5402-5: Description: Heli-Coil Professional Thread Repair Kit .
Designed using state-of-the-art technology and with customers in mind. Insert Size: Drill Size: Wire Thread Insert Length: 1D: 1.5D: 2D: 2.5D: 3D: 1/8-40 : 3.3 mm : 0.125 : 0.188 : 0.250 : 0.313 : 0.375 : 3/16-24 : 5.0 mm : 0.188 : 0.281 : 0.375 : 0.469 : 0.563 : 1/4-20 : 6.7 mm : 0.250 : 0.375 : 0.500 : 0.625 : 0.750 : 5/16-18 : 21/64 : 0.313 : 0.469 : 0.625 : 0.781 : 0.938 : 3/8-16 : 25/64 : 0.375 : 0.563 : 0.750 : 0.938 : 1.125 : 7/16-14 : 29/64 : 0.438 : 0.656 : 0.875 :
In the part file, show the holes drilled and tapped for the heli-coil insert, Using a custom hole file is the best way to handle that information.

source.

Drill Size: 21/64".
Pro Tip - The proper installation depth of a HeliCoil insert is -1/2 turn below the top of the original hole.
Available in 303 and 316 stainless steel; Drill, tap and thread in like ordinary fasteners; Standard O.D.
Thread Tap; Type Heli-Coil; Tap Size 3/8 Inch; TPI 16 TPI; Thread Length 0.562 Inch; Used on 5521-6 Thread Repairs Kit; Part Number: 819-6.
The chart legend says that "F" falls between 1/4" and 17/64" bit size. YEa heli-coils have their own taps that aren't to metric or SAE spec it's it's own thing.
5/16-24 : 8.2 mm : 0.312 : 0.469 : 0.625 : 0.781 : 0.938 : 3/8-24 : 9.8 mm : 0.375 : 0.562 : 0.750 : 0.938 : 1.125 : 7/16-20 : 29/64 : 0.438 : 0.656 : 0.875 : 1.094 : 1.313 : 1/2-20 : 33/64 : 0.500 : 0.750 : 1.000 : 1.250 : 1.500 : 9/16-18 : 37/64 : 0.562 : 0.844 : 1.125 : 1.406 : 1.688 : 5/8-18 : 41/64 : 0.625 : 0.938 : 1.250 : 1.563 : 1.875 : 3/4-16 : 49/64 : 0.750 : 1.125 : 1.500 : 1.875 : 2.250 : 7/8-14 A tap and die set is a useful all-in-one set of hand tools for creating threads in metalworking.
I looked at a tap chart and it says for 5/16-18 tap to use "F" for drill bit size.
Inch SetsSame Tap Size (Taper, Plug, and Bottoming Chamfer) Drill Bit . When we talk about the 5/16 tap, keep in mind that there are two measurement variations; an 18 tap and a 24 tap.
Quick & Hassle Free.
printable chart downloads at the bottom of the page.
With Heli-Coil threads, tapped holes are strengthened and thread life is dramatically increased. Contact us for more information.
53 2-56 .0700 No.
BSW, BSP, BSF, BA, NPT and ISO metric thread sizes.
Tap Chart - UNC/UNF Threads Tap size NF/NC UNF/UNC Threads per inch Basic major dia (inches) Basic effective dia (inches) Basic minor dia of ext.
25 12 Tap and install, as well as Tang Removal. 5402-5: Description: Heli-Coil Professional Thread Repair Kit .
tap drill diameters for thread cutting nominal size d1 unc unf unef unjc unjf m mf mj npsm npsc npsf rp_ 0.2756 7.000 5/16 -24 unjf m8x1 lk-m8 rd 9x 1/10 0.2795 7.100 mj8x1 0.2813 9/32 k 7.145 nominal size d1 unc unf unef unjc unjf m mf mj npsm npsc npsf rp_
29 10-24 .1495 No.
Order Heli-Coil Straight Flute Hand Tap , 5/16"-24 , Plug , Uncoated , 4 Flutes, 5FPB at Zoro.com.
STI 5/16"-24 Thread Direction.
Tap the hole using the Heli-Coil tap supplied in the kit. Top Rated Seller Top Rated Seller. The inserts come with a Tap and Helicoil installation on how to drill.
