---
product_id: 17976266
title: "Irwin Tools IRWIN 10239CB Unibit 2-Steps Cobalt Alloy Steel Step Drill Bit for 1/2-Inch and 3/4-Inch KO, Black"
brand: "irwin"
price: "Bs.1268"
currency: BOB
in_stock: true
reviews_count: 10
category: "Irwin"
url: https://www.desertcart.bo/products/17976266-irwin-tools-irwin-10239cb-unibit-2-steps-cobalt-alloy-steel
store_origin: BO
region: Bolivia
---

# Dual hole sizes: 7/8" & 1-1/8" precision fit Hex shank for secure drill chuck grip Cobalt Alloy Steel for extreme durability Irwin Tools IRWIN 10239CB Unibit 2-Steps Cobalt Alloy Steel Step Drill Bit for 1/2-Inch and 3/4-Inch KO, Black

**Brand:** irwin
**Price:** Bs.1268
**Availability:** ✅ In Stock

## Summary

> 🔧 Drill Like a Pro, Last Like a Legend

## Quick Answers

- **What is this?** Irwin Tools IRWIN 10239CB Unibit 2-Steps Cobalt Alloy Steel Step Drill Bit for 1/2-Inch and 3/4-Inch KO, Black by irwin
- **How much does it cost?** Bs.1268 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.bo](https://www.desertcart.bo/products/17976266-irwin-tools-irwin-10239cb-unibit-2-steps-cobalt-alloy-steel)

## Best For

- irwin enthusiasts

## Why This Product

- Trusted irwin brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Smooth Spiral Flute:** Single flute spiral design optimizes chip removal and reduces heat, extending bit life and improving efficiency.
- • **Versatile & Reliable:** Ideal for industrial, DIY, and even delicate tasks like guitar luthier work—trusted by pros who demand perfection.
- • **Secure Hex Shank Grip:** Hex shank ensures zero slippage in your drill, delivering consistent, clean cuts every time.
- • **Precision Dual-Step Design:** Two exact hole sizes (7/8" & 1-1/8") tailored for 1/2" and 3/4" knockout applications—no guesswork, just perfect fit.
- • **Built to Last with Cobalt Alloy:** Engineered from premium cobalt steel to conquer the toughest metals and plastics without dulling.

## Overview

The Irwin 10239CB Unibit is a high-performance step drill bit crafted from cobalt alloy steel, designed for precision drilling of 7/8" and 1-1/8" holes. Featuring a hex shank for secure grip and a spiral flute for efficient chip removal, this durable tool excels in metal, plastic, and specialty applications, making it a must-have for professionals and serious DIYers seeking longevity and flawless results.

## Description

Product Description Step Drill Bit, Material Cobalt Alloy Steel, Steam Oxide Finish, Number of Hole Sizes 2, Shank Size 7/16 In., Size Range 7/8 In. to 1-1/8 In., Sizes Included 7/8 In., 1-1/8 In., Number of Flutes 1, Shank Type Hex, Bit Length 3-1/8 In. From the Manufacturer Irwin Unibit Cobalt is made of high speed steel, this step drill bit will last longer in the toughest of materials. Irwin Industrial Tools 10239CB 9 2 Hole Sizes (7/8-Inch and 1-1/8-Inch )for 1/2-Inch and 3/4-Inch KO

