Farewell to Burrs

It is inevitable to have burrs on the cutting or hole-drilling edge during the milling while milling parts. The size of burr is usually relevant to tool wear condition, feeding and rotary speed, material properties, cutting fluid, etc. The left burrs on the workpiece not only could get operatives scrapped, but also could lead the dimensions exceeding the tolerance. Therefore, CNC manufacturers all regard burrs as a huge enemy against workpiece quality. Previously, APPORO shared a case study on deburring the die casting parts. In that case, burrs formed on account of reamer wearing, and after APPORO promptly renewed the reamers, conducted a full inspection, and removed the burrs, we coped with the quality crisis.

Most burrs on the end/edge of the parts could be removed on the CNC machine through chamfering(*Ref). However, some have to be manually removed as the burrs are where the machine can hardly perform, resulting in the high overall manufacturing cost. If you ever encounter the above situation, take a look at two concrete cases below. See how APPORO make excellent use of decades of experience in CNC manufacturing to overcome all kinds of challenges.

Across Milling Burrs

Basically, milling is about cutting round bar materials into required ID/OD dimensions with high-speed rotary tools. If we are to mill flat surface onto the cylindrical side of round bar materials, the CNC milling machine should be installed with driven tool holders, where face milling cutters are mounted. When it comes to the step of face milling on the side, the round bar stops spinning and aligns the face milling cutter with the part to be machined. Then, the milling cutter starts spinning in right/down or left/right direction to side mill the workpieces, until the depth and width across flats are as required.


but highly possible to cause burrs at the end of the flat surface.
We use two cutters to precisely and quickly face mill the rod, but highly possible to cause burrs at the end of the flat surface.


From the poppet stem photo above, the head of this OD 8.0 mm workpiece features 7.0 mm width across flats. In other words, the surface has to be 0.5 mm in-depth on one side. First, APPORO used two cutters with 7.0 mm space in-between to face mill the 8.0 mm OD with symmetry from the end of the workpiece, in the same direction with the axis. The processing was precise and quick, but highly possible to cause burrs at the end of the flat surface, which was also around the edge of finish part of the workpiece. As there were not sufficient tool holders in that CNC lathe machine, it was impossible to remove the burrs on the machine. In that way, APPORO could only manually remove the burrs with a pneumatic deburring tool. However, the inconsistent force exertion led to the uneven chamfers and the disqualification.

To manually remove the burrs with pneumatic deburring tool led to the uneven chamfers.
The inconsistent force exertion led to the uneven chamfers marked by red arrows. The undercut marked by red circle is very rough due to the fact that the cutting tool is worn out.


When APPORO reviewed all the milling process, we decided to substitute a better CNC lathe machine with more functions, installing face milling tools in its driven tool holders on the side. So, we can machine the 7.0 mm across flats directly. When the 0.5 mm deep surface is completed on one side, the C axis of the lathe machine rotates by 180 degrees and machines 0.5 mm deep surface with an end mill. In the following, APPORO uses the chamfering tool to remove the burrs from the four edges. After this adjustment, APPORO stays away from the risk of inconsistent force exertion of manual deburring and enhances the production efficiency.

To mill the across flats and remove the burrs directly on a powerful CNC lathe.
To mill the across flats and remove the burrs directly on a powerful CNC lathe machine.


Burrs from Hole Drilling on Slopes

Generally, after hole drilling, noticeable burrs formed around the edge of the exit surface. If there is still enough space around the hole, chamfering to deburr is still available. However, if the exit surface is not perpendicular to the hole, meaning that the exit surface is a slope or curve, chamfering is not an option to deburr. Here are some alternative plans we can adopt:

1.) Blast

Using the momentum of the high-pressure gas to strike the surface of the workpiece. Available to polish the surface and deburr with evenness and efficiency. However, after blasting the surface could turn slightly matte.

2.) Tumble

The tumble theory applied to have tooling rub against the workpiece with high frequency. Available to polish the surface and deburr with evenness and efficiency. Unavailable for overlong/overweight workpiece or workpiece with external thread.

