# Hand-Screw Clamp Hewn Tool Library · https://hewn.build/tools/hand-screw-clamp Corrected: An independent reviewer read this entry and found corrections. They have been applied to the text, and the reviewer re-checked the correction that mattered most for safety and found it done; the others have not been re-checked yet. The list at the end is the record of what changed. Cite as: "Hand-Screw Clamp." Hewn Tool Library, hewn.build/tools/hand-screw-clamp. Reviewed 2026-07-29. --- ## identity **Name**: the **hand-screw clamp** (also **"hand screw"**, **"handscrew"**, **wooden screw clamp**, **cabinetmaker's clamp**), a clamp with two hardwood jaws set by two separately adjusted screws, so the jaws can be set substantially parallel for even pressure on parallel-sided work, or deliberately angled to bear on tapered or irregular work. **Each of the two screws engages pivoting threaded nuts in both jaws; turning the screws independently changes both the opening and the angle between the jaws.** The wooden jaws are not simply threaded onto the screws [HS1][HS2]. **Regional / alternate names**: simply "handscrews" in shop use. **Caution, corpus-correcting**: the current maker's product named "Pony Hand Clamp" is a different, unrelated tool, a spring clamp with rubber pads, not this one [HS3]. Current sellers also use "handscrew" for adjacent all-steel and toolmaker-style clamps, so category boundaries need care. **Family / category**: Clamping / holding tools. Fourth entry in the Clamping Family, joining [[Bar Clamp (F-Clamp)]] (Run 258), [[Parallel-Jaw Clamp]] (Run 259) and [[Pipe Clamp]] (Run 260), which already cite the Jorgensen and Holman patents as ancestors. Related fixed twin-screw vises are ancestors or alternatives in function, not interchangeable copies. **One line**: two hardwood jaws on two independently turned screws, giving broad-faced, portable clamping with directly adjustable jaw angle [HS1][HS4]. --- ## ✦ how NOT to use it **not-for**: treating a loose hand-screw clamp as a machine fixture (see `correct use`); veneer or high-force work (reasoned inference, above); loading work the jaws cannot fully seat. **dangerous**: this section replaces the earlier pinch warning, which did not cover inspection, loading or ejection. The hand-clamp hazards, low-energy but real: - **Pinch and crush.** Fingers and hands can be caught at the pivoting jaw-handle joint and in the closing jaws. A Sawmill Creek reply advises always picking the clamp up by its handles to avoid painful pinches when it pivots [HS17]. Keep fingers out of the closing and pivoting zones. - **Split or cracked jaws; damaged handles; bent screws; fouled threads; loose pivot hardware.** Inspect before each use; do not use a clamp with any of these (see `correct use`). - **Work ejecting or shifting.** Unstable work, poor bearing or uneven loading can make work squirt out or the clamp shift. Seat the work deeply with full-face bearing and stop if it moves. - **Excess leverage.** Hand force only. No wrench, pipe, bar or striking force; excess torque can crack a jaw, bend a screw or damage the work. (No first-person account of a cracked jaw from over-tightening was located; the mechanical possibility is stated, not an incident.) - **Racking.** Turning the two screws unevenly can rack the jaws and twist an assembly; alternate adjustments [HS27]. - **Contaminated or damaged faces.** Dirt, dried glue, damaged jaws, excess pressure, narrow contact or protruding steel hardware can mark work, and wood jaws can stick to squeeze-out. Inspect and clean the jaws, control pressure, and use suitable cauls or liners on delicate or finished work. - **Powered machinery adds separate hazards.