📏 Dowel Pin Hole Size Calculator
Size dowel pin holes for press, locating, slip, and wood fits across metal, plastic, and woodworking jobs.
📌 Presets
📝 Inputs
📊 Results
🧰 Hole Material Guide
📈 Common Pin Sizes
| Pin | Finished hole | Method | Use |
|---|---|---|---|
| 1/8 in | 0.126-0.128 in | Press | Fixture locators |
| 3/16 in | 0.188-0.190 in | Slip | Panel alignment |
| 1/4 in | 0.250-0.253 in | Locating | Shop jigs |
| 5 mm | 5.00-5.02 mm | Wood | Cabinet joinery |
| 6 mm | 6.00-6.03 mm | Locating | Machine plates |
| 8 mm | 8.01-8.03 mm | Slip | Casework |
| 10 mm | 10.02-10.05 mm | Press | Heavy locators |
| 12 mm | 12.03-12.06 mm | Repair | Oversize bores |
🔧 Fit Class Reference
| Fit | Delta | Tolerance | Note |
|---|---|---|---|
| Press | -0.0004 in | 0.0002 in | Light interference |
| Locating | 0.0000 in | 0.0003 in | Repeatable fit |
| Slip | +0.0006 in | 0.0005 in | Easy assembly |
| Loose | +0.0015 in | 0.0010 in | Fast install |
| Wood | +0.0040 in | 0.0020 in | Allow for swell |
| Repair | +0.0100 in | 0.0025 in | Sleeve or bushing |
| Metric press | -0.01 mm | 0.01 mm | Fine machine fit |
| Metric slip | +0.02 mm | 0.02 mm | Quick assembly |
📑 Material Guidance
| Material | Allowance | Tool | Note |
|---|---|---|---|
| Steel | 0.0002-0.0005 | Reamer | Very stable |
| Aluminum | 0.0005-0.0010 | Sharp drill | Cut cleanly |
| Cast iron | 0.0002-0.0006 | Reamer | Short chips |
| Hardwood | 0.003-0.008 | Brad point | Drill from both faces |
| Softwood | 0.005-0.012 | Brad point | Expect movement |
| Plywood | 0.004-0.009 | Spur bit | Prevent tearout |
| MDF | 0.006-0.013 | Sharp drill | Dust matters |
| Plastic | 0.002-0.006 | Slow drill | Keep it cool |
💡 Prep Drill Guide
| Method | Leave stock | Final step | Note |
|---|---|---|---|
| Drill only | 0.000 in | Drill to size | Fastest option |
| Drill + ream | 0.005 in | Use reamer | Best all-round fit |
| Precision ream | 0.008 in | Finish ream | Tight locating fit |
| Wood dowel | 0.010 in | Glue set | Allow for swell |
| Oversize repair | 0.012 in | Sleeve fit | Fix worn holes |
| Metric drill | 0.12 mm | Finish drill | Use exact metric |
| Metric ream | 0.20 mm | Finish ream | Clean bore |
| Wood cleanup | 0.15 mm | Chamfer edge | Helps start pin |
💡 Tips
⚠ Safety Note
Get the right size for dowel pin holes, one from those things that can make or break a project. You must consider the relation between the diameter of the pin and that of the hole, keeping in mind the flexibility of the dowel and of the hole material. That factor weighs more than the size of the dowel.
Standard dowel pins have M6 tolerance, which is the usual standard everywhere. For the hole commonly you choose H7 tolerance. H7 reamers easily present themselves.
How to Choose the Right Hole Size for Dowel Pins
If the pin must enter by simple pressure from fingers, H7 for the hole tolerance works well. For instance, for such fit the hole size should be 3.00 mm +0.01 mm, -0.00 mm.
Press fit dowel pins own a bit larger tolerance and are made for usage with a hole a bit smaller than the diameter of the pin. That difference between diameters of pin and hole calls interference, that creates tension to limit motion. For press fit holes occasionally use P7 tolerance.
For 1/2″ dowel pin those limits are 0.4989″/0.4996″. Everything that gives good press for fixturing with hand tools and hammer.
Pinned joints normally have press fit aspect and slip fit aspect. The holes of the press fit aspect is round. At the slip fit aspect usually is round hole together with slotted hole.
The slotted hole cares about concentricity tolerance. The slip fit tolerance accepts the size of the dowel pin, while the slot allow misalignment.
For soft materials as aluminum or zinc castings you usually reduce the size limits by 0.0005 inches. Aluminum tooling easily move when you insert the pins. Dowel standards are.1250 and.1252 (two tenths over).
If you use normal.125 reamer, go with the two-tenths over dowel and.1255 or.126 compatible hole according to fit needs.
About depth because transition and interference fits require it, you recommend 2x until 3x the nominal diameter of the pin. For clearance fits you advise lower depths to reduce the risk of sticking of the pin around 1x until 2x the diamete. For reamed hole of 1/4″ dowel,.2495″ reamer well serves.
Start with at least.250 diameter, later with 7/32″, ultimately with 15/64 endmill for straightness. Only drill probably does not give precise hole for dowel pin. Typical are upper/lower reamer set.
One reamer are a bit too small for interference fit, the other a bit too large for slip fit. Must be good shoulder to stop the pin in the depth, but also sufficient through hole for push it out later.
In woodworking the dowel must not be tight, so that glue enter the cracks between dowel and wooden joints. Hole of same size as the dowel well works only with manufactured dowel.