3.) The universal deburring tool

A unique chamfer tool with its cutter and spring attached. It allows removing the burrs around the edge on both ends at a time. Unavailable for hole under 3mm ID.

Can’t figure out how to deal with the nightmare of burrs? It is time to contact APPORO now. APPORO is going to help you overcome all the problems in manufacturing, based on our experience for decades in this field!


*Ref: Learn more about Chamfering.

Thread Before and After Plating (Part 2)

How to Control the Thread Size Before Plating?

As it is mentioned previously, the goal of OD control can be easily reached under stable CNC processing. Generally, after CNC processing, the threads of a non-plated component have to pass the thread gauge inspection so as to pass the QC inspection. Nevertheless, for components that need to undergo plating process, the manufacturing and inspection procedures will be different from the former. According to the requirement of our Swiss dental equipment supplier client, APPORO has to be discreet than ever for inspections. See the examples below:

Based on the required plating film thickness, APPORO has to leave some room for it during CNC processing, and use the pre-plated thread gauges for inspections. See the photo below. If the required plating film thickness is 1-3um, the major, pitch, and minor diameters should all be +0.02/-0mm larger than the standard dimensions when manufacturing the internal thread M13.2×0.3-6H. Then, the threads need to pass the inspections of the enlarged customized M13.2×0.3-6H +0.02/-0mm plug gauge before plating. After plating, the internal threads need to pass the inspections of a standard M13.2×0.3-6H plug gauge. Once they pass the inspection, they can be approved for shipment. If there is an external thread on the plated component, after CNC processing, the pre-plated ring gauge inspection will be necessary. And then, the inspection of a standard ring gauge should then be conducted.


What we can do without pre-plated gauges?

However, the customized pre-plated plug/ring gauges are all expensive, which are only needed for components that demand extremely high precision, but not for all components. With the long time CNC manufacturing experience, APPORO suggests to use NO GO of the standard thread gauge for the inspection criterion for threads before plating. That is, the threads could perfectly screw in the NO GO of the standard thread gauge without loosing. After plating, the threads have to pass the standard thread gauge inspections, a.k.a. GO and NO GO inspections.

This inspection is more available for components with plating film under 5um thickness. For components with plating film over 5um thickness, as its plating is for anti-corrosion purpose, and the precision requirement of it is usually lower. Even the ready made standard screws and nuts can be the inspection tools. Or, before plating the threads should be able to screw in the NO GO of the standard thread gauge but slightly loose. And then, the threads should pass the GO and NO GO inspections after plating.


When it comes to manufacture pre-plated thread, we have to leave some room for plating during CNC processing.
To use NO GO of the standard thread gauge for the inspection criterion for threads before plating. After plating, the threads have to pass the standard thread gauge inspections.


Plating and thread making are common techniques when speaking of CNC manufacturing components. Before and after different procedures, the concern will also be different. APPORO has devoted long time and and much efforts to CNC processing techniques, systematically learning from the processing experience in this field and turning it into application to increase the manufacturing efficiency and yield rates. Should you have any technical questions relevant to controlling size before/after plating, do not hesitate to contact us.


Learn more about thread gauge measurement:
Thread Gauge for instant measurement

Design Matters (Part 3) – Warping

Undoubtedly, part warping is a nightmare for both manufacturers and customers. It can affect the functionality of a part or lead to assembly failure. Generally, part warping is due to residual stress, which can be highly relevant to the choice of materials, dimensions of the part, and manufacturing conditions.


Warped part can be straightened.
Warped part is mainly caused by the residue stress of the material

Read more

Diamond Knurling Operation on CNC Lathe

Knurling is to feature patterns onto the CNC machined components.
Knurling is to feature patterns onto the CNC components.

As mentioned previously in “Cross Knurling Profile DIN 82-RGV”, knurling is a manufacturing process to feature straight, crossed, angled, diamond-like lines or pattern onto the CNC components. Usually, we use DIN 82 knurling specification standard for most CNC machining cases. If diamond knurling is required, we shall use DIN 82-RGE which is featured with diamond-like 30° cross male knurling. Also, we may consider DIN 82-RGV which is featured with cross knurling pattern as an alternative for customized purpose.

