling and boring jigs were eliminated and fixtures finished on the jig borers enabled rough and simi finish milling to be done more accurately. Finished pieces coming off the jig borer were for all intents and purposes ready for assembly.

The Hauser Works in Bienne, Switzerland made planer type jig borers very similar to the SIP. They had settings by leadsvrews.

Mitsui Seiki in Japan made a dead nuts Knockoff of the SIP. They used optical settings on standard scales even on their No 3 and No 4 and No 5 machines where as SIP made the MP 3K and the MP 4G and the MP 5E with screw settings. Mitsui Seiki's are NICE!

It is ironic that the Ameicans were slow to adopt the practice. Even more Ironic is the fact that when I toured Pratt & Whitney in the late 1960's they were still using jigs and fixtures to machine parts for their lathes! While the Swiss and Germans were merely "spotting up" bearing surfaces, Pratt & Whitney was handscraping the hell out out of them and testing with straight edges and big old test arbors.

As an aside here, you will notice that the long ways on the Deckel Milling machine are fine milled, you can see te cutter marks, they are not even "flaked". The mating surfaces are "spotted in". GearHeads worship the Deckel, but if Bridgeport tried that their factory would be beset by mobs of irate machinists carrying torches, tar and feathers.

The third arrangement of jig borers is the Horizontal Spindle type. In 1948, Dixi of Switzerland introduced the Dixi 60. It looked just like a horizontal boring mill except the spindle head was guided on twin upright columns. Feed motion was Hydraulic and settings wee optical. An in built rotary table with optical settings was standard.

When that thing hit the market I am sure there were some worried looks and fast heart rates in Geneva. (That is, if Swiss Hearts can actually be made to beat fast with excitement - I have never seen an excited Swiss)

Dixi is still very much active in the CNC industry. Their series 75 manually controlled machines are something right out of science fiction. Scotty's boring mill. How else could he keep that piece of junk, The Enterprise, going after His Captain kept wrecking it?

The best known horizontal jig borer in the USA is of course DeVlig's "Jigmil" EVERY machine tool plant I have ever toured has at least one. There are even "Jigmil Shops" who specialze in doing contract boring work. The setting system uses micrometers and end standards with an automatic positioning system. for the horizontal and vertical axes. The feed motion is mechanical. The third axis is the machine's boring bar spindle. There is an optional turret type depth stop system for the bar.

During the 1960's Lucas, Giddings and Lewis and Cincinnati Gilbert made super accurate versions of their horizontal boring mills and sold them as horizontal jig borers. they had varying systems of setting but the auto position like the one DeVlieg used was the dominant one.

I am not sure, but I believe the auto position works was made by an independent outfit since a lot of machines used it and there were no patent fights that I know of. DeVlig did get mad at Lucas when Lucas introduced their model 3 SP and 4 SP Super Precision Horizontal Jig Borers. Lucas made only one of each and then backed off. Personally I would have LOVED to get into That Fight. Lucas wasn't even close to a patent infringement and I think the Lucas was a better machine.

The three dominant setting systems for jig borers are the end measure and micrometer system, the leadscrew system and the optically read standard scale system.

The Pratt & Whitney and the Fosdick used the end measure system. It is the same system that can be installed on any machine. There are troughs laid along the X and Y axes. There is a fixed stop on one of the moving or stationary members and a dial indicator on the other. Cylindrical end measuring rods of whole inch lengths are laid in the troughs along with a cylindrical setting micrometer gradated in "tenths". The moving member is then carefully moved so as to contact the rods and micrometer and bring them up to the indicator so that the idicator, also graduated in "tenths" reads zero. This is done for the initial setting. All subsequent settings involve either adding or subtracting end standards and rsetting the micrometers for fractional inch settings. The machine is "In Position" when the dial ndicator reads zero.

The dial indicators are good, you can see a half a tenth and estimate a quarter.

The end standards are good when they are new, but they can be subject to wear and they carry their additive errors when laid end to end. They are not good in a dirty environment and they shouldn't be handled too much when doing fine work (body heat)

The micrometers are questionable. they read to the tenth by vernier just like a shop mike. They are subject to error just like a shop mike and they are a devil to calibrate to "tenth" accuracy.

