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

When Does an Aerospace Company change the Plane?

The answer is when they have to bore a horizontal hole on a vertical machining center.

The combination of a right angle head and a CBER precision boring system allows anyone to change the plane.

Recently an aerospace company contacted us about an application they had for boring a horizontal hole on a vertical machining center. They knew were making boring heads that fit into ER collet holders so they inquired about the possibility of our producing a boring head to fit into an ER16 collet holder.  They had a right angle head that used ER16 collets and they wanted to use it for boring their horizontal hole.

We had just successfully finished our CBER16 prototypes and were beginning our first production run of parts so they would be ready for introduction at IMTS2010. We sent them one of the prototypes they asked if we could extend the range so they could bore a 1.000-inch diameter bore.  We designed an offset head to accomplish their request (The black insert holders in the photo).  An additional dilemma was discovered when the flush nut design collet nut was added as a requirement. We had to quickly do some redesign to the CBER16 so the flush nut could be used.

Again the voice of the customer has given us a new product to carry forward. We will be adding extended range insert holders to our CBER16 and CBER20 precision Boring Systems.

If you need to change the plane or stretch the limits give us a call 800.854.7441 or e-mail us at cmw@criterionmachineworks.com we enjoy the challenges

Product Line Expands because of The Voice of the Customer

A couple of months ago we were contacted by a machinery dealer who had seen our ads for the CBER boring system (you can read about it in our earlier blogs). They wanted to know if we could make ER32 to ER25, ER32 to ER20 and an ER32 to ER16 adaptors. We discussed the application, which was to give their customer a quick-change system for their turning center that was tooled with ER32 collet holders. After looking at the request we determined we could do the ER20 and ER16 sizes but not the ER25.

ER to ER Adaptor

While we were working on the design we realized this would be a natural extension for our CBER system. Our customers will be able to take advantage of the boring ranges of the CBER20 and the CBER16 products in their ER32 holders. We will not be able to have everything ready for IMTS 2010 but we will have it ready by the end of the year. If you have any questions about the CBER system or the ER to ER adaptors please contact us at 800.831.7444 or by e-mail at cmw@criterionmachineworks.com.