Is an Economical Solution One that Saves Money?

CBER32 Boring System in a CT40 Holder

The CBER boring system is an economical solution according to a customer I worked with the other day.

Here is his story:

A new Criterion customer called asking about the proper use of his CBER boring system. He had just received it and was preparing to bore his first .875 +.0002/-.0000" in diameter bore. I asked if he had purchased a collet nut with it or was going to use one he already had in his shop. He had purchased a collet nut but his operator had not used it. He had put an existing collet nut on the system. The existing collet nut had to be replaced with the purchased collet nut as the extractor lip interfered with the CBER system fitting in the ER collet holder properly.

We then talked about how much material was left to be bored out. He had left .010" per side put it was not enough because the nose radius of his insert was .015". I explained that he would not get the proper cutting action with the insert and if he could leave .020/.025" per side it would make it easier for him to produce the bore and the finish he required. He was going to change that for the next production run of parts he had to make.

We went on to discuss how to set the tool and make small diameter adjustments using the flat on the insert side of the boring head. We also discussed the appropriate RPM and feed rate he should be using for the material he was cutting.

The next day he called back to let us know the CBER system was exactly what he needed to do the job and was easy to use. He decided he is going to leave it set for the .875" diameter size and purchased additional systems for the other 4 or 5 size bores he makes. His reasoning was the cost of the CBER system being 1/4 of the other system he had looked at he could leave them set and reduce the cost of his set-up every time he set-up a production run. Truly, an economic solution for him.

Old Dog - New Trick

One of the most difficult aspects of boring is attaining the correct RPM for the cutting tool. Boring heads are design to move off center so you can enlarge the ID of a hole. This movement creates an imbalance which requires a slower RPM to ensure the bore can be produced. There are a number of approaches for correcting the imbalance. Some manufacturers restrict the amount of off-set so the boring head has minimal imbalance and others have some form of movable weights.

CB-202B Boring Head with Balance Kit
US Patent 7,309,194 B2

Criterion had a unique situation because we had been producing boring heads for over 65 years. Our philosophy was to give our customer as large a boring range as possible with one boring head.  Time has changed manufacturing technology and higher speeds have become important. We did not want to limit the range but we did want to meet the needs of today's manufacturing. Our solution was to develop a unique balancing system for our 202 series of boring heads. The US patent office agreed and issued a patent for the system. So by looking up your bore size, selecting the correct components and settings a boring head made over 50 years ago can spin at 5,000 RPM. This was unheard of when the boring head was first made but very achievable today.

So I would say the adage of "you can't teach and old dog new tricks" is not true.

What is the value of a balanced boring head? First and foremost is increased productivity. Another benefit is improved  tool life because the cutting tool now can operate at its optimum speed.

50 Years of Service - Is it Time to Retire?

For over 50 years Criterion Machine Works has produced the DBL series of boring heads. These boring heads were designed for manual milling machines that predominately used R-8 shanks. The mounting end was chamfered to match the spindle diameter of the R-8 shank. 

DBL-202B Boring Head
Designed for Manual Milling Machines

In its day this was one of the most popular boring heads available. It offered the user a large range from .250” to 6.687” in diameter. The .001” on diameter dial adjustment was equal or more precise than other models available at the time. It was not uncommon for machine shops to be started with the purchase of a Bridgeport Mill, a set of R-8 collets, a Kurt vise and a Criterion DBL boring head.

CB-202B Boring Head
Designed for CNC Machining Centers

As CNC machining centers grew in popularity, we introduced our CB Style Boring Head. The CB series boring heads were designed with a larger mounting face to be compatible with the tool holders used on CNC machines. The larger mounting surface also gives a more rigid and stable connection for performing a boring operation. All the ranges and adjustability features of the various DBL models were maintained in the CB design.






The CB style boring heads will perform equally as well as the DBL style in a manual milling machining operations. Unfortunately, the same is not true of the DBL style the smaller mounting surface is a disadvantage in CNC machining center operations.

IMTS2010 Generates a lot of Interest in CBER

IMTS Visitors discussing CBER applications

IMTS 2010 generated a lot of interest in the CBER product line. The ability to convert standard ER collet holders into precision boring systems was exciting to many of the visitors to our booth. In the past modular boring systems required special tool holders most of which we unique to the manufacturer of modular system. The special holders increased the cost of the boring systems and limited the ability of the user to use different systems because of these costs.

CBER on Display at IMTS 

A number of our visitors wanted to discuss using the CBER products in their swiss machine as well as in live tooling applications for the mill/turn centers. Precision boring in these applications has not been common in the past because of the physical limitations of the holding systems. This is no longer the case because so many of these machines are tooled for ER collet holders.







We thank all of the visitors to our booth and look forward to working with you and meeting the needs of your precision boring requirements,

Manufacturer chooses Boring instead of Interpolation – Reduces cycle time by 50%

Products Engineering Corporation Combination Square Kit

Products Engineering Corporation (www.pectools.com) has been producing precision tools in Southern California since 1960.  One of their most popular products is a combination square that requires two precision concentric bores and two precision concentric diameters for the tool to function properly.