** Presenting a clamped assembly to a rotating blade or cutter adds contact, kickback and projectile hazards that hand clamping does not have. See `correct use`; defer to the machine manual and an anchored fixture. **damaging**: unevenly turned screws (racking); jaws swollen or warped by moisture. The maker's care guidance says to store clamps in a dry, well-ventilated area to reduce swelling or warping [HS28]. Glue-swollen, stuck jaws have forum remedies (tapping the jaw near the handle with a dead-blow mallet, working a putty knife between the jaws) [HS29]. Stiff screws: forum-reported fixes are fine steel wool and paste wax; the posts warn against silicone products because silicone can later cause finish-adhesion problems [HS30]. These last three rest on forum and snippet-level sources. **beginner-trap**: not understanding the two-screw technique (see human side), and neglecting thread maintenance. A mismatch between a hand-screw and a one-handed bar or parallel-jaw clamp is a repeated confusion in the sources [HS22]. **lineage-misuse**: expecting one-handed, single-motion operation like a bar clamp. Clamping a hand-screw in a bench vise or to a table is a forum-accepted workaround, not a misuse [HS17]. Citing the "Pony Hand Clamp" product page for this tool would misattribute specifications [HS3]. --- ## correct use **What it is good at.** Broad-faced portable clamping of parallel, tapered, irregular and delicate wooden parts, when the work is fully seated and the clamp is used within its capacity. Also useful as an auxiliary holding point when itself held in a bench vise or clamped to a bench, as forum accounts describe [HS17]. The two screws directly set both opening and jaw angle; among the compared corpus clamps this is distinctive, and other clamp families can handle angled work with swivel pads, cauls, wedges, bands or dedicated fixtures. **Before each use: inspect.** Check the jaws for splits and cracks. Check handles, screws, threads and pivoting nuts: look for damaged handles, bent screws, fouled or damaged threads and loose hardware. Clean the bearing faces of dirt and dried glue. Do not use a clamp with a cracked jaw, damaged handle, bent screw, binding thread or loose pivot hardware. **Loading.** 1. Use a clamp whose capacity suits the work. 2. Open and position both screws, set the jaws to conform to the work, and seat the work deeply, with as much stable full-face bearing as practical. 3. Alternate adjustments between the two screws to avoid racking. 4. Apply only the pressure needed. **Use only hand force on the handles: never add a wrench, pipe or bar, and never strike the handles.** 5. Keep fingers out of the closing and pivoting zones; pick the clamp up by its handles, not by reaching into the jaw gap. 6. **Stop** if a jaw cracks, hardware binds or the work shifts. **Parallel and skewed work, one goal.** The goal is maximum stable face contact without twisting, slipping or overstressing the jaws. For parallel-sided stock, keep the loaded faces substantially parallel. For tapered stock, use controlled angular adjustment. Neither is a universal rule. The Van Dyke habit of using the same handle in the same hand, and the reader's parallel-first method, are two practitioner approaches [HS22]. **Powered machinery. A hand-screw clamp is not a machine fixture by itself.** - A hand-screw clamp may be incorporated into a purpose-designed workholding fixture when the machine manufacturer and operation permit it. Do not treat a loose hand-screw clamp as a universal substitute for a secured vise or a machine-specific fixture. - *Drill press.* OSHA's Drill Press eTool page, re-read in this pass, warns that the drill can catch and twist hand-held stock, names poor operator judgment as a common cause of accidents, and says a hold-down fixture should be used rather than the hands where feasible [HS35]. The reviewer reports OSHA training material that a drill-press vise must itself be clamped to the table `[manual, relayed]` [HS36]. Secure the work or fixture to the table. - *Bandsaw.* OSHA's Band Saws page, re-read in this pass, says to use a push stick to control stock near the blade and a special jig or fixture when cutting small pieces, and lists guarding as an engineering control [HS37]. Use the specified guard, push device, hold-down, sled or jig, and keep hands out of the cutting path. - *Router table or shaper.