Review: My 3rd Irwin cobalt Unibit - This is the 3rd Irwin cobalt Unibit I've bought over the last few years. (3 various sizes) A quick summary: Irwin tools are dependable and are of very good quality. I know I can get the job done if I'm using an Irwin tool or bit. My last Unibit was used to drill 120 nickel sized holes into stainless steel plating. (about 1/8" thick) (used a drill press). I was in a hurry and didn't use any drilling oil. The Irwin survived that task but reached its limitation which was more than I expected. I bought this particular Irwin 10234CB to drill a 13/16" hole into my Weber 10020 Smokey Joe Silver Charcoal Grill, Black . I wanted to install a 3" River Country (RC-T3W) Adjustable Professional BBQ, Grill, Smoker Thermometer (50 to 550F) (see my photo on product page) and this Unibit did the job effortlessly. (ate through that lid like it was plastic) Irwin Unibits are pretty expensive compared to other brands, but if you want the very best and longevity, definitely get Irwin cobalt bits. *** Don't forget to use drilling oil (or any oil for that matter, even olive oil) to extend the life of your bits.
Review: Drilling guitar endpin jack holes. - I bought this bit as part of my tool kit to drill endpin jack holes in expensive guitars to mount the endpin jacks for internal pickups. Any drill bit will make a hole, but I wanted to make sure the wood on the guitars would be in perfect condition after the hole was drilled. Causing serious damage to a $5,000 guitar can ruin a guy's day, especially if he's the owner of the guitar. Typically, if no prior hole exists, a new 1/4" hole is drilled with a sharp brad point drill bit, followed by a precision tapered reamer from a guitar luthier supply house. However, sometimes a smaller hole already exists where a strap button was screwed in or a tapered end pin was press fit into a tapered hole. Perhaps the tapered endpin was even glued into the tapered hole and can't be removed without drilling. If a strap button had been screwed in, then the screw hole could be filled and a new hole could be drilled as if none had ever existed, followed by the precision reamer to safely bring the hole to its final dimension. On the other hand, this Irwin Unibit could be used to drill a tapered hole, using the strap button screw hole as a pilot hole, followed by the precision reamer to bring the hole to its final dimension. I have used the Unibit for this exact purpose, and it worked beautifully, with no damage to the guitar. If a tapered wooden strap button has been glued in, the button can be carefully sawed off near its base, and the hole can be drilled with a brad point bit and then reamed, just like the situation where no hole ever existed. But no sawing is needed if a punch is used in the center of the wooden end pin, a 1/8" pilot hole is drilled with a normal twist metal bit or a brad point bit, and the the Unibit is used to drill through the strap button and into the guitar. Eventually, as the Unibit goes deeper, a tapered hole is formed that is larger than the strap button, and the button is drilled completely away, leaving only a nicely tapered hole for the precision reamer to follow and finish to final dimension. The Unibit can be used after drilling a pilot hole, without using the precision reamer. If that is done, it is best to stop drilling with the Unibit when it reaches the 15/32" step and then finish the hole with a standard 15/32" metal twist bit that will tend to self-center. Or, the Unibit can be used to fully penetrate the guitar base and end block, leaving a 1/2" hole that is slightly oversized for most endpin jacks, but completely usable. Alternatively, buy the 12mm Unibit, which is 15/32", and the hole will be exactly the right size. The precision reamer from the well-known guitar luthier supply house is strongly recommended, but even just the Unibit will safely do a good job. Do put blue painter's tape where the hole will be drilled to help protect the wood from damage. DON'T use the cheap tapered hand reamers, including the one from Irwin -- they do not make good, concentric holes in wood. I've tried -- and failed miserably. The cobalt Unibit is not necessary. The standard (less expensive) tool steel works well, just not as long as the cobalt. For $10 more, the cobalt seems to be the better deal if it is used often. This is a must have tool in a guitar workshop.

## Features

- Country of Origin:United States
- Package length:18.0"
- Package width:18.0"
- Package height:21.0"

## Technical Specifications

| Specification | Value |
|---------------|-------|
| ASIN | B00126FI0I |
| Best Sellers Rank | #31,294 in Industrial & Scientific ( See Top 100 in Industrial & Scientific ) #51 in Step Drill Bits |
| Brand | IRWIN |
| Cutting Diameter | 1.13 Inches |
| Date First Available | March 30, 2009 |
| Department | Unisex-Adult |
| Finish Type | Cobalt Alloy Steel |
| Global Trade Identification Number | 00038548099231 |
| Is Discontinued By Manufacturer | No |
| Item Weight | 3.2 ounces |
| Item dimensions L x W x H | 3 x 6.1 inches |
| Item model number | 10232-P |
| Manufacturer | Irwin |
| Material | Cobalt Alloy Steel |
| Number of Flutes | 1 |
| Number of Pieces | 2 |
| Shank Type | Hex |
| Surface Recommendation | Metal |
| Tool Flute Type | Spiral |
| UPC | 038548099231 640024945286 |
| Unit Count | 1.0 Count |

## Product Details

- **Brand:** IRWIN
- **Cutting Diameter:** 1.13 Inches
- **Finish Type:** Cobalt Alloy Steel
- **Material:** Cobalt Alloy Steel
- **Shank Type:** Hex

## Images

![Irwin Tools IRWIN 10239CB Unibit 2-Steps Cobalt Alloy Steel Step Drill Bit for 1/2-Inch and 3/4-Inch KO, Black - Image 1](https://m.media-amazon.com/images/I/210pWkVt3+L.jpg)
![Irwin Tools IRWIN 10239CB Unibit 2-Steps Cobalt Alloy Steel Step Drill Bit for 1/2-Inch and 3/4-Inch KO, Black - Image 2](https://m.media-amazon.com/images/I/41PghzHQs4L.jpg)

## Available Options

This product comes in different **Size, Style** options.

