Annex A (informative) — Collected rail sections

The requirements that make a panel fit a row are in 5.3. Everything else about a rail, an insert, and a screw is practice, collected here: the section EIS recommends for a new rail (A.0), catalog rail sections (A.1, A.2), and the screw that fits each (A.3).

The T-strut height is drawing 5280006. The inner face is the 34560-184 section with the mounting hole on the cavity center.

Constant	Value	Source
T-strut height across the panel	7.391 mm	Vector, drawing 5280006
Inner face, in from the mounting hole	5.075 mm	Schroff, 34560-184

A.0 Recommended section, strip, and screw

A new rail that stays inside these limits takes the 5.0 mm × 2.0 mm M3 strip most Eurorack cases use and a 6, 8, or 10 mm screw. They are the envelope of the two extrusions EIS measured, the Vector T-strut at the small end and the Schroff L-KD at the large, rounded; a rail built another way conforms if it meets 5.3.

Rail section	millimeters
Height, across the panel	7.0 to 10.0
Depth, front face to back face (F + D + G)	25.0 to 28.5
Lip, if present, across the panel	at most 1.5
Lip, if present, into the case	at most 3.1
Groove, across	at least 5.0
Groove, into the rail	at least 2.0

A lip is optional. Where present it covers at most 1.5 mm across the panel and extends at most 3.1 mm into the case from the mounting face, corner radius included. The groove admits a rectangular insert 5.0 mm across and 2.0 mm thick; a larger groove is fine so long as that rectangle enters and stays. The throat in front of the insert clears 3.0 mm (RAIL-009). EIS recommends that a rail maker publish the insert seat, the screw-cavity depth D, and a screw length that fits the window (RAIL-009).

Threaded strip	millimeters
Across the groove	5.0
Thickness	1.5 to 2.0
Hole pitch	5.08 (RAIL-001)
First hole, from one end	3.58
Margin past the last hole	6.08

An N HP strip is N × 5.08 + 4.58 mm long with N holes, or cut from a longer strip; the first hole and end margin are measured on the Schroff 34561-484 model. A slide nut fits inside the same 5.0 mm × 2.0 mm section; a DIN 562 M3 square nut, 5.5 mm across flats, does not, and M3 slide nuts for Eurorack rails are made to the groove.

Screw
Lengths	6, 8, or 10 mm, measured under the head; each is the pick for at least one rail in A.3
Insert tap drill	2.5 mm, the Schroff figure
Head	Pan head with an H, Z, or hexalobular recess (ISO 7045:2011, ISO 14583:2011); at most 7.0 mm across (RAIL-010)
Finish	Zinc-plated steel, black-finished steel, or A2 stainless steel
Pick	The shortest length inside the window; where a catalog rail's seat is not published, the longest that does not bottom out through a 1.6 mm panel, then confirm three threads engage (RAIL-008)

The numbers are in data/rail.json, data/insert.json, and data/screw.json, where the M2.5 and #4-40 rows are marked as subrack hardware outside EIS; tools/rail.py, tools/insert.py, tools/insert_card.py, and tools/screw.py check them and draw the cards.

A.1 Sections with a 6 mm or 8 mm screw

The sections on this sheet are Vector TS100, Gie-Tec 125010, and the Tiptop Audio Z-rail. Gie-Tec 125010 has a 3.8 mm lip and the Z-rail is shallower than 25.0 mm, so a new rail does not copy either; both remain reference sections. Each takes a mounting screw of 8 mm or shorter: 6 mm or 1/4 in on Vector and Gie-Tec, at most 8 mm or 5/16 in on the Z-rail. The table below also carries the sections in A.2.

The card is drawn by vendors/collected.py in the reference repository from the three vendor models; the letters are the datasheet figures in the table below.

A is the distance from the centerline to the upper edge, the outer face. B is the distance from the centerline to the lower edge, the inner face. Outer span is a pair of the same section with the centerlines 122.5 mm apart. It runs from one outer edge to the other, 122.5 mm + 2 × A. C is the center of the hole that fastens the rail to the enclosure. Cx is that center's distance from the front face, into the case. Cy is its distance from the centerline, positive toward the inner edge. F is the lip, from the left edge of the section to the front panel's mounting face. A rail with no lip has F = 0. D is the depth of the screw cavity, from that mounting face along the centerline to the metal that closes the cavity. G is the depth behind the cavity, from that metal to the back face. The depth of the section, from the front face to the back face, is F + D + G.