The leadscrew setting system is the most popular on jig borers. SIP, Hauser and Moore and many others use it. It is accurate and fast and trouble free. Moore made only small jig borers and they were obsessive about the lead accuracy of their measuring screws. The screws had a special modifcation of the Acme Thread form and Moore was able to fine finish the screws to fantastic accuracy over ther entire length. The Moore is the only jig borer that I know of that reads directly from the screws without compensation. The Moore has to be one of the finest jig boring machines ever made.

I love and have run many Swiss machines, I own a Hauser and Desire a Dixi, I have apprenticed at The National Bureau of Standards - I am in AWE of the Moore!

The Swiss have been encountering the problem of lead errors in measuring screws of great length for almost a century. They are masters of the compensated screw. On a jig borer they allow the vernier of the measuring dial to turn about its center. a linkage from the vernier extends to mid axis of the machine. The moving member has attached to it a flat metal compensator plate.

A follower from the linkage to the vernier bears against the compensator plate. When the jig borer is assembled, a standard scale is laid parallel with the axis and a measuring microscope is installed in the machine spindle. The axis is moved with the screw and the readings from the standard scale and the dial attached to the screw are compared. Any errors in lead are ccompesated for by removing sufficient metal from the compensator plate to bring the vernier and dial reading into conformity with the reading of the standard scale. This correction gets rid of both periodic lead errors abd cumulative lead errors.

Compensated screws are trouble free, very accurate and no more prone to wear then Moore's fine screws. If Moore wanted to make a jig borer with a 20 inch travel or greater, they most likely would have to use compensation. The laws of physics start ot bear down really hard when measuring accurately over lng lengths.

When the Swiss want to use an automatic dividing engine to graduate standard scales, the compensator bar is set up to turn the nut of the lead screw, thereby advancing or retareding the moving element. The leadscrew is rotated by a rachet mechanism consequently the Move has to be made accurately even though it is not manually set.

A variation of this systemis used on the Swiss rotary tables. it is the reason they can claim such high angular accuracy on small diameter tables. Moore, again, uses fantastically accurate worm gears and the table gear is the most accurate worm wheel made.

Optical setting. Since the Laws of Physics are administered by a cruel judge, the only really accurate way to measure long distances is by optical means. For machine tools and measuring machines, this means optically read standard scales. SIP and Dixi and Mitsui Seiki are the top names in jig borers set by standard scales. the Deckel LK series is optically set as is the Oerlikon. The first three manufacturers are significant in that they each divide and check their own scales. There are variations on the optical reading systems. Some require the operator to peer through an eyepiece. The SIP and the Mitsui Seiki use projection screens to show the scale division. That is much easier on the eye. All optical systems use a short movement micrometer to move the index mark for small fractional settings. On the SIP machines graduated in inches, the standard scale is divided to the even tenth of an inch. The setting micrometer moves the index through distances less than that. Since everything on the projection screen is highly magnfied, any error in the setting micrometer screw is diminished by the magnification.

SIP scales are not numbered, the graduation just shows in the projection screen as a clear line. There are ordinary scales attached to the axes and simple re settable pointers. Settings are very fast and very easy, an amazement considering the the fact that the machine is working to metrological accuracy.

Settings on he Dixi are more complicated, their scale is both numbered and graduated and both the numbers and graduations appear in the field of view. I find this to be a severe strain on my eyes which aren't too good anyway.I think this may have had an effect on Dixi's sales in this country. There are many Dixi machines in the USA, but they are not nearly as numerous as the SIP machines of the same capacity.

All optical systems are good to the "tenth" and they will stay good forever. The scales grow and shrink at the same rate as the machine. They show the true position of the moving member and develop no wear. Sadly, jig borers wear out around the setting scales. I have seen some truly ratty SIP No 6's and 6A's.

There are a lot of mis comceptions about jig borers. When "jig borer" is mentioned we usually think of the Senior Craftsman, usually with an accent who cossets the machine and is quite tight lipped about tecniques of running it. It ain't necessairily so. Most certainly jig borers must be kept out of each of the ham handed pig, but ordinary people do quite well running them. I am of the belief that if women found out how Truly Cool running a jig borer is, we in the machine shop business would be turning out a lot more very accurate work and spending a lot less money on troublesome CNC machines.

Jig borers may be a bit "formal" in the way the settings ae made, but they are Fast! Once you get the hang of it, moves are made very quickly and the confidence level is very high. I can work much faster doing co ordinate location on my Hauser No 5 than I can do work of lesser accuracy on a Bridgeport. The machine doesn't deflect. Set the measurements, figure how much to take off, dial it in and You're There. Holes are ROUND and To Size! You can ruff out a work piece on any ratty old mill and take a clean up cut on the jig borer and come out with a masterpiece. And it's easy!