Buy American for a Better America! Download 1 MB #18. Tap size Drilling chart provides a list of standard size taps, specifying the diameter and thread spacing, for fractional, metric, and screw sizes.
Find your HELI-COIL MASTER THREAD REPAIR KIT, WITH 12 INSERTS/TOOL/TAP, THREAD 5/16-24, 0.469 IN L at Grainger Canada, formerly Acklands-Grainger.
1.ill to allow full tap depth shown Dr in chart.
c/sink dia.
Model # DWADT1224.


Please allow up to 24 hours for a response to a special tool request. AU $149.00.
Heil-Coil Tap; Heli-Coil has the most effective and universally accepted method of thread repair; Thread - Size and Length: 3/8"-16 x .562; Required Drill Size: 25/64" U.S.S. Make sure this fits by entering your model number. Just a general piece of FYI, most metric threads (standard too but using as example) the hole is drilled about 1mm smaller than the thread spec size..for example, M6 x 1.0 is drilled 5.2mm, M8 x 1.25 is drilled about 7mm etc..etc.. this is for room to cut threads for the overall
36 8-32 .1360 No. Tap the hole with the special size tap supplied in the kit.
Heli-Coil Tap For 5/16-18 Insert Discontinued : Package Price Heil-Coil Tap; Heli-Coil has the most effective and universally accepted method of thread repair; Thread - Size and Length: 5/16"-18 x .469" Required Drill Size: 21/64" U.S.S.
screw thread gauge | metric and sae | recommends drill bit & tap size (bcp675) 5/16 - 24 unf - 2bsti go p.d. Includes 12 inserts, complete instructions, Heli-Coil tap and installation tool Used for repairing tapped holes Made from high quality material Comes in carded packing Easy to use
steel, plastic.
PRACTICAL FORMULA - INCH SIZES TO ESTABLISH TAP DRILL SIZES FOR INCH SIZE ROLL FORMING TAPS TAP DRIIL SIZE = Basic Tap 0.0. (.0068 x % of Thread Desired) Threads Per Inch 068 x 250 = .228 Dia.
Paradur 5/16-24 UNF-3B wire insert tap HSS-E Spiral flute helicoil tap unused. 47 4-40 .0890 No. With over 1.6M products and 24/7 customer service we have supplies and solutions for every industry. 18-8 stainless 3/8-24 UNF screws in undiluted muriatic acid (pool acid).
Heli-Coil Inserts are The Original. Overall Lg. F. 17/64. 5/16 (0.3125)-24.
25 12
Figuring out what size drill bit you need for a 5/16 tap starts with understanding a bit about sizing differences.
of Flutes: Pitch Dia.
Helicoil Drilling Data - Metric.
I know 6mm uses 7x1.00.
5/16 UNF Helicoil Thread Repair Kit Rally Race Road Free P&P Free P&P Free P&P. Click to enlarge. Internal Thread Size 5/16-24; Thread Type UNF; Thread Direction Right Hand; Length 0.625 in; Free Coil Dia. Blind holes should be at least half a diameter deeper than the length of engagement. Will gas prices stop you from off-roading?
BIG-SERT is a heavy wall solid bushing, easy to install with positive placement. This product is made of high-quality materials to serve you for years to come.
This wire is then wound into a spiral coil which, when installed into Heli-Coil tapped holes, provides permanent conventional 60 Internal Screw threads.
Sponsored. 43 5-40 .1015 No.
For production runs, prototype work, salvage and repair, Heli-Coil offers a range
4.
0.360.
$39.59. TAP DRILL SIZES FOR FORMING TAPS INCH Tap Size Drill Size Decimal Equivalent Percentage of Thread 0-80 1.35 mm 0.0531 75 1-64 1.65 mm 0.0650 75 5/16-24 7.40 mm 0.2913 75 5/16-24 7.50 mm 0.2953 60 3/8-16 8.75 mm 0.3445 70 3/8-16 8.80 mm 0.3465 65 3/8-24 9.00 mm 0.3443 70 3/8-24 T 0.3580 60
Reply #5 on: October 19, 2011, 01:39:28 pm .
5/16 (.3125)-24 8191-5CN 3891-5CN .469 .625 56193-5-2 .0050 3/8 (.3750)-24 8191-6CN 3891-6CN .562 .750 56193-6-2 .0050 standard Heli-Coil Inserts. The correct size drill bit for 10-24 tap is a #25 drill bit, the measurement being 5/32. A 10-24 cap comes in two different thread counts. Thus the size of the drill bit for each one is entirely different.