Combination square bodies waiting to be loaded on the pallet

Products Engineering Corporation manufactures their combination square bodies on a Haas VF-1 machining center with a Midaco pallet shuttle. Each pallet is designed to hold 19 bodies at a time. Michael Berlin, Quality Assurance Manager at PEC, explained that they had been circle interpolating the two bores with satisfactory results but each pallet had a 28-minute cycle time. He wanted to improve the cycle time and possibly the quality of the bores so he started researching alternative hole-making methods.

A pallet of bodies in the Haas

Michael contacted Criterion about the possibility of a boring system that could bore his casting without any additional hole preparation. One bore is 2.500” in diameter while the other bore is slightly larger.  It was decided that the Cri-Bore modular boring system would be the best choice for this operation. The Cri-Bore system would give him easy adjustability and the single point tool would produce the bore he required. We determined the appropriate SFPM for his material was in the 400 – 700 range with a feed rate around .002” per revolution.  Michael said changing from circle interpolating to boring has reduced his cycle time from 28 minutes a pallet to 14 minutes a pallet and improved the quality of his bores.

Because of the success of the boring operation, Michael Berlin contacted Criterion again to see if we could help him with the mating part. Michael asked if we had any products that could cut outside diameters on his vertical machining centers. He was using circle interpolation on these parts also and a pallet of parts was taking 47 minutes to manufacture. We proposed using the Large Diameter Cri-Bore System with the cutting tip turned 180 degrees and a counterbalance weight added so the correct SFPM could be achieved. Some minor modifications to the insert holder were needed so the existing fixturing could be used. The SFPM and the feed rate were the same for this operation as the previous. Products Engineering Corporation’s change to our LCB1.5 Modular Boring System reduced the cycle time for this operation by 16 minutes. In addition to the reduction in time there was also an improvement in quality on these parts. A pallet of combination square bodies now can be made in 31 minutes.

A pallet of parts for OD Turning in the Haas

Completed parts ready for the next operation


A special Thank you to the management of Products Engineering Corporation for selecting Criterion for this project and allowing us to Photograph, Video Record and write about this project . If you would like to see the video log on to our youtube channel.

www.youtube.com/user/CriterionMW

More Chatter Check Your Overhang

I had the opportunity (and fun) of taking a technical call from a “New” customer not just to Criterion but also to boring. He was calling because the finish in his bore looked like a rasp it had some much chatter in it. He was attempting to make a 1-1/4” diameter bore 5” deep. His tolerance was +/- .002” and the material was 4140. The 3/4" diameter boring bar projected out of his boring head 8”. He had tried changing his RPM and changing his feed rates but nothing was working. He had slowed his RPM down to less than 200 hundred and his feed rate was less than .001 IPR; nothing was working for him.

We talked about some general rules of thumb for boring. First the depth to diameter ratio of a boring tool is critical to successfully boring a hole. The general rule for steel boring tools is 4:1, heavy metal boring tools is 6:1 and solid carbide tools is 8:1.  So his 8” projection with a 3/4” bar gave him a better than 10:1 ratio making it difficult if not impossible to achieve a satisfactory bore.

The second general rule is to use the largest diameter boring tool that will fit into the bore while still giving you clearance to evacuate chips from the bore. This gives maximum rigidity to your operation and helps to insure that you make the precision bore you need

The third general rule is to make sure your depth of cut is enough to clear the nose radius of the tool you are using ( I wrote about this in an earlier blog). His depth of cut was greater than the nose radius so this was not part of the problem.

The last issue we discussed was operating the tool at the correct surface feet per minute (SFPM) for the bore diameter. For his operation and the carbide he was using in steel with a hardness of about 30 R/C the starting point was 600 RPM with a feed rate of 2.0 IPM. This was based on the material he was cutting and the amount of off-set on his boring head.

The “Fun” for me was the customer had modified his program while we talked and had some else cut the bar so it only project slightly over 5” from the boring head. He asked if I could stay on the line while he tried the new program. I could hear the machine make the cut in the back ground and the customer describe it over the phone. He successfully bored the hole and was excited about what he had just learned. It is fun to help customers solve issues they have making their parts. If you would like us to try and help you with a boring problem don't hesitate to contact us. 

Modular Boring with HSK Connection

We have expanded our Modular Boring System with the addition of HSK 63A and HSK100A Tool Holders for the CB1.5, CB2, and CB3 size modular units. These New Shanks can quickly be connected to the Cri-Twin or Cri-Bore Modular Boring Systems as well as our CB Style Boring Heads designed specifically for CNC Boring.


The rigidity of the HSK andCB style connection and the strength of our dove-tail design gives you maximum strength and rigidity during the boring operations. Our modular boring systems are available with either .001″ or .000050″ direct reading adjustment dials.

Criterion also has a full line of V-flange, BT-flange, NMTB holders, and other holders and adapters to choose from. We have been producing Precision Boring Products for 75 Years.

We look forward to working with you on any of your precision hole making applications