Jig borers are quiet as a mouse and strong as a bull. Even the little ones just love cutting alloy steel and cast iron. Rough out a piece of Carpenter's Stentor and finish it on a jig borer. You will find out the capabilities of the fine machine and also find out what an absolutely superb alloy Stentor is. I did it and I didn't use carbide tools and I ran at sane speed and feed rates - Wow!

Most people think aluminum is easy to work with, but I see a lot of trash passed off as machine work in aluminum. Aluminum bends, it scrooches, it gets hot and changes shape right while you measure it. Aluminum turns all right but it mills awfully. That is why there are so many fly cutters sold to the Bridgeport set. My revenge has been to hog the nasty stuff out and let it cool. Then I let Mr. Hauser have his way with the thing. Ooooh Yeah!

I don't think the jig borer will ever be as popular in this country as it was. However if your shop regularly makes a product and you can find someone of even temperament to run a jig borer, it may be a good idea to invest in one. Jig borers solve many problems with geometrc accuracy that otherwise cost time and money to correct at assembly or lead to outright rejects. Those who own a jig borer also own a co ordiante measuring machine. almost one third of the work going across the table of my jig borer is measurement work. The jig borer will not only tell you how long or wide an object is, it will show if the piece is truly square. Using a sine bar and gauge blocks, angles can be checked to very high accuracy just by indicating the setup along an axis of the jig borer.
We are talking split minutes here.

Well, maybe you don't want a jig borer in your shop. If you do too much inspection with it you will get to wondering how any of the stuff you or your guys mill on a Bridgeport would ever get through a critical inspection. Then you will start to worry and end up being difficult to live with. Your wife will leave you and take the kids and the shop might have to be sold to pay for the divorce. See? Jig Borers can be Dangerous. Even "Weapons of Mass Production".

You author has been James Kizale, serious machine nut, and actual working machinist who is tryng to stay in business running a small machine shop. I don't
think I am a masochist, but right now this is the only thing I know how to do. I wish sometimes that I had taken Piano Lessons!

I use a Moore #2 in my shop for fine finish work. It is an incredible machine.

I have another old book put out by the Moore company,called"Precision Hole Location".I don't have it here with me,and can't give any further particulars,especially since I moved recently,and some stuff is still packed up.The Moore book also talked about how holes were gotten in before the advent of modern machines.

"I am of the belief that if women found out how Truly Cool running a jig borer is, we in the machine shop business would be turning out a lot more very accurate work and spending a lot less money on troublesome CNC machines."

There are anecdotal photos of women during WW-II operating Monarch 10EEs turning out super-precision parts for who knows what on a production basis.

Mabel the Machinist!

It is probably not an accident that many 10EEs wound up in our country's advanced weapons labs.

GearHeads worship the Deckel

Click to expand...

Being a gearhead and a Deckel owner, please please JimK tell us more about the LK, I think I would like one for jig boring and jig grinding and need your charming enthusiasum to to tip me over the edge and give me an excusee to get one

Jim K brought up the co ordinate measuring capibility of the jigbore machine. I find that very true.
The Moore #2 is so easy to use. I have joint problems from years of cranking vert mill handles. The Moore is just easier and better for many of the things I do, the X travel hand wheel doesnt travel with the table, so its always in reach. You want to keep a mill around for cutting key slots for example.
The Moore spindle assembly is very precision fit in the spindle housing, The spindle bearings under extra heavy preload allows the use of extended bars with much less being prone to chatter.
For sure not the all perpose tool that a Smithy is "just kidding" but still may be usefull for many things. Sort of a good companion tool to a Monarch EE, or Hardinge lathe for example.
I have posted in the past using the jigbore for moving around dowl pins on motorcyle engine case halfs to bring them in register, For this job the Moore is so much better then the vert mill.

I pick up a used Linley jig bore 1968 model last year made. The machine was at a company I worked for about 7 years ago. They bought the machine to tool for a job for the nave in 1968. Ran the mache for about 50 hours and then it sat untill I can along and paid $200/US.The machine is a nice little toy. Also if anyone need a copy of part list for this machine I have the paper work when machine was new.