* CCOHS's Shapers page, re-read in this pass, says to keep guards in position, use jigs, fixtures, holders and hold-down push blocks, fasten the work securely in a jig, and not rest the hands near the edge of the stock being cut [HS38]. The same applies at a router table, subject to its manual. - The safe arrangement depends on the machine, cut direction, stock geometry, blade or cutter exposure and manufacturer instructions. Defer to the exact machine manual and an anchored, purpose-designed fixture. --- ## ✦ matching, the workbench's first read **does**: broad-faced portable clamping with directly adjustable jaw angle [HS4]; clamps panel edges when set to parallel contact [HS12]; holds work above the bench for carving or planing, as a forum-reported practice [HS17]. **suits**: tapered, irregular, parallel and delicate wooden parts, conditioned on adequate face contact and capacity; furniture-leg and rail glue-ups with a taper; restoration work on irregular parts; edge alignment on panel glue-ups where alignment matters more than maximum force [HS17]. **kit-fit**: *pairs with* a bench vise (as an auxiliary holding point) and with band clamps (as a stop or ledge on a splayed leg), per forum accounts [HS17]. *Substitutes for* a bench vise in some one-off holding situations. *Cannot replace* the maximum even force of a parallel-jaw clamp on a flat glue-up, nor the reach and speed of a bar or pipe clamp for production-volume work. **Comparative advantage, not exclusivity.** Among the compared corpus clamps, the hand-screw is distinctive because its two screws directly set both opening and jaw angle; other clamp families may handle angled work with swivel pads, cauls, wedges, bands or dedicated fixtures. Wooden faces spread load and, kept clean, offer broad, relatively low-marring contact [HS24]. **Powered-machine matching, conditional.** Not a direct use case. The hand-screw clamp is a **conditional component** of a machine-specific fixture, only where the machine manual and the operation permit it and the work or fixture is anchored as required (see `correct use`). **not-for**: high-force veneer pressing or production-speed repetitive clamping, held as reasoned inference only. No source names hand-screws as unsuitable for veneering; several forum posters describe reaching for a parallel-jaw or bar clamp first [HS25]. Also not for any work that cannot be fully seated within the clamp's capacity. **access**: simple in concept; the two-screw operation has a documented learning curve, per a trade-magazine instructor's account and a forum novice's report [HS22]. **revival**: a maker may pick this up for the broad wooden bearing faces and the direct jaw-angle control, as forum accounts describe [HS17]. --- ## anatomy - **Jaws.** Two flat hardwood blocks, hard maple on every current line surveyed in the original run. No maker specification for birch was found; treat "maple or birch" as maple-confirmed, birch-unconfirmed [HS10][HS11][HS12]. - **Two screws and pivoting nuts.** Traditionally wood, now steel spindles on the surveyed lines, engaging pivoting threaded nuts or shafts in both jaws. Jorgensen's literature advertises a "double-lead thread," a thread-geometry term meaning faster travel per turn; it is not the same thing as having two screws. Whether the current production meets that spec was not independently confirmed [HS10]. - **Handles.** Turned hardwood handles on each spindle, with ferrules and removable pins on Dubuque's line [HS12]. - **Positional convention.** Forum practice speaks of the "end" and "middle" screw or handle; not a formal part name [HS17]. --- ## variations (living) *Survey scope and date.* The original run surveyed four lines on 2026-07-16 (Jorgensen, Bessey, Dubuque Clamp Works, Rockler). It was not repeated in this pass, product availability changes, and four selected brands are not the whole market. - **Jorgensen "Classic Adjustable Handscrew":** four sizes, #3/0 (6" jaw / 3" max opening), #0 (8"/4 1/2"), #1 (10"/6"), #2 (12"/8") [HS10]. - **Bessey "Parallel Wood Hand Screw"** (HS-8, HS-12, LHS-10): HS-12 listed as 12" jaw, 9 1/4" max capacity, 6" throat [HS11]. - **Dubuque Clamp Works:** listed sizes 4" to 14", oil-treated hard maple [HS12]. - **Rockler house brand:** a 6" model was the only one confirmed [HS13]. - **Among these four surveyed lines, no composite-jaw, deep-throat or steel-collar hybrid was found.** That is a result of this limited survey, not a finding about the whole market. - **Naming collision, not a variation:** "Pony Hand Clamp" is an unrelated spring clamp [HS3]. --- ## trades Primarily woodworking and cabinetmaking (furniture assembly, chair and leg repair, carving-stage workholding). No cross-trade use was confirmed in the sources found. --- ## lineage **Ancestors, in layers.