Time-Sert - helicoil alternative. We have been Canada's premiere industrial supplier for over 125 years with superior service and quality.
$59.29.
Product Overview.
0.090. Steel,Magnesium,Plastic.
Return this item for free.
Note that the M6 is a 1.0 mm pitch so even if the helicoil tap was the same diameter the pitch wouldn't work.
We are Proudly American Made for 119+ years. Is it better to drill a smaller (1/4") or a bigger (17/64") hole?
0.831.
24 x 3 21 22 x 1 21 tap size drill size tap size drill size 27 x 3 24 22 x 1.5 20.5 1/8 x 27 S (Letter) 8.8 1/8 x 27 R (Letter) 8.6 30 x 3.5 26.5 22 x 2 20 1/4 x 18 29/64 11.5 1/4 x 18 7/16 11.1
Buying American made products benefits us all and makes the USA a stronger country. Check with the manufacturer of any hardware to check all and all information.
Make up a guide as others have suggested, drill it for the helicoil. Aluminum.
You can get away with a 1/8 inch drill for a 1/4-20 tap in a pinch. Similarly, what size drill bit do I use for a 5/16 tap? OBW0549. Looking at the "Tap Drill Chart" section at the bottom, they recommend an "F" drill for a 5/16"-18 fastener. Next up from that is 5/16-18 (F tap drill = 6.5278mm) or -24 (I tap drill = 6.9088mm) UNC = Unified National Coarse; UNF = Unified National Fine; UNEF = Unified National Extra-Fine
Download 280 KB #17. These taps have a bright finish that provides a smooth, polished surface.
Includes 12 inserts, complete instructions, Heli-Coil tap and installation tool Used for repairing tapped holes Made from high quality material Comes in carded packing Easy to use That does not hold true for STI threads.
Tap size: NF/NC UNF/UNC: Threads per inch: Basic major dia (inches) Basic effective dia (inches) Basic minor dia of ext.
sti helicoil drill size chart nominal.
Looking for Helical Insert, SS, 5/16-24, PK500?
U.N.C 7/16 14 Taper Tap $ 24.00 Add to cart View Product; U.N.C 3/8 16 Bottoming Tap $ 18.00 Add to cart View Product; U.N.C 1/2 13 Bottoming Tap $ 30.00 Add to cart View Product; U.N.C 5/16 18 Intermediate Tap $ 15.00 Add to cart View Product
This should help whenever you run into a situation you need to drill a pilot hole and are not sure the size bit. The regular sized normal tap used to chase out/clean up the threads will say 5/8-11 and so will the heli-coil tap, with the exception of those 3 letters STI.
HeliCoil Thread Repair Kit#5521-1 Size 12-24 Drill Size 15/64 This HeliCoil Thread Repair Kit comes with a package of 12 Inserts size 12-24 x.324 Part No.
There is nothing more aggravating when you just don't know what size drill bit to use for a pilot. DEWALT.
To screw in the thread insert, all you need is the Smart installation mandrel of similar size as a tap.
Manufacturer Part No.
STI stands for "Screw Thread Insert" and those 3 letters makes all the difference .
This product is made of high-quality materials to serve you for years to come.
If there is at least 6 good threads, go with the original bolt and loctite threadlocker.
Inch Thread Size. Thread Size Type.
29 10-24 .1495 No. Buy It Now
Max.
2-in-11-1/2 Npt 7-Flute Carbon Steel Tap.
The tap size chart provides a list of standard size taps, specifying the diameter and thread spacing, for fractional, metric, and screw sizes.
UNIFIED.
Drill bit size for 5/16-18 tap. Item Weight.
Manual Tools Heli-Coil offers a complete line of tooling together with a full array of STI taps, gages and tang break-off tools.
4-40 to 3/4"-10 Helicoil Thread Insert Repair HSS Tap - Select Size . Drill it the appropriate size for an M6 insert. Fractional sizes are listed in inches, while metric sizes are listed in millimeters following the letter "M".
telephone orders. Drill America.
Brand: Helicoil.
Max. 3.
This tap and clearance drill chart shows tap and clearance drill sizes for standard threads.