There is a Moore number 3 in our shop sitting where it was put the day it was brought in. Didn't really know what to make of it until now. We're technically "storing" it for a friend but after reading this thread maybe I'll move it over into the small machine area and wire it in.

I dont have this machine anymore {I sent it to another enthusiast in Canada} but am proud to have saved it for £100. It was SIP No 166 which must have been early 1920s. I was paying a quick visit to a dealer ,and said "what is that jig borer doing outside?",he said "well,its going for scrap, you can have it for £100 if you like".At least it still exists. If a smaller jig borer came along you never know, I might be tempted!!
Ted

So many enthusiests so little time!
To Jimm K, Yikes! I'm glad you don't REALY like the subject(hee hee)
I have to say that my time spent on the Devlieg 54K120 Spiromatic would be considerd the highth of my career. This machine had an Anilam Comando positioner on it and was re-fitted with ball screws on the X and Y and re-scraped by a company that spared no expence befor we got it.
WOW! was that nice! To be able to put anything up on the table and have it come off again exactly the way the print demands is great.
Of corse that is our job as a machinist but to struggle with a lesser machine on the same part offten makes me wonder if I should have chosen some other occupation.
Actualy I enjoy it so much that I keep several machines at home so I can practice some of the more anceient arts on the lathe, mill,shaper, and the universal grinder.
I reciently added a Linley jig borer to my line up and am in need of tooling or at least one example so I can replicate more.
Have a friend with a No. 2 Moore in his home shop... he looks like he is praying at an alter when he uses it!
I wouldn't say I'm exactly jelouse but he does have a Monarch EE 12x24 lathe too...
Well at least my shop is air conditioned.

merl

Well guys, I just heard a lot of good stuff about
Jig Borers like Moore and Fosdick but have not heard
Nothing about Atlantic Jig borers, any of you have any experience with the make ?
Also any of you knows if a Jig Borer can perform a
Cylinder boring (Smal cylinders) like motorcycles ?

TBandy

Also any of you knows if a Jig Borer can perform a
Cylinder boring (Smal cylinders) like motorcycles ?

Click to expand...

If longest bore you want to do is about 80% of quill travel, maybe so.

My 3B Pratt & Whitney claims to have 9" quill travel, but that is with quill stop removed. More like 7" in normal use.

John

A lathe is really much better for boring motorcycle cylinders.

A lathe is really much better for boring motorcycle cylinders.
---------------------------------------------
How would you do a two cyclinder in a lathe
Having worked in a motorshop as a crankshaft and camgrinder I can tell you that we never did a cyclinder in a lathe

How would you do a two cyclinder in a lathe

I think he is thinking in a 4 jaws independent chuck
But too many time centering ..

centering would be a pain in the @ss if you had any heat finns also relationship to cyclinder base
http://www.allstates.com/C4Tooling.html

What is a Jig Borer Used For

I realize that this is an old thread, but wanted to respond anyway as someone had a question regarding boring small (motorcycle) cylinders on a Moore Jig Borer (and also a lathe). I've recently accomplished that by way of fabricating a combination torque plate and jig with which to hold a Harley Evolution Cylinder upside down. The plates are torqued per HD specifications and the cylinder is secured to the table and centered using an axial dial indicator. I use a homemade boring head with a carbide tipped lathe tool, which looks something like a "flat" flycutter. This is placed in a Moore micrometer head for the cutting operation and is easily adjustable. The feed rate is set at .003". If someone will explain how to attach photos I'll be glad to do that. DISREGARD . . . THINK I FIGURED IT OUT.
As for boring in a lathe, the same jig could be used according to my mentor, who has taught machine shop in community colleges as well as at Nissan. The jig and cylinder would be mounted to a face plate, clamps lightly torqued, and rough-centered against a bull center mounted in the tailstock. Fine centered would be accomplished with a dial indicator and tapping the assembly with a mallet as needed for centering. Mount a large boring bar and start boring! To address one comment, cylinder fins would not be an issue mounted in a jig as I have described.
I managed to get a good deal on a fine Moore #2 off of the internet. It was a job travelling to Ohio to pick it up (it weighs 3,200 lbs) and getting it into my shop (helpers had to hang off the back of a forklift to keep the wheels on the ground for steering), but it is truly an amazing piece of equipment and I really appreciate hearing from experienced machinists on the subject.
Will be glad to discuss further if anyone is interested. Happy New Year!
Jim H. (Jim's V-Twin).