Guide · Clamps, T-track and inserts
M6 vs 1/4-20 (and M8) spoilboard threads: which hardware fits
M6 and 1/4-20 bolts are not interchangeable. How to match clamps and bolts to your spoilboard, table or track, with the threads makers state.
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Picks that fit
- Genmitsu Upgrade CNC Router Vise Clamp, low-profile aluminum toe clamp (101‑63‑VC), 2 or 4 piecesCheck price on Amazon
- Genmitsu Mini Vise Clamps for CNC routers (101‑63‑MVC), 2 or 4 piecesCheck price on Amazon
- POWERTEC 1/4‑20 T-track bolts, 3‑1/2 in long, 20 pack (QTB1006)Check price on Amazon
Short answer
Find the thread your table, track or inserts already use, then buy clamps and bolts in that thread. M6 (metric, 6 mm, 1.0 mm pitch) and 1/4-20 (inch, 1/4 inch, 20 threads per inch) are close in size but not interchangeable: a bolt of one will not properly engage a hole of the other. M8 is a third common size with its own hardware.
Picks that fitAll picks and how to choose
Three threads you will see
- M6 x 1.0: a 6 mm metric bolt with 1.0 mm between threads.
- 1/4-20: a 1/4 inch (6.35 mm) inch bolt with 20 threads per inch, a pitch of about 1.27 mm.
- M8 x 1.25: an 8 mm metric bolt, larger than both.
M6 and 1/4-20 differ in diameter and pitch by small amounts. That is exactly why they get mixed up: a wrong bolt may start and then bind, or spin loose. Never force a bolt that does not thread in by hand.
Examples from makers
What the makers state for their own systems:
- Carbide 3D Essential Clamps come with 4 M6 x 20 and 4 M6 x 30 socket head screws.[1] Carbide 3D says that M6 hardware is for its Hybrid Table and Teez-Nutz, and that the clamps can be used with 1/4 inch hardware on your own T-track or threaded inserts.[1] The clamp accepts either bolt; the bolt still has to match the hole.
- Crush-It clamps are not intended for the Shapeoko 3, which has no Hybrid Table, but Carbide 3D says they can be used on a fixture plate with M6 holes.[2]
- Crush-It Nutz 'n Bolts contains M6 x 1.0 bolts, six each in 16, 20, 25, 30, 35 and 40 mm lengths, and 12 Teez Nutz, for Carbide 3D machines with a Hybrid Table.[3]
- Genmitsu's low-profile toe clamp (101-63-VC) uses M6 screws and nuts and measures 106 x 22 x 15 mm.[4] Genmitsu lists it for T-track tables, hybrid tables, and MDF or aluminum spoilboards with M6 holes, on its 4030 and larger machines.[4]
- Onefinity's QCW uses a 1/4-20 track, and Onefinity said in an official October 2021 forum post that a standard 1/4-20 bolt head fits.[5]
| System | Thread | Source |
|---|---|---|
| Carbide 3D Hybrid Table, Teez-Nutz | M6 x 1.0 | Carbide 3D |
| Carbide 3D threaded inserts | M6 x 1 or 1/4-20 | Carbide 3D |
| Genmitsu toe clamp (4030 and larger) | M6 | Genmitsu |
| Onefinity QCW track | 1/4-20 | Onefinity forum, 2021 |
| E-Z LOK wood inserts | 1/4-20, M6, 5/16-18, M8 | E-Z LOK |
Picks that fit2 products
For M6 spoilboards, M6 hybrid tables or T-track that takes M6 hardware: choose the 101-63-VC toe clamp or the smaller 101-63-MVC mini vise clamp, in the 2- or 4-piece pack.
More on choosing
Both use M6 hardware per Genmitsu; not for 1/4-20 holes.
Smaller M6 clamp for small machines
Genmitsu Mini Vise Clamps for CNC routers (101‑63‑MVC), 2 or 4 pieces
Picks that fit1 product
For 1/4-20 T-track: choose QTB1006, 1/4-20 T-bolts 3-1/2 in long in a 20-pack. POWERTEC says they fit Universal T-track or larger, not 1/4 in or Mini T-track.
More on choosing
If buying on Amazon, check that Ships from / Sold by is Amazon.com or POWERTEC.
1/4-20 T-bolts for universal track
POWERTEC 1/4‑20 T-track bolts, 3‑1/2 in long, 20 pack (QTB1006)
Inserts: same thread, different drill
If you are adding threads to an MDF spoilboard, the insert sets the thread. Inserts come in M6 and 1/4-20: Carbide 3D sells both, 13 mm long with a 6 mm hex drive and a recommended 9 mm pilot hole.[6] E-Z LOK also lists M8 x 1.25 wood inserts, with a 33/64 inch drill for E-Z Knife, 7/16 inch for E-Z Hex and 15/32 inch for the 370-M8-BR Finsert.[7]
The drill depends on the insert, not just the thread. For M6 x 1.0, E-Z LOK lists 25/64 inch for E-Z Knife, 23/64 inch for E-Z Hex and 21/64 inch for the 270-M6-BR Finsert.[7] More in threaded inserts for a CNC spoilboard.
Picks that fit2 products
Pick the thread your clamps use. M6: choose E-Z LOK 900610-13 (M6-1.0 x 13 mm flanged, 50 pack). 1/4-20: choose the EZ-901420-10 kit (10 flanged 1/4-20 inserts with drill and drive tool).
More on choosing
Both are E-Z Hex inserts E-Z LOK lists for soft woods such as MDF.
M6 inserts for an MDF spoilboard
E-Z LOK E-Z Hex threaded insert for soft wood, flanged, M6‑1.0 x 13 mm (900610‑13), 50 pack
1/4-20 insert kit for soft wood
E-Z LOK E-Z Hex 1/4‑20 x 10 mm flanged insert installation kit for soft wood (EZ‑901420‑10)
Before you buy
- Check the machine or table maker's documentation for the thread.
- Try a known bolt by hand in one hole. If it binds after a turn or two, stop: it is probably the other thread.
- Buy every clamp bolt, T-bolt and insert in that one thread, and keep the spares together.
Next
Questions
Is my spoilboard M6 or 1/4-20?
Check the machine or table maker's documentation, or the hardware that came with it. Carbide 3D's Hybrid Table hardware is M6, and Onefinity said in 2021 that its QCW uses a 1/4-20 track.[3][5]
Can I mix M6 and 1/4-20 clamps?
Only if each clamp gets bolts in the thread of the hole or track it goes into. A clamp body may accept either bolt (Carbide 3D says its Essential Clamps can be used with 1/4 inch hardware on your own track or inserts), but an M6 bolt and a 1/4-20 bolt are not interchangeable.[1]
What thread does a Onefinity QCW use?
Onefinity stated in an official October 2021 forum post that the QCW uses a 1/4-20 track and that a standard 1/4-20 bolt head fits.[5]
Do M6 and 1/4-20 inserts need the same drill?
Not always. E-Z LOK lists drills per part number, and the same internal thread can need different drills in different insert families. Use the insert maker's chart.[7]