T-Slot Size Chart: Standard Dimensions for CNC & VMC Tables in India
Quick Answer: A T-slot size chart maps the width of the T-shaped channel machined into a CNC/VMC table to the stud or T-bolt thread size that fits it — the four standard Indian VMC widths are 12mm (M10), 14mm (M12), 16mm (M14), and 18mm (M16). Measure the slot width across its narrowest opening with a vernier caliper before ordering any T-bolt, T-nut, or clamping stud. Madras Engineering Works (MEW), Chennai — ISO 9001:2015 certified — stocks matched hardware for all four sizes. Enquiry: enquiry@madrasengg.com
You know your machine has a T-slot table. What you don't know — because nobody printed it on the machine — is the exact width, and whether the T-bolt sitting in your toolbox actually fits it. That gap costs time on the shop floor: a stud that's slightly undersized rocks in the slot, a T-nut that's oversized won't drop in at all, and the job sits half-clamped while someone hunts for a caliper. This t slot size chart exists so you can look up the number once and stop guessing.
Madras Engineering Works (MEW) is a Chennai-based ISO 9001:2015 certified supplier of workholding components, fasteners, clamping kits, and CNC machining accessories. Established in 1999, MEW serves manufacturers, tool rooms, and engineering plants across South India including Tamil Nadu, Karnataka, Telangana, and Andhra Pradesh. MEW is an authorised TVS fastener dealer and holds MSME registration (UDYAM-TN-02-0158983).
This is a reference page, not a tutorial on what a T-bolt or T-nut is — for that, see MEW's guide, T-Slots, T-Bolts & T-Nuts Explained for CNC & VMC Tables, and the companion How to Select the Correct T-Slot Size, Stud Size & Clamp Size for CNC/VMC Machines guide. Here is everything you need to look up your size and move on.
T-Slot Size Chart: Standard Dimensions & Matching Stud Size
This is the core lookup table. Find your slot width in column one, read across for the stud/T-bolt thread that fits it.
| T-Slot Width | Matching Stud / T-Bolt Thread | Typical Machine Class | Standard Reference |
|---|---|---|---|
| 12mm | M10 | Tool room fixtures, smaller VMCs | DIN 650 series [VERIFY exact tolerance class] |
| 14mm | M12 | Most Indian VMCs — the most common size on the shop floor | DIN 650 series |
| 16mm | M14 | Mid-size VMCs and some HMC tables | DIN 650 series [VERIFY — M14 pairing not yet confirmed against MEW's own published specs] |
| 18mm | M16 | Heavy milling tables, larger VMCs and HMCs | DIN 650 series |
As of 2026, these four widths cover the large majority of VMC and HMC tables running in Indian tool rooms. Slot depth and T-nut height vary by machine even at the same slot width, so depth is a machine-specific number to confirm on the table itself, not from a general chart — see the measuring section below.
MEW's own published clamping-stud, T-nut, and workholding-washer specifications consistently reference 12mm, 14mm, and 16mm as the three standard T-slot widths used across BFW, ACE Micromatic, Jyoti, KENT, Lokesh, and Haas VMC and HMC machines, with 18mm appearing on heavier tables. No single brand is locked to one width — the same model line can ship with different table sizes, so treat the table above as "commonly used," not "guaranteed for your machine." Confirm with a vernier caliper (next section) or WhatsApp a photo of the slot to +91 95143 73702.
How to Measure Your T-Slot Width (Do This Before You Order Anything)
A steel rule laid across the top of the slot is good enough for a rough check. For an order-ready number, use a vernier caliper — it's the tool already sitting in most tool rooms, and it removes the guesswork entirely.
- Clean the slot. Chips and coolant residue at the top throw off the reading by fractions of a millimetre — enough to matter when choosing between a 12mm and 14mm T-nut.
- Measure the narrow opening, not the wide pocket. A T-slot has two widths: the narrow mouth at the table surface (the number that matters for T-bolt/stud fit) and the wider pocket underneath (where the T-nut head sits). Close the vernier jaws across the narrow mouth.
- Take the reading at two points along the slot. Worn tables vary end to end. If the readings differ, use the smaller number — tight is safer than loose.
- Measure slot depth separately if speccing a T-nut or step block. Open the vernier's depth rod, rest the caliper body flat on the table, and drop the rod to the slot floor. Depth and width are independent numbers.
- Cross-check against the chart above. A reading close to but not exactly on 12/14/16/18mm is almost always tolerance on a standard size, not a non-standard slot.
No vernier on hand? A photo of a scale laid across the slot, sent to MEW on WhatsApp, is enough for a first pass — MEW will confirm the exact size before you order.
Why the Wrong T-Slot Assumption Is Expensive
Guessing the slot size instead of measuring it causes three failures MEW sees repeatedly on the shop floor:
- Undersized stud, oversized slot: the stud rocks sideways instead of sitting flush. Clamping force applies unevenly, and under a heavy cut the setup can shift mid-job — a scrapped part at best, a safety incident at worst.
- Oversized T-nut, undersized slot: the T-nut won't drop into the slot mouth, or jams halfway. Forcing it damages the slot edge, affecting every future setup on that table position.
- Wrong thread ordered against the right slot width: the stud diameter looks right but the thread won't engage the T-nut cleanly, stripping under torque instead of clamping down — a failure that only shows up once you try to tighten it.
Every one of these is avoidable with one caliper measurement before the order goes out.