Visit the Drill America Store.
Helicoil Insert, Superalloy (Inconel, Hastelloy, Alloy 20) Helical Screw Thread Inserts, commonly called by their trade-name Heli-Coil, are inserts made from diamond shaped coiled wire. JB Tool Sales 304 Stainless Steel, Internal Thread Size M16x2, Thread Type MC, Thread Direction Right Hand, Length 24mm, Free Coil Dia. I had a requirement to hold down parts by 5/16-24 STI (Helicoil thread) The standard 3/8-24 UNF SHCS is .014 to big to fit into these holes. WE GLADLY COMBINE SHIP. - 120 deg.
Pro Tip - The proper installation depth of a HeliCoil insert is -1/2 turn below the top of the original hole.
.
36.
0100/16.02: 2969 kB /
For M 12 to M 16 thread inserts.
& FREE Returns. maximun.
Brand New. threads (inches) Basic minor dia of int.
5/16-24: CTF-5SRP-H2: CTF-5SRP-H3: CTF-5SRB-H2: CTF-5SRB-H3: CTF-5SPP-H2: CTF-5SPP-H3: CTF-5SFB-H2: CTF-5SFB-H3: 3/8-24: Thread Size Tap Dimensions Number of Flutes; Length Overall A Length of Thread B Length of Square C
The resultant surface finish is a mirror-like 8-16 micro inches. THREAD TAP DRILL SIZE CLASS 2B MIN.
2 (0.086)-56.
When I do Helicoil repairs, I go with the recommended drill size for steel/iron parts, and use some kind of oil for the tap, preferably cutting oil, but motor oil will work.
View All.
The insert is screwed into an internally threaded hole, and the internal surface of the insert provides a threaded surface that is stronger that the parent material. HELICOIL/STANLEY: Thread Size: 5/16-24: Thread Type: Unified Fine Thread (UNF) Type: Oversize Bottoming Tap: Units: Inch: 4-40 OVSZ HELI-COIL BOTTOMING TAP: View Details: 3891-4CN375: 1/4-28 LKG OVSZ HELI-COIL INS: View Details: 56193-8-2: 1/2-20 OVSZ HELI-COIL BOTTOMING: View Details: Manufacturers. .3395 heli-coil i usually ship (95%) of my listings same day if paid for by 3:00 p.m. est.all items can be returned for a full refund within 30 days upon receiving the item. The insert is screwed into an internally threaded hole, and the internal surface of the insert provides a threaded surface that is stronger that the parent material. 9.85 + 4.52 P&P + 4.52 P&P + 4.52 P&P.
1977 CB550F.
Internal Thread Size: 5/16-24 UNF; Length: 0.312" (1xD), 0.469" (1.5xD), 0.625" (2xD) Material: 18-8 (304) Stainless Steel; Type: Free Running; Tap Size: 5/16-24 STI; Drill Size: 21/64" Quickly and easily repair stripped or damaged threads, or create stronger original threads in die castings or plastics with our Helical Screw Thread Inserts.
For plug Taps 5/16" or M8 and smaller.
131PCS Helicoil Type Thread Repair Kit rethread Stripped Metric M5 M6 M8 M10 M12.
Letter drill bit sizes: the sizes are indicated in letters, from size A (the smallest) to size Z (the largest).
C $19.14.
C $12.94 to C $46.24.
In House Design Engineer Build/Tech Thread
Copyrights All Rights Reserved Thor International Pte Ltd, 2019
One way I could reverse-engineer the diameter of the tap would be to measure the diameter of the helicoil insert (16.5mm) but then I'd need to know how much smaller a thread I need to tap.
Add a vehicle Standard Coarse Packaged - 5/16"-18 x .469 - Material Stainless Steel (0 reviews) | R1185-5. Universal 5/16"-18 SAE UNC Thread Repair Kit (12 Pieces) (5521-5) by HeliCoil. Manual Tools Heli-Coil offers a complete line of tooling together with a full array of STI taps, gages and tang break-off tools. (EXAMPLE 1/4-20 Tap with 65% Thread) = .
Re: Tap size for 8 x 1.25 Helicoil. But if the helicoil repair is to be done in an alum part, such as an alum intake manifold, then i use a drill that is 1/64 smaller than the recommended drill size. Thread Size: 5/16-24: Short Insert: 1191-5CN312: Medium Insert: 1191-5CN469: Long Insert: 1191-5CN625: Drill: 21/64: high speed steel Heli-Coil tap and an installation tool.