Read more

Effects of CNC Machining on Part Distortion

With recent increase in demand for more ultra precision machining designs for improving performance requirements, we are facing a great challenge in this kind of CNC machining services. Generally speaking, the greatest challenge when machining these components is part distortion. For instance, removing material up to 80 % on CNC machines to produce monolithic components replacing multi part assemblies has become common in aerospace, automobile, precision instrument industries. These kind of components might have similar appearance features such as thin wall, very long length, etc.

What Is Part Distortion?

Part distortion is defined as the deviation of part appearance from original shape after released from the fixture. Generally speaking, distortion could come from several variables such as type of material, inherent residual stresses in bulk material, residual stresses induced from CNC machining, part design, etc. In the most cases, the dominant factor of part distortion is the inherent residual stresses in the part. In general, these inherent residual stresses usually come from different manufacturing processes, i.e. quenching, stretching forging, extrusions, casting, welding, machining, forming, and etc.

CNC Machining Part Distortion
Residual stresses induced from CNC machining may cause parts deforming.


How Can I Minimize Part Distortion?

Distortion is a common challenge in manufacturing industrial components. The suggestions to minimize or eliminate distortion shows as below:

1.) The length to thickness ratio of the part design is lower than 10:1.

2.) Pre-heat treating the metal part prior to manufacturing for stress relieve. For instance, the general stress relieve condition for AISI 4340 alloy steel is at 650-670°C for 2hrs, slow cooling furnace.

3.) As per our experience of CNC machining service, distortion increases with the cutter size at constant feed, speed, depth of cut and material removal rates.

4.) Considering that WEDM process involves being fully-submerged, it imposes nearly no stress on the metal part.


With optimized manufacturing process flow, we are able to minimizing any deformation on all the CNC machined parts. Also, to select the suitable cutting tools and CNC machining parameters is of utmost importance. Note that the choice of cutting tools size is key to strike the balance between the productivity and geometrical constraints of the component. By the way, you can learn more about:

1.) Larger Corner Radii Reduced CNC Machining Cost

2.) 4 Things That Will Impact Your Manufacturing Costs



Shrinking and Distortion in Deep Slotting Parts

Parts after machining, cold rolling and welding usually generate internal residual stresses which may result in serious and unacceptable shrinking or distortion. Whatever the parts are made of metal or plastic. Recently, we are running a CNC machining project of rotor shaft for our Singapore client. At current, this project is still in First Article status. The rotor shaft is part of motor assembly which basically includes a rotor shaft and motor shaft. The motor shaft will be inserted into a deep, accurate, diameter Ø5 H7 (+0.012/-0mm) hole on the rotor shaft. There is a deep slotting cut for enlarging the hole when assembling. However, after deep slotting, the hole size will be slightly reduced and also out of tolerance which lead to a complaint happened. Our customer was using pin gauge 5mm to check the hole. When checking, the pin gauge must go all the way till depth 18.0mm, but failed.


CNC machining Rotor Shaft, shrinking may happen after deep slotting.
The rotor shaft shrinking after deep slotting


Root Cause for Shrinking Parts

In the meantime, after inner discussion, we believe that the downsize hole was caused by internal residual stresses. Prior to slotting, we had full inspection that the diameter 5mm pin gauge could go all the way as it is indicated in the drawing. In that way, we list two possible reasons for the situation below:

  1. The drawing says the internal hole is Ø5 H7 x 18mm, and we did machine the hole into 18mm in depth accordingly, even into 18.5mm.
  2. Besides, the internal stress would be very likely to lead the hole to slightly shrinking after slotting. Then, it will be unreasonable to meet the tolerance H7 standard after slotting. We suggest our customer to insert the pin gauge harder. So, it will not be a problem for the pin to go into the internal hole.


In conclusion, as the dimension was machined exactly based on the drawing, we think the situation is taken full control of by us.​Therefore, We recommend our customer to move forward to the mass production.​​


If you have similar design with deep slotting, send your 2D and 3D drawing files to our international team of engineers for a free quote. We look forward to cooperating with you. Please check our RFQ process and send us email.

