Sec Form 3 Filing - May John @ Fathom Digital Manufacturing Corp - 2021-12-23

FORM 3 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person May John 2. Issuer Name and Ticker or Trading Symbol Fathom Digital Manufacturing Corp [ FATH] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) X __ Director X __ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) 80 SW 8TH ST, SUITE 2750 3. Date of Earliest Transaction (MM/DD/YY) 12/23/2021 (Street) MIAMI, FL33130 4. If Amendment, Date Original Filed (MM/DD/YY) 6. Individual or Joint/Group Filing (Check Applicable Line) _____ Form filed by One Reporting Person __ X __ Form filed by More than One Reporting Person (City) (State) (Zip)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned 1.Title of Security (Instr. 3) 2. Transaction Date (MM/DD/YY) 2A. Deemed Execution Date, if any (MM/DD/YY) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Class A Common Stock( 1 ) 22,420,144 I CORE Industrial Partners Fund I Parallel, LP( 2 ) Class B Common Stock 63,377,883 I CORE Industrial Partners Fund I, LP( 2 )

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities) 1. Title of Derivative Security (Instr. 3) 2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (MM/DD/YY) 3A. Deemed Execution Date, if any (MM/DD/YY) 4. Transaction Code (Instr. 8) 5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5) 6. Date Exercisable and Expiration Date (MM/DD/YY) 7. Title and Amount of Underlying Securities (Instr. 3 and 4) 8. Price of Derivative Security (Instr. 5) 9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4) Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares Earnout Shares( 3 ) ( 3 ) ( 3 ) ( 3 ) Class B Common Stock 4,717,507 I CORE Industrial Partners Fund I, LP Earnout Shares( 3 ) ( 3 ) ( 3 ) ( 3 ) Class A LLC Units 4,717,507 I CORE Industrial Partners Fund I, LP Class A LLC Units( 4 ) ( 4 ) ( 4 ) ( 4 ) Class A Common Stock 63,377,883 I CORE Industrial Partners Fund I, LP Earnout Shares( 5 ) ( 5 ) ( 5 ) ( 5 ) Class A Common Stock 1,668,834 I CORE Industrial Partners Fund I Parallel, LP

Reporting Owners Reporting Owner Name / Address Relationships Director 10% Owner Officer Other May John 80 SW 8TH ST, SUITE 2750 MIAMI, FL33130 X X CORE Industrial Partners Fund I, L.P. 150 NORTH RIVERSIDE DRIVE, SUITE 2050 CHICAGO, IL60606 X X CORE Industrial Partners Fund I Parallel, L.P. 150 NORTH RIVERSIDE DRIVE, SUITE 2050 CHICAGO, IL60606 X X CORE INDUSTRIAL FUND PARTNERS GP I, LLC 150 NORTH RIVERSIDE DRIVE, SUITE 2050 CHICAGO, IL60606 X X Signatures CORE INDUSTRIAL PARTNERS FUND I, LP, BY: CORE INDUSTRIAL FUND PARTNERS GP I, LLC, /s/John May, as Authorized Person, by James R. Brown as Attorney-in-Fact 01/03/2022 Signature of Reporting Person Date CORE INDUSTRIAL PARTNERS FUND I PARALLEL, LP, BY: CORE INDUSTRIAL FUND PARTNERS GP I, LLC, /s/John May, as Authorized Person, by James R. Brown as Attorney-in-Fact 01/03/2022 Signature of Reporting Person Date CORE INDUSTRIAL FUND PARTNERS GP I, LLC, /s/John May, as Authorized Person, by James R. Brown as Attorney-in-Fact 01/03/2022 Signature of Reporting Person Date JOHN MAY, /s/John May, by James R. Brown as Attorney-in-Fact 01/03/2022 Signature of Reporting Person Date

Explanation of Responses:

( 1 )On December 23, 2021 (the "Effective Time"), the Issuer, formerly known as Altimar Acquisition Corp. II, acquired Fathom Holdco, LLC ("Fathom") pursuant to a Business Combination Agreement by and among the Issuer, Fathom and certain other parties thereto (the "Business Combination Agreement"). Pursuant to the Business Combination Agreement, at the Effective Time, the outstanding equity interests of Fathom held by the Reporting Person were converted into the right to receive shares of the Issuer's Class A Common Stock or a combination of the Issuer's Class B Common Stock and a like number of Fathom's Class A LLC Units, as applicable. Shares of Class B Common Stock have no economic rights (other than the right to receive the par value of such shares in connection with the liquidation, dissolution or winding up of the Issuer), and each share of Class B Common Stock entitles its holder to one vote per share. ( 2 )Mr. May is a director of the Issuer and sole managing member of CORE Industrial Fund Partners GP I, LLC ("CORE Fund I GP"). CORE Fund I GP is the sole general partner of each of CORE Industrial Partners Fund I, LP ("CORE Fund I") and CORE Industrial Partners Fund I Parallel, LP ("CORE Fund I Parallel", and collectively with CORE Fund I, the "CORE Funds"). Consequently, Mr. May and CORE Fund I GP may be deemed the beneficial owners of the shares held by the CORE Funds, but each disclaims beneficial ownership of such securities except to the extent of their pecuniary interest therein. ( 3 )The Reporting Person holds an aggregate of 4,717,507 shares of Class B Common Stock and 4,717,507 Class A LLC Units that are subject to forfeiture. These earnout shares will vest in three equal tranches, with each tranche vesting at each of the following share price thresholds: $12.50, $15.00 and $20.00. The achievement of the price threshold will be determined based on a volume-weighted average price ("VWAP") of the Class B Common Stock or Class A LLC Units, as applicable, for 20 trading days within any 30 trading day period or a change of control transaction of the issuer that implies the same per share value as the applicable price threshold. The earnout period will be five years from the date of the closing of the Business Combination or December 23, 2026. If such vesting requirements are not achieved during the five-year earnout period, such earnout shares will be forfeited. ( 4 )The Class A LLC Units are exchangeable (upon delivery of a corresponding number of shares of the Issuer's Class B Common Stock (as reported on Table I hereof)) for shares of the Issuer's Class A Common Stock on a one-for-one basis or an equivalent amount of cash at the option of Fathom pursuant to the terms of the Second Amended and Restated LLC Operating Agreement of Fathom. ( 5 )The Reporting Person holds an aggregate of 1,668,834 shares of Class A Common Stock that are subject to forfeiture. These earnout shares will vest in three equal tranches, with each tranche vesting at each of the following share price thresholds: $12.50, $15.00 and $20.00. The achievement of the price threshold will be determined based on a VWAP of the Class A common stock for 20 trading days within any 30 trading day period or a change of control transaction of the issuer that implies the same per share value as the applicable price threshold. The earnout period will be five years from the date of the closing of the Business Combination or December 23, 2026. If such vesting requirements are not achieved during the five-year earnout period, such earnout shares will be forfeited.

Remarks: Exhibit 24 - Powers of Attorney

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