** Functional ancestry, documented patents and direct product lineage are three different things, and this entry does not merge them. - **Twin-screw wooden workholding is documented by the seventeenth century.** Newlin Grist Mill's account of the double-screw describes related devices associated with Moxon, Randle Holme and Félibien `[manual, relayed]` [HS33]. These are related double-screw vises, not proof of the portable modern clamp, and the route from those vises to the portable hand-screw clamp is not established here. - **A trade name already existed.** Lane's patent text says the basic wooden clamp was "commonly called" a hand-screw by tradespeople, and an 1887 R. Bliss catalog uses "Hand Screws" as settled trade language [HS5][HS7]. An 1882 patent (US 266,887, Thomas Reno) states that earlier hand screw-clamps had been made with a set of wooden screws `[manual, relayed]` [HS34]. That is evidence of an existing multi-screw hand-clamp category, not of the modern pivoting-nut form. - **US 214,403** ("Improvement in Hand Screw-Clamps," Wilbur F. Lane, Boston, granted April 15, 1879; filed August 31, 1878). Its sole claim recites two jaws, two handled screws, swiveling nuts and swiveling bearings, and the text says the arrangement lets the jaws be inclined to each other and lets one jaw's clamping face sit ahead of the other [HS5]. *Re-read in this pass through a fetch summary only.* Its mechanism (a screw through a swivel nut on one jaw and a bearing on the other) is not the Jorgensen right/left-thread form. **What this establishes, and what it does not.** The earliest U.S. patent located in this research that appears to describe independently adjustable screws is Lane's 1879 patent. This establishes an earlier documented claim than Jorgensen, **not first invention**, first manufacture, uninterrupted lineage, or that no earlier patent or non-patent example exists. The entry's earlier claim that this made the usual Jorgensen credit "22 years late" is withdrawn. A directly auditable Lane patent image or official record should be attached before the entry quotes Lane's wording. - **Intermediate wooden and composite clamp patents (1882 to 1889)** per a specialist clamp-patent list: US 266,887, 296,622, 324,803, 357,524, 386,279, 410,815 [HS6]. **Named but not independently verified;** inventor attributions (including a search-surfaced "Reno" on US 296,622) could not be confirmed and are not asserted. - **R. Bliss Manufacturing Company** (Pawtucket, RI) published the 1887 catalog "Genuine Bliss Hand Screws" [HS7]. Sources disagree on Rufus Bliss's founding year (1832 versus 1842), unresolved [HS8]. **Patent claims in the portable-clamp family.** Patents document claims, not craft invention. - **US 687,836** ("Clamp"), Hans Jorgensen, Chicago, filed Aug. 30, 1901, granted Dec. 3, 1901. Re-read in this pass through a fetch summary: two jaws each with lateral bores holding journaled shafts, flaring openings that let the screws pivot, right- and left-hand threaded screws so both jaws stay engaged with both screws, angular setting of the jaws without a filler block, and a claimed doubling of speed of operation [HS1]. This documents the pivoting-nut, right/left-thread form that closely resembles the modern product. - **US 1,403,958** ("Clamp"), Harry V. Holman, Chicago, filed May 9, 1921, granted Jan. 17, 1922. Describes itself as an improvement on Jorgensen's patent; replaces a through bore with a blind bore capped by a glued wooden plug, to give increased strength and durability `[manual, relayed]` [HS9]. Harry V. Holman was the son of Adele V. Holman, who later owned the company (see human side). **Descendants and contemporaries (by mechanism).** - **[[Parallel-Jaw Clamp]]** is a brand-name descendant, not a mechanism descendant (the Jorgensen name continues; the mechanism changed completely) [PJ3][PJ4, cited in that entry]. - **[[Bar Clamp (F-Clamp)]] and [[Pipe Clamp]]** occupy the same general niche with a different, single-screw-on-a-bar mechanism. - **Modern lines.** Jorgensen, Bessey, Dubuque Clamp Works and Rockler are the four lines surveyed in the original run (2026-07-16); see `variations` for what was found and what was not. --- ## history **Key evolutions (Petroski lens), stated as patent claims.** - **Lane, 1879.