4 Things That Will Impact Your Manufacturing Costs (Part 2)

A few days ago, we have talked about various factors which may affect your manufacturing costs in previous article. In short, material costs are directly relative to part quality and durability. And, surface treatment costs have significantly increased recently due to strictly environmental policy. No doubt, if you are working out a CNC machining project, APPORO can help you figuring out the manufacturing cost accordingly. Learn more about: How To Work With APPORO

Apart from the above two factors, there are still others which can affect your manufacturing costs:

3.) Manufacturing Process

Generally speaking, the slower the machining process is, the much higher precision is. For example, WEDM(Wire Electrical Discharge Machining) is one of the slowest metal machining process in the world. A series of rapidly recurring current discharges between two electrodes cut the profile of bulk material. Mostly used for stamping die cutting and prototyping which required high accuracy quality.

Furthermore, the complexity of design do play an important role in manufacturing costs. High challenge designs usually require cutting-edge machining facility for optimized quality. However, the investment in high-end machinery will also increase the cost of your project. Though, the advanced equipments can provide a great machining experience.

4.) Lead Time of Your Project

If you need a time effective production run, this can impact the cost depending on the project. To manufacture a project quickly is much more costly than a longer lead time. You may wonder what factors do have impact in a fast lead time project. Generally speaking, there are usually various necessary procedures prior to part manufacturing. For instance, to arrange CNC machines and engineers from mass production lines, to prepare customized jig and tooling. Urgent project results in much more impact from general mass production runs. In contrast, a longer turnaround can usually minimize capacity losses.

Customized Jigs and Tooling used in quickly manufacturing processes
Customized Jigs and Tooling

Get A Quote For Your Next Project

Via above various factors, a CNC machining services manufacturer can evaluate a quote your project. At APPORO, we can provide you with a competitive price. Pls send us your RFQ to get a free quote. Our production lines can offer a wide range of manufacturing processes to support your inquiry.

4 Things That Will Impact Your Manufacturing Costs (Part 1)

So far, to exactly predict machining time and manufacturing costs can be very difficult. For instance, factory location, facility or even politics do have impact on the quotes of manufacturing. Sometimes, to request a quote for your manufacturing project feels like looking for a needle in a haystack. In fact, you can still have an initial concept of cost even without 2D and 3D CAD drawings.

Various factor which have impact on manufacturing cost for CNC machining services
Top-end CNC machinery can manufacture high quality parts.


 What is included in Manufacturing Costs?

Generally speaking, there are various factors which directly have impact on the cost of CNC machining services. For instance, materials used, dimensions of the part, quantity per batch, manufacturing process applied, post processing used. Furthermore, auxiliary processing equipment can also affect the cost of manufacturing project such as customized cutting tools, jigs and tooling. In spite of above, there are still some basic guidelines which will have impact on your project. Hopefully, this can be grateful for your evaluation in early planning stage.

1.) Material Costs

Obviously, different type of material costs are largely various from each other. Nowadays, material cost is getting more transparency of pricing due to freely global trading. You can get a roughly idea of material cost by looking for local price for raw material. Furthermore, parts made of cheaper material is likely lack of durability or poor quality compared to high-end material. However, parts made of high-end material usually means more manufacturing lead time for good quality.

Manufacturing costs is relative to many factors.
Various factors may affect your manufacturing costs.


2.) Surface Treatment Costs

Surface treatments are generally for cosmetic and anti-rust purpose. In the past, the chemical solution used in most of surface treatment process are usually with toxic hazards. Actually, the proportion of surface treatment cost in total manufacturing cost were not so high. Nowadays, the directive of RoHS(*Ref.1) has strictly restricted these hazardous substances. At the same time, surface treatment costs are getting higher due to stricter environment policy. For a roughly estimation, the heavier the weight, the more expensive the surface treatment cost.

