Two coaxial bushings in one component require finish honing to Ø12.7 H8 and Ø17.463 H8. Both bores have a tolerance of 0/+0.027 mm and a surface target of Ra 1.6 µm. The smaller bushing is made of stainless 15-5PH, while the larger one is made of hard C63020 bronze. The application therefore combines different diameters, stock allowances and machining characteristics.
The solution is a manually actuated stepped komprEXACT with two separately specified honing zones. Material-specific honing stones, matched guide diameters and defined entry sizes allow both bushings to be machined with the same tool. The tool is intended for use with a hand-held drill; after insertion, an adjusting sleeve brings the stones into contact with the bore walls.
| Characteristic | Small bushing | Large bushing |
|---|---|---|
| Finished diameter | Ø12.7 H8 | Ø17.463 H8 |
| Tolerance | 0/+0.027 mm | 0/+0.027 mm |
| Material | 15-5PH stainless steel | C63020 hard bronze |
| Stock allowance on diameter | 0.10 mm | 0.10–0.12 mm |
| Surface target | Ra 1.6 µm | Ra 1.6 µm |
| Entry diameter | Ø12.3 mm | Ø17.063 mm |
| Guide diameter | Ø12.4 mm | Ø17.2 mm |
| Honing-stone specification | for 15-5PH | for C63020 |
| Tool characteristic | Configuration |
|---|---|
| Tool principle | manually expanding stepped komprEXACT |
| Number of carriers | four carriers with separate honing zones |
| Actuation | turn the adjusting sleeve after insertion |
| Drive | hand-held drill |
| Approved overall length | approximately 305 mm |
| Maximum body diameter | approximately Ø46 mm |
The two bushings differ in more than diameter. 15-5PH and hard bronze load the honing stones differently. Using the same abrasive specification on both steps would therefore create an unnecessary risk of uneven stock removal, different surfaces and unequal wear.
The stock allowances are also different. The smaller bushing has 0.10 mm on diameter, while the larger one has 0.10 to 0.12 mm. The tool must guide both machining zones securely without either step losing guidance during entry or withdrawal. At the same time, the guides must not obstruct insertion into the pre-machined bores.
Because the project documents tool design and drawing approval, the source material contains no production measurements or tool-life data. Process capability must therefore be confirmed by trials on the actual component.
Material-specific stone specifications: The Ø12.7 mm zone is specified for 15-5PH, while the Ø17.463 mm zone is specified for C63020. Abrasive grit, bond and wear behaviour can therefore be matched to each machining position.
Defined entry geometry: The honing stones are ground to the two finished diameters. Entry diameters of Ø12.3 mm and Ø17.063 mm allow safe insertion. The stones are brought into contact only after the tool is inside the component.
Matched guidance: Guide diameters of Ø12.4 mm and Ø17.2 mm stabilise the tool even if it moves slightly farther forward or backward during manual honing. The stepped guidance thus supports coaxial alignment of the two honing zones.
Compact manual application: The tool is designed for a hand-held drill. Operation and expansion remain mechanically straightforward: insert the tool, turn the adjusting sleeve, bring the stones into contact and perform the honing stroke in a controlled manner.
During the approval process, the different materials were explicitly assigned to the two honing zones. The guides were also adjusted to Ø12.4 mm and Ø17.2 mm. The approved drawing confirms the finished diameters, entry diameters and material-specific stone arrangement.
The design therefore provides a sound basis for machining both bushings, but it does not replace process acceptance. Before production use, size development, form, surface value, crosshatch and wear must be checked separately for both materials. Despite common actuation, the two honing zones may develop different wear rates.
A documented initial capability run with measurements before and after honing is therefore recommended. Expansion should place both diameters within H8 without unnecessarily overworking either material side.
Why are two different honing-stone specifications used? 15-5PH and C63020 have different machining and wear characteristics. Separate specifications allow grit, bond and cutting behaviour to be matched to each honing zone.
Why does the tool have two guide diameters? The guides stabilise the stepped tool in both bushings. Alignment is retained even if the tool shifts axially during the manual stroke.
How is the tool inserted into the component? The stones initially remain at the smaller entry diameters of Ø12.3 mm and Ø17.063 mm. After insertion, the adjusting sleeve is turned until the stones contact the bore walls.
Can both honing zones be expected to wear at the same rate? No. Their materials, allowances and diameters differ. Wear must be monitored for each zone and compensated by regrinding or an adjusted stone specification when required.
Which results are documented? The available records document the enquiry, technical design and approved tool drawing. They do not contain measurements from production machining.
The stepped komprEXACT combines two H8 honing zones in one compact, manually actuated tool. The key is not only the stepped geometry, but the separate specification for 15-5PH and C63020. Entry and guide diameters support safe handling and coaxial guidance in the component.
The approved design provides the technical basis for finish honing Ø12.7 H8 and Ø17.463 H8 to Ra 1.6 µm. Component trials remain necessary before production release because size development and wear must be evaluated separately for both honing zones.