# TLS not working with some bits
**URL:** https://forum.sienci.com/t/tls-not-working-with-some-bits/27084
**Category:** 🛠️ Assembly
**Created:** [September 10, 2026, 7:17pm UTC](https://forum.sienci.com/t/tls-not-working-with-some-bits/27084 "2026-09-10T19:17:21Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@GreenMachine](https://forum.sienci.com/u/GreenMachine)
#### Post date: [September 10, 2026, 7:17pm UTC](https://forum.sienci.com/t/tls-not-working-with-some-bits/27084/1 "2026-09-10T19:17:21Z")
I’m currently setting up a 4x4 Altmill with ATC, the TLS seems to work with some bits but not others. All bits are carbide, length below spindle is between 2 and 2.5 inches. The TLS will set offset on some bits, but on others it will just push the TLS sensor down until it falls off. Occasionally, some bits that successfully get an offset will not when I repeat the process and I will get an Alarm 4.
The bits that do not work on the TLS, can successfully work with the XYZ Autoprobe however.
Any ideas?
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### Author:  [@Chucky\_ott](https://forum.sienci.com/u/Chucky_ott)
#### Post date: [September 10, 2026, 10:09pm UTC](https://forum.sienci.com/t/tls-not-working-with-some-bits/27084/2 "2026-09-10T22:09:32Z")
@GreenMachine Any coating on the bit that would prevent conductivity?
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### Author:  [@GreenMachine](https://forum.sienci.com/u/GreenMachine)
#### Post date: [September 10, 2026, 11:21pm UTC](https://forum.sienci.com/t/tls-not-working-with-some-bits/27084/3 "2026-09-10T23:21:47Z")
The most problematic one has TiAlN coating, but it works on the Autoprobe, just not the TLS.
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### Author:  [@Altmillal1114](https://forum.sienci.com/u/Altmillal1114)
#### Post date: [September 11, 2026, 10:22am UTC](https://forum.sienci.com/t/tls-not-working-with-some-bits/27084/4 "2026-09-11T10:22:54Z")
its a spring issue. You can reach out to support to send them new one or just get one from amazon [uxcell 10Pcs Compression Spring,304 Stainless Steel 12mmOD,0.6mmWD,10mmFL | Mechanical Spring,for Shop Home Repair Project,Silver Tone: Amazon.com: Industrial & Scientific](https://www.amazon.com/dp/B0FHKN412K?ref=ppx_yo2ov_dt_b_fed_asin_title&th=1)