Surface treatment may cost more nowadays.
Surface treatment: Anodizing


Learn more: 4 Thing That Will Impact Your Manufacturing Costs (Part 2)


*Ref.1: See more about the directive of RoHS

Annealing a Connector Part for Crimping

Annealing(*Ref. 1) is one of well-known heat treatment process. Actually, it can limits the potential for metal cracking during the cold-working process. Commonly used in applications where a component is bent or crimped. At APPORO, our CNC machining services are also including annealing heat treatment for customized purpose.

A complete annealing process for steel involves:

1.) Heating the metal to above its austenitic temperature.

2.) Maintaining the high temperature for sufficient time to allow the material to fully form austenitic grain structure.

3.) Slowly cool down in the furnace to obtain equilibrium micro crystal structure.

After that, the ductile steel will become relatively lower hardness, yield strength and tensile strength. Generally speaking, the annealed metal is much more soft and ready for further cold working, such like bending, stamping, extrusion, rolling or forging.

Case Study about Cable Terminal Annealing

Recently, we were running a CNC machining service project for automobile industrial application. The item is a cable terminal with electrical eyelet, made of free cutting steel 12L14 with blue zinc plating surface treatment. The cable terminals were well machined, zinc plated and inspected at our CNC production lines.  However, our customer has rejected the first articles due to crack when crimped. See below photo.

Cable Terminal without heat treatment, maybe cracked when crimped.
Cable Terminal without Annealing


The cable terminal with electrical eyelet is to fit with cable wire, then crimping for connection purpose. However, the metal is good for cold working, but usually brittle and lack of ductility. Therefore, it is not preferable for further crimping process. Generally speaking, a perfect crimping require the metal with softer and more malleable state. Annealing can be the best treatment to solve this situation.


As a result, we has sent the cable terminal for annealing prior to zinc plating process. After that, a crimping test by using a pliers is for quality approval. Below photo shows that the cable terminal is with more ductility and staying perfect without any cracks.

Cable Terminal after annealing, still ductile after crimping
Cable Terminal after annealing

We are well experience with electrical connector via our CNC machining services production lines. You can also visit our official site for more understand about our core services. Should you have any inquiry for above items, do not hesitate to send us RFQ for free project review.

*Ref. 1 See more about Annealing in Wikipedia

Make Your Own CAD Drawing

Computer-aided design(*Ref. 1), so called CAD, is widely used in most industries to improve the efficiency and quality of design. Furthermore, CAD drawing output in the electronic file is highly conducive to communicate with designer and manufacturer. Also, it creates a great platform carrying complete information for CNC machining service manufacturer. Generally, we prefer reading, modifying and creating 2D and 3D CAD drawing files by using CAD software.

The way to create your own CAD drawing.
Create Your Own CAD Drawing


The Way to Create CAD Drawing

Recently, CAD software do helpful for rapid and easy engineering modeling in various industries. For example, automotive, aerospace industries, reverse engineering(*Ref. 2), PCB design, animation design, industrial and architectural design. In summary, below procedures show how we use CAD software to create 2D and 3D CAD drawing:

1.) to start from creating 3D CAD object

  • create 2D elevation drafting
  • form and modify 3D object by extrusion, revolve, sweep, emboss functions

2.) to create 2D print from 3D CAD

  • start a new .dwg drawing file
  • place various but less view sides of 3D model
  • mark dimensions detailed but simplified
  • mark important notices

How to Get CAD Software?

Currently, CAD program is a necessary powerful tool to use in CNC machining service project. A CAD software with good design should be capable of creating both 2D drawing and 3D modeling. Generally, it is usually hard to choose the best modeling software for different market sector. It is because various aspects and the wide range of features are available in these CAD tools. The essential elements of good CAD software are as below:

  • 2D Drawing Tools
  • 3D Modeling Tools
  • Textures
  • Transparency Options
  • Lighting Effects
  • Hatching
  • Photo-realistic Rendering


At present, it is easy to get lots of free CAD software for personal or professional modeling purpose. Should you have any questions about CAD software application, do not hesitate to send us email.


*Ref. 1 Computer-aided design-Wikipedia

*Ref. 2 Reverse Engineering: From Real Component to Print