** Lane's patent frames the fix as letting the jaws be inclined when requisite, without adding a block to grip tapered or irregular work [HS5]. This is an earlier patent claim than Jorgensen's, and the entry does not treat it as invention priority (see lineage). - **Jorgensen's stated problem, 1901.** The patent says the clamps then in general use required jaws held parallel, so irregular blocks needed a third piece, which it calls troublesome. His right- and left-hand screws keep both jaws engaged with both screws and let both handles turn in the same sense [HS1]. The right/left-thread pivoting-nut construction is the documented contribution of this patent. Whether it is "Jorgensen's genuine contribution over Lane" is a comparison this review did not make against Lane's full text, and is not asserted. - **Holman, 1922.** A blind-bore nut seat replaced a through bore to strengthen the jaw, per the patent's stated purpose `[manual, relayed]` [HS9]. A clean small instance of a stated failure point and its stated fix. - **Maker history.** The Adjustable Clamp Company (Jorgensen/Pony) ran Chicago production for 113 years before suspending US operations on May 19, 2016, per the company's official statement (via Lost Art Press) and a Woodworker's Journal report on the 2017 GreatStar Industrial acquisition [HS14][HS15]. These two were not re-read in this pass. One retailer's copy describes Dubuque Clamp Works as effectively the sole remaining US maker; that is a seller's marketing claim, not an audited census, and is not asserted here [HS16]. --- ## ✦ human side **The people this tool belongs to.** Cabinetmakers, restorers, carvers and other woodworkers who hold odd, tapered or non-parallel pieces. Forum accounts describe collectors who keep buying the tool for jobs other clamps in this corpus do less directly [HS17]. **A founding story, reported by a museum blog.** Adele V. Holman (1861 to 1932), a former touring vocalist, is reported by the Made-in-Chicago Museum to have bought into the Adjustable Clamp Company in 1907 and bought out co-founder Marcus W. Russ's remaining shares in 1914, signing as "A. V. Holman" to obscure her gender [HS18]. **Unresolved conflict:** the company's own "Our Story" page states Holman co-founded in 1903 with Jorgensen and Russ, while HS18 says she joined in 1907. This entry cannot say which is right [HS18][HS19]. Her son Harry V. Holman is the patentee of the 1922 improvement; genealogical specifics beyond that connection are not verified [HS21]. **An instructor's account, as reported in a trade magazine.** Bob Van Dyke, writing in Fine Woodworking #261 (May/June 2017), says hand screws are "one of the most useful tools and one of the most misunderstood," that he nearly gave up on them, and that holding the same handle in the same hand built consistent habit [HS22]. A reader comment (user-7138398, Oct 2019) argued for a different method: get the jaws parallel first, then turn both handles together for final tightening. This is anecdotal evidence from a magazine and its readers. **A forum thread, anecdotal.** Sawmill Creek's "Do YOU use handscrew clamps?" (Frederick Skelly, Aug. 6, 2020) is a thread of forum handles reporting personal practice: balance compared with a bar clamp, large glue-ups with many clamps, retired clamps used as clamping ledges or an improvised vise [HS17]. Contributors are pseudonymous and are not independently verified. --- ## ✦ proof of existence - **Earliest U.S. patent located in this research** that appears to describe independently adjustable screws: US 214,403, Wilbur F. Lane, granted April 15, 1879. A patent claim, not first invention [HS5]. - **Smithsonian NMAH:** two "Hand Screw" object records attributed to R. Bliss Mfg. Co., IDs MC.308419.01 and MC.308419.02 [HS31][HS32]. Not re-opened in this pass. - **1887 trade catalog:** "Genuine Bliss Hand Screws," R. Bliss Manufacturing Co., Internet Archive [HS7]. - **Patents, as patent claims:** US 214,403 (1879, Lane); US 687,836 (1901, Jorgensen); US 1,403,958 (1922, Holman). Jorgensen and Lane were re-read in this pass through fetch summaries only; Holman is carried from the original run and the review. - **Company history:** the 2016 US-operations suspension and 2017 acquisition, per the company statement and a trade report [HS14][HS15]. - The earlier "safely secures small parts at the drill press, router table, or bandsaw" line is removed as a proof or use claim. --- ## references *[kind: book | video | blog | forum | reddit | museum | patent | named_maker | archaeological | regulator]. Labels: patents are patent claims; maker pages are product claims; regulator pages are safety requirements; forum and magazine items are anecdotal.