Please log in here to access all benefits, including promotional discounts and faster checkouts.

Carmex Single Threading Insert holder - For Carbide External/Internal Threading Inserts - SR0021H21
| Insert Size | 21 |
| Shank Diameter | 20 |
| Shank Material | Steel |
| Reach | 40 |
| Overall Length | 94 |
| Minimum Bore Diameter | 21 |
Learn more about Klarna
The Carmex Single Threading Insert Holder SR0021H21 is a precision tool holder designed to accept carbide external and internal threading inserts for CNC milling. Part of the Mill-Thread family, it enables reliable, repeatable thread milling on modern CNC machines without the need for traditional taps or dies.
It’s built for shops and professionals—engineers, machinists, and operators—who need fast, consistent threading performance. With this holder, you can leverage indexable carbide inserts to boost cutting speeds, improve productivity, and reduce overall tooling costs on threaded jobs.
- Internal coolant bore: Delivers coolant directly to the cutting edge, helping reduce insert wear, improve chip evacuation, and produce cleaner thread finishes.
- Engineered for Mill-Thread carbide inserts: Supports high-speed threading with multi-tooth carbide inserts, delivering faster cycle times and reliable seating for consistent threads.
- Cost-effective tooling option: Lower tooling costs compared with taps and dies, while maintaining threading quality and repeatable results across multiple jobs.
When you pair the Carmex SR0021H21 with compatible threading inserts, you gain a versatile, low-downtime solution that streamlines your threading workflows. The internal coolant bore helps maintain stable cutting conditions, while the holder’s robust build and Mill-Thread compatibility deliver dependable performance across a range of materials. This means fewer tool changes, more productive cycles, and consistent thread quality that you can trust on every job.
| Insert Size | 21 |
| Shank Diameter | 20 |
| Shank Material | Steel |
| Reach | 40 |
| Overall Length | 94 |
| Minimum Bore Diameter | 21 |
| Flutes | 1 |
| Neck Diameter | 16.5 |
| Insert Screw | S21 |
| Torx Key | K21 |
| Extension | N/A |
What time are Protool open?
We are open Monday to Friday between 8:30am and 5pm.
Do you offer Free Next Day delivery?
Yes! We offer Free Next Day delivery via Royal Mail Tracked 24 on all orders over £50 ex VAT*. We also offer Free DPD Local Next Day delivery on all orders over £100 ex VAT*.
We also offer the following:
- Royal Mail Tracked 24 — £5.90 (FREE on orders over £50 ex VAT*). Order before 4:30pm for next day delivery. No signature required.
- DPD Local Next Day — £8.00 (FREE on orders over £100 ex VAT*). Standard next day delivery to UK mainland addresses.
- Royal Mail Special Delivery — £12.50. Guaranteed delivery before 1pm the next working day.
- DPD Saturday Delivery — £25.00. Must be ordered on Friday before 4pm. Pre-12pm delivery.
For delivery to Scottish Highlands & Islands, Northern Ireland, Republic of Ireland, or overseas locations, additional charges apply. Please see our delivery page for full details, or call us on 01732 887 334.
*T's & C's and exclusions apply. Please see our delivery page for more information on all our services.
Full Range: Carmex Single Threading Insert holders - For Carbide External/Internal Threading Inserts
View full collection →You are viewing SR0021H21. Click any other SKU to view its full details.
| Product SKU | Insert Size | Shank Diameter | Reach | Overall Length | Minimum Bore Diameter | Neck Diameter | Price | Stock | Order |
|---|---|---|---|---|---|---|---|---|---|
| SR0009H12 | 12 | 20 | 14 | 85 | 9.5 | 7.5 | £91.20 | 5 days | |
| SR0010H12 | 12 | 20 | 16 | 85 | 9.9 | 7.6 | £100.72 | 5 days | |
| SR0012F14 | 14 | 20 | 20 | 75 | 12 | 8.9 | £79.68 | 5 days | |
| SR0014H14 | 14 | 20 | 25 | 85 | 14.5 | 11.2 | £87.62 | 5 days | |
| SR0017H14 | 14 | 20 | 30 | 85 | 17 | 13.4 | £98.02 | 5 days | |
| SR0018H21 | 21 | 20 | 30 | 85 | 18 | 14.4 | £121.04 | 5 days | |
| SR0021H21 Viewing | 21 | 20 | 40 | 94 | 21 | 16.5 | £127.84 | In Stock | |
| SR0029J30 | 30 | 25 | 50 | 110 | 29 | 22.4 | £156.08 | 5 days | |
| SR0048M40 | 40 | 40 | 78 | 153 | 48 | 35 | £212.46 | 5 days |
No products match your filters.