Columns marked datasheet come from the vendor drawing, printed there or measured on that sheet. Columns marked derived are calculated from them. G is the published depth from the front face to the back face, minus F, minus D.

The enclosure screw fastens the rail to the side of the case, through the hole at C. The published module screw is the panel fastener the vendor, or the case built on that rail, names. Vector names a #4-40 groove nut, NT4-7PA. Doepfer fastens to Gie-Tec 125010 with an M3×6 DIN 7985. TipTop names an M3 strip and no length. Schroff's own front-panel screw is an M2.5×12.3 collar screw, for 2.5 mm Schroff panels. HEITEC names none. The screw EIS picks for each section is in A.3.

Section	A	B	Outer span	Cx	Cy	F	G	D	Enclosure screw	Published module screw
	datasheet	datasheet	derived	datasheet	datasheet	datasheet	derived	datasheet	datasheet	datasheet
Vector TS100	3.696	3.696	129.892	12.700, 22.38	−0.67, 0	0	19.558	5.842	#10-32 UNC, HD90	#4-40 groove nut NT4-7PA
Gie-Tec 125010	4.99	5.01	132.48	14.12	0.17	3.8	22.38	4.92	M4	M3×6 DIN 7985 (Doepfer)
Tiptop Z-rail	5.00	4.99	132.50	13.93	0	2.83	13.43	7.52	M4	M3, no length
Schroff 34560 L-KD	5.03	4.97	132.56	15.75	0.17	3.00	16.50	9.00	M4×14 Torx 20	M2.5×12.3 collar screw
Schroff 34560 L-OD	5.02	4.98	132.54	12.97	0	0	16.78	9.15	M4×14 Torx 20	M2.5×12.3 collar screw
Schroff 34560 H-KD	5.00	4.98	132.50	15.75	0	3.00	21.55	9.00	M4×14 Torx 20	M2.5×12.3 collar screw
HEITEC 9908.721	4.75	5.25	132.00	15.25, 35.25	−0.75	3.00	26.60	8.85	M4×12	not published
Minimum	3.696	3.696	129.892	12.700	−0.75	0	13.43	4.92	—	—
Maximum	5.03	5.25	132.56	35.25	0.17	3.8	26.60	9.15	—	—

Minimum and Maximum are the extremes of the dimension columns. Where a section has two holes, both are counted. Those columns are millimeters. The screw columns are the published fastener, and they have no minimum or maximum.

A.2 Sections with a 10 mm screw

These four sections have screw cavities 8.85 mm to 9.15 mm deep. On L-KD, the one whose seat is measured, a 6 mm screw does not reach the strip. The 10 mm mounting screw fastens them. Schroff L-KD and L-OD are inside the recommended rail limits. H-KD and 9908.721 are deeper than 28.50 mm behind the mounting face, so a new rail does not copy them. They remain reference sections for cases already built on them.

The seat in L-KD is measured on the 34560-184 section. The strip groove runs from 8.2 mm to 10.4 mm behind the front face, which is 5.2 mm to 7.4 mm behind the mounting face, and the cavity closes 9.00 mm behind the mounting face. The other three sections are catalog figures that do not show the insert seat.

A.3 Mounting-screw picks

Each pick is the shortest screw inside the length window of 5.3. M3 is the EIS thread; the M2.5 and #4-40 columns are for cases built on subrack hardware. "At most" marks a section whose insert seat is not published. That length is the longest that does not bottom out through a 1.6 mm panel.

Section	M3	M2.5	#4-40 UNC
Vector TS100	6 mm, only on a throat above 3.0 mm	6 mm	1/4 in
Gie-Tec 125010	6 mm	6 mm	1/4 in
Tiptop Z-rail	at most 8 mm	at most 8 mm	at most 5/16 in
Schroff 34560 L-KD	10 mm	10 mm	3/8 in
Schroff 34560 L-OD	at most 10 mm	at most 10 mm	at most 3/8 in
Schroff 34560 H-KD	at most 10 mm	at most 10 mm	at most 3/8 in
HEITEC 9908.721	at most 10 mm	at most 10 mm	at most 3/8 in

The Vector throat on drawing 5280006 is 0.115 in, +0.015 / −0, which is 2.921 mm to 3.302 mm. An M3 screw, 3.0 mm nominal, passes only when the throat is made above its nominal. #4-40, at 2.845 mm, and M2.5 pass at any throat inside the tolerance. Seats and cavities are in data/screw-fits.json. tools/screw.py computes this table.