* - **[HS1]** US Patent 687,836, Hans Jorgensen, "Clamp," filed Aug. 30 1901, granted Dec. 3 1901. Patent claim. patents.google.com/patent/US687836A/en - **[HS2]** Infinity Tools, "Dubuque Handscrew Clamps." Retailer product claim. infinitytools.com/products/dubuque-handscrew-clamps - **[HS3]** Pony Jorgensen, "Pony Hand clamp." Product claim; confirms the naming collision. ponyjorgensen.com/product/pony-hand-clamp - **[HS4]** Lane US 214,403 (HS5) read with Infinity Tools' plain-language explanation of jaw-skew capability (HS2/HS24). Patent claim plus retailer. - **[HS5]** US Patent 214,403, Wilbur F. Lane, "Improvement in Hand Screw-Clamps," granted April 15 1879. Patent claim. patents.google.com/patent/US214403A/en (re-read this pass via fetch summary; the review notes this page did not render for him and asks for an image or official record). - **[HS6]** theclampguy.info, chronological list of US wooden and composite clamp patents. Blog/specialist list; inventor names not verified. theclampguy.info/ptnt.htm - **[HS7]** "Genuine Bliss Hand Screws," R. Bliss Manufacturing Co., 1887 trade catalog. archive.org/details/r-bliss-mfg-co-1887 - **[HS8]** netris.org, "Rufus Bliss, wood screw & clamp maker." Biographical blog; founding-year conflict unresolved. netris.org/RIToolmakers/BLISS-RUFUS/BLISS-RUFUS.html - **[HS9]** US Patent 1,403,958, Harry V. Holman, "Clamp," filed May 9 1921, granted Jan. 17 1922. Patent claim. patents.google.com/patent/US1403958A/en - **[HS10]** Pony Jorgensen, "Classic Jorgensen Adjustable Handscrew." Product claim. ponyjorgensen.com/product/classic-jorgensen-adjustable-handscrew - **[HS11]** The Home Depot, Bessey HS-12 listing. Retailer product claim. - **[HS12]** Infinity Tools, Dubuque handscrew page. Retailer product claim. - **[HS13]** The Woodsmith Store, Rockler 6" Handscrew Clamp. Retailer product claim. - **[HS14]** Lost Art Press blog, "Pony Tools Suspends Operations," May 30 2016, with official company statement. Maker statement via blog. - **[HS15]** Chris Marshall, "GreatStar Industrial Acquires Adjustable Clamp Company," Woodworker's Journal, June 6 2017. Trade press. - **[HS16]** Infinity Tools blog copy on Dubuque as sole remaining US maker. Retailer marketing claim; unaudited. Not asserted. - **[HS17]** "Do YOU use handscrew clamps?", Frederick Skelly, Sawmill Creek Woodworking Community, Aug 6 2020. Forum, anecdotal, pseudonymous. sawmillcreek.org/threads/do-you-use-handscrew-clamps.284908 - **[HS18]** Made-in-Chicago Museum, "Adjustable Clamp Company, est. 1903." Museum blog. madeinchicagomuseum.com/single-post/adjustable-clamp-co - **[HS19]** Pony Jorgensen, "Our Story." Company page; founding-date conflict with HS18. ponyjorgensen.com/about - **[HS20]** Cross-check of HS18 and HS19. Internal; unresolved. - **[HS21]** Made-in-Chicago Museum (as HS18), Holman family relationship. Museum blog. - **[HS22]** Bob Van Dyke (with Ben Strano), Fine Woodworking #261, May/June 2017, with reader comments. Trade press and comments, anecdotal. finewoodworking.com/2017/03/29/hand-screw-bob-van-dyke - **[HS23]** Infinity Tools blog on small-part holding at power tools. **Retained only as a retailer claim; the claim itself is withdrawn from this entry (see Fix 1).** - **[HS24]** Infinity Tools FAQ, hand-screw versus bar-clamp comparison language. Retailer product claim. - **[HS25]** Reasoned inference from general clamping and veneering literature; no named source. Labeled inference. - **[HS26]** *Replaced.