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Face spiral on a disc as a drill feed: scroll driving a rack
How does a spiral on a disc give a drill its feed? · Hardware · basis: Xem Studio design following Brown No. 99 (1868)
Also called: drill feed scroll, spiral feed, scroll and rack, face spiral rack, avance de taladro por espiral frontal, Bohrvorschub mit Spiralscheibe und Zahnstange
Exact dimensions. True size, with no printing tolerance added.
- sizes
- 4 in table
Notes
- Resize: multiply every length by one factor k and the motion stays identical: angles, ratios, timing and the formulas below do not change, because a mechanism's motion depends only on the ratios of its lengths. Here, scales with k: feed per turn, rack height over the face; stays the same: disc, rack.
- Resize: fit clearances stay in mm (a slide fit is the same gap at any size); keep every printed wall and pin at least two nozzle widths; mass grows with k³ but part strength only with k², so at k = 2 parts are about 8× heavier and 4× stronger: check pins and thin links when scaling up.
- A spiral rib on the face of a disc engages a rack that slides radially over it: every turn of the disc moves the rack one pitch (3.14 mm) outward or inward — a slow, smooth feed from a continuously turning disc, the scroll-chuck principle used for the feed motion of drilling machines (the rack is on the drill's spindle sleeve).
- The rib's radial section is the module 1 basic rack; the feed rack's teeth were generated by the rib across the rack's 8 mm width, so they curve to follow the spiral and mesh without binding. With this 8.4-turn scroll (r 20 → 46.39) the 6-tooth rack stays fully on the rib over about ±3 mm of travel about the drawn position; a longer scroll gives a longer stroke. Checked at six positions over two turns: no overlap beyond contact.
- Brown's No. 99 (spiral guide on the face of a disc, drilling-machine feed). Drawn with the disc turned 90°, the rack's centre 31.78 mm from the disc's axis; the rack's guide is not drawn.
- Parts (each has its own page): face-spiral-disc-m1-r20-8-4turns-d100, face-spiral-feed-rack-m1-6t-w8, linear-shafts-h6.
- Brown's movement No. 99 (1868) shows it; this model is a Xem Studio design following his figure, every part at true size.
Face spiral on a disc as a drill feed: scroll driving a rack size chart
| parameter | value |
|---|---|
| disc | Ø100 × 6, spiral r 20 → 46.39 (8.4 turns) |
| feed per turn | 3.14 mm |
| rack | 6 T, module 1, 19.05 long |
| rack height over the face | pitch line 1.25 mm |
Where the files are
Other publishers' files are linked, not hosted. "verify" = check the license at the link before commercial use.
| Henry T. Brown (1868, public domain) | Five Hundred and Seven Mechanical Movements — scan on archive.org | web | Publisher's page; dimensions are facts |
| 507movements.com | Brown's movement No. 99: figure, his text and an animation | web | Publisher's page; dimensions are facts |
Free files
★ Free files 1 parts. Xem Studio design: free to use, print and sell things from; not to be republished as files. Xem Studio Design License. index.json
| face-spiral-rack-feed-mechanism-assembly | Assembled mechanism, all parts placed at one pose (STEP keeps each part separate) | STEP · STL |
https://xemstudio.com/mcp to Claude, ChatGPT, Cursor or any MCP client (free, no account, one minute) and it can look up exact sizes, mating fits and free STEP/STL from every chat.Plain text: sheet.txt · JSON: /api/geometry?object=face-spiral-rack-feed-mechanism
Fits with
Questions
How does a spiral on a disc give a drill its feed?
A spiral rib on the face of a disc engages a rack that slides radially over it: every turn of the disc moves the rack one pitch (3.14 mm) outward or inward — a slow, smooth feed from a continuously turning disc, the scroll-chuck principle used for the feed motion of drilling machines (the rack is on the drill's spindle sleeve).