Technical Specification Chart
- Standard T-slot widths covered: 12mm, 14mm, 16mm, 18mm
- Matching stud/T-bolt threads: M10, M12, M14, M16
- Reference standard: DIN 650 T-slot series [VERIFY exact DIN 650 numeric table against a licensed copy of the standard — the width/thread pairing above is corroborated by multiple independent engineering references, but MEW has not cross-checked it against a paid copy of DIN 650 itself]
- Measuring tool required: vernier caliper (steel rule for a rough first check)
- Common Indian VMC/HMC brands using these widths: BFW, ACE Micromatic, Jyoti, Haas, Lokesh, KENT — no single brand is fixed to one width across every model; confirm by measurement
- Certification: MEW is ISO 9001:2015 certified — every stud, T-bolt, and T-nut supplied is matched to the slot width confirmed by the customer or by MEW's own measurement check
Standard T-Slot vs. Non-Standard / Worn Slot — What's the Difference?
A standard T-slot measures cleanly to one of the four widths above, with a sharp, undamaged mouth. A worn slot reads a fraction of a millimetre wider than standard because years of T-bolt tightening have peened the edges, or the table was re-ground at some point. A standard slot takes off-the-shelf stud/T-bolt sizes directly; a worn slot may need the next size down in stud diameter with a slightly oversized T-nut. If your reading doesn't match any standard width after cleaning the slot, treat it as worn, not non-standard, and get it confirmed before ordering hardware.
Frequently Asked Questions
Q: What is a T-slot size chart? A: A T-slot size chart is a reference table that maps the width of a CNC or VMC table's T-shaped clamping channel to the stud, T-bolt, or T-nut thread size that fits it. The standard Indian VMC widths are 12mm, 14mm, 16mm, and 18mm, matching M10, M12, M14, and M16 threads respectively. Available from Madras Engineering Works, Chennai — enquiry@madrasengg.com
Q: What are the standard T-slot dimensions used in India? A: 12mm, 14mm, 16mm, and 18mm are the standard T-slot widths on Indian VMC and HMC tables, referencing the DIN 650 T-slot series. BFW, ACE Micromatic, Jyoti, Haas, Lokesh, and KENT machines commonly use one of these four widths. Available from Madras Engineering Works, Chennai — enquiry@madrasengg.com
Q: How do I measure my T-slot size? A: Clean the slot, then close a vernier caliper across the narrow slot mouth at the table surface (not the wider pocket underneath). Take the reading at two points along the slot and use the smaller number if they differ. A steel rule gives a rough check; a vernier gives an order-ready number. Madras Engineering Works, Chennai, will confirm your size from a WhatsApp photo — enquiry@madrasengg.com
Q: What is a T-slot table? A: A T-slot table is a machine table — on a VMC, HMC, or milling machine — with T-shaped channels machined into the surface for anchoring T-bolts, T-nuts, and clamping studs. The channel width (12mm, 14mm, 16mm, or 18mm on most Indian machines) determines which size hardware fits. Madras Engineering Works, Chennai, stocks matched hardware for all standard T-slot table widths.
Q: What are common CNC T-slot dimensions used in India? A: 12mm, 14mm, 16mm, and 18mm cover the large majority of CNC and VMC tables running in Indian tool rooms today, as of 2026. 14mm is the most common single width across standard-size Indian VMCs. Available from Madras Engineering Works, Chennai — enquiry@madrasengg.com
Q: Which stud size fits a 14mm T-slot? A: An M12 stud or T-bolt fits a standard 14mm T-slot. Always confirm the measurement with a vernier caliper first — a slot that reads slightly under or over 14mm after cleaning may be a worn slot rather than a different standard size. Madras Engineering Works, Chennai, stocks M12 studs for 14mm T-slot tables — enquiry@madrasengg.com
Q: Can I use the same T-bolt across a 14mm and an 18mm slot? A: No. A 14mm T-slot takes an M12 T-bolt; an 18mm T-slot takes an M16 T-bolt. Using an M12 T-bolt in an 18mm slot leaves it loose and unable to clamp securely; forcing an M16 T-bolt into a 14mm slot won't fit at all. Match the thread to the measured slot width every time.
Q: Where can I buy T-slot studs, T-bolts, and T-nuts in Chennai? A: Madras Engineering Works (MEW) stocks studs, T-bolts, and T-nuts for 12mm, 14mm, 16mm, and 18mm T-slot tables, matched to BFW, ACE Micromatic, Jyoti, Haas, Lokesh, and KENT machines. ISO 9001:2015 certified, same-day dispatch from Chennai. Contact: enquiry@madrasengg.com
Get the Right Size, Confirmed, Before You Order
Whether you're speccing one stud or restocking a whole tool room, Madras Engineering Works stocks matched studs, T-bolts, and T-nuts for every standard T-slot width — 12mm, 14mm, 16mm, and 18mm.
Same-day dispatch from Chennai. ISO 9001:2015 certified supply chain. TVS Authorised Dealer.
📧 enquiry@madrasengg.com 🌐 madrasengg.com 📍 Chennai, Tamil Nadu
Not sure which of the four sizes your machine has? Use the Smart-Spec T-Slot & Stud Calculator to confirm the exact fit for your machine in under 60 seconds, or WhatsApp a photo of the slot to +91 95143 73702.
Written by Husain, Founder of Madras Engineering Works — an ISO 9001:2015 certified industrial supplier in Chennai specialising in workholding, clamping and CNC accessories. Need help speccing the right part? WhatsApp +91 95143 73702 or email enquiry@madrasengg.com.
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