* The earlier generic "OSHA-adjacent pinch-point literature" tag is dropped. The pinch hazard now rests on the forum reply in HS17 and the controls drawn from the review. - **[HS27]** Racking of an assembly from unevenly turned clamps. *Replaced:* no exact source; stated as a mechanical consequence of the two-screw design and labeled inference. - **[HS28]** Pony Jorgensen blog, "Guide to Handscrew Clamps," storage guidance. Maker blog. ponyjorgensen.com/blogs/mastering-woodworking-role-of-handscrew-clamps. Not re-fetched in full. - **[HS29]** LumberJocks, stuck-clamp thread. Forum, snippet-level. lumberjocks.com/threads/help-with-stuck-clamp.239633 - **[HS30]** Forum guidance on paste wax and avoiding silicone, aggregated across threads. Forum, snippet-level; not a single exact source. - **[HS31]** Smithsonian NMAH, "Hand Screw," MC.308419.01, nmah_656836. Museum. americanhistory.si.edu/collections/object/nmah_656836 - **[HS32]** Smithsonian NMAH, "Hand Screw," MC.308419.02, nmah_656835. Museum. americanhistory.si.edu/collections/object/nmah_656835 - **[HS33]** [Newlin Grist Mill, "Tools of the Trade: The Double-Screw"](https://newlingristmill.org/tools-of-the-trade-the-double-screw/). Museum blog; added from the review; not read in this pass. Supports related seventeenth-century twin-screw workholding, not direct descent. - **[HS34]** [US 266,887, Thomas Reno, "Clamp" (1882)](https://patents.google.com/patent/US266887A/en). Patent claim; added from the review; not read in this pass. - **[HS35]** [OSHA Woodworking eTool, Drill Press](https://www.osha.gov/etools/woodworking/production/machines-tools/drill-press). Regulator guidance; re-read this pass via fetch summary. - **[HS36]** [OSHA Drill Press Trainer Script](https://www.osha.gov/sites/default/files/2021-04/Drill%20Press%20-%20Trainer%20Script.pdf). Regulator training material; relayed via the reviewer; not read. - **[HS37]** [OSHA Woodworking eTool, Band Saws](https://www.osha.gov/etools/woodworking/production/machines-tools/band-saws). Regulator guidance; re-read this pass via fetch summary. - **[HS38]** [CCOHS, Woodworking Machines: Shapers](https://www.ccohs.ca/oshanswers/safety_haz/woodwork/shaper.html). Safety authority; re-read this pass via fetch summary. The reviewer also names [CCOHS Band Saws](https://www.ccohs.ca/oshanswers/safety_haz/woodwork/band_saw.html), [CCOHS Push Sticks and Push Blocks](https://www.ccohs.ca/oshanswers/safety_haz/woodwork/push_stk.html), [OSHA Shapers](https://www.osha.gov/etools/woodworking/production/machines-tools/shapers) and [29 CFR 1910.213](https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.213) `[manual, relayed]`; none was read here, and none makes a loose hand-screw clamp a universal machine-safety device. --- ## The reviewer's corrections (10) - `BLOCKER` — 1. Replace the universal power-tool safety claim with machine-specific workholding rules — Exact claim: “safely holding small parts at a drill press, router table, or bandsaw with the operator's fingers well clear” - `BLOCKER` — 2. Add a complete hand-clamp safety and inspection envelope — Exact claim: The current safety treatment is largely a pinch warning and does not provide pre-use, loading, or misuse controls. - `SHOULD-FIX` — 3. Separate “earliest patent found” from invention or historical priority — Exact claim: Lane's 1879 patent is the “earliest patent found claiming the defining double-independent-screw mechanism,” making the common Jorgensen credit “22 years late.” - `SHOULD-FIX` — 4. Replace the single-screw-to-Lane lineage with a bounded twin-screw history — Exact claim: The ancestry runs from a “single-screw/non-adjustable predecessor” to Lane, Jorgensen, and Holman. - `SHOULD-FIX` — 5. Bound the current-market and maker claims to the actual survey — Exact claim: “Every current product across all four brands is the same basic architecture”; “no composite-jaw, deep-throat, or steel-collar hybrid” is a “genuine current-market gap”; related sole-maker and category-wide claims. - `SHOULD-FIX` — 6. Narrow “non-marring” and “no metal-on-wood contact” claims — Exact claim: “no metal-on-wood contact anywhere in the clamping path”; the jaws are effectively non-marring. - `SHOULD-FIX` — 7. Narrow the uniqueness claim — Exact claim: “The hand-screw alone offers jaw-angle capability no other corpus clamp can match.” - `SHOULD-FIX` — 8. Resolve the operating-technique conflict instead of preserving two incompatible rules — Exact claim: The entry presents conflicting advice about whether the jaws should remain parallel or be deliberately skewed during tightening. - `SHOULD-FIX` — 9. Repair source traceability and confidence — Exact claim: References `[HS25]` through `[HS30]` and the current MEDIUM-HIGH confidence grade. - `MINOR` — 10. Correct the modern mechanism wording — Exact claim: “Each jaw is independently threaded onto two screws.”