We continue to build on the momentum we experienced in the fourth quarter and expect 2021 to be stronger than our expectations 90 days ago.
Yesterday, we announced our intent to acquire Airtech Vacuum Group from EagleTree Capital for $470 million.
Airtech had revenue of $85 million with EBITDA margin in the mid-30s range in 2020.
This deal, which we expect to close in the second quarter, will then create a $200 million pneumatics platform within our Health & Science Technology segment.
The positive momentum in order trends continued in the first quarter, both compared to prior year and sequentially, allowing us to build $59 million of backlog in the quarter.
Q1 orders were also up 4% organically versus Q1 of 2019.
Q1 orders of $711 million were up 10% overall and up 6% organically as we built $59 million of backlog in the quarter.
First-quarter sales of $652 million were up 10% overall and 6% organically.
We experienced growth across all our segments, with over 75% of our business units increasing year over year.
Q1 gross margin contracted 80 basis points to 44.9% but was up 110 basis points sequentially.
First-quarter operating margin was 23.9%, up 40 basis points compared to prior year.
Adjusted operating margin was 24.3%, up 80 basis points compared to last year, driven by the increased volume and the impact of cost actions taken last year, offset by the gross margin pressure I just mentioned.
Our Q1 effective tax rate was 22.6%, which was higher than the prior-year ETR of 20% due to a decrease in the excess tax benefits from share-based compensation.
This drove a $0.05 headwind on earnings per share for the quarter.
First-quarter adjusted net income was $115 million, resulting in adjusted earnings per share of $1.51, up $0.18 or 14% over prior year.
Excluding the $0.05 tax headwind, adjusted earnings per share would have been up $0.23 or 17%.
Finally, free cash flow for the quarter was $95 million, up 32% compared to prior year and was 82% of adjusted net income.
Adjusted operating income increased $18 million for the quarter compared to prior year.
Our 6% organic growth contributed approximately $13 million flowing through at our prior-year gross margin rate.
The impact of previous discretionary cost controls contributed $5 million, and we were able to net $4 million from price productivity, partially offset by inflation.
After accounting for $2 million of negative mix, our organic flow-through was extremely strong at 58%.
Flow-through was then negatively impacted by the $3 million charge related to the inventory reserve I discussed on the last slide and the dilutive impact of acquisitions and FX, getting to a reported flow-through of 32%.
For the second quarter, we are projecting earnings per share to range from $1.60 to $1.63, with organic revenue growth of 18% to 20%, and operating margins of approximately 24.5%.
The second quarter effective tax rate is expected to be about 23%, and we expect a 2% top-line benefit from the impact of FX.
Corporate costs in the second quarter are expected to be around $21 million, with the increase primarily driven by the M&A investments we discussed earlier.
We are increasing our full-year earnings per share guidance from $5.65 to $5.95, up to $6.05 to $6.20.
We are also increasing our full-year organic revenue growth from 6% to 8%, up to 9% to 10%.
We expect operating margins of approximately 24 and a half percent.
We expect FX to provide a 1% benefit to top-line results.
Our full-year effective tax rate is expected to be around 23%.
Capital expenditures are anticipated to be around $55 million.
Free cash flow is now expected to be 115% to 120% of net income.
And corporate costs are expected to be approximately $74 million for the full year.

Summary:
First-quarter sales of $652 million were up 10% overall and 6% organically.
First-quarter adjusted net income was $115 million, resulting in adjusted earnings per share of $1.51, up $0.18 or 14% over prior year.
For the second quarter, we are projecting earnings per share to range from $1.60 to $1.63, with organic revenue growth of 18% to 20%, and operating margins of approximately 24.5%.
We are increasing our full-year earnings per share guidance from $5.65 to $5.95, up to $6.05 to $6.20.
We are also increasing our full-year organic revenue growth from 6% to 8%, up to 9% to 10%.