Helical Screw Thread Inserts, commonly called by their trade-name Heli-Coil, are inserts made from diamond shaped coiled wire. Recoil Taps or Helicoil Taps or STI Taps or Screw Thread Insert Tap are used with Recoil Inserts or Helicoil Inserts only.
4147-5-1 - 5/16-24 HELI-COIL TWINSERT REPAIR KIT 5/16-24 X 1.5D OUTER INS (20), 5/16-24 F/R INNER INS (20), 5/16-24 LKG INNER INS (20), 5/16-24 OUTER INS INSTALLATION TOOL (1), 5/16-24 STI TWINS BOTTOMING TAP (1), OUTER INS TANG BREAK-OFF TOOL (1) New Account .
Inserts with internal thread size of 5/16-18 or larger are furnished with four locking keys.
38 6-32 .1065 No. 0.312, 0.468, 0.624 In Inserts, 1 Each of a Drill, High Speed Steel Tap, Tang Removal Tool and Installation Tool.
Drill and tang removal tools are NOT available as replacement parts. Idle speed: 950 rpm at p = 6.3 bar (adjustable via air pressure) For the loose processing of HELICOIL Classic and HELICOIL Plus in sizes M 2.5 to M 26 x 1.5. An old rule-of-thumb is that in a threaded hole in steel, the length of engagement should be at least 1.5 times the diameter of the screw, and in cast iron or brass, 1.8 to 2 times the diameter. $43.55 | 9% OFF. Thread Size: 5/16-24: Short Insert: 1191-5CN312: Medium Insert: 1191-5CN469: Long Insert: 1191-5CN625: Drill: 21/64: high speed steel Heli-Coil tap and an installation tool.
- All sizes and information are for reference only.
helicoil insert ~ length:0.469" ~ thread:5/16-24 ~ material:corrosion resistant steel CROSS REFERENCE PART NUMBERS (PER NATIONAL STOCK 5/16-24: CTF-5SRP-H2: CTF-5SRP-H3: CTF-5SRB-H2: CTF-5SRB-H3: CTF-5SPP-H2: CTF-5SPP-H3: CTF-5SFB-H2: CTF-5SFB-H3: 3/8-24: Thread Size Tap Dimensions Number of Flutes; Length Overall A Length of Thread B Length of Square C
47 4-40 .0890 No. Size: Decimal Size Equivalent: No.
HeliCoil Thread Insert Kit 5/16"-24 x .469 - NAPA Auto Parts
System of Measurement Inch Thread Size Show 5/16"- 24 Installed Length 0.25" to 0.499" 0.5" to 0.999" For Maximum Hole Diameter 0.125" to 0.249" 0.25" to 0.499" 0.5" to 0.999" Number of Inserts Included 6 10 36 60 Drill Bit Size 13/64" 17/64" 21/64" 25/64" 29/64" 33/64" Thread Direction Material Stainless Steel For Minimum Material Thickness Major Diameter Thread Pitch UNIFIED COARSE 1 (.073)-64 .0832 .0843 .0850 .0764 .0823 .0958 .01563
29.
Tap sizes are shown as hole size threads per mm (millimeter).
Includes 12 inserts, complete instructions, Heli-Coil tap and installation tool. $80.41.
PunkinHead , Dec 3, 2021. Size 5/16"-24; Length 0.468, 0.624 in, 12 Ea. This wire is then wound into a spiral coil which, when installed into Heli-Coil tapped holes, provides permanent conventional 60 Internal Screw threads. Heli-Coil Inserts are The Original. E-Z Coil inserts, also known as wire or helical threaded inserts, quickly repair or reinforce tapped holes in soft metals.
Our M5 x 0.8 Helical Thread Inserts will quickly and easily repair stripped or damaged. 0.390. SKU: 3465.
131Pc Thread Repair Kit HSS Drill Helicoil Repair Kit SAE 1/4" 5/16" Inch W/Case.
Weight:
50 3-48 .0785 No. 8.3mm weight: 254g size: 5/16" unf thread: 24 tpi unf use on: commando, twins, singles.
The product is 5/16-18Thread RepairKit.