## Customer Reviews

### ⭐⭐⭐⭐⭐ My 3rd Irwin cobalt Unibit
*by J***U on September 13, 2014*

This is the 3rd Irwin cobalt Unibit I've bought over the last few years. (3 various sizes) A quick summary: Irwin tools are dependable and are of very good quality. I know I can get the job done if I'm using an Irwin tool or bit. My last Unibit was used to drill 120 nickel sized holes into stainless steel plating. (about 1/8" thick) (used a drill press). I was in a hurry and didn't use any drilling oil. The Irwin survived that task but reached its limitation which was more than I expected. I bought this particular Irwin 10234CB to drill a 13/16" hole into my Weber 10020 Smokey Joe Silver Charcoal Grill, Black . I wanted to install a 3" River Country (RC-T3W) Adjustable Professional BBQ, Grill, Smoker Thermometer (50 to 550F) (see my photo on product page) and this Unibit did the job effortlessly. (ate through that lid like it was plastic) Irwin Unibits are pretty expensive compared to other brands, but if you want the very best and longevity, definitely get Irwin cobalt bits. *** Don't forget to use drilling oil (or any oil for that matter, even olive oil) to extend the life of your bits.

### ⭐⭐⭐⭐⭐ Drilling guitar endpin jack holes.
*by A***N on June 8, 2015*

I bought this bit as part of my tool kit to drill endpin jack holes in expensive guitars to mount the endpin jacks for internal pickups. Any drill bit will make a hole, but I wanted to make sure the wood on the guitars would be in perfect condition after the hole was drilled. Causing serious damage to a $5,000 guitar can ruin a guy's day, especially if he's the owner of the guitar. Typically, if no prior hole exists, a new 1/4" hole is drilled with a sharp brad point drill bit, followed by a precision tapered reamer from a guitar luthier supply house. However, sometimes a smaller hole already exists where a strap button was screwed in or a tapered end pin was press fit into a tapered hole. Perhaps the tapered endpin was even glued into the tapered hole and can't be removed without drilling. If a strap button had been screwed in, then the screw hole could be filled and a new hole could be drilled as if none had ever existed, followed by the precision reamer to safely bring the hole to its final dimension. On the other hand, this Irwin Unibit could be used to drill a tapered hole, using the strap button screw hole as a pilot hole, followed by the precision reamer to bring the hole to its final dimension. I have used the Unibit for this exact purpose, and it worked beautifully, with no damage to the guitar. If a tapered wooden strap button has been glued in, the button can be carefully sawed off near its base, and the hole can be drilled with a brad point bit and then reamed, just like the situation where no hole ever existed. But no sawing is needed if a punch is used in the center of the wooden end pin, a 1/8" pilot hole is drilled with a normal twist metal bit or a brad point bit, and the the Unibit is used to drill through the strap button and into the guitar. Eventually, as the Unibit goes deeper, a tapered hole is formed that is larger than the strap button, and the button is drilled completely away, leaving only a nicely tapered hole for the precision reamer to follow and finish to final dimension. The Unibit can be used after drilling a pilot hole, without using the precision reamer. If that is done, it is best to stop drilling with the Unibit when it reaches the 15/32" step and then finish the hole with a standard 15/32" metal twist bit that will tend to self-center. Or, the Unibit can be used to fully penetrate the guitar base and end block, leaving a 1/2" hole that is slightly oversized for most endpin jacks, but completely usable. Alternatively, buy the 12mm Unibit, which is 15/32", and the hole will be exactly the right size. The precision reamer from the well-known guitar luthier supply house is strongly recommended, but even just the Unibit will safely do a good job. Do put blue painter's tape where the hole will be drilled to help protect the wood from damage. DON'T use the cheap tapered hand reamers, including the one from Irwin -- they do not make good, concentric holes in wood. I've tried -- and failed miserably. The cobalt Unibit is not necessary. The standard (less expensive) tool steel works well, just not as long as the cobalt. For $10 more, the cobalt seems to be the better deal if it is used often. This is a must have tool in a guitar workshop.

### ⭐⭐⭐⭐⭐ Nice, clean, perfect holes
*by A***D on September 14, 2012*

I needed to make larger holes in steel sheet metal. Traditional drill bits bind up in the hole when you get close to fully drilling through the hole. Adjustable circle hole cutters and expanding bits can be dangerous if used free hand, and sometimes even used in the drill press. All of these types can twist your wrist badly if you are using them free hand. I decided to try this step bit and see how they worked. It was fantastic! I drilled a large enough pilot hole with a twist bit, and then started feeding the step bit in the hole. It cut smoothly and did not bind up at all. The hole it made was perfectly round and no burs left on the front side. It did leave burs on the backside of the metal, but I simply did a very light drill with this step bit on the back just enough to knock off the burs. Presto...a clean wonderful hole was drilled quickly. I am now a true believer in step bits. This bit also kept its edge very well. I highly recommend this product.

## Frequently Bought Together

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*Product available on Desertcart Bolivia*
*Store origin: BO*
*Last updated: 2026-02-17*