For production runs, prototype work, salvage and repair, Heli-Coil offers a range
Heli-Coil inserts work in any part or material aluminum, magnesium, cast iron, bronze, etc.
Remove the fastener from the hole. 1-14 4 Flute HSS GH4 STI Straight Flute Plug Tap Helicoil 8193-16. Emhart Teknologies Heli-Coil Bulletin 2003 Tel.
5/16"-24 Stainless Steel E-Z Coil Helical Threaded Inserts Internal Thread Size: 5/16"-24. 53 2-56 .0700 No. 38 6-32 .1065 No.
These kits will repair holes that were repaired by helicoil, perma-coil, uni-coil, recoil or any other simular coil style insert that has failed.
Tap Chart Helicoil Threads - provides tap sizes and drill sizes for Helicoil threads. unified coarse.
Also included in smaller size kits a tang removal tool and quantities of three lengths of inserts.
Tap Size: 5/16-24 STI.
Universal 5/16"-24 SAE UNF Thread Repair Kit (12 Pieces) (5528-5) by HeliCoil.
$40.30.
Free Running; Tap Size: M5 x Add threads to holes in preparation for installing helical inserts.
21/64 (0.3281) 21/64 (0.3281) 3/8 (0. Technical data.
Easy-to-use printable tap drill chart and drill bit sizes table available for a FREE download on our website.
The product is manufactured in China. Some of the other sizes are specials though.
Previous product.
5/16"-24.
5/16"-24 Helicoil Insert for Metal 18-8 Stainless Steel UNF.
Designed using state-of-the-art technology and with customers in mind.
Home TAPS WIRE INSERT/HELICOIL-VARIOUS.
$59.
Quick & Hassle Free. A 100% thread is 3/4 qtr, or (6/8 th ), of the full 60 triangle which is the maximum allowed height of a full thread, the "V" shape, including flats.
5/16 18. 50 3-48 .0785 No.
5/16" - 24tpi unf thread repair kit comprising of drill, tap, insert tool, tang break tool and ten stainless wire thread inserts (1.5 x diameter).
Lower cost than similar taps from competitors. Number drill bit sizes: the sizes are indicated in numbers, range from size 80 (the smallest) to size 1 (the largest).Number and letter sizes are commonly used for twist drill bits rather than
With over 1.6M products and 24/7 customer service we have supplies and solutions for every industry.
UNF BOLT 5/16" x 24 @ 1".
Length: 0.469" (1.5x diameter) Material: 18-8 (304) Stainless Steel. (203) 924-4737 Fax (800) 732-3116 Mexico Tel 52-5-326-7100 Fax 52-5-326-7141 www.emhart.com Heli-Coil screw thread inserts Heli-Coil inserts are preci-sion formed screw thread coils worked into a diamond shape. minimum.
Heli-Coil thread data - inch Pitch Diameter 3B 2B Minor Diameter Nominal Thread Size Min.
Tap Size.
first 100,000 miles.
I haven't checked but I imagine that all the helicoil taps are non-standard threads. 1.
This provides strong internal threads that are corrosion resistant and withstand temperatures to 800F. 5/16"-24 Stainless steel helical inserts are used to reinforce and repair tapped holes in soft metals.
Quickly and easily repair stripped or damaged threads, or create stronger original threads in die castings or plastics with our Helical Screw Thread Inserts.
Tap Sizes Included: Thread Type: Thread Lg. HELI-COIL. Your final file is the assembly with the heli-coils inserted.
It is made from high quality material and is extremely long lasting.
Make Clean Threads With Taps and Dies. Tap the hole to the original depth using the special bottoming tap.
Find it at Grainger.com. All taps available in larger sizes, H.S.S./GT, Spiral Point/Flute + Long Series, Also DIENUTS + L/H. Very special is the blade position control.
threads (inches)
Download 55 KB #20.
Status: Y Related Items We will follow up with you via email within 24-36 hours.
24 Feb 2019 Email List Templates Read More.
for pricing and availability.
0.110. NOTE: The tap drill size of a hole that will be cold form tapped is usually bigger than it cutting tap counterpart.
- Dior Lip Maximizer Cherry
- Large Plastic Placemats
- Red Fishnet Tights Plus Size
- Brooklyn Museum Design
- Men's Running Sleeveless Tops
- Nike Air Max '